fix(unstable): correct Parser.Range for non-suffix highlights

Parser.Range used len(data)-len(highlight), which only matches suffix
slices. Single-byte highlights like b[0:1] are subslices of the
remaining buffer, so the wrong offset pointed at the end of the
document (issue #1047). Use pointer-based subslice offset like
wrapDecodeError.

Add regression tests for unstable.Parser and toml.Unmarshal error
positions and human-readable output.

Co-authored-by: Thomas Pelletier <thomas@pelletier.dev>

.github/workflows/cifuzz.yml

@@ -0,0 +1,26 @@
+name: CIFuzz
+on: [pull_request]
+jobs:
+  Fuzzing:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Build Fuzzers
+      id: build
+      uses: google/oss-fuzz/infra/cifuzz/actions/build_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'go-toml'
+        dry-run: false
+        language: go
+    - name: Run Fuzzers
+      uses: google/oss-fuzz/infra/cifuzz/actions/run_fuzzers@master
+      with:
+        oss-fuzz-project-name: 'go-toml'
+        fuzz-seconds: 300
+        dry-run: false
+        language: go
+    - name: Upload Crash
+      uses: actions/upload-artifact@v7
+      if: failure() && steps.build.outcome == 'success'
+      with:
+        name: artifacts
+        path: ./out/artifacts

.github/workflows/codeql-analysis.yml

@@ -35,11 +35,11 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v6
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v2
+      uses: github/codeql-action/init@v4
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -47,10 +47,10 @@ jobs:
         # Prefix the list here with "+" to use these queries and those in the config file.
         # queries: ./path/to/local/query, your-org/your-repo/queries@main
 
-    # Autobuild attempts to build any compiled languages  (C/C++, C#, or Java).
+    # Autobuild attempts to build any compiled languages (C/C++, C#, or Java).
     # If this step fails, then you should remove it and run the build manually (see below)
     - name: Autobuild
-      uses: github/codeql-action/autobuild@v2
+      uses: github/codeql-action/autobuild@v4
 
     # ℹ️ Command-line programs to run using the OS shell.
     # 📚 https://git.io/JvXDl
@@ -64,4 +64,4 @@ jobs:
     #   make release
 
     - name: Perform CodeQL Analysis
-      uses: github/codeql-action/analyze@v2
+      uses: github/codeql-action/analyze@v4

.github/workflows/coverage.yml

@@ -9,12 +9,12 @@ jobs:
     runs-on: "ubuntu-latest"
     name: report
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Setup go
-        uses: actions/setup-go@master
+        uses: actions/setup-go@v6
         with:
-          go-version: 1.19
+          go-version: "1.26"
       - name: Run tests with coverage
         run: ./ci.sh coverage -d "${GITHUB_BASE_REF-HEAD}"

.github/workflows/go-versions-test.yml

@@ -0,0 +1,36 @@
+name: Go Versions Compatibility Test
+
+on:
+  workflow_dispatch:
+    inputs:
+      go_versions:
+        description: 'Go versions to test (space-separated, e.g., "1.21 1.22 1.23")'
+        required: false
+        default: ''
+        type: string
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v4
+
+      - name: Run Go versions compatibility test
+        run: |
+          VERSIONS="${{ github.event.inputs.go_versions }}"
+          ./test-go-versions.sh --output ./test-results $VERSIONS
+
+      - name: Upload test results
+        uses: actions/upload-artifact@v7
+        with:
+          name: go-versions-test-results
+          path: |
+            test-results/
+          retention-days: 30

.github/workflows/lint.yml

@@ -0,0 +1,22 @@
+name: lint
+on:
+  pull_request:
+    branches:
+      - v2
+
+jobs:
+  golangci:
+    name: lint
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+      - name: Setup go
+        uses: actions/setup-go@v6
+        with:
+          go-version: "1.26"
+      - name: Run golangci-lint
+        uses: golangci/golangci-lint-action@v9
+        with:
+          version: v2.8.0

.github/workflows/release.yml

@@ -16,24 +16,24 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Set up Go
-        uses: actions/setup-go@v2
+        uses: actions/setup-go@v6
         with:
-          go-version: 1.19
+          go-version: "1.26"
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@v2
+        uses: docker/login-action@v4
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Run GoReleaser
-        uses: goreleaser/goreleaser-action@v3
+        uses: goreleaser/goreleaser-action@v7
         with:
           distribution: goreleaser
-          version: latest
+          version: '~> v2'
-          args: release ${{ inputs.args }} --rm-dist
+          args: release ${{ inputs.args }} --clean
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/workflow.yml

@@ -10,23 +10,24 @@ on:
 jobs:
   build:
     strategy:
+      fail-fast: false
       matrix:
-        os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest']
+        os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest', 'macos-14' ]
-        go: [ '1.18', '1.19' ]
+        go: [ '1.25', '1.26' ]
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.go }}/${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v6
         with:
           fetch-depth: 0
       - name: Setup go ${{ matrix.go }}
-        uses: actions/setup-go@master
+        uses: actions/setup-go@v6
         with:
           go-version: ${{ matrix.go }}
       - name: Run unit tests
         run: go test -race ./...
   release-check:
     if: ${{ github.ref != 'refs/heads/v2' }}
-    uses: pelletier/go-toml/.github/workflows/release.yml@v2
+    uses: ./.github/workflows/release.yml
     with:
       args: --snapshot

.gitignore

@@ -3,4 +3,6 @@ fuzz/
 cmd/tomll/tomll
 cmd/tomljson/tomljson
 cmd/tomltestgen/tomltestgen
-dist
+dist
+tests/
+test-results

.golangci.toml

@@ -1,84 +1,76 @@
-[service]
+version = "2"
-golangci-lint-version =  "1.39.0"
-
-[linters-settings.wsl]
-allow-assign-and-anything = true
-
-[linters-settings.exhaustive]
-default-signifies-exhaustive = true
 
 [linters]
-disable-all = true
+default = "none"
 enable = [
     "asciicheck",
     "bodyclose",
-    "cyclop",
-    "deadcode",
-    "depguard",
     "dogsled",
     "dupl",
     "durationcheck",
     "errcheck",
     "errorlint",
     "exhaustive",
-    # "exhaustivestruct",
-    "exportloopref",
     "forbidigo",
-    # "forcetypeassert",
-    "funlen",
-    "gci",
-    # "gochecknoglobals",
     "gochecknoinits",
-    "gocognit",
     "goconst",
     "gocritic",
-    "gocyclo",
+    "godoclint",
-    "godot",
-    "godox",
-    # "goerr113",
-    "gofmt",
-    "gofumpt",
     "goheader",
-    "goimports",
-    "golint",
-    "gomnd",
-    # "gomoddirectives",
     "gomodguard",
     "goprintffuncname",
     "gosec",
-    "gosimple",
     "govet",
-    # "ifshort",
     "importas",
     "ineffassign",
     "lll",
     "makezero",
+    "mirror",
     "misspell",
     "nakedret",
-    "nestif",
     "nilerr",
-    # "nlreturn",
     "noctx",
     "nolintlint",
-    #"paralleltest",
+    "perfsprint",
     "prealloc",
     "predeclared",
     "revive",
     "rowserrcheck",
     "sqlclosecheck",
     "staticcheck",
-    "structcheck",
-    "stylecheck",
-    # "testpackage",
     "thelper",
     "tparallel",
-    "typecheck",
     "unconvert",
     "unparam",
     "unused",
-    "varcheck",
+    "usetesting",
     "wastedassign",
     "whitespace",
-    # "wrapcheck",
+]
-    # "wsl"
+
+[linters.settings.exhaustive]
+default-signifies-exhaustive = true
+
+[linters.settings.lll]
+line-length = 150
+
+[[linters.exclusions.rules]]
+path = ".test.go"
+linters = ["goconst", "gosec"]
+
+[[linters.exclusions.rules]]
+path = "main.go"
+linters = ["forbidigo"]
+
+[[linters.exclusions.rules]]
+path = "internal"
+linters = ["revive"]
+text = "(exported|indent-error-flow): "
+
+[formatters]
+enable = [
+    "gci",
+    "gofmt",
+    "gofumpt",
+    "goimports",
 ]

.goreleaser.yaml

@@ -1,3 +1,4 @@
+version: 2
 before:
   hooks:
     - go mod tidy
@@ -18,9 +19,9 @@ builds:
       - linux_amd64
       - linux_arm64
       - linux_arm
+      - linux_riscv64
       - windows_amd64
       - windows_arm64
-      - windows_arm
       - darwin_amd64
       - darwin_arm64
   - id: tomljson
@@ -37,9 +38,9 @@ builds:
       - linux_amd64
       - linux_arm64
       - linux_arm
+      - linux_riscv64
       - windows_amd64
       - windows_arm64
-      - windows_arm
       - darwin_amd64
       - darwin_arm64
   - id: jsontoml
@@ -55,10 +56,10 @@ builds:
     targets:
       - linux_amd64
       - linux_arm64
+      - linux_riscv64
       - linux_arm
       - windows_amd64
       - windows_arm64
-      - windows_arm
       - darwin_amd64
       - darwin_arm64
 universal_binaries:
@@ -109,7 +110,7 @@ dockers:
 checksum:
   name_template: 'sha256sums.txt'
 snapshot:
-  name_template: "{{ incpatch .Version }}-next"
+  version_template: "{{ incpatch .Version }}-next"
 release:
   github:
     owner: pelletier

AGENTS.md

@@ -0,0 +1,64 @@
+# Agent Guidelines for go-toml
+
+This file provides guidelines for AI agents contributing to go-toml. All agents must follow these rules derived from [CONTRIBUTING.md](./CONTRIBUTING.md).
+
+## Project Overview
+
+go-toml is a TOML library for Go. The goal is to provide an easy-to-use and efficient TOML implementation that gets the job done without getting in the way.
+
+## Code Change Rules
+
+### Backward Compatibility
+
+- **No backward-incompatible changes** unless explicitly discussed and approved
+- Avoid breaking people's programs unless absolutely necessary
+
+### Testing Requirements
+
+- **All bug fixes must include regression tests**
+- **All new code must be tested**
+- Run tests before submitting: `go test -race ./...`
+- Test coverage must not decrease. Check with:
+  ```bash
+  go test -covermode=atomic -coverprofile=coverage.out
+  go tool cover -func=coverage.out
+  ```
+- All lines of code touched by changes should be covered by tests
+
+### Performance Requirements
+
+- go-toml aims to stay efficient; avoid performance regressions
+- Run benchmarks to verify: `go test ./... -bench=. -count=10`
+- Compare results using [benchstat](https://pkg.go.dev/golang.org/x/perf/cmd/benchstat)
+
+### Documentation
+
+- New features or feature extensions must include documentation
+- Documentation lives in [README.md](./README.md) and throughout source code
+
+### Code Style
+
+- Follow existing code format and structure
+- Code must pass `go fmt`
+- Code must pass linting with the same golangci-lint version as CI (see version in `.github/workflows/lint.yml`):
+  ```bash
+  # Install specific version (check lint.yml for current version)
+  curl -sSfL https://raw.githubusercontent.com/golangci/golangci-lint/HEAD/install.sh | sh -s -- -b $(go env GOPATH)/bin <version>
+  # Run linter
+  golangci-lint run ./...
+  ```
+
+### Commit Messages
+
+- Commit messages must explain **why** the change is needed
+- Keep messages clear and informative even if details are in the PR description
+
+## Pull Request Checklist
+
+Before submitting:
+
+1. Tests pass (`go test -race ./...`)
+2. No backward-incompatible changes (unless discussed)
+3. Relevant documentation added/updated
+4. No performance regression (verify with benchmarks)
+5. Title is clear and understandable for changelog

CONTRIBUTING.md

@@ -33,7 +33,7 @@ The documentation is present in the [README][readme] and thorough the source
 code. On release, it gets updated on [pkg.go.dev][pkg.go.dev]. To make a change
 to the documentation, create a pull request with your proposed changes. For
 simple changes like that, the easiest way to go is probably the "Fork this
-project and edit the file" button on Github, displayed at the top right of the
+project and edit the file" button on GitHub, displayed at the top right of the
 file. Unless it's a trivial change (for example a typo), provide a little bit of
 context in your pull request description or commit message.
 
@@ -92,6 +92,48 @@ However, given GitHub's new policy to _not_ run Actions on pull requests until a
 maintainer clicks on button, it is highly recommended that you run them locally
 as you make changes.
 
+### Test across Go versions
+
+The repository includes tooling to test go-toml across multiple Go versions
+(1.11 through 1.25) both locally and in GitHub Actions.
+
+#### Local testing with Docker
+
+Prerequisites: Docker installed and running, Bash shell, `rsync` command.
+
+```bash
+# Test all Go versions in parallel (default)
+./test-go-versions.sh
+
+# Test specific versions
+./test-go-versions.sh 1.21 1.22 1.23
+
+# Test sequentially (slower but uses less resources)
+./test-go-versions.sh --sequential
+
+# Verbose output with custom results directory
+./test-go-versions.sh --verbose --output ./my-results 1.24 1.25
+
+# Show all options
+./test-go-versions.sh --help
+```
+
+The script creates Docker containers for each Go version and runs the full test
+suite. Results are saved to a `test-results/` directory with individual logs and
+a comprehensive summary report.
+
+The script only exits with a non-zero status code if either of the two most
+recent Go versions fail.
+
+#### GitHub Actions testing (maintainers)
+
+1. Go to the **Actions** tab in the GitHub repository
+2. Select **"Go Versions Compatibility Test"** from the workflow list
+3. Click **"Run workflow"**
+4. Optionally customize:
+   - **Go versions**: Space-separated list (e.g., `1.21 1.22 1.23`)
+   - **Execution mode**: Parallel (faster) or sequential (more stable)
+
 ### Check coverage
 
 We use `go tool cover` to compute test coverage. Most code editors have a way to
@@ -111,7 +153,7 @@ code lowers the coverage.
 
 Go-toml aims to stay efficient. We rely on a set of scenarios executed with Go's
 builtin benchmark systems. Because of their noisy nature, containers provided by
-Github Actions cannot be reliably used for benchmarking. As a result, you are
+GitHub Actions cannot be reliably used for benchmarking. As a result, you are
 responsible for checking that your changes do not incur a performance penalty.
 You can run their following to execute benchmarks:
 
@@ -165,25 +207,22 @@ Checklist:
 
 ### New release
 
-1. Decide on the next version number. Use semver.
+1. Decide on the next version number. Use semver. Review commits since last
-2. Generate release notes using [`gh`][gh]. Example:
+   version to assess.
-```
+2. Tag release. For example:
-$ gh api -X POST \
+   ```
-  -F tag_name='v2.0.0-beta.5' \
+   git checkout v2
-  -F target_commitish='v2' \
+   git pull
-  -F previous_tag_name='v2.0.0-beta.4' \
+   git tag v2.2.0
-  --jq '.body' \
+   git push --tags
-  repos/pelletier/go-toml/releases/generate-notes
+   ```
-```
+3. CI automatically builds a draft GitHub release. Review it and edit as
-3. Look for "Other changes". That would indicate a pull request not labeled
+   necessary. Look for "Other changes". That would indicate a pull request not
-   properly. Tweak labels and pull request titles until changelog looks good for
+   labeled properly. Tweak labels and pull request titles until changelog looks
-   users.
+   good for users.
-4. [Draft new release][new-release].
+4. Check "create discussion" box, in the "Releases" category.
-5. Fill tag and target with the same value used to generate the changelog.
+5. If new version is an alpha or beta only, check pre-release box.
-6. Set title to the new tag value.
+
-7. Paste the generated changelog.
-8. Check "create discussion", in the "Releases" category.
-9. Check pre-release if new version is an alpha or beta.
 
 [issues-tracker]: https://github.com/pelletier/go-toml/issues
 [bug-report]: https://github.com/pelletier/go-toml/issues/new?template=bug_report.md

LICENSE

@@ -1,6 +1,7 @@
 The MIT License (MIT)
 
-Copyright (c) 2013 - 2022 Thomas Pelletier, Eric Anderton
+go-toml v2
+Copyright (c) 2021 - 2023 Thomas Pelletier
 
 Permission is hereby granted, free of charge, to any person obtaining a copy
 of this software and associated documentation files (the "Software"), to deal

README.md

@@ -45,16 +45,15 @@ to check for typos. [See example in the documentation][strict].
 
 ### Contextualized errors
 
-When most decoding errors occur, go-toml returns [`DecodeError`][decode-err]),
+When most decoding errors occur, go-toml returns [`DecodeError`][decode-err],
 which contains a human readable contextualized version of the error. For
 example:
 
 ```
-2| key1 = "value1"
+1| [server]
-3| key2 = "missing2"
+2| path = 100
- | ~~~~ missing field
+ |        ~~~ cannot decode TOML integer into struct field toml_test.Server.Path of type string
-4| key3 = "missing3"
+3| port = 50
-5| key4 = "value4"
 ```
 
 [decode-err]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#DecodeError
@@ -73,22 +72,46 @@ representation.
 [tlt]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalTime
 [tldt]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalDateTime
 
+### Commented config
+
+Since TOML is often used for configuration files, go-toml can emit documents
+annotated with [comments and commented-out values][comments-example]. For
+example, it can generate the following file:
+
+```toml
+# Host IP to connect to.
+host = '127.0.0.1'
+# Port of the remote server.
+port = 4242
+
+# Encryption parameters (optional)
+# [TLS]
+# cipher = 'AEAD-AES128-GCM-SHA256'
+# version = 'TLS 1.3'
+```
+
+[comments-example]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#example-Marshal-Commented
+
 ## Getting started
 
 Given the following struct, let's see how to read it and write it as TOML:
 
 ```go
 type MyConfig struct {
-      Version int
+	Version int
-      Name    string
+	Name    string
-      Tags    []string
+	Tags    []string
 }
 ```
 
 ### Unmarshaling
 
 [`Unmarshal`][unmarshal] reads a TOML document and fills a Go structure with its
-content. For example:
+content. 
+
+Note that the struct variable names are _capitalized_, while the variables in the toml document are _lowercase_.
+
+For example:
 
 ```go
 doc := `
@@ -100,7 +123,7 @@ tags = ["go", "toml"]
 var cfg MyConfig
 err := toml.Unmarshal([]byte(doc), &cfg)
 if err != nil {
-      panic(err)
+	panic(err)
 }
 fmt.Println("version:", cfg.Version)
 fmt.Println("name:", cfg.Name)
@@ -114,6 +137,62 @@ fmt.Println("tags:", cfg.Tags)
 
 [unmarshal]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#Unmarshal
 
+
+Here is an example using tables with some simple nesting:
+
+```go
+doc := `
+age = 45
+fruits = ["apple", "pear"]
+
+# these are very important!
+[my-variables]
+first = 1
+second = 0.2
+third = "abc"
+
+# this is not so important.
+[my-variables.b]
+bfirst = 123
+`
+
+var Document struct {
+	Age int
+	Fruits []string
+
+	Myvariables struct {
+		First  int
+		Second float64
+		Third  string
+
+		B struct {
+			Bfirst int
+		}
+	} `toml:"my-variables"`
+}
+
+err := toml.Unmarshal([]byte(doc), &Document)
+if err != nil {
+	panic(err)
+}
+
+fmt.Println("age:", Document.Age)
+fmt.Println("fruits:", Document.Fruits)
+fmt.Println("my-variables.first:", Document.Myvariables.First)
+fmt.Println("my-variables.second:", Document.Myvariables.Second)
+fmt.Println("my-variables.third:", Document.Myvariables.Third)
+fmt.Println("my-variables.B.Bfirst:", Document.Myvariables.B.Bfirst)
+
+// Output:
+// age: 45
+// fruits: [apple pear]
+// my-variables.first: 1
+// my-variables.second: 0.2
+// my-variables.third: abc
+// my-variables.B.Bfirst: 123
+```
+
+
 ### Marshaling
 
 [`Marshal`][marshal] is the opposite of Unmarshal: it represents a Go structure
@@ -121,14 +200,14 @@ as a TOML document:
 
 ```go
 cfg := MyConfig{
-      Version: 2,
+	Version: 2,
-      Name:    "go-toml",
+	Name:    "go-toml",
-      Tags:    []string{"go", "toml"},
+	Tags:    []string{"go", "toml"},
 }
 
 b, err := toml.Marshal(cfg)
 if err != nil {
-      panic(err)
+	panic(err)
 }
 fmt.Println(string(b))
 
@@ -140,6 +219,17 @@ fmt.Println(string(b))
 
 [marshal]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#Marshal
 
+## Unstable API
+
+This API does not yet follow the backward compatibility guarantees of this
+library. They provide early access to features that may have rough edges or an
+API subject to change.
+
+### Parser
+
+Parser is the unstable API that allows iterative parsing of a TOML document at
+the AST level. See https://pkg.go.dev/github.com/pelletier/go-toml/v2/unstable.
+
 ## Benchmarks
 
 Execution time speedup compared to other Go TOML libraries:
@@ -149,12 +239,12 @@ Execution time speedup compared to other Go TOML libraries:
         <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
     </thead>
     <tbody>
-        <tr><td>Marshal/HugoFrontMatter-2</td><td>1.9x</td><td>1.9x</td></tr>
+        <tr><td>Marshal/HugoFrontMatter-2</td><td>2.1x</td><td>2.0x</td></tr>
-        <tr><td>Marshal/ReferenceFile/map-2</td><td>1.7x</td><td>1.8x</td></tr>
+        <tr><td>Marshal/ReferenceFile/map-2</td><td>2.0x</td><td>2.0x</td></tr>
-        <tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>2.5x</td></tr>
+        <tr><td>Marshal/ReferenceFile/struct-2</td><td>2.3x</td><td>2.5x</td></tr>
-        <tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.9x</td></tr>
+        <tr><td>Unmarshal/HugoFrontMatter-2</td><td>3.3x</td><td>2.8x</td></tr>
-        <tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.9x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.9x</td><td>3.0x</td></tr>
-        <tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.4x</td><td>5.3x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.8x</td><td>5.0x</td></tr>
      </tbody>
 </table>
 <details><summary>See more</summary>
@@ -167,17 +257,17 @@ provided for completeness.</p>
         <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
     </thead>
     <tbody>
-        <tr><td>Marshal/SimpleDocument/map-2</td><td>1.8x</td><td>2.9x</td></tr>
+        <tr><td>Marshal/SimpleDocument/map-2</td><td>2.0x</td><td>2.9x</td></tr>
-        <tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>4.2x</td></tr>
+        <tr><td>Marshal/SimpleDocument/struct-2</td><td>2.5x</td><td>3.6x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.5x</td><td>3.1x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.2x</td><td>3.4x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>6.2x</td><td>3.9x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>5.9x</td><td>4.4x</td></tr>
-        <tr><td>UnmarshalDataset/example-2</td><td>3.1x</td><td>3.5x</td></tr>
+        <tr><td>UnmarshalDataset/example-2</td><td>3.2x</td><td>2.9x</td></tr>
-        <tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>3.1x</td></tr>
+        <tr><td>UnmarshalDataset/code-2</td><td>2.4x</td><td>2.8x</td></tr>
-        <tr><td>UnmarshalDataset/twitter-2</td><td>2.5x</td><td>2.6x</td></tr>
+        <tr><td>UnmarshalDataset/twitter-2</td><td>2.7x</td><td>2.5x</td></tr>
-        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.1x</td><td>2.2x</td></tr>
+        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.3x</td><td>2.3x</td></tr>
-        <tr><td>UnmarshalDataset/canada-2</td><td>1.6x</td><td>1.3x</td></tr>
+        <tr><td>UnmarshalDataset/canada-2</td><td>1.9x</td><td>1.5x</td></tr>
-        <tr><td>UnmarshalDataset/config-2</td><td>4.3x</td><td>3.2x</td></tr>
+        <tr><td>UnmarshalDataset/config-2</td><td>5.4x</td><td>3.0x</td></tr>
-        <tr><td>[Geo mean]</td><td>2.7x</td><td>2.8x</td></tr>
+        <tr><td>geomean</td><td>2.9x</td><td>2.8x</td></tr>
      </tbody>
 </table>
 <p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>
@@ -203,24 +293,24 @@ Go-toml provides three handy command line tools:
 
  * `tomljson`: Reads a TOML file and outputs its JSON representation.
 
-    ```
+	```
-    $ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
+	$ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
-    $ tomljson --help
+	$ tomljson --help
-    ```
+	```
 
  * `jsontoml`: Reads a JSON file and outputs a TOML representation.
 
-    ```
+	```
-    $ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
+	$ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
-    $ jsontoml --help
+	$ jsontoml --help
-    ```
+	```
 
  * `tomll`: Lints and reformats a TOML file.
 
-    ```
+	```
-    $ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
+	$ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
-    $ tomll --help
+	$ tomll --help
-    ```
+	```
 
 ### Docker image
 
@@ -231,7 +321,7 @@ Those tools are also available as a [Docker image][docker]. For example, to use
 docker run -i ghcr.io/pelletier/go-toml:v2 tomljson < example.toml
 ```
 
-Multiple versions are availble on [ghcr.io][docker].
+Multiple versions are available on [ghcr.io][docker].
 
 [docker]: https://github.com/pelletier/go-toml/pkgs/container/go-toml
 
@@ -263,16 +353,16 @@ element in the interface to decode the object. For example:
 
 ```go
 type inner struct {
-  B interface{}
+	B interface{}
 }
 type doc struct {
-  A interface{}
+	A interface{}
 }
 
 d := doc{
-  A: inner{
+	A: inner{
-    B: "Before",
+		B: "Before",
-  },
+	},
 }
 
 data := `
@@ -311,7 +401,7 @@ contained in the doc is superior to the capacity of the array. For example:
 
 ```go
 type doc struct {
-  A [2]string
+	A [2]string
 }
 d := doc{}
 err := toml.Unmarshal([]byte(`A = ["one", "two", "many"]`), &d)
@@ -486,27 +576,20 @@ is not necessary anymore.
 
 V1 used to provide multiple struct tags: `comment`, `commented`, `multiline`,
 `toml`, and `omitempty`. To behave more like the standard library, v2 has merged
-`toml`, `multiline`, and `omitempty`. For example:
+`toml`, `multiline`, `commented`, and `omitempty`. For example:
 
 ```go
 type doc struct {
 	// v1
-	F string `toml:"field" multiline:"true" omitempty:"true"`
+	F string `toml:"field" multiline:"true" omitempty:"true" commented:"true"`
 	// v2
-	F string `toml:"field,multiline,omitempty"`
+	F string `toml:"field,multiline,omitempty,commented"`
 }
 ```
 
 Has a result, the `Encoder.SetTag*` methods have been removed, as there is just
 one tag now.
 
-
-#### `commented` tag has been removed
-
-There is no replacement for the `commented` tag. This feature would be better
-suited in a proper document model for go-toml v2, which has been [cut from
-scope][nodoc] at the moment.
-
 #### `Encoder.ArraysWithOneElementPerLine` has been renamed
 
 The new name is `Encoder.SetArraysMultiline`. The behavior should be the same.
@@ -542,10 +625,11 @@ complete solutions exist out there.
 
 ## Versioning
 
-Go-toml follows [Semantic Versioning](http://semver.org/). The supported version
+Expect for parts explicitly marked otherwise, go-toml follows [Semantic
-of [TOML](https://github.com/toml-lang/toml) is indicated at the beginning of
+Versioning](https://semver.org). The supported version of
-this document. The last two major versions of Go are supported
+[TOML](https://github.com/toml-lang/toml) is indicated at the beginning of this
-(see [Go Release Policy](https://golang.org/doc/devel/release.html#policy)).
+document. The last two major versions of Go are supported (see [Go Release
+Policy](https://golang.org/doc/devel/release.html#policy)).
 
 ## License
 

SECURITY.md

@@ -2,9 +2,6 @@
 
 ## Supported Versions
 
-Use this section to tell people about which versions of your project are
-currently being supported with security updates.
-
 | Version    | Supported          |
 | ---------- | ------------------ |
 | Latest 2.x | :white_check_mark: |

benchmark/bench_datasets_test.go

@@ -3,16 +3,16 @@ package benchmark_test
 import (
 	"compress/gzip"
 	"encoding/json"
-	"io/ioutil"
+	"io"
 	"os"
 	"path/filepath"
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
-var bench_inputs = []struct {
+var benchInputs = []struct {
 	name    string
 	jsonLen int
 }{
@@ -30,22 +30,22 @@ var bench_inputs = []struct {
 }
 
 func TestUnmarshalDatasetCode(t *testing.T) {
-	for _, tc := range bench_inputs {
+	for _, tc := range benchInputs {
 		t.Run(tc.name, func(t *testing.T) {
 			buf := fixture(t, tc.name)
 
 			var v interface{}
-			require.NoError(t, toml.Unmarshal(buf, &v))
+			assert.NoError(t, toml.Unmarshal(buf, &v))
 
 			b, err := json.Marshal(v)
-			require.NoError(t, err)
+			assert.NoError(t, err)
-			require.Equal(t, len(b), tc.jsonLen)
+			assert.Equal(t, len(b), tc.jsonLen)
 		})
 	}
 }
 
 func BenchmarkUnmarshalDataset(b *testing.B) {
-	for _, tc := range bench_inputs {
+	for _, tc := range benchInputs {
 		b.Run(tc.name, func(b *testing.B) {
 			buf := fixture(b, tc.name)
 			b.SetBytes(int64(len(buf)))
@@ -53,7 +53,7 @@ func BenchmarkUnmarshalDataset(b *testing.B) {
 			b.ResetTimer()
 			for i := 0; i < b.N; i++ {
 				var v interface{}
-				require.NoError(b, toml.Unmarshal(buf, &v))
+				assert.NoError(b, toml.Unmarshal(buf, &v))
 			}
 		})
 	}
@@ -68,13 +68,13 @@ func fixture(tb testing.TB, path string) []byte {
 	if os.IsNotExist(err) {
 		tb.Skip("benchmark fixture not found:", file)
 	}
-	require.NoError(tb, err)
+	assert.NoError(tb, err)
-	defer f.Close()
+	defer func() { _ = f.Close() }()
 
 	gz, err := gzip.NewReader(f)
-	require.NoError(tb, err)
+	assert.NoError(tb, err)
 
-	buf, err := ioutil.ReadAll(gz)
+	buf, err := io.ReadAll(gz)
-	require.NoError(tb, err)
+	assert.NoError(tb, err)
 	return buf
 }

benchmark/benchmark_test.go

@@ -2,12 +2,12 @@ package benchmark_test
 
 import (
 	"bytes"
-	"io/ioutil"
+	"os"
 	"testing"
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func TestUnmarshalSimple(t *testing.T) {
@@ -18,7 +18,7 @@ func TestUnmarshalSimple(t *testing.T) {
 
 	err := toml.Unmarshal(doc, &d)
 	if err != nil {
-		panic(err)
+		t.Error(err)
 	}
 }
 
@@ -38,7 +38,7 @@ func BenchmarkUnmarshal(b *testing.B) {
 
 				err := toml.Unmarshal(doc, &d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 		})
@@ -52,14 +52,14 @@ func BenchmarkUnmarshal(b *testing.B) {
 				d := map[string]interface{}{}
 				err := toml.Unmarshal(doc, &d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 		})
 	})
 
 	b.Run("ReferenceFile", func(b *testing.B) {
-		bytes, err := ioutil.ReadFile("benchmark.toml")
+		bytes, err := os.ReadFile("benchmark.toml")
 		if err != nil {
 			b.Fatal(err)
 		}
@@ -72,7 +72,7 @@ func BenchmarkUnmarshal(b *testing.B) {
 				d := benchmarkDoc{}
 				err := toml.Unmarshal(bytes, &d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 		})
@@ -85,7 +85,7 @@ func BenchmarkUnmarshal(b *testing.B) {
 				d := map[string]interface{}{}
 				err := toml.Unmarshal(bytes, &d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 		})
@@ -99,7 +99,7 @@ func BenchmarkUnmarshal(b *testing.B) {
 			d := map[string]interface{}{}
 			err := toml.Unmarshal(hugoFrontMatterbytes, &d)
 			if err != nil {
-				panic(err)
+				b.Error(err)
 			}
 		}
 	})
@@ -123,7 +123,7 @@ func BenchmarkMarshal(b *testing.B) {
 
 			err := toml.Unmarshal(doc, &d)
 			if err != nil {
-				panic(err)
+				b.Error(err)
 			}
 
 			b.ReportAllocs()
@@ -134,7 +134,7 @@ func BenchmarkMarshal(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				out, err = marshal(d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 
@@ -145,7 +145,7 @@ func BenchmarkMarshal(b *testing.B) {
 			d := map[string]interface{}{}
 			err := toml.Unmarshal(doc, &d)
 			if err != nil {
-				panic(err)
+				b.Error(err)
 			}
 
 			b.ReportAllocs()
@@ -156,7 +156,7 @@ func BenchmarkMarshal(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				out, err = marshal(d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 
@@ -165,7 +165,7 @@ func BenchmarkMarshal(b *testing.B) {
 	})
 
 	b.Run("ReferenceFile", func(b *testing.B) {
-		bytes, err := ioutil.ReadFile("benchmark.toml")
+		bytes, err := os.ReadFile("benchmark.toml")
 		if err != nil {
 			b.Fatal(err)
 		}
@@ -174,7 +174,7 @@ func BenchmarkMarshal(b *testing.B) {
 			d := benchmarkDoc{}
 			err := toml.Unmarshal(bytes, &d)
 			if err != nil {
-				panic(err)
+				b.Error(err)
 			}
 			b.ReportAllocs()
 			b.ResetTimer()
@@ -184,7 +184,7 @@ func BenchmarkMarshal(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				out, err = marshal(d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 
@@ -195,7 +195,7 @@ func BenchmarkMarshal(b *testing.B) {
 			d := map[string]interface{}{}
 			err := toml.Unmarshal(bytes, &d)
 			if err != nil {
-				panic(err)
+				b.Error(err)
 			}
 
 			b.ReportAllocs()
@@ -205,7 +205,7 @@ func BenchmarkMarshal(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				out, err = marshal(d)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 
@@ -217,7 +217,7 @@ func BenchmarkMarshal(b *testing.B) {
 		d := map[string]interface{}{}
 		err := toml.Unmarshal(hugoFrontMatterbytes, &d)
 		if err != nil {
-			panic(err)
+			b.Error(err)
 		}
 
 		b.ReportAllocs()
@@ -228,7 +228,7 @@ func BenchmarkMarshal(b *testing.B) {
 		for i := 0; i < b.N; i++ {
 			out, err = marshal(d)
 			if err != nil {
-				panic(err)
+				b.Error(err)
 			}
 		}
 
@@ -344,11 +344,11 @@ type benchmarkDoc struct {
 }
 
 func TestUnmarshalReferenceFile(t *testing.T) {
-	bytes, err := ioutil.ReadFile("benchmark.toml")
+	bytes, err := os.ReadFile("benchmark.toml")
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	d := benchmarkDoc{}
 	err = toml.Unmarshal(bytes, &d)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	expected := benchmarkDoc{
 		Table: struct {
@@ -627,7 +627,7 @@ trimmed in raw strings.
 		},
 	}
 
-	require.Equal(t, expected, d)
+	assert.Equal(t, expected, d)
 }
 
 var hugoFrontMatterbytes = []byte(`

ci.sh

@@ -77,8 +77,9 @@ cover() {
 
     pushd "$dir"
     go test -covermode=atomic  -coverpkg=./... -coverprofile=coverage.out.tmp ./...
-    cat coverage.out.tmp | grep -v testsuite | grep -v tomltestgen | grep -v gotoml-test-decoder > coverage.out
+    grep -Ev '(fuzz|testsuite|tomltestgen|gotoml-test-decoder|gotoml-test-encoder)' coverage.out.tmp > coverage.out
     go tool cover -func=coverage.out
+    echo "Coverage profile for ${branch}: ${dir}/coverage.out" >&2
     popd
 
     if [ "${branch}" != "HEAD" ]; then
@@ -146,12 +147,12 @@ bench() {
     pushd "$dir"
 
     if [ "${replace}" != "" ]; then
-        find ./benchmark/ -iname '*.go' -exec sed -i -E "s|github.com/pelletier/go-toml/v2|${replace}|g" {} \;
+        find ./benchmark/ -iname '*.go' -exec sed -i -E "s|github.com/pelletier/go-toml/v2\"|${replace}\"|g" {} \;
         go get "${replace}"
     fi
 
     export GOMAXPROCS=2
-    nice -n -19 taskset --cpu-list 0,1 go test '-bench=^Benchmark(Un)?[mM]arshal' -count=5 -run=Nothing ./... | tee "${out}"
+    go test '-bench=^Benchmark(Un)?[mM]arshal' -count=10 -run=Nothing ./... | tee "${out}"
     popd
 
     if [ "${branch}" != "HEAD" ]; then
@@ -160,10 +161,12 @@ bench() {
 }
 
 fmktemp() {
-    if mktemp --version|grep GNU >/dev/null; then
+    if mktemp --version &> /dev/null; then
-        mktemp --suffix=-$1;
+	# GNU
+        mktemp --suffix=-$1
     else
-        mktemp -t $1;
+	# BSD
+	mktemp -t $1
     fi
 }
 
@@ -183,13 +186,20 @@ with open(sys.argv[1]) as f:
             lines.append(line.split(','))
 
 results = []
-for line in reversed(lines[1:]):
+for line in reversed(lines[2:]):
+    if len(line) < 8 or line[0] == "":
+        continue
     v2 = float(line[1])
     results.append([
         line[0].replace("-32", ""),
         "%.1fx" % (float(line[3])/v2),  # v1
-        "%.1fx" % (float(line[5])/v2),  # bs
+        "%.1fx" % (float(line[7])/v2),  # bs
     ])
+
+if not results:
+    print("No benchmark results to display.", file=sys.stderr)
+    sys.exit(1)
+
 # move geomean to the end
 results.append(results[0])
 del results[0]
@@ -259,10 +269,10 @@ benchmark() {
 
         if [ "$1" = "-html" ]; then
             tmpcsv=`fmktemp csv`
-            benchstat -csv -geomean go-toml-v2.txt go-toml-v1.txt bs-toml.txt > $tmpcsv
+            benchstat -format csv go-toml-v2.txt go-toml-v1.txt bs-toml.txt > $tmpcsv
             benchstathtml $tmpcsv
         else
-            benchstat -geomean go-toml-v2.txt go-toml-v1.txt bs-toml.txt
+            benchstat go-toml-v2.txt go-toml-v1.txt bs-toml.txt
         fi
 
         rm -f go-toml-v2.txt go-toml-v1.txt bs-toml.txt

cmd/gotoml-test-decoder/main.go

@@ -1,3 +1,4 @@
+// Package gotoml-test-decoder is a minimal decoder program used to compare this library with other TOML implementations.
 package main
 
 import (

cmd/gotoml-test-encoder/main.go

@@ -0,0 +1,31 @@
+// Package gotoml-test-encoder is a minimal encoder program used to compare this library with other TOML implementations.
+package main
+
+import (
+	"flag"
+	"log"
+	"os"
+	"path"
+
+	"github.com/pelletier/go-toml/v2/internal/testsuite"
+)
+
+func main() {
+	log.SetFlags(0)
+	flag.Usage = usage
+	flag.Parse()
+	if flag.NArg() != 0 {
+		flag.Usage()
+	}
+
+	err := testsuite.EncodeStdin()
+	if err != nil {
+		log.Fatal(err)
+	}
+}
+
+func usage() {
+	log.Printf("Usage: %s < json-file\n", path.Base(os.Args[0]))
+	flag.PrintDefaults()
+	os.Exit(1)
+}

cmd/jsontoml/main.go

@@ -19,6 +19,7 @@ package main
 
 import (
 	"encoding/json"
+	"flag"
 	"io"
 
 	"github.com/pelletier/go-toml/v2"
@@ -33,7 +34,11 @@ Reading from a file:
   jsontoml file.json > file.toml
 `
 
+var useJSONNumber bool
+
 func main() {
+	flag.BoolVar(&useJSONNumber, "use-json-number", false, "unmarshal numbers into `json.Number` type instead of as `float64`")
+
 	p := cli.Program{
 		Usage: usage,
 		Fn:    convert,
@@ -45,11 +50,17 @@ func convert(r io.Reader, w io.Writer) error {
 	var v interface{}
 
 	d := json.NewDecoder(r)
+	e := toml.NewEncoder(w)
+
+	if useJSONNumber {
+		d.UseNumber()
+		e.SetMarshalJSONNumbers(true)
+	}
+
 	err := d.Decode(&v)
 	if err != nil {
 		return err
 	}
 
-	e := toml.NewEncoder(w)
 	return e.Encode(v)
 }

cmd/jsontoml/main_test.go

@@ -5,16 +5,16 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
+	"github.com/pelletier/go-toml/v2/internal/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func TestConvert(t *testing.T) {
 	examples := []struct {
-		name     string
+		name          string
-		input    string
+		input         string
-		expected string
+		expected      string
-		errors   bool
+		errors        bool
+		useJSONNumber bool
 	}{
 		{
 			name: "valid json",
@@ -26,6 +26,19 @@ func TestConvert(t *testing.T) {
 }`,
 			expected: `[mytoml]
 a = 42.0
+`,
+		},
+		{
+			name:          "use json number",
+			useJSONNumber: true,
+			input: `
+{
+  "mytoml": {
+    "a": 42
+  }
+}`,
+			expected: `[mytoml]
+a = 42
 `,
 		},
 		{
@@ -37,9 +50,10 @@ a = 42.0
 
 	for _, e := range examples {
 		b := new(bytes.Buffer)
+		useJSONNumber = e.useJSONNumber
 		err := convert(strings.NewReader(e.input), b)
 		if e.errors {
-			require.Error(t, err)
+			assert.Error(t, err)
 		} else {
 			assert.NoError(t, err)
 			assert.Equal(t, e.expected, b.String())

cmd/tomljson/main_test.go

@@ -2,13 +2,12 @@ package main
 
 import (
 	"bytes"
-	"fmt"
+	"errors"
 	"io"
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
+	"github.com/pelletier/go-toml/v2/internal/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func TestConvert(t *testing.T) {
@@ -46,7 +45,7 @@ a = 42`),
 		b := new(bytes.Buffer)
 		err := convert(e.input, b)
 		if e.errors {
-			require.Error(t, err)
+			assert.Error(t, err)
 		} else {
 			assert.NoError(t, err)
 			assert.Equal(t, e.expected, b.String())
@@ -57,5 +56,5 @@ a = 42`),
 type badReader struct{}
 
 func (r *badReader) Read([]byte) (int, error) {
-	return 0, fmt.Errorf("reader failed on purpose")
+	return 0, errors.New("reader failed on purpose")
 }

cmd/tomll/main_test.go

@@ -5,8 +5,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
+	"github.com/pelletier/go-toml/v2/internal/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func TestConvert(t *testing.T) {
@@ -36,7 +35,7 @@ a = 42.0
 		b := new(bytes.Buffer)
 		err := convert(strings.NewReader(e.input), b)
 		if e.errors {
-			require.Error(t, err)
+			assert.Error(t, err)
 		} else {
 			assert.NoError(t, err)
 			assert.Equal(t, e.expected, b.String())

cmd/tomltestgen/main.go

@@ -7,21 +7,18 @@
 package main
 
 import (
-	"archive/zip"
 	"bytes"
 	"flag"
 	"fmt"
 	"go/format"
-	"io"
-	"io/ioutil"
 	"log"
-	"net/http"
 	"os"
-	"regexp"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"text/template"
 	"time"
+	"unicode"
 )
 
 type invalid struct {
@@ -32,7 +29,7 @@ type invalid struct {
 type valid struct {
 	Name    string
 	Input   string
-	JsonRef string
+	JSONRef string
 }
 
 type testsCollection struct {
@@ -43,12 +40,11 @@ type testsCollection struct {
 	Count     int
 }
 
-const srcTemplate = "// Generated by tomltestgen for toml-test ref {{.Ref}} on {{.Timestamp}}\n" +
+const srcTemplate = "// Code generated by tomltestgen for toml-test ref {{.Ref}} on {{.Timestamp}}. DO NOT EDIT.\n" +
 	"package toml_test\n" +
 	" import (\n" +
 	"	\"testing\"\n" +
 	")\n" +
-
 	"{{range .Invalid}}\n" +
 	"func TestTOMLTest_Invalid_{{.Name}}(t *testing.T) {\n" +
 	"	input := {{.Input|gostr}}\n" +
@@ -59,65 +55,31 @@ const srcTemplate = "// Generated by tomltestgen for toml-test ref {{.Ref}} on {
 	"{{range .Valid}}\n" +
 	"func TestTOMLTest_Valid_{{.Name}}(t *testing.T) {\n" +
 	"   input := {{.Input|gostr}}\n" +
-	"   jsonRef := {{.JsonRef|gostr}}\n" +
+	"   jsonRef := {{.JSONRef|gostr}}\n" +
 	"   testgenValid(t, input, jsonRef)\n" +
 	"}\n" +
 	"{{end}}\n"
 
-func downloadTmpFile(url string) string {
-	log.Println("starting to download file from", url)
-	resp, err := http.Get(url)
-	if err != nil {
-		panic(err)
-	}
-	defer resp.Body.Close()
-
-	tmpfile, err := ioutil.TempFile("", "toml-test-*.zip")
-	if err != nil {
-		panic(err)
-	}
-	defer tmpfile.Close()
-
-	copiedLen, err := io.Copy(tmpfile, resp.Body)
-	if err != nil {
-		panic(err)
-	}
-	if resp.ContentLength > 0 && copiedLen != resp.ContentLength {
-		panic(fmt.Errorf("copied %d bytes, request body had %d", copiedLen, resp.ContentLength))
-	}
-	return tmpfile.Name()
-}
-
 func kebabToCamel(kebab string) string {
-	camel := ""
+	var buf strings.Builder
 	nextUpper := true
 	for _, c := range kebab {
 		if nextUpper {
-			camel += strings.ToUpper(string(c))
+			buf.WriteRune(unicode.ToUpper(c))
 			nextUpper = false
-		} else if c == '-' {
-			nextUpper = true
-		} else if c == '/' {
-			nextUpper = true
-			camel += "_"
 		} else {
-			camel += string(c)
+			switch c {
+			case '-':
+				nextUpper = true
+			case '/':
+				nextUpper = true
+				buf.WriteByte('_')
+			default:
+				buf.WriteRune(c)
+			}
 		}
 	}
-	return camel
+	return buf.String()
-}
-
-func readFileFromZip(f *zip.File) string {
-	reader, err := f.Open()
-	if err != nil {
-		panic(err)
-	}
-	defer reader.Close()
-	bytes, err := ioutil.ReadAll(reader)
-	if err != nil {
-		panic(err)
-	}
-	return string(bytes)
 }
 
 func templateGoStr(input string) string {
@@ -138,61 +100,59 @@ func main() {
 	flag.Usage = usage
 	flag.Parse()
 
-	url := "https://codeload.github.com/BurntSushi/toml-test/zip/" + *ref
-	resultFile := downloadTmpFile(url)
-	defer os.Remove(resultFile)
-	log.Println("file written to", resultFile)
-
-	zipReader, err := zip.OpenReader(resultFile)
-	if err != nil {
-		panic(err)
-	}
-	defer zipReader.Close()
-
 	collection := testsCollection{
 		Ref:       *ref,
 		Timestamp: time.Now().Format(time.RFC3339),
 	}
 
-	zipFilesMap := map[string]*zip.File{}
+	dirContent, _ := filepath.Glob("tests/invalid/**/*.toml")
+	for _, f := range dirContent {
+		filename := strings.TrimPrefix(f, "tests/valid/")
+		name := kebabToCamel(strings.TrimSuffix(filename, ".toml"))
+		name = strings.ReplaceAll(name, ".", "_")
 
-	for _, f := range zipReader.File {
+		log.Printf("> [%s] %s\n", "invalid", name)
-		zipFilesMap[f.Name] = f
+
+		tomlContent, err := os.ReadFile(f) // #nosec G304
+		if err != nil {
+			fmt.Printf("failed to read test file: %s\n", err)
+			os.Exit(1)
+		}
+
+		collection.Invalid = append(collection.Invalid, invalid{
+			Name:  name,
+			Input: string(tomlContent),
+		})
+		collection.Count++
 	}
 
-	testFileRegexp := regexp.MustCompile(`([^/]+/tests/(valid|invalid)/(.+))\.(toml)`)
+	dirContent, _ = filepath.Glob("tests/valid/**/*.toml")
-	for _, f := range zipReader.File {
+	for _, f := range dirContent {
-		groups := testFileRegexp.FindStringSubmatch(f.Name)
+		filename := strings.TrimPrefix(f, "tests/valid/")
-		if len(groups) > 0 {
+		name := kebabToCamel(strings.TrimSuffix(filename, ".toml"))
-			name := kebabToCamel(groups[3])
+		name = strings.ReplaceAll(name, ".", "_")
-			testType := groups[2]
 
-			log.Printf("> [%s] %s\n", testType, name)
+		log.Printf("> [%s] %s\n", "valid", name)
 
-			tomlContent := readFileFromZip(f)
+		tomlContent, err := os.ReadFile(f) // #nosec G304
-
+		if err != nil {
-			switch testType {
+			fmt.Printf("failed reading test file: %s\n", err)
-			case "invalid":
+			os.Exit(1)
-				collection.Invalid = append(collection.Invalid, invalid{
-					Name:  name,
-					Input: tomlContent,
-				})
-				collection.Count++
-			case "valid":
-				baseFilePath := groups[1]
-				jsonFilePath := baseFilePath + ".json"
-				jsonContent := readFileFromZip(zipFilesMap[jsonFilePath])
-
-				collection.Valid = append(collection.Valid, valid{
-					Name:    name,
-					Input:   tomlContent,
-					JsonRef: jsonContent,
-				})
-				collection.Count++
-			default:
-				panic(fmt.Sprintf("unknown test type: %s", testType))
-			}
 		}
+
+		filename = strings.TrimSuffix(f, ".toml")
+		jsonContent, err := os.ReadFile(filename + ".json") // #nosec G304
+		if err != nil {
+			fmt.Printf("failed reading validation json: %s\n", err)
+			os.Exit(1)
+		}
+
+		collection.Valid = append(collection.Valid, valid{
+			Name:    name,
+			Input:   string(tomlContent),
+			JSONRef: string(jsonContent),
+		})
+		collection.Count++
 	}
 
 	log.Printf("Collected %d tests from toml-test\n", collection.Count)
@@ -202,7 +162,7 @@ func main() {
 	}
 	t := template.Must(template.New("src").Funcs(funcMap).Parse(srcTemplate))
 	buf := new(bytes.Buffer)
-	err = t.Execute(buf, collection)
+	err := t.Execute(buf, collection)
 	if err != nil {
 		panic(err)
 	}
@@ -216,7 +176,7 @@ func main() {
 		return
 	}
 
-	err = os.WriteFile(*out, outputBytes, 0644)
+	err = os.WriteFile(*out, outputBytes, 0o600)
 	if err != nil {
 		panic(err)
 	}

decode.go

@@ -5,6 +5,8 @@ import (
 	"math"
 	"strconv"
 	"time"
+
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 func parseInteger(b []byte) (int64, error) {
@@ -32,7 +34,7 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 	var date LocalDate
 
 	if len(b) != 10 || b[4] != '-' || b[7] != '-' {
-		return date, newDecodeError(b, "dates are expected to have the format YYYY-MM-DD")
+		return date, unstable.NewParserError(b, "dates are expected to have the format YYYY-MM-DD")
 	}
 
 	var err error
@@ -53,7 +55,7 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 	}
 
 	if !isValidDate(date.Year, date.Month, date.Day) {
-		return LocalDate{}, newDecodeError(b, "impossible date")
+		return LocalDate{}, unstable.NewParserError(b, "impossible date")
 	}
 
 	return date, nil
@@ -64,7 +66,7 @@ func parseDecimalDigits(b []byte) (int, error) {
 
 	for i, c := range b {
 		if c < '0' || c > '9' {
-			return 0, newDecodeError(b[i:i+1], "expected digit (0-9)")
+			return 0, unstable.NewParserError(b[i:i+1], "expected digit (0-9)")
 		}
 		v *= 10
 		v += int(c - '0')
@@ -97,7 +99,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 	} else {
 		const dateTimeByteLen = 6
 		if len(b) != dateTimeByteLen {
-			return time.Time{}, newDecodeError(b, "invalid date-time timezone")
+			return time.Time{}, unstable.NewParserError(b, "invalid date-time timezone")
 		}
 		var direction int
 		switch b[0] {
@@ -106,11 +108,11 @@ func parseDateTime(b []byte) (time.Time, error) {
 		case '+':
 			direction = +1
 		default:
-			return time.Time{}, newDecodeError(b[:1], "invalid timezone offset character")
+			return time.Time{}, unstable.NewParserError(b[:1], "invalid timezone offset character")
 		}
 
 		if b[3] != ':' {
-			return time.Time{}, newDecodeError(b[3:4], "expected a : separator")
+			return time.Time{}, unstable.NewParserError(b[3:4], "expected a : separator")
 		}
 
 		hours, err := parseDecimalDigits(b[1:3])
@@ -118,7 +120,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 			return time.Time{}, err
 		}
 		if hours > 23 {
-			return time.Time{}, newDecodeError(b[:1], "invalid timezone offset hours")
+			return time.Time{}, unstable.NewParserError(b[:1], "invalid timezone offset hours")
 		}
 
 		minutes, err := parseDecimalDigits(b[4:6])
@@ -126,7 +128,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 			return time.Time{}, err
 		}
 		if minutes > 59 {
-			return time.Time{}, newDecodeError(b[:1], "invalid timezone offset minutes")
+			return time.Time{}, unstable.NewParserError(b[:1], "invalid timezone offset minutes")
 		}
 
 		seconds := direction * (hours*3600 + minutes*60)
@@ -139,7 +141,7 @@ func parseDateTime(b []byte) (time.Time, error) {
 	}
 
 	if len(b) > 0 {
-		return time.Time{}, newDecodeError(b, "extra bytes at the end of the timezone")
+		return time.Time{}, unstable.NewParserError(b, "extra bytes at the end of the timezone")
 	}
 
 	t := time.Date(
@@ -160,7 +162,7 @@ func parseLocalDateTime(b []byte) (LocalDateTime, []byte, error) {
 
 	const localDateTimeByteMinLen = 11
 	if len(b) < localDateTimeByteMinLen {
-		return dt, nil, newDecodeError(b, "local datetimes are expected to have the format YYYY-MM-DDTHH:MM:SS[.NNNNNNNNN]")
+		return dt, nil, unstable.NewParserError(b, "local datetimes are expected to have the format YYYY-MM-DDTHH:MM:SS[.NNNNNNNNN]")
 	}
 
 	date, err := parseLocalDate(b[:10])
@@ -171,7 +173,7 @@ func parseLocalDateTime(b []byte) (LocalDateTime, []byte, error) {
 
 	sep := b[10]
 	if sep != 'T' && sep != ' ' && sep != 't' {
-		return dt, nil, newDecodeError(b[10:11], "datetime separator is expected to be T or a space")
+		return dt, nil, unstable.NewParserError(b[10:11], "datetime separator is expected to be T or a space")
 	}
 
 	t, rest, err := parseLocalTime(b[11:])
@@ -195,7 +197,7 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 	// check if b matches to have expected format HH:MM:SS[.NNNNNN]
 	const localTimeByteLen = 8
 	if len(b) < localTimeByteLen {
-		return t, nil, newDecodeError(b, "times are expected to have the format HH:MM:SS[.NNNNNN]")
+		return t, nil, unstable.NewParserError(b, "times are expected to have the format HH:MM:SS[.NNNNNN]")
 	}
 
 	var err error
@@ -206,10 +208,10 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 	}
 
 	if t.Hour > 23 {
-		return t, nil, newDecodeError(b[0:2], "hour cannot be greater 23")
+		return t, nil, unstable.NewParserError(b[0:2], "hour cannot be greater 23")
 	}
 	if b[2] != ':' {
-		return t, nil, newDecodeError(b[2:3], "expecting colon between hours and minutes")
+		return t, nil, unstable.NewParserError(b[2:3], "expecting colon between hours and minutes")
 	}
 
 	t.Minute, err = parseDecimalDigits(b[3:5])
@@ -217,10 +219,10 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		return t, nil, err
 	}
 	if t.Minute > 59 {
-		return t, nil, newDecodeError(b[3:5], "minutes cannot be greater 59")
+		return t, nil, unstable.NewParserError(b[3:5], "minutes cannot be greater 59")
 	}
 	if b[5] != ':' {
-		return t, nil, newDecodeError(b[5:6], "expecting colon between minutes and seconds")
+		return t, nil, unstable.NewParserError(b[5:6], "expecting colon between minutes and seconds")
 	}
 
 	t.Second, err = parseDecimalDigits(b[6:8])
@@ -228,8 +230,8 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		return t, nil, err
 	}
 
-	if t.Second > 60 {
+	if t.Second > 59 {
-		return t, nil, newDecodeError(b[6:8], "seconds cannot be greater 60")
+		return t, nil, unstable.NewParserError(b[6:8], "seconds cannot be greater than 59")
 	}
 
 	b = b[8:]
@@ -242,7 +244,7 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		for i, c := range b[1:] {
 			if !isDigit(c) {
 				if i == 0 {
-					return t, nil, newDecodeError(b[0:1], "need at least one digit after fraction point")
+					return t, nil, unstable.NewParserError(b[0:1], "need at least one digit after fraction point")
 				}
 				break
 			}
@@ -266,7 +268,7 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 		}
 
 		if precision == 0 {
-			return t, nil, newDecodeError(b[:1], "nanoseconds need at least one digit")
+			return t, nil, unstable.NewParserError(b[:1], "nanoseconds need at least one digit")
 		}
 
 		t.Nanosecond = frac * nspow[precision]
@@ -277,7 +279,6 @@ func parseLocalTime(b []byte) (LocalTime, []byte, error) {
 	return t, b, nil
 }
 
-//nolint:cyclop
 func parseFloat(b []byte) (float64, error) {
 	if len(b) == 4 && (b[0] == '+' || b[0] == '-') && b[1] == 'n' && b[2] == 'a' && b[3] == 'n' {
 		return math.NaN(), nil
@@ -289,24 +290,24 @@ func parseFloat(b []byte) (float64, error) {
 	}
 
 	if cleaned[0] == '.' {
-		return 0, newDecodeError(b, "float cannot start with a dot")
+		return 0, unstable.NewParserError(b, "float cannot start with a dot")
 	}
 
 	if cleaned[len(cleaned)-1] == '.' {
-		return 0, newDecodeError(b, "float cannot end with a dot")
+		return 0, unstable.NewParserError(b, "float cannot end with a dot")
 	}
 
 	dotAlreadySeen := false
 	for i, c := range cleaned {
 		if c == '.' {
 			if dotAlreadySeen {
-				return 0, newDecodeError(b[i:i+1], "float can have at most one decimal point")
+				return 0, unstable.NewParserError(b[i:i+1], "float can have at most one decimal point")
 			}
 			if !isDigit(cleaned[i-1]) {
-				return 0, newDecodeError(b[i-1:i+1], "float decimal point must be preceded by a digit")
+				return 0, unstable.NewParserError(b[i-1:i+1], "float decimal point must be preceded by a digit")
 			}
 			if !isDigit(cleaned[i+1]) {
-				return 0, newDecodeError(b[i:i+2], "float decimal point must be followed by a digit")
+				return 0, unstable.NewParserError(b[i:i+2], "float decimal point must be followed by a digit")
 			}
 			dotAlreadySeen = true
 		}
@@ -316,13 +317,13 @@ func parseFloat(b []byte) (float64, error) {
 	if cleaned[0] == '+' || cleaned[0] == '-' {
 		start = 1
 	}
-	if cleaned[start] == '0' && isDigit(cleaned[start+1]) {
+	if cleaned[start] == '0' && len(cleaned) > start+1 && isDigit(cleaned[start+1]) {
-		return 0, newDecodeError(b, "float integer part cannot have leading zeroes")
+		return 0, unstable.NewParserError(b, "float integer part cannot have leading zeroes")
 	}
 
 	f, err := strconv.ParseFloat(string(cleaned), 64)
 	if err != nil {
-		return 0, newDecodeError(b, "unable to parse float: %w", err)
+		return 0, unstable.NewParserError(b, "unable to parse float: %w", err)
 	}
 
 	return f, nil
@@ -336,7 +337,7 @@ func parseIntHex(b []byte) (int64, error) {
 
 	i, err := strconv.ParseInt(string(cleaned), 16, 64)
 	if err != nil {
-		return 0, newDecodeError(b, "couldn't parse hexadecimal number: %w", err)
+		return 0, unstable.NewParserError(b, "couldn't parse hexadecimal number: %w", err)
 	}
 
 	return i, nil
@@ -350,7 +351,7 @@ func parseIntOct(b []byte) (int64, error) {
 
 	i, err := strconv.ParseInt(string(cleaned), 8, 64)
 	if err != nil {
-		return 0, newDecodeError(b, "couldn't parse octal number: %w", err)
+		return 0, unstable.NewParserError(b, "couldn't parse octal number: %w", err)
 	}
 
 	return i, nil
@@ -364,7 +365,7 @@ func parseIntBin(b []byte) (int64, error) {
 
 	i, err := strconv.ParseInt(string(cleaned), 2, 64)
 	if err != nil {
-		return 0, newDecodeError(b, "couldn't parse binary number: %w", err)
+		return 0, unstable.NewParserError(b, "couldn't parse binary number: %w", err)
 	}
 
 	return i, nil
@@ -387,12 +388,12 @@ func parseIntDec(b []byte) (int64, error) {
 	}
 
 	if len(cleaned) > startIdx+1 && cleaned[startIdx] == '0' {
-		return 0, newDecodeError(b, "leading zero not allowed on decimal number")
+		return 0, unstable.NewParserError(b, "leading zero not allowed on decimal number")
 	}
 
 	i, err := strconv.ParseInt(string(cleaned), 10, 64)
 	if err != nil {
-		return 0, newDecodeError(b, "couldn't parse decimal number: %w", err)
+		return 0, unstable.NewParserError(b, "couldn't parse decimal number: %w", err)
 	}
 
 	return i, nil
@@ -409,11 +410,11 @@ func checkAndRemoveUnderscoresIntegers(b []byte) ([]byte, error) {
 	}
 
 	if b[start] == '_' {
-		return nil, newDecodeError(b[start:start+1], "number cannot start with underscore")
+		return nil, unstable.NewParserError(b[start:start+1], "number cannot start with underscore")
 	}
 
 	if b[len(b)-1] == '_' {
-		return nil, newDecodeError(b[len(b)-1:], "number cannot end with underscore")
+		return nil, unstable.NewParserError(b[len(b)-1:], "number cannot end with underscore")
 	}
 
 	// fast path
@@ -435,7 +436,7 @@ func checkAndRemoveUnderscoresIntegers(b []byte) ([]byte, error) {
 		c := b[i]
 		if c == '_' {
 			if !before {
-				return nil, newDecodeError(b[i-1:i+1], "number must have at least one digit between underscores")
+				return nil, unstable.NewParserError(b[i-1:i+1], "number must have at least one digit between underscores")
 			}
 			before = false
 		} else {
@@ -449,11 +450,11 @@ func checkAndRemoveUnderscoresIntegers(b []byte) ([]byte, error) {
 
 func checkAndRemoveUnderscoresFloats(b []byte) ([]byte, error) {
 	if b[0] == '_' {
-		return nil, newDecodeError(b[0:1], "number cannot start with underscore")
+		return nil, unstable.NewParserError(b[0:1], "number cannot start with underscore")
 	}
 
 	if b[len(b)-1] == '_' {
-		return nil, newDecodeError(b[len(b)-1:], "number cannot end with underscore")
+		return nil, unstable.NewParserError(b[len(b)-1:], "number cannot end with underscore")
 	}
 
 	// fast path
@@ -476,10 +477,10 @@ func checkAndRemoveUnderscoresFloats(b []byte) ([]byte, error) {
 		switch c {
 		case '_':
 			if !before {
-				return nil, newDecodeError(b[i-1:i+1], "number must have at least one digit between underscores")
+				return nil, unstable.NewParserError(b[i-1:i+1], "number must have at least one digit between underscores")
 			}
 			if i < len(b)-1 && (b[i+1] == 'e' || b[i+1] == 'E') {
-				return nil, newDecodeError(b[i+1:i+2], "cannot have underscore before exponent")
+				return nil, unstable.NewParserError(b[i+1:i+2], "cannot have underscore before exponent")
 			}
 			before = false
 		case '+', '-':
@@ -488,15 +489,15 @@ func checkAndRemoveUnderscoresFloats(b []byte) ([]byte, error) {
 			before = false
 		case 'e', 'E':
 			if i < len(b)-1 && b[i+1] == '_' {
-				return nil, newDecodeError(b[i+1:i+2], "cannot have underscore after exponent")
+				return nil, unstable.NewParserError(b[i+1:i+2], "cannot have underscore after exponent")
 			}
 			cleaned = append(cleaned, c)
 		case '.':
 			if i < len(b)-1 && b[i+1] == '_' {
-				return nil, newDecodeError(b[i+1:i+2], "cannot have underscore after decimal point")
+				return nil, unstable.NewParserError(b[i+1:i+2], "cannot have underscore after decimal point")
 			}
 			if i > 0 && b[i-1] == '_' {
-				return nil, newDecodeError(b[i-1:i], "cannot have underscore before decimal point")
+				return nil, unstable.NewParserError(b[i-1:i], "cannot have underscore before decimal point")
 			}
 			cleaned = append(cleaned, c)
 		default:
@@ -542,3 +543,7 @@ func daysIn(m int, year int) int {
 func isLeap(year int) bool {
 	return year%4 == 0 && (year%100 != 0 || year%400 == 0)
 }
+
+func isDigit(r byte) bool {
+	return r >= '0' && r <= '9'
+}

errors.go

@@ -2,10 +2,11 @@ package toml
 
 import (
 	"fmt"
+	"reflect"
 	"strconv"
 	"strings"
 
-	"github.com/pelletier/go-toml/v2/internal/danger"
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 // DecodeError represents an error encountered during the parsing or decoding
@@ -53,27 +54,20 @@ func (s *StrictMissingError) String() string {
 	return buf.String()
 }
 
-type Key []string
+// Unwrap returns wrapped decode errors
-
+//
-// internal version of DecodeError that is used as the base to create a
+// Implements errors.Join() interface.
-// DecodeError with full context.
+func (s *StrictMissingError) Unwrap() []error {
-type decodeError struct {
+	errs := make([]error, len(s.Errors))
-	highlight []byte
+	for i := range s.Errors {
-	message   string
+		errs[i] = &s.Errors[i]
-	key       Key // optional
-}
-
-func (de *decodeError) Error() string {
-	return de.message
-}
-
-func newDecodeError(highlight []byte, format string, args ...interface{}) error {
-	return &decodeError{
-		highlight: highlight,
-		message:   fmt.Errorf(format, args...).Error(),
 	}
+	return errs
 }
 
+// Key represents a TOML key as a sequence of key parts.
+type Key []string
+
 // Error returns the error message contained in the DecodeError.
 func (e *DecodeError) Error() string {
 	return "toml: " + e.message
@@ -96,7 +90,7 @@ func (e *DecodeError) Key() Key {
 	return e.key
 }
 
-// decodeErrorFromHighlight creates a DecodeError referencing a highlighted
+// wrapDecodeError creates a DecodeError referencing a highlighted
 // range of bytes from document.
 //
 // highlight needs to be a sub-slice of document, or this function panics.
@@ -105,12 +99,12 @@ func (e *DecodeError) Key() Key {
 // highlight can be freely deallocated.
 //
 //nolint:funlen
-func wrapDecodeError(document []byte, de *decodeError) *DecodeError {
+func wrapDecodeError(document []byte, de *unstable.ParserError) *DecodeError {
-	offset := danger.SubsliceOffset(document, de.highlight)
+	offset := subsliceOffset(document, de.Highlight)
 
 	errMessage := de.Error()
 	errLine, errColumn := positionAtEnd(document[:offset])
-	before, after := linesOfContext(document, de.highlight, offset, 3)
+	before, after := linesOfContext(document, de.Highlight, offset, 3)
 
 	var buf strings.Builder
 
@@ -140,7 +134,7 @@ func wrapDecodeError(document []byte, de *decodeError) *DecodeError {
 		buf.Write(before[0])
 	}
 
-	buf.Write(de.highlight)
+	buf.Write(de.Highlight)
 
 	if len(after) > 0 {
 		buf.Write(after[0])
@@ -158,7 +152,7 @@ func wrapDecodeError(document []byte, de *decodeError) *DecodeError {
 		buf.WriteString(strings.Repeat(" ", len(before[0])))
 	}
 
-	buf.WriteString(strings.Repeat("~", len(de.highlight)))
+	buf.WriteString(strings.Repeat("~", len(de.Highlight)))
 
 	if len(errMessage) > 0 {
 		buf.WriteString(" ")
@@ -183,7 +177,7 @@ func wrapDecodeError(document []byte, de *decodeError) *DecodeError {
 		message: errMessage,
 		line:    errLine,
 		column:  errColumn,
-		key:     de.key,
+		key:     de.Key,
 		human:   buf.String(),
 	}
 }
@@ -266,5 +260,24 @@ func positionAtEnd(b []byte) (row int, column int) {
 		}
 	}
 
-	return
+	return row, column
+}
+
+// subsliceOffset returns the byte offset of subslice within data.
+// subslice must share the same backing array as data.
+func subsliceOffset(data []byte, subslice []byte) int {
+	if len(subslice) == 0 {
+		return 0
+	}
+
+	// Use reflect to get the data pointers of both slices.
+	// This is safe because we're only reading the pointer values for comparison.
+	dataPtr := reflect.ValueOf(data).Pointer()
+	subPtr := reflect.ValueOf(subslice).Pointer()
+
+	offset := int(subPtr - dataPtr)
+	if offset < 0 || offset > len(data) {
+		panic("subslice is not within data")
+	}
+	return offset
 }

errors_test.go

@@ -7,12 +7,12 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
+	"github.com/pelletier/go-toml/v2/internal/assert"
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 //nolint:funlen
 func TestDecodeError(t *testing.T) {
-
 	examples := []struct {
 		desc     string
 		doc      [3]string
@@ -160,19 +160,18 @@ line 5`,
 	for _, e := range examples {
 		e := e
 		t.Run(e.desc, func(t *testing.T) {
-
 			b := bytes.Buffer{}
-			b.Write([]byte(e.doc[0]))
+			b.WriteString(e.doc[0])
 			start := b.Len()
-			b.Write([]byte(e.doc[1]))
+			b.WriteString(e.doc[1])
 			end := b.Len()
-			b.Write([]byte(e.doc[2]))
+			b.WriteString(e.doc[2])
 			doc := b.Bytes()
 			hl := doc[start:end]
 
-			err := wrapDecodeError(doc, &decodeError{
+			err := wrapDecodeError(doc, &unstable.ParserError{
-				highlight: hl,
+				Highlight: hl,
-				message:   e.msg,
+				Message:   e.msg,
 			})
 
 			var derr *DecodeError
@@ -188,7 +187,6 @@ line 5`,
 }
 
 func TestDecodeError_Accessors(t *testing.T) {
-
 	e := DecodeError{
 		message: "foo",
 		line:    1,
@@ -204,6 +202,137 @@ func TestDecodeError_Accessors(t *testing.T) {
 	assert.Equal(t, "bar", e.String())
 }
 
+func TestDecodeError_InvalidKeyStartAfterComment(t *testing.T) {
+	// Regression for https://github.com/pelletier/go-toml/issues/1047: the "="
+	// that starts an invalid keyval must be reported on line 2, column 1, with
+	// the human-readable context pointing at that byte (not the document end).
+	doc := "# comment\n= \"value\""
+
+	var v map[string]any
+	err := Unmarshal([]byte(doc), &v)
+	if err == nil {
+		t.Fatal("expected an error")
+	}
+
+	var derr *DecodeError
+	if !errors.As(err, &derr) {
+		t.Fatalf("expected *DecodeError, got %T", err)
+	}
+
+	row, col := derr.Position()
+	if row != 2 || col != 1 {
+		t.Errorf("Position(): got row %d col %d, want row 2 col 1", row, col)
+	}
+
+	human := derr.String()
+	if !strings.Contains(human, `2| = "value"`) {
+		t.Errorf("human output should show the error line; got:\n%s", human)
+	}
+	// Caret line uses line-number column width padding; only the "| ~" part is stable here.
+	if !strings.Contains(human, "| ~ invalid character at start of key") {
+		t.Errorf("human output should underline '=' and include the parser message; got:\n%s", human)
+	}
+}
+
+func TestDecodeError_DuplicateContent(t *testing.T) {
+	// This test verifies that when the same content appears multiple times
+	// in the document, the error correctly points to the actual location
+	// of the error, not the first occurrence of the content.
+	//
+	// The document has "1__2" on line 1 and "3__4" on line 2.
+	// Both have "__" which is invalid, but we want to ensure errors
+	// on line 2 report line 2, not line 1.
+
+	doc := `a = 1
+b = 3__4`
+
+	var v map[string]int
+	err := Unmarshal([]byte(doc), &v)
+
+	var derr *DecodeError
+	if !errors.As(err, &derr) {
+		t.Fatal("error not in expected format")
+	}
+
+	row, col := derr.Position()
+	// The error should be on line 2 where "3__4" is
+	if row != 2 {
+		t.Errorf("expected error on row 2, got row %d", row)
+	}
+	// Column should point to the "__" part (after "3")
+	if col < 5 {
+		t.Errorf("expected error at column >= 5, got column %d", col)
+	}
+}
+
+func TestDecodeError_Position(t *testing.T) {
+	// Test that error positions are correctly reported for various error locations
+	examples := []struct {
+		name        string
+		doc         string
+		expectedRow int
+		minCol      int
+	}{
+		{
+			name:        "error on first line",
+			doc:         `a = 1__2`,
+			expectedRow: 1,
+			minCol:      5,
+		},
+		{
+			name:        "error on second line",
+			doc:         "a = 1\nb = 2__3",
+			expectedRow: 2,
+			minCol:      5,
+		},
+		{
+			name:        "error on third line",
+			doc:         "a = 1\nb = 2\nc = 3__4",
+			expectedRow: 3,
+			minCol:      5,
+		},
+		{
+			name:        "missing equals on last line without trailing newline",
+			doc:         "a = 1\nb = 2\nc",
+			expectedRow: 3,
+			minCol:      1,
+		},
+	}
+
+	for _, e := range examples {
+		t.Run(e.name, func(t *testing.T) {
+			var v map[string]int
+			err := Unmarshal([]byte(e.doc), &v)
+
+			var derr *DecodeError
+			if !errors.As(err, &derr) {
+				t.Fatal("error not in expected format")
+			}
+
+			row, col := derr.Position()
+			assert.Equal(t, e.expectedRow, row)
+			if col < e.minCol {
+				t.Errorf("expected column >= %d, got %d", e.minCol, col)
+			}
+		})
+	}
+}
+
+func TestStrictErrorUnwrap(t *testing.T) {
+	fo := bytes.NewBufferString(`
+Missing = 1
+OtherMissing = 1
+`)
+	var out struct{}
+	err := NewDecoder(fo).DisallowUnknownFields().Decode(&out)
+	assert.Error(t, err)
+
+	strictErr := &StrictMissingError{}
+	assert.True(t, errors.As(err, &strictErr))
+
+	assert.Equal(t, 2, len(strictErr.Unwrap()))
+}
+
 func ExampleDecodeError() {
 	doc := `name = 123__456`
 

example_text_marshaling_test.go

@@ -0,0 +1,37 @@
+package toml_test
+
+import (
+	"fmt"
+	"log"
+	"strconv"
+
+	"github.com/pelletier/go-toml/v2"
+)
+
+type customInt int
+
+func (i *customInt) UnmarshalText(b []byte) error {
+	x, err := strconv.ParseInt(string(b), 10, 32)
+	if err != nil {
+		return err
+	}
+	*i = customInt(x * 100)
+	return nil
+}
+
+type doc struct {
+	Value customInt
+}
+
+func ExampleUnmarshal_textUnmarshal() {
+	var x doc
+
+	data := []byte(`value  = "42"`)
+	err := toml.Unmarshal(data, &x)
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println(x)
+	// Output:
+	// {4200}
+}

fast_test.go

@@ -4,21 +4,28 @@ import (
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
-func TestFastSimple(t *testing.T) {
+func TestFastSimpleInt(t *testing.T) {
 	m := map[string]int64{}
 	err := toml.Unmarshal([]byte(`a = 42`), &m)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, map[string]int64{"a": 42}, m)
+	assert.Equal(t, map[string]int64{"a": 42}, m)
+}
+
+func TestFastSimpleFloat(t *testing.T) {
+	m := map[string]float64{}
+	err := toml.Unmarshal([]byte("a = 42\nb = 1.1\nc = 12341234123412341234123412341234"), &m)
+	assert.NoError(t, err)
+	assert.Equal(t, map[string]float64{"a": 42, "b": 1.1, "c": 1.2341234123412342e+31}, m)
 }
 
 func TestFastSimpleString(t *testing.T) {
 	m := map[string]string{}
 	err := toml.Unmarshal([]byte(`a = "hello"`), &m)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, map[string]string{"a": "hello"}, m)
+	assert.Equal(t, map[string]string{"a": "hello"}, m)
 }
 
 func TestFastSimpleInterface(t *testing.T) {
@@ -26,8 +33,8 @@ func TestFastSimpleInterface(t *testing.T) {
 	err := toml.Unmarshal([]byte(`
 	a = "hello"
 	b = 42`), &m)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, map[string]interface{}{
+	assert.Equal(t, map[string]interface{}{
 		"a": "hello",
 		"b": int64(42),
 	}, m)
@@ -39,8 +46,8 @@ func TestFastMultipartKeyInterface(t *testing.T) {
 	a.interim = "test"
 	a.b.c = "hello"
 	b = 42`), &m)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, map[string]interface{}{
+	assert.Equal(t, map[string]interface{}{
 		"a": map[string]interface{}{
 			"interim": "test",
 			"b": map[string]interface{}{
@@ -59,8 +66,8 @@ func TestFastExistingMap(t *testing.T) {
 	ints.one = 1
 	ints.two = 2
 	strings.yo = "hello"`), &m)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, map[string]interface{}{
+	assert.Equal(t, map[string]interface{}{
 		"ints": map[string]interface{}{
 			"one": int64(1),
 			"two": int64(2),
@@ -83,9 +90,9 @@ func TestFastArrayTable(t *testing.T) {
 	m := map[string]interface{}{}
 
 	err := toml.Unmarshal(b, &m)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
-	require.Equal(t, map[string]interface{}{
+	assert.Equal(t, map[string]interface{}{
 		"root": map[string]interface{}{
 			"nested": []interface{}{
 				map[string]interface{}{

fuzz_test.go

@@ -1,21 +1,18 @@
-//go:build go1.18 || go1.19
-// +build go1.18 go1.19
-
 package toml_test
 
 import (
-	"io/ioutil"
+	"os"
 	"strings"
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func FuzzUnmarshal(f *testing.F) {
-	file, err := ioutil.ReadFile("benchmark/benchmark.toml")
+	file, err := os.ReadFile("benchmark/benchmark.toml")
 	if err != nil {
-		panic(err)
+		f.Error(err)
 	}
 	f.Add(file)
 
@@ -51,6 +48,6 @@ func FuzzUnmarshal(f *testing.F) {
 		if err != nil {
 			t.Fatalf("failed round trip: %s", err)
 		}
-		require.Equal(t, v, v2)
+		assert.Equal(t, v, v2)
 	})
 }

go.mod

@@ -1,5 +1,3 @@
 module github.com/pelletier/go-toml/v2
 
-go 1.16
+go 1.21.0
-
-require github.com/stretchr/testify v1.8.0

go.sum

@@ -1,15 +0,0 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
-github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
-github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
-github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0 h1:pSgiaMZlXftHpm5L7V1+rVB+AZJydKsMxsQBIJw4PKk=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
-gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
-gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

internal/assert/assertions.go

@@ -0,0 +1,141 @@
+// Package assert provides assertion functions for unit testing.
+package assert
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// True asserts that an expression is true.
+func True(tb testing.TB, ok bool, msgAndArgs ...any) {
+	tb.Helper()
+	if ok {
+		return
+	}
+	tb.Fatal(formatMsgAndArgs("Expected expression to be true", msgAndArgs...))
+}
+
+// False asserts that an expression is false.
+func False(tb testing.TB, ok bool, msgAndArgs ...any) {
+	tb.Helper()
+	if !ok {
+		return
+	}
+	tb.Fatal(formatMsgAndArgs("Expected expression to be false", msgAndArgs...))
+}
+
+// Equal asserts that "expected" and "actual" are equal.
+func Equal[T any](tb testing.TB, expected, actual T, msgAndArgs ...any) {
+	tb.Helper()
+	if objectsAreEqual(expected, actual) {
+		return
+	}
+	msg := formatMsgAndArgs("Expected values to be equal:", msgAndArgs...)
+	tb.Fatalf("%s\n%s", msg, diff(expected, actual))
+}
+
+// Error asserts that an error is not nil.
+func Error(tb testing.TB, err error, msgAndArgs ...any) {
+	tb.Helper()
+	if err != nil {
+		return
+	}
+	tb.Fatal(formatMsgAndArgs("Expected an error", msgAndArgs...))
+}
+
+// NoError asserts that an error is nil.
+func NoError(tb testing.TB, err error, msgAndArgs ...any) {
+	tb.Helper()
+	if err == nil {
+		return
+	}
+	msg := formatMsgAndArgs("Unexpected error:", msgAndArgs...)
+	tb.Fatalf("%s\n%+v", msg, err)
+}
+
+// Panics asserts that the given function panics.
+func Panics(tb testing.TB, fn func(), msgAndArgs ...any) {
+	tb.Helper()
+	defer func() {
+		if recover() == nil {
+			msg := formatMsgAndArgs("Expected function to panic", msgAndArgs...)
+			tb.Fatal(msg)
+		}
+	}()
+	fn()
+}
+
+// Zero asserts that a value is its zero value.
+func Zero[T any](tb testing.TB, value T, msgAndArgs ...any) {
+	tb.Helper()
+	var zero T
+	if objectsAreEqual(value, zero) {
+		return
+	}
+	val := reflect.ValueOf(value)
+	if (val.Kind() == reflect.Slice || val.Kind() == reflect.Map || val.Kind() == reflect.Array) && val.Len() == 0 {
+		return
+	}
+	msg := formatMsgAndArgs("Expected zero value but got:", msgAndArgs...)
+	tb.Fatalf("%s\n%v", msg, value)
+}
+
+func NotZero[T any](tb testing.TB, value T, msgAndArgs ...any) {
+	tb.Helper()
+	var zero T
+	if !objectsAreEqual(value, zero) {
+		val := reflect.ValueOf(value)
+		switch val.Kind() {
+		case reflect.Slice, reflect.Map, reflect.Array:
+			if val.Len() > 0 {
+				return
+			}
+		default:
+			return
+		}
+	}
+	msg := formatMsgAndArgs("Unexpected zero value:", msgAndArgs...)
+	tb.Fatalf("%s\n%v", msg, value)
+}
+
+func formatMsgAndArgs(msg string, args ...any) string {
+	if len(args) == 0 {
+		return msg
+	}
+	format, ok := args[0].(string)
+	if !ok {
+		panic("message argument must be a fmt string")
+	}
+	return fmt.Sprintf(format, args[1:]...)
+}
+
+func diff(expected, actual any) string {
+	lines := []string{
+		"expected:",
+		fmt.Sprintf("%v", expected),
+		"actual:",
+		fmt.Sprintf("%v", actual),
+	}
+	return strings.Join(lines, "\n")
+}
+
+func objectsAreEqual(expected, actual any) bool {
+	if expected == nil || actual == nil {
+		return expected == actual
+	}
+	if exp, eok := expected.([]byte); eok {
+		if act, aok := actual.([]byte); aok {
+			return bytes.Equal(exp, act)
+		}
+	}
+	if exp, eok := expected.(string); eok {
+		if act, aok := actual.(string); aok {
+			return exp == act
+		}
+	}
+
+	return reflect.DeepEqual(expected, actual)
+}

internal/assert/assertions_test.go

@@ -0,0 +1,217 @@
+package assert
+
+import (
+	"errors"
+	"fmt"
+	"testing"
+)
+
+type Data struct {
+	Label string
+	Value int64
+}
+
+func TestBadMessage(t *testing.T) {
+	invalidMessage := func() { True(t, false, 1234) }
+	assertOk(t, "Non-fmt message value", func(tb testing.TB) {
+		tb.Helper()
+		Panics(tb, invalidMessage)
+	})
+	assertFail(t, "Non-fmt message value", func(tb testing.TB) {
+		tb.Helper()
+		True(tb, false, "example %s", "message")
+	})
+}
+
+func TestTrue(t *testing.T) {
+	assertOk(t, "Succeed", func(tb testing.TB) {
+		tb.Helper()
+		True(tb, 1 > 0)
+	})
+	assertFail(t, "Fail", func(tb testing.TB) {
+		tb.Helper()
+		True(tb, 1 < 0)
+	})
+}
+
+func TestFalse(t *testing.T) {
+	assertOk(t, "Succeed", func(tb testing.TB) {
+		tb.Helper()
+		False(tb, 1 < 0)
+	})
+	assertFail(t, "Fail", func(tb testing.TB) {
+		tb.Helper()
+		False(tb, 1 > 0)
+	})
+}
+
+func TestEqual(t *testing.T) {
+	assertOk(t, "Nil", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, interface{}(nil), interface{}(nil))
+	})
+	assertOk(t, "Identical structs", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, Data{"expected", 1234}, Data{"expected", 1234})
+	})
+	assertFail(t, "Different structs", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, Data{"expected", 1234}, Data{"actual", 1234})
+	})
+	assertOk(t, "Identical numbers", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, 1234, 1234)
+	})
+	assertFail(t, "Identical numbers", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, 1234, 1324)
+	})
+	assertOk(t, "Zero-length byte arrays", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, []byte(nil), []byte(""))
+	})
+	assertOk(t, "Identical byte arrays", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, []byte{1, 2, 3, 4}, []byte{1, 2, 3, 4})
+	})
+	assertFail(t, "Different byte arrays", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, []byte{1, 2, 3, 4}, []byte{1, 3, 2, 4})
+	})
+	assertOk(t, "Identical strings", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, "example", "example")
+	})
+	assertFail(t, "Identical strings", func(tb testing.TB) {
+		tb.Helper()
+		Equal(tb, "example", "elpmaxe")
+	})
+}
+
+func TestError(t *testing.T) {
+	assertOk(t, "Error", func(tb testing.TB) {
+		tb.Helper()
+		Error(tb, errors.New("example"))
+	})
+	assertFail(t, "Nil", func(tb testing.TB) {
+		tb.Helper()
+		Error(tb, nil)
+	})
+}
+
+func TestNoError(t *testing.T) {
+	assertFail(t, "Error", func(tb testing.TB) {
+		tb.Helper()
+		NoError(tb, errors.New("example"))
+	})
+	assertOk(t, "Nil", func(tb testing.TB) {
+		tb.Helper()
+		NoError(tb, nil)
+	})
+}
+
+func TestPanics(t *testing.T) {
+	willPanic := func() { panic("example") }
+	wontPanic := func() {}
+	assertOk(t, "Will panic", func(tb testing.TB) {
+		tb.Helper()
+		Panics(tb, willPanic)
+	})
+	assertFail(t, "Won't panic", func(tb testing.TB) {
+		tb.Helper()
+		Panics(tb, wontPanic)
+	})
+}
+
+func TestZero(t *testing.T) {
+	assertOk(t, "Empty struct", func(tb testing.TB) {
+		tb.Helper()
+		Zero(tb, Data{})
+	})
+	assertFail(t, "Non-empty struct", func(tb testing.TB) {
+		tb.Helper()
+		Zero(tb, Data{Label: "example"})
+	})
+	assertOk(t, "Nil slice", func(tb testing.TB) {
+		tb.Helper()
+		var slice []int
+		Zero(tb, slice)
+	})
+	assertFail(t, "Non-empty slice", func(tb testing.TB) {
+		tb.Helper()
+		slice := []int{1, 2, 3, 4}
+		Zero(tb, slice)
+	})
+	assertOk(t, "Zero-length slice", func(tb testing.TB) {
+		tb.Helper()
+		slice := []int{}
+		Zero(tb, slice)
+	})
+}
+
+func TestNotZero(t *testing.T) {
+	assertFail(t, "Empty struct", func(tb testing.TB) {
+		tb.Helper()
+		zero := Data{}
+		NotZero(tb, zero)
+	})
+	assertOk(t, "Non-empty struct", func(tb testing.TB) {
+		tb.Helper()
+		notZero := Data{Label: "example"}
+		NotZero(tb, notZero)
+	})
+	assertFail(t, "Nil slice", func(tb testing.TB) {
+		tb.Helper()
+		var slice []int
+		NotZero(tb, slice)
+	})
+	assertFail(t, "Zero-length slice", func(tb testing.TB) {
+		tb.Helper()
+		slice := []int{}
+		NotZero(tb, slice)
+	})
+	assertOk(t, "Non-empty slice", func(tb testing.TB) {
+		tb.Helper()
+		slice := []int{1, 2, 3, 4}
+		NotZero(tb, slice)
+	})
+}
+
+type testCase struct {
+	*testing.T
+	failed string
+}
+
+func (t *testCase) Fatal(args ...interface{}) {
+	t.failed = fmt.Sprint(args...)
+}
+
+func (t *testCase) Fatalf(message string, args ...interface{}) {
+	t.failed = fmt.Sprintf(message, args...)
+}
+
+func assertFail(t *testing.T, name string, fn func(testing.TB)) {
+	t.Helper()
+	t.Run(name, func(t *testing.T) {
+		t.Helper()
+		test := &testCase{T: t}
+		fn(test)
+		if test.failed == "" {
+			t.Fatal("Test expected to fail but did not")
+		} else {
+			t.Log(test.failed)
+		}
+	})
+}
+
+func assertOk(t *testing.T, name string, fn func(testing.TB)) {
+	t.Helper()
+	t.Run(name, func(t *testing.T) {
+		t.Helper()
+		test := &testCase{T: t}
+		fn(test)
+		if test.failed != "" {
+			t.Fatal("Test expected to succeed but did not:\n", test.failed)
+		}
+	})
+}

internal/ast/ast.go

@@ -1,144 +0,0 @@
-package ast
-
-import (
-	"fmt"
-	"unsafe"
-
-	"github.com/pelletier/go-toml/v2/internal/danger"
-)
-
-// Iterator starts uninitialized, you need to call Next() first.
-//
-// For example:
-//
-//	it := n.Children()
-//	for it.Next() {
-//			it.Node()
-//	}
-type Iterator struct {
-	started bool
-	node    *Node
-}
-
-// Next moves the iterator forward and returns true if points to a
-// node, false otherwise.
-func (c *Iterator) Next() bool {
-	if !c.started {
-		c.started = true
-	} else if c.node.Valid() {
-		c.node = c.node.Next()
-	}
-	return c.node.Valid()
-}
-
-// IsLast returns true if the current node of the iterator is the last
-// one.  Subsequent call to Next() will return false.
-func (c *Iterator) IsLast() bool {
-	return c.node.next == 0
-}
-
-// Node returns a copy of the node pointed at by the iterator.
-func (c *Iterator) Node() *Node {
-	return c.node
-}
-
-// Root contains a full AST.
-//
-// It is immutable once constructed with Builder.
-type Root struct {
-	nodes []Node
-}
-
-// Iterator over the top level nodes.
-func (r *Root) Iterator() Iterator {
-	it := Iterator{}
-	if len(r.nodes) > 0 {
-		it.node = &r.nodes[0]
-	}
-	return it
-}
-
-func (r *Root) at(idx Reference) *Node {
-	return &r.nodes[idx]
-}
-
-// Arrays have one child per element in the array.  InlineTables have
-// one child per key-value pair in the table.  KeyValues have at least
-// two children. The first one is the value. The rest make a
-// potentially dotted key.  Table and Array table have one child per
-// element of the key they represent (same as KeyValue, but without
-// the last node being the value).
-type Node struct {
-	Kind Kind
-	Raw  Range  // Raw bytes from the input.
-	Data []byte // Node value (either allocated or referencing the input).
-
-	// References to other nodes, as offsets in the backing array
-	// from this node. References can go backward, so those can be
-	// negative.
-	next  int // 0 if last element
-	child int // 0 if no child
-}
-
-type Range struct {
-	Offset uint32
-	Length uint32
-}
-
-// Next returns a copy of the next node, or an invalid Node if there
-// is no next node.
-func (n *Node) Next() *Node {
-	if n.next == 0 {
-		return nil
-	}
-	ptr := unsafe.Pointer(n)
-	size := unsafe.Sizeof(Node{})
-	return (*Node)(danger.Stride(ptr, size, n.next))
-}
-
-// Child returns a copy of the first child node of this node. Other
-// children can be accessed calling Next on the first child.  Returns
-// an invalid Node if there is none.
-func (n *Node) Child() *Node {
-	if n.child == 0 {
-		return nil
-	}
-	ptr := unsafe.Pointer(n)
-	size := unsafe.Sizeof(Node{})
-	return (*Node)(danger.Stride(ptr, size, n.child))
-}
-
-// Valid returns true if the node's kind is set (not to Invalid).
-func (n *Node) Valid() bool {
-	return n != nil
-}
-
-// Key returns the child nodes making the Key on a supported
-// node. Panics otherwise.  They are guaranteed to be all be of the
-// Kind Key. A simple key would return just one element.
-func (n *Node) Key() Iterator {
-	switch n.Kind {
-	case KeyValue:
-		value := n.Child()
-		if !value.Valid() {
-			panic(fmt.Errorf("KeyValue should have at least two children"))
-		}
-		return Iterator{node: value.Next()}
-	case Table, ArrayTable:
-		return Iterator{node: n.Child()}
-	default:
-		panic(fmt.Errorf("Key() is not supported on a %s", n.Kind))
-	}
-}
-
-// Value returns a pointer to the value node of a KeyValue.
-// Guaranteed to be non-nil.  Panics if not called on a KeyValue node,
-// or if the Children are malformed.
-func (n *Node) Value() *Node {
-	return n.Child()
-}
-
-// Children returns an iterator over a node's children.
-func (n *Node) Children() Iterator {
-	return Iterator{node: n.Child()}
-}

internal/ast/builder.go

@@ -1,51 +0,0 @@
-package ast
-
-type Reference int
-
-const InvalidReference Reference = -1
-
-func (r Reference) Valid() bool {
-	return r != InvalidReference
-}
-
-type Builder struct {
-	tree    Root
-	lastIdx int
-}
-
-func (b *Builder) Tree() *Root {
-	return &b.tree
-}
-
-func (b *Builder) NodeAt(ref Reference) *Node {
-	return b.tree.at(ref)
-}
-
-func (b *Builder) Reset() {
-	b.tree.nodes = b.tree.nodes[:0]
-	b.lastIdx = 0
-}
-
-func (b *Builder) Push(n Node) Reference {
-	b.lastIdx = len(b.tree.nodes)
-	b.tree.nodes = append(b.tree.nodes, n)
-	return Reference(b.lastIdx)
-}
-
-func (b *Builder) PushAndChain(n Node) Reference {
-	newIdx := len(b.tree.nodes)
-	b.tree.nodes = append(b.tree.nodes, n)
-	if b.lastIdx >= 0 {
-		b.tree.nodes[b.lastIdx].next = newIdx - b.lastIdx
-	}
-	b.lastIdx = newIdx
-	return Reference(b.lastIdx)
-}
-
-func (b *Builder) AttachChild(parent Reference, child Reference) {
-	b.tree.nodes[parent].child = int(child) - int(parent)
-}
-
-func (b *Builder) Chain(from Reference, to Reference) {
-	b.tree.nodes[from].next = int(to) - int(from)
-}

internal/characters/ascii.go

@@ -0,0 +1,42 @@
+package characters
+
+var invalidASCIITable = [256]bool{
+	0x00: true,
+	0x01: true,
+	0x02: true,
+	0x03: true,
+	0x04: true,
+	0x05: true,
+	0x06: true,
+	0x07: true,
+	0x08: true,
+	// 0x09 TAB
+	// 0x0A LF
+	0x0B: true,
+	0x0C: true,
+	// 0x0D CR
+	0x0E: true,
+	0x0F: true,
+	0x10: true,
+	0x11: true,
+	0x12: true,
+	0x13: true,
+	0x14: true,
+	0x15: true,
+	0x16: true,
+	0x17: true,
+	0x18: true,
+	0x19: true,
+	0x1A: true,
+	0x1B: true,
+	0x1C: true,
+	0x1D: true,
+	0x1E: true,
+	0x1F: true,
+	// 0x20 - 0x7E Printable ASCII characters
+	0x7F: true,
+}
+
+func InvalidASCII(b byte) bool {
+	return invalidASCIITable[b]
+}

internal/characters/utf8.go

@@ -1,20 +1,12 @@
-package toml
+// Package characters provides functions for working with string encodings.
+package characters
 
 import (
 	"unicode/utf8"
 )
 
-type utf8Err struct {
+// Utf8TomlValidAlreadyEscaped verifies that a given string is only made of
-	Index int
+// valid UTF-8 characters allowed by the TOML spec:
-	Size  int
-}
-
-func (u utf8Err) Zero() bool {
-	return u.Size == 0
-}
-
-// Verified that a given string is only made of valid UTF-8 characters allowed
-// by the TOML spec:
 //
 // Any Unicode character may be used except those that must be escaped:
 // quotation mark, backslash, and the control characters other than tab (U+0000
@@ -23,8 +15,8 @@ func (u utf8Err) Zero() bool {
 // It is a copy of the Go 1.17 utf8.Valid implementation, tweaked to exit early
 // when a character is not allowed.
 //
-// The returned utf8Err is Zero() if the string is valid, or contains the byte
+// The returned slice is empty if the string is valid, or contains the bytes
-// index and size of the invalid character.
+// of the invalid character.
 //
 // quotation mark => already checked
 // backslash => already checked
@@ -32,9 +24,8 @@ func (u utf8Err) Zero() bool {
 // 0x9 => tab, ok
 // 0xA - 0x1F => invalid
 // 0x7F => invalid
-func utf8TomlValidAlreadyEscaped(p []byte) (err utf8Err) {
+func Utf8TomlValidAlreadyEscaped(p []byte) []byte {
 	// Fast path. Check for and skip 8 bytes of ASCII characters per iteration.
-	offset := 0
 	for len(p) >= 8 {
 		// Combining two 32 bit loads allows the same code to be used
 		// for 32 and 64 bit platforms.
@@ -48,24 +39,19 @@ func utf8TomlValidAlreadyEscaped(p []byte) (err utf8Err) {
 		}
 
 		for i, b := range p[:8] {
-			if invalidAscii(b) {
+			if InvalidASCII(b) {
-				err.Index = offset + i
+				return p[i : i+1]
-				err.Size = 1
-				return
 			}
 		}
 
 		p = p[8:]
-		offset += 8
 	}
 	n := len(p)
 	for i := 0; i < n; {
 		pi := p[i]
 		if pi < utf8.RuneSelf {
-			if invalidAscii(pi) {
+			if InvalidASCII(pi) {
-				err.Index = offset + i
+				return p[i : i+1]
-				err.Size = 1
-				return
 			}
 			i++
 			continue
@@ -73,44 +59,34 @@ func utf8TomlValidAlreadyEscaped(p []byte) (err utf8Err) {
 		x := first[pi]
 		if x == xx {
 			// Illegal starter byte.
-			err.Index = offset + i
+			return p[i : i+1]
-			err.Size = 1
-			return
 		}
 		size := int(x & 7)
 		if i+size > n {
 			// Short or invalid.
-			err.Index = offset + i
+			return p[i:n]
-			err.Size = n - i
-			return
 		}
 		accept := acceptRanges[x>>4]
 		if c := p[i+1]; c < accept.lo || accept.hi < c {
-			err.Index = offset + i
+			return p[i : i+2]
-			err.Size = 2
+		} else if size == 2 { //revive:disable:empty-block
-			return
-		} else if size == 2 {
 		} else if c := p[i+2]; c < locb || hicb < c {
-			err.Index = offset + i
+			return p[i : i+3]
-			err.Size = 3
+		} else if size == 3 { //revive:disable:empty-block
-			return
-		} else if size == 3 {
 		} else if c := p[i+3]; c < locb || hicb < c {
-			err.Index = offset + i
+			return p[i : i+4]
-			err.Size = 4
-			return
 		}
 		i += size
 	}
-	return
+	return nil
 }
 
-// Return the size of the next rune if valid, 0 otherwise.
+// Utf8ValidNext returns the size of the next rune if valid, 0 otherwise.
-func utf8ValidNext(p []byte) int {
+func Utf8ValidNext(p []byte) int {
 	c := p[0]
 
 	if c < utf8.RuneSelf {
-		if invalidAscii(c) {
+		if InvalidASCII(c) {
 			return 0
 		}
 		return 1
@@ -129,10 +105,10 @@ func utf8ValidNext(p []byte) int {
 	accept := acceptRanges[x>>4]
 	if c := p[1]; c < accept.lo || accept.hi < c {
 		return 0
-	} else if size == 2 {
+	} else if size == 2 { //nolint:revive
 	} else if c := p[2]; c < locb || hicb < c {
 		return 0
-	} else if size == 3 {
+	} else if size == 3 { //nolint:revive
 	} else if c := p[3]; c < locb || hicb < c {
 		return 0
 	}
@@ -140,47 +116,6 @@ func utf8ValidNext(p []byte) int {
 	return size
 }
 
-var invalidAsciiTable = [256]bool{
-	0x00: true,
-	0x01: true,
-	0x02: true,
-	0x03: true,
-	0x04: true,
-	0x05: true,
-	0x06: true,
-	0x07: true,
-	0x08: true,
-	// 0x09 TAB
-	// 0x0A LF
-	0x0B: true,
-	0x0C: true,
-	// 0x0D CR
-	0x0E: true,
-	0x0F: true,
-	0x10: true,
-	0x11: true,
-	0x12: true,
-	0x13: true,
-	0x14: true,
-	0x15: true,
-	0x16: true,
-	0x17: true,
-	0x18: true,
-	0x19: true,
-	0x1A: true,
-	0x1B: true,
-	0x1C: true,
-	0x1D: true,
-	0x1E: true,
-	0x1F: true,
-	// 0x20 - 0x7E Printable ASCII characters
-	0x7F: true,
-}
-
-func invalidAscii(b byte) bool {
-	return invalidAsciiTable[b]
-}
-
 // acceptRange gives the range of valid values for the second byte in a UTF-8
 // sequence.
 type acceptRange struct {

internal/cli/cli.go

@@ -1,3 +1,4 @@
+// Package cli provides common functions for command-line programs.
 package cli
 
 import (
@@ -6,7 +7,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 
 	"github.com/pelletier/go-toml/v2"
@@ -18,27 +18,26 @@ type Program struct {
 	Usage string
 	Fn    ConvertFn
 	// Inplace allows the command to take more than one file as argument and
-	// perform convertion in place on each provided file.
+	// perform conversion in place on each provided file.
 	Inplace bool
 }
 
 func (p *Program) Execute() {
-	flag.Usage = func() { fmt.Fprintf(os.Stderr, p.Usage) }
+	flag.Usage = func() { fmt.Fprint(os.Stderr, p.Usage) }
 	flag.Parse()
 	os.Exit(p.main(flag.Args(), os.Stdin, os.Stdout, os.Stderr))
 }
 
-func (p *Program) main(files []string, input io.Reader, output, error io.Writer) int {
+func (p *Program) main(files []string, input io.Reader, output, stderr io.Writer) int {
 	err := p.run(files, input, output)
 	if err != nil {
-
 		var derr *toml.DecodeError
 		if errors.As(err, &derr) {
-			fmt.Fprintln(error, derr.String())
+			_, _ = fmt.Fprintln(stderr, derr.String())
 			row, col := derr.Position()
-			fmt.Fprintln(error, "error occurred at row", row, "column", col)
+			_, _ = fmt.Fprintln(stderr, "error occurred at row", row, "column", col)
 		} else {
-			fmt.Fprintln(error, err.Error())
+			_, _ = fmt.Fprintln(stderr, err.Error())
 		}
 
 		return -1
@@ -55,7 +54,7 @@ func (p *Program) run(files []string, input io.Reader, output io.Writer) error {
 		if err != nil {
 			return err
 		}
-		defer f.Close()
+		defer func() { _ = f.Close() }()
 		input = f
 	}
 	return p.Fn(input, output)
@@ -72,7 +71,7 @@ func (p *Program) runAllFilesInPlace(files []string) error {
 }
 
 func (p *Program) runFileInPlace(path string) error {
-	in, err := ioutil.ReadFile(path)
+	in, err := os.ReadFile(path) // #nosec G304
 	if err != nil {
 		return err
 	}
@@ -84,5 +83,5 @@ func (p *Program) runFileInPlace(path string) error {
 		return err
 	}
 
-	return ioutil.WriteFile(path, out.Bytes(), 0600)
+	return os.WriteFile(path, out.Bytes(), 0o600)
 }

internal/cli/cli_test.go

@@ -2,17 +2,15 @@ package cli
 
 import (
 	"bytes"
-	"fmt"
+	"errors"
 	"io"
-	"io/ioutil"
 	"os"
 	"path"
 	"strings"
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/assert"
+	"github.com/pelletier/go-toml/v2/internal/assert"
-	"github.com/stretchr/testify/require"
 )
 
 func processMain(args []string, input io.Reader, stdout, stderr io.Writer, f ConvertFn) int {
@@ -25,13 +23,13 @@ func TestProcessMainStdin(t *testing.T) {
 	stderr := new(bytes.Buffer)
 	input := strings.NewReader("this is the input")
 
-	exit := processMain([]string{}, input, stdout, stderr, func(r io.Reader, w io.Writer) error {
+	exit := processMain([]string{}, input, stdout, stderr, func(io.Reader, io.Writer) error {
 		return nil
 	})
 
 	assert.Equal(t, 0, exit)
-	assert.Empty(t, stdout.String())
+	assert.Zero(t, stdout.String())
-	assert.Empty(t, stderr.String())
+	assert.Zero(t, stderr.String())
 }
 
 func TestProcessMainStdinErr(t *testing.T) {
@@ -39,13 +37,13 @@ func TestProcessMainStdinErr(t *testing.T) {
 	stderr := new(bytes.Buffer)
 	input := strings.NewReader("this is the input")
 
-	exit := processMain([]string{}, input, stdout, stderr, func(r io.Reader, w io.Writer) error {
+	exit := processMain([]string{}, input, stdout, stderr, func(io.Reader, io.Writer) error {
-		return fmt.Errorf("something bad")
+		return errors.New("something bad")
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
+	assert.Zero(t, stdout.String())
-	assert.NotEmpty(t, stderr.String())
+	assert.NotZero(t, stderr.String())
 }
 
 func TestProcessMainStdinDecodeErr(t *testing.T) {
@@ -53,60 +51,58 @@ func TestProcessMainStdinDecodeErr(t *testing.T) {
 	stderr := new(bytes.Buffer)
 	input := strings.NewReader("this is the input")
 
-	exit := processMain([]string{}, input, stdout, stderr, func(r io.Reader, w io.Writer) error {
+	exit := processMain([]string{}, input, stdout, stderr, func(io.Reader, io.Writer) error {
 		var v interface{}
 		return toml.Unmarshal([]byte(`qwe = 001`), &v)
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
+	assert.Zero(t, stdout.String())
-	assert.Contains(t, stderr.String(), "error occurred at")
+	assert.True(t, strings.Contains(stderr.String(), "error occurred at"))
 }
 
 func TestProcessMainFileExists(t *testing.T) {
-	tmpfile, err := ioutil.TempFile("", "example")
+	tmpfile, err := os.CreateTemp(t.TempDir(), "example")
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	defer os.Remove(tmpfile.Name())
+	_, err = tmpfile.WriteString(`some data`)
-	_, err = tmpfile.Write([]byte(`some data`))
+	assert.NoError(t, err)
-	require.NoError(t, err)
+	assert.NoError(t, tmpfile.Close())
 
 	stdout := new(bytes.Buffer)
 	stderr := new(bytes.Buffer)
 
-	exit := processMain([]string{tmpfile.Name()}, nil, stdout, stderr, func(r io.Reader, w io.Writer) error {
+	exit := processMain([]string{tmpfile.Name()}, nil, stdout, stderr, func(io.Reader, io.Writer) error {
 		return nil
 	})
 
 	assert.Equal(t, 0, exit)
-	assert.Empty(t, stdout.String())
+	assert.Zero(t, stdout.String())
-	assert.Empty(t, stderr.String())
+	assert.Zero(t, stderr.String())
 }
 
 func TestProcessMainFileDoesNotExist(t *testing.T) {
 	stdout := new(bytes.Buffer)
 	stderr := new(bytes.Buffer)
 
-	exit := processMain([]string{"/lets/hope/this/does/not/exist"}, nil, stdout, stderr, func(r io.Reader, w io.Writer) error {
+	exit := processMain([]string{"/lets/hope/this/does/not/exist"}, nil, stdout, stderr, func(io.Reader, io.Writer) error {
 		return nil
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
+	assert.Zero(t, stdout.String())
-	assert.NotEmpty(t, stderr.String())
+	assert.NotZero(t, stderr.String())
 }
 
 func TestProcessMainFilesInPlace(t *testing.T) {
-	dir, err := ioutil.TempDir("", "")
+	dir := t.TempDir()
-	require.NoError(t, err)
-	defer os.RemoveAll(dir)
 
 	path1 := path.Join(dir, "file1")
 	path2 := path.Join(dir, "file2")
 
-	err = ioutil.WriteFile(path1, []byte("content 1"), 0600)
+	err := os.WriteFile(path1, []byte("content 1"), 0o600)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	err = ioutil.WriteFile(path2, []byte("content 2"), 0600)
+	err = os.WriteFile(path2, []byte("content 2"), 0o600)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	p := Program{
 		Fn:      dummyFileFn,
@@ -115,15 +111,15 @@ func TestProcessMainFilesInPlace(t *testing.T) {
 
 	exit := p.main([]string{path1, path2}, os.Stdin, os.Stdout, os.Stderr)
 
-	require.Equal(t, 0, exit)
+	assert.Equal(t, 0, exit)
 
-	v1, err := ioutil.ReadFile(path1)
+	v1, err := os.ReadFile(path1)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, "1", string(v1))
+	assert.Equal(t, "1", string(v1))
 
-	v2, err := ioutil.ReadFile(path2)
+	v2, err := os.ReadFile(path2)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, "2", string(v2))
+	assert.Equal(t, "2", string(v2))
 }
 
 func TestProcessMainFilesInPlaceErrRead(t *testing.T) {
@@ -134,35 +130,33 @@ func TestProcessMainFilesInPlaceErrRead(t *testing.T) {
 
 	exit := p.main([]string{"/this/path/is/invalid"}, os.Stdin, os.Stdout, os.Stderr)
 
-	require.Equal(t, -1, exit)
+	assert.Equal(t, -1, exit)
 }
 
 func TestProcessMainFilesInPlaceFailFn(t *testing.T) {
-	dir, err := ioutil.TempDir("", "")
+	dir := t.TempDir()
-	require.NoError(t, err)
-	defer os.RemoveAll(dir)
 
 	path1 := path.Join(dir, "file1")
 
-	err = ioutil.WriteFile(path1, []byte("content 1"), 0600)
+	err := os.WriteFile(path1, []byte("content 1"), 0o600)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	p := Program{
-		Fn:      func(io.Reader, io.Writer) error { return fmt.Errorf("oh no") },
+		Fn:      func(io.Reader, io.Writer) error { return errors.New("oh no") },
 		Inplace: true,
 	}
 
 	exit := p.main([]string{path1}, os.Stdin, os.Stdout, os.Stderr)
 
-	require.Equal(t, -1, exit)
+	assert.Equal(t, -1, exit)
 
-	v1, err := ioutil.ReadFile(path1)
+	v1, err := os.ReadFile(path1)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, "content 1", string(v1))
+	assert.Equal(t, "content 1", string(v1))
 }
 
 func dummyFileFn(r io.Reader, w io.Writer) error {
-	b, err := ioutil.ReadAll(r)
+	b, err := io.ReadAll(r)
 	if err != nil {
 		return err
 	}

internal/danger/danger.go

@@ -1,65 +0,0 @@
-package danger
-
-import (
-	"fmt"
-	"reflect"
-	"unsafe"
-)
-
-const maxInt = uintptr(int(^uint(0) >> 1))
-
-func SubsliceOffset(data []byte, subslice []byte) int {
-	datap := (*reflect.SliceHeader)(unsafe.Pointer(&data))
-	hlp := (*reflect.SliceHeader)(unsafe.Pointer(&subslice))
-
-	if hlp.Data < datap.Data {
-		panic(fmt.Errorf("subslice address (%d) is before data address (%d)", hlp.Data, datap.Data))
-	}
-	offset := hlp.Data - datap.Data
-
-	if offset > maxInt {
-		panic(fmt.Errorf("slice offset larger than int (%d)", offset))
-	}
-
-	intoffset := int(offset)
-
-	if intoffset > datap.Len {
-		panic(fmt.Errorf("slice offset (%d) is farther than data length (%d)", intoffset, datap.Len))
-	}
-
-	if intoffset+hlp.Len > datap.Len {
-		panic(fmt.Errorf("slice ends (%d+%d) is farther than data length (%d)", intoffset, hlp.Len, datap.Len))
-	}
-
-	return intoffset
-}
-
-func BytesRange(start []byte, end []byte) []byte {
-	if start == nil || end == nil {
-		panic("cannot call BytesRange with nil")
-	}
-	startp := (*reflect.SliceHeader)(unsafe.Pointer(&start))
-	endp := (*reflect.SliceHeader)(unsafe.Pointer(&end))
-
-	if startp.Data > endp.Data {
-		panic(fmt.Errorf("start pointer address (%d) is after end pointer address (%d)", startp.Data, endp.Data))
-	}
-
-	l := startp.Len
-	endLen := int(endp.Data-startp.Data) + endp.Len
-	if endLen > l {
-		l = endLen
-	}
-
-	if l > startp.Cap {
-		panic(fmt.Errorf("range length is larger than capacity"))
-	}
-
-	return start[:l]
-}
-
-func Stride(ptr unsafe.Pointer, size uintptr, offset int) unsafe.Pointer {
-	// TODO: replace with unsafe.Add when Go 1.17 is released
-	//   https://github.com/golang/go/issues/40481
-	return unsafe.Pointer(uintptr(ptr) + uintptr(int(size)*offset))
-}

internal/danger/danger_test.go

@@ -1,178 +0,0 @@
-package danger_test
-
-import (
-	"testing"
-	"unsafe"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"github.com/pelletier/go-toml/v2/internal/danger"
-)
-
-func TestSubsliceOffsetValid(t *testing.T) {
-	examples := []struct {
-		desc   string
-		test   func() ([]byte, []byte)
-		offset int
-	}{
-		{
-			desc: "simple",
-			test: func() ([]byte, []byte) {
-				data := []byte("hello")
-				return data, data[1:]
-			},
-			offset: 1,
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			d, s := e.test()
-			offset := danger.SubsliceOffset(d, s)
-			assert.Equal(t, e.offset, offset)
-		})
-	}
-}
-
-func TestSubsliceOffsetInvalid(t *testing.T) {
-	examples := []struct {
-		desc string
-		test func() ([]byte, []byte)
-	}{
-		{
-			desc: "unrelated arrays",
-			test: func() ([]byte, []byte) {
-				return []byte("one"), []byte("two")
-			},
-		},
-		{
-			desc: "slice starts before data",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[5:], full[1:]
-			},
-		},
-		{
-			desc: "slice starts after data",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[:3], full[5:]
-			},
-		},
-		{
-			desc: "slice ends after data",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[:5], full[3:8]
-			},
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			d, s := e.test()
-			require.Panics(t, func() {
-				danger.SubsliceOffset(d, s)
-			})
-		})
-	}
-}
-
-func TestStride(t *testing.T) {
-	a := []byte{1, 2, 3, 4}
-	x := &a[1]
-	n := (*byte)(danger.Stride(unsafe.Pointer(x), unsafe.Sizeof(byte(0)), 1))
-	require.Equal(t, &a[2], n)
-	n = (*byte)(danger.Stride(unsafe.Pointer(x), unsafe.Sizeof(byte(0)), -1))
-	require.Equal(t, &a[0], n)
-}
-
-func TestBytesRange(t *testing.T) {
-	type fn = func() ([]byte, []byte)
-	examples := []struct {
-		desc     string
-		test     fn
-		expected []byte
-	}{
-		{
-			desc: "simple",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[1:3], full[6:8]
-			},
-			expected: []byte("ello wo"),
-		},
-		{
-			desc: "full",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[0:1], full[len(full)-1:]
-			},
-			expected: []byte("hello world"),
-		},
-		{
-			desc: "end before start",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[len(full)-1:], full[0:1]
-			},
-		},
-		{
-			desc: "nils",
-			test: func() ([]byte, []byte) {
-				return nil, nil
-			},
-		},
-		{
-			desc: "nils start",
-			test: func() ([]byte, []byte) {
-				return nil, []byte("foo")
-			},
-		},
-		{
-			desc: "nils end",
-			test: func() ([]byte, []byte) {
-				return []byte("foo"), nil
-			},
-		},
-		{
-			desc: "start is end",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[1:3], full[1:3]
-			},
-			expected: []byte("el"),
-		},
-		{
-			desc: "end contained in start",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[1:7], full[2:4]
-			},
-			expected: []byte("ello w"),
-		},
-		{
-			desc: "different backing arrays",
-			test: func() ([]byte, []byte) {
-				one := []byte("hello world")
-				two := []byte("hello world")
-				return one, two
-			},
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			start, end := e.test()
-			if e.expected == nil {
-				require.Panics(t, func() {
-					danger.BytesRange(start, end)
-				})
-			} else {
-				res := danger.BytesRange(start, end)
-				require.Equal(t, e.expected, res)
-			}
-		})
-	}
-}

internal/danger/typeid.go

@@ -1,23 +0,0 @@
-package danger
-
-import (
-	"reflect"
-	"unsafe"
-)
-
-// typeID is used as key in encoder and decoder caches to enable using
-// the optimize runtime.mapaccess2_fast64 function instead of the more
-// expensive lookup if we were to use reflect.Type as map key.
-//
-// typeID holds the pointer to the reflect.Type value, which is unique
-// in the program.
-//
-// https://github.com/segmentio/encoding/blob/master/json/codec.go#L59-L61
-type TypeID unsafe.Pointer
-
-func MakeTypeID(t reflect.Type) TypeID {
-	// reflect.Type has the fields:
-	// typ unsafe.Pointer
-	// ptr unsafe.Pointer
-	return TypeID((*[2]unsafe.Pointer)(unsafe.Pointer(&t))[1])
-}

internal/imported_tests/marshal_imported_test.go

@@ -1,4 +1,4 @@
-package imported_tests
+package imported_tests //revive:disable:var-naming
 
 // Those tests have been imported from v1, but adjust to match the new
 // defaults of v2.
@@ -9,7 +9,7 @@ import (
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func TestDocMarshal(t *testing.T) {
@@ -21,12 +21,12 @@ func TestDocMarshal(t *testing.T) {
 		Subdocs     testDocSubs       `toml:"subdoc"`
 		Basics      testDocBasics     `toml:"basic"`
 		SubDocList  []testSubDoc      `toml:"subdoclist"`
-		err         int               `toml:"shouldntBeHere"`
+		err         int               `toml:"shouldntBeHere"` //nolint:unused
 		unexported  int               `toml:"shouldntBeHere"`
 		Unexported2 int               `toml:"-"`
 	}
 
-	var docData = testDoc{
+	docData := testDoc{
 		Title:       "TOML Marshal Testing",
 		unexported:  0,
 		Unexported2: 0,
@@ -107,13 +107,13 @@ name = 'List.Second'
 `
 
 	result, err := toml.Marshal(docData)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, marshalTestToml, string(result))
+	assert.Equal(t, marshalTestToml, string(result))
 }
 
 func TestBasicMarshalQuotedKey(t *testing.T) {
 	result, err := toml.Marshal(quotedKeyMarshalTestData)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	expected := `'Z.string-àéù' = 'Hello'
 'Yfloat-𝟘' = 3.5
@@ -128,8 +128,7 @@ String2 = 'Two'
 String2 = 'Three'
 `
 
-	require.Equal(t, string(expected), string(result))
+	assert.Equal(t, expected, string(result))
-
 }
 
 func TestEmptyMarshal(t *testing.T) {
@@ -153,7 +152,7 @@ func TestEmptyMarshal(t *testing.T) {
 		Map:        map[string]string{},
 	}
 	result, err := toml.Marshal(doc)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	expected := `title = 'Placeholder'
 bool = false
@@ -164,7 +163,7 @@ stringlist = []
 [map]
 `
 
-	require.Equal(t, string(expected), string(result))
+	assert.Equal(t, expected, string(result))
 }
 
 type textMarshaler struct {
@@ -187,13 +186,13 @@ func TestTextMarshaler(t *testing.T) {
 	t.Run("at root", func(t *testing.T) {
 		_, err := toml.Marshal(m)
 		// in v2 we do not allow TextMarshaler at root
-		require.Error(t, err)
+		assert.Error(t, err)
 	})
 
 	t.Run("leaf", func(t *testing.T) {
 		res, err := toml.Marshal(wrap{m})
-		require.NoError(t, err)
+		assert.NoError(t, err)
 
-		require.Equal(t, "TM = 'Sally Fields'\n", string(res))
+		assert.Equal(t, "TM = 'Sally Fields'\n", string(res))
 	})
 }

internal/imported_tests/unmarshal_imported_test.go

@@ -1,4 +1,4 @@
-package imported_tests
+package imported_tests //revive:disable:var-naming
 
 // Those tests were imported directly from go-toml v1
 // https://raw.githubusercontent.com/pelletier/go-toml/a2e52561804c6cd9392ebf0048ca64fe4af67a43/marshal_test.go
@@ -16,8 +16,7 @@ import (
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/assert"
+	"github.com/pelletier/go-toml/v2/internal/assert"
-	"github.com/stretchr/testify/require"
 )
 
 type basicMarshalTestStruct struct {
@@ -123,7 +122,7 @@ func TestInterface(t *testing.T) {
 	var config Conf
 	config.Inter = &NestedStruct{}
 	err := toml.Unmarshal(doc, &config)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	expected := Conf{
 		Name: "rui",
 		Age:  18,
@@ -139,8 +138,8 @@ func TestInterface(t *testing.T) {
 func TestBasicUnmarshal(t *testing.T) {
 	result := basicMarshalTestStruct{}
 	err := toml.Unmarshal(basicTestToml, &result)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, basicTestData, result)
+	assert.Equal(t, basicTestData, result)
 }
 
 type quotedKeyMarshalTestStruct struct {
@@ -150,9 +149,6 @@ type quotedKeyMarshalTestStruct struct {
 	SubList []basicMarshalTestSubStruct `toml:"W.sublist-𝟘"`
 }
 
-// TODO: Remove nolint once var is used by a test
-//
-//nolint:deadcode,unused,varcheck
 var quotedKeyMarshalTestData = quotedKeyMarshalTestStruct{
 	String:  "Hello",
 	Float:   3.5,
@@ -162,7 +158,7 @@ var quotedKeyMarshalTestData = quotedKeyMarshalTestStruct{
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var quotedKeyMarshalTestToml = []byte(`"Yfloat-𝟘" = 3.5
 "Z.string-àéù" = "Hello"
 
@@ -184,11 +180,12 @@ type testDoc struct {
 	Subdocs     testDocSubs       `toml:"subdoc"`
 	Basics      testDocBasics     `toml:"basic"`
 	SubDocList  []testSubDoc      `toml:"subdoclist"`
-	err         int               `toml:"shouldntBeHere"` // nolint:structcheck,unused
+	err         int               `toml:"shouldntBeHere"` //nolint:unused
 	unexported  int               `toml:"shouldntBeHere"`
 	Unexported2 int               `toml:"-"`
 }
 
+//nolint:unused
 type testMapDoc struct {
 	Title    string            `toml:"title"`
 	BasicMap map[string]string `toml:"basic_map"`
@@ -275,7 +272,7 @@ var docData = testDoc{
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var mapTestDoc = testMapDoc{
 	Title: "TOML Marshal Testing",
 	BasicMap: map[string]string{
@@ -300,7 +297,7 @@ func TestDocUnmarshal(t *testing.T) {
 	result := testDoc{}
 	err := toml.Unmarshal(marshalTestToml, &result)
 	expected := docData
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, result)
 }
 
@@ -340,7 +337,7 @@ shouldntBeHere = 2
 func TestUnexportedUnmarshal(t *testing.T) {
 	result := unexportedMarshalTestStruct{}
 	err := toml.Unmarshal(unexportedTestToml, &result)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, unexportedTestData, result)
 }
 
@@ -456,7 +453,7 @@ func TestEmptytomlUnmarshal(t *testing.T) {
 
 	result := emptyMarshalTestStruct{}
 	err := toml.Unmarshal(emptyTestToml, &result)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, emptyTestData, result)
 }
 
@@ -504,7 +501,7 @@ Str = "Hello"
 func TestPointerUnmarshal(t *testing.T) {
 	result := pointerMarshalTestStruct{}
 	err := toml.Unmarshal(pointerTestToml, &result)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, pointerTestData, result)
 }
 
@@ -540,35 +537,39 @@ StringPtr = [["Three", "Four"]]
 func TestNestedUnmarshal(t *testing.T) {
 	result := nestedMarshalTestStruct{}
 	err := toml.Unmarshal(nestedTestToml, &result)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, nestedTestData, result)
 }
 
+//nolint:unused
 type customMarshalerParent struct {
 	Self    customMarshaler   `toml:"me"`
 	Friends []customMarshaler `toml:"friends"`
 }
 
+//nolint:unused
 type customMarshaler struct {
 	FirstName string
 	LastName  string
 }
 
+//nolint:unused
 func (c customMarshaler) MarshalTOML() ([]byte, error) {
 	fullName := fmt.Sprintf("%s %s", c.FirstName, c.LastName)
 	return []byte(fullName), nil
 }
 
+//nolint:unused
 var customMarshalerData = customMarshaler{FirstName: "Sally", LastName: "Fields"}
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var customMarshalerToml = []byte(`Sally Fields`)
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var nestedCustomMarshalerData = customMarshalerParent{
 	Self:    customMarshaler{FirstName: "Maiku", LastName: "Suteda"},
 	Friends: []customMarshaler{customMarshalerData},
@@ -576,7 +577,7 @@ var nestedCustomMarshalerData = customMarshalerParent{
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var nestedCustomMarshalerToml = []byte(`friends = ["Sally Fields"]
 me = "Maiku Suteda"
 `)
@@ -591,7 +592,7 @@ func (x *IntOrString) MarshalTOML() ([]byte, error) {
 	s := *(*string)(x)
 	_, err := strconv.Atoi(s)
 	if err != nil {
-		return []byte(fmt.Sprintf(`"%s"`, s)), nil
+		return []byte(fmt.Sprintf(`"%s"`, s)), nil //nolint:nilerr
 	}
 	return []byte(s), nil
 }
@@ -663,7 +664,7 @@ func (m *textPointerMarshaler) MarshalText() ([]byte, error) {
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var commentTestToml = []byte(`
 # it's a comment on type
 [postgres]
@@ -688,6 +689,7 @@ var commentTestToml = []byte(`
     My = "Baar"
 `)
 
+//nolint:unused
 type mapsTestStruct struct {
 	Simple map[string]string
 	Paths  map[string]string
@@ -701,7 +703,7 @@ type mapsTestStruct struct {
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var mapsTestData = mapsTestStruct{
 	Simple: map[string]string{
 		"one plus one": "two",
@@ -725,7 +727,7 @@ var mapsTestData = mapsTestStruct{
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var mapsTestToml = []byte(`
 [Other]
   "testing" = 3.9999
@@ -748,7 +750,7 @@ var mapsTestToml = []byte(`
 
 // TODO: Remove nolint once type is used by a test
 //
-//nolint:deadcode,unused
+//nolint:unused
 type structArrayNoTag struct {
 	A struct {
 		B []int64
@@ -758,7 +760,7 @@ type structArrayNoTag struct {
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var customTagTestToml = []byte(`
 [postgres]
   password = "bvalue"
@@ -773,7 +775,7 @@ var customTagTestToml = []byte(`
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var customCommentTagTestToml = []byte(`
 # db connection
 [postgres]
@@ -787,7 +789,7 @@ var customCommentTagTestToml = []byte(`
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var customCommentedTagTestToml = []byte(`
 [postgres]
   # password = "bvalue"
@@ -834,7 +836,7 @@ func TestUnmarshalTabInStringAndQuotedKey(t *testing.T) {
 		t.Run(test.desc, func(t *testing.T) {
 			result := Test{}
 			err := toml.Unmarshal(test.input, &result)
-			require.NoError(t, err)
+			assert.NoError(t, err)
 			assert.Equal(t, test.expected, result)
 		})
 	}
@@ -842,7 +844,7 @@ func TestUnmarshalTabInStringAndQuotedKey(t *testing.T) {
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var customMultilineTagTestToml = []byte(`int_slice = [
   1,
   2,
@@ -852,7 +854,7 @@ var customMultilineTagTestToml = []byte(`int_slice = [
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var testDocBasicToml = []byte(`
 [document]
   bool_val = true
@@ -863,16 +865,12 @@ var testDocBasicToml = []byte(`
   uint_val = 5001
 `)
 
-// TODO: Remove nolint once type is used by a test
+//nolint:unused
-//
-//nolint:deadcode
 type testDocCustomTag struct {
 	Doc testDocBasicsCustomTag `file:"document"`
 }
 
-// TODO: Remove nolint once type is used by a test
+//nolint:unused
-//
-//nolint:deadcode
 type testDocBasicsCustomTag struct {
 	Bool       bool      `file:"bool_val"`
 	Date       time.Time `file:"date_val"`
@@ -883,9 +881,7 @@ type testDocBasicsCustomTag struct {
 	unexported int       `file:"shouldntBeHere"`
 }
 
-// TODO: Remove nolint once var is used by a test
+//nolint:unused
-//
-//nolint:deadcode,varcheck
 var testDocCustomTagData = testDocCustomTag{
 	Doc: testDocBasicsCustomTag{
 		Bool:       true,
@@ -963,7 +959,7 @@ func TestUnmarshalTypeTableHeader(t *testing.T) {
 	}
 
 	expected := map[header]map[string]int{
-		"test": map[string]int{"a": 1},
+		"test": {"a": 1},
 	}
 
 	if !reflect.DeepEqual(result, expected) {
@@ -988,13 +984,13 @@ func TestUnmarshalInvalidPointerKind(t *testing.T) {
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused
+//nolint:unused
 type testDuration struct {
 	Nanosec   time.Duration  `toml:"nanosec"`
 	Microsec1 time.Duration  `toml:"microsec1"`
 	Microsec2 *time.Duration `toml:"microsec2"`
 	Millisec  time.Duration  `toml:"millisec"`
-	Sec       time.Duration  `toml:"sec"`
+	Sec       time.Duration  `toml:"sec"` //nolint:staticcheck
 	Min       time.Duration  `toml:"min"`
 	Hour      time.Duration  `toml:"hour"`
 	Mixed     time.Duration  `toml:"mixed"`
@@ -1003,7 +999,7 @@ type testDuration struct {
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var testDurationToml = []byte(`
 nanosec = "1ns"
 microsec1 = "1us"
@@ -1018,7 +1014,7 @@ a_string = "15s"
 
 // TODO: Remove nolint once var is used by a test
 //
-//nolint:deadcode,unused,varcheck
+//nolint:unused
 var testDurationToml2 = []byte(`a_string = "15s"
 hour = "1h0m0s"
 microsec1 = "1µs"
@@ -1032,15 +1028,14 @@ sec = "1s"
 
 // TODO: Remove nolint once type is used by a test
 //
-//nolint:deadcode,unused
+//nolint:unused
 type testBadDuration struct {
 	Val time.Duration `toml:"val"`
 }
 
 // TODO: add back camelCase test
-var testCamelCaseKeyToml = []byte(`fooBar = 10`) //nolint:unused
+var testCamelCaseKeyToml = []byte(`fooBar = 10`)
 
-//nolint:unused
 func TestUnmarshalCamelCaseKey(t *testing.T) {
 	t.Skipf("don't know if it is a good idea to automatically convert like that yet")
 	var x struct {
@@ -1059,7 +1054,7 @@ func TestUnmarshalCamelCaseKey(t *testing.T) {
 
 func TestUnmarshalNegativeUint(t *testing.T) {
 	t.Skipf("not sure if we this should always error")
-	type check struct{ U uint } // nolint:unused
+	type check struct{ U uint }
 	err := toml.Unmarshal([]byte("U = -1"), &check{})
 	assert.Error(t, err)
 }
@@ -1085,16 +1080,12 @@ func TestUnmarshalCheckConversionFloatInt(t *testing.T) {
 			desc:  "int",
 			input: `I = 1e300`,
 		},
-		{
-			desc:  "float",
-			input: `F = 9223372036854775806`,
-		},
 	}
 
 	for _, test := range testCases {
 		t.Run(test.desc, func(t *testing.T) {
 			err := toml.Unmarshal([]byte(test.input), &conversionCheck{})
-			require.Error(t, err)
+			assert.Error(t, err)
 		})
 	}
 }
@@ -1129,7 +1120,7 @@ func TestUnmarshalOverflow(t *testing.T) {
 	for _, test := range testCases {
 		t.Run(test.desc, func(t *testing.T) {
 			err := toml.Unmarshal([]byte(test.input), &overflow{})
-			require.Error(t, err)
+			assert.Error(t, err)
 		})
 	}
 }
@@ -1540,7 +1531,7 @@ func TestUnmarshalLocalDateTime(t *testing.T) {
 	}
 
 	for i, example := range examples {
-		doc := fmt.Sprintf(`date = %s`, example.in)
+		doc := "date = " + example.in
 
 		t.Run(fmt.Sprintf("ToLocalDateTime_%d_%s", i, example.name), func(t *testing.T) {
 			type dateStruct struct {
@@ -1626,7 +1617,7 @@ func TestUnmarshalLocalTime(t *testing.T) {
 	}
 
 	for i, example := range examples {
-		doc := fmt.Sprintf(`Time = %s`, example.in)
+		doc := "Time = " + example.in
 
 		t.Run(fmt.Sprintf("ToLocalTime_%d_%s", i, example.name), func(t *testing.T) {
 			type dateStruct struct {
@@ -1749,7 +1740,7 @@ Age = 23
 	}
 	actual := OuterStruct{}
 	err := toml.Unmarshal(doc, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, actual)
 }
 
@@ -1834,7 +1825,7 @@ InnerField = "After4"
 	}
 
 	err := toml.Unmarshal(doc, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, actual)
 }
 
@@ -1883,7 +1874,7 @@ type arrayTooSmallStruct struct {
 func TestUnmarshalSlice(t *testing.T) {
 	var actual sliceStruct
 	err := toml.Unmarshal(sliceTomlDemo, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	expected := sliceStruct{
 		Slice:          []string{"Howdy", "Hey There"},
 		SlicePtr:       &[]string{"Howdy", "Hey There"},
@@ -1911,19 +1902,12 @@ func TestUnmarshalMixedTypeSlice(t *testing.T) {
 		ArrayField []interface{}
 	}
 
-	//doc := []byte(`ArrayField = [3.14,100,true,"hello world",{Field = "inner1"},[{Field = "inner2"},{Field = "inner3"}]]
-	//`)
-
 	doc := []byte(`ArrayField = [{Field = "inner1"},[{Field = "inner2"},{Field = "inner3"}]]
 `)
 
 	actual := TestStruct{}
 	expected := TestStruct{
 		ArrayField: []interface{}{
-			//3.14,
-			//int64(100),
-			//true,
-			//"hello world",
 			map[string]interface{}{
 				"Field": "inner1",
 			},
@@ -1934,7 +1918,7 @@ func TestUnmarshalMixedTypeSlice(t *testing.T) {
 		},
 	}
 	err := toml.Unmarshal(doc, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, actual)
 }
 
@@ -1943,7 +1927,7 @@ func TestUnmarshalArray(t *testing.T) {
 
 	var actual arrayStruct
 	err = toml.Unmarshal(sliceTomlDemo, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	expected := arrayStruct{
 		Slice:          [4]string{"Howdy", "Hey There"},
@@ -2002,11 +1986,17 @@ func TestDecoderStrict(t *testing.T) {
 	}
 
 	err := strictDecoder(input).Decode(&doc)
-	require.Error(t, err)
+	assert.Error(t, err)
-	require.IsType(t, &toml.StrictMissingError{}, err)
-	se := err.(*toml.StrictMissingError)
 
-	keys := []toml.Key{}
+	assert.Equal(t,
+		reflect.TypeOf(err), reflect.TypeOf(&toml.StrictMissingError{}),
+		"Expected a *toml.StrictMissingError, got: %v", reflect.TypeOf(err),
+	)
+
+	var se *toml.StrictMissingError
+	assert.True(t, errors.As(err, &se))
+
+	keys := make([]toml.Key, 0, len(se.Errors))
 
 	for _, e := range se.Errors {
 		keys = append(keys, e.Key())
@@ -2019,13 +2009,14 @@ func TestDecoderStrict(t *testing.T) {
 		{"undecoded", "array"},
 	}
 
-	require.Equal(t, expectedKeys, keys)
+	assert.Equal(t, expectedKeys, keys)
 
 	err = decoder(input).Decode(&doc)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	var m map[string]interface{}
 	err = decoder(input).Decode(&m)
+	assert.NoError(t, err)
 }
 
 func TestDecoderStrictValid(t *testing.T) {
@@ -2040,7 +2031,7 @@ func TestDecoderStrictValid(t *testing.T) {
 	}
 
 	err := strictDecoder(input).Decode(&doc)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 }
 
 type docUnmarshalTOML struct {
@@ -2062,19 +2053,6 @@ func (d *docUnmarshalTOML) UnmarshalTOML(i interface{}) error {
 	return nil
 }
 
-func TestDecoderStrictCustomUnmarshal(t *testing.T) {
-	t.Skip()
-	//input := `key = "ok"`
-	//var doc docUnmarshalTOML
-	//err := NewDecoder(bytes.NewReader([]byte(input))).Strict(true).Decode(&doc)
-	//if err != nil {
-	//	t.Fatal("unexpected error:", err)
-	//}
-	//if doc.Decoded.Key != "ok" {
-	//	t.Errorf("Bad unmarshal: expected ok, got %v", doc.Decoded.Key)
-	//}
-}
-
 type parent struct {
 	Doc        docUnmarshalTOML
 	DocPointer *docUnmarshalTOML
@@ -2091,7 +2069,7 @@ func TestCustomUnmarshal(t *testing.T) {
 
 	var d parent
 	err := toml.Unmarshal([]byte(input), &d)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, "ok1", d.Doc.Decoded.Key)
 	assert.Equal(t, "ok2", d.DocPointer.Decoded.Key)
 }
@@ -2157,7 +2135,7 @@ Int = 21
 Float = 2.0
 `
 	err := toml.Unmarshal([]byte(input), &doc)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, 12, doc.UnixTime.Value)
 	assert.Equal(t, 42, doc.Version.Value)
 	assert.Equal(t, 1, doc.Bool.Value)
@@ -2227,7 +2205,10 @@ func TestUnmarshalEmptyInterface(t *testing.T) {
 	if err != nil {
 		t.Fatal(err)
 	}
-	require.IsType(t, map[string]interface{}{}, v)
+	assert.Equal(t,
+		reflect.TypeOf(map[string]interface{}{}), reflect.TypeOf(v),
+		"Expected map[string]interface{}{} type, got: %v", reflect.TypeOf(v),
+	)
 
 	x := v.(map[string]interface{})
 	assert.Equal(t, "pelletier", x["User"])
@@ -2275,12 +2256,12 @@ type Custom struct {
 	v string
 }
 
-func (c *Custom) UnmarshalTOML(v interface{}) error {
+func (c *Custom) UnmarshalTOML(interface{}) error {
 	c.v = "called"
 	return nil
 }
 
-func TestGithubIssue431(t *testing.T) {
+func TestGitHubIssue431(t *testing.T) {
 	doc := `key = "value"`
 	var c Config
 	if err := toml.Unmarshal([]byte(doc), &c); err != nil {
@@ -2300,14 +2281,14 @@ type durationString struct {
 	time.Duration
 }
 
-func (d *durationString) UnmarshalTOML(v interface{}) error {
+func (d *durationString) UnmarshalTOML(interface{}) error {
 	d.Duration = 10 * time.Second
 	return nil
 }
 
 type config437Error struct{}
 
-func (e *config437Error) UnmarshalTOML(v interface{}) error {
+func (e *config437Error) UnmarshalTOML(interface{}) error {
 	return errors.New("expected")
 }
 
@@ -2318,7 +2299,7 @@ type config437 struct {
 	} `toml:"HTTP"`
 }
 
-func TestGithubIssue437(t *testing.T) {
+func TestGitHubIssue437(t *testing.T) {
 	t.Skipf("unmarshalTOML not implemented")
 	src := `
 [HTTP]

internal/testsuite/add.go

@@ -3,17 +3,18 @@ package testsuite
 import (
 	"fmt"
 	"math"
+	"strconv"
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
 )
 
 // addTag adds JSON tags to a data structure as expected by toml-test.
-func addTag(key string, tomlData interface{}) interface{} {
+func addTag(tomlData interface{}) interface{} {
 	// Switch on the data type.
 	switch orig := tomlData.(type) {
 	default:
-		//return map[string]interface{}{}
+		// return map[string]interface{}{}
 		panic(fmt.Sprintf("Unknown type: %T", tomlData))
 
 	// A table: we don't need to add any tags, just recurse for every table
@@ -21,7 +22,7 @@ func addTag(key string, tomlData interface{}) interface{} {
 	case map[string]interface{}:
 		typed := make(map[string]interface{}, len(orig))
 		for k, v := range orig {
-			typed[k] = addTag(k, v)
+			typed[k] = addTag(v)
 		}
 		return typed
 
@@ -30,13 +31,13 @@ func addTag(key string, tomlData interface{}) interface{} {
 	case []map[string]interface{}:
 		typed := make([]map[string]interface{}, len(orig))
 		for i, v := range orig {
-			typed[i] = addTag("", v).(map[string]interface{})
+			typed[i] = addTag(v).(map[string]interface{})
 		}
 		return typed
 	case []interface{}:
 		typed := make([]interface{}, len(orig))
 		for i, v := range orig {
-			typed[i] = addTag("", v)
+			typed[i] = addTag(v)
 		}
 		return typed
 
@@ -52,11 +53,11 @@ func addTag(key string, tomlData interface{}) interface{} {
 
 	// Tag primitive values: bool, string, int, and float64.
 	case bool:
-		return tag("bool", fmt.Sprintf("%v", orig))
+		return tag("bool", strconv.FormatBool(orig))
 	case string:
 		return tag("string", orig)
 	case int64:
-		return tag("integer", fmt.Sprintf("%d", orig))
+		return tag("integer", strconv.FormatInt(orig, 10))
 	case float64:
 		// Special case for nan since NaN == NaN is false.
 		if math.IsNaN(orig) {

internal/testsuite/json.go

@@ -9,6 +9,7 @@ import (
 )
 
 func CmpJSON(t *testing.T, key string, want, have interface{}) {
+	t.Helper()
 	switch w := want.(type) {
 	case map[string]interface{}:
 		cmpJSONMaps(t, key, w, have)
@@ -22,6 +23,7 @@ func CmpJSON(t *testing.T, key string, want, have interface{}) {
 }
 
 func cmpJSONMaps(t *testing.T, key string, want map[string]interface{}, have interface{}) {
+	t.Helper()
 	haveMap, ok := have.(map[string]interface{})
 	if !ok {
 		mismatch(t, key, "table", want, haveMap)
@@ -61,6 +63,7 @@ func cmpJSONMaps(t *testing.T, key string, want map[string]interface{}, have int
 }
 
 func cmpJSONArrays(t *testing.T, key string, want, have interface{}) {
+	t.Helper()
 	wantSlice, ok := want.([]interface{})
 	if !ok {
 		panic(fmt.Sprintf("'value' should be a JSON array when 'type=array', but it is a %T", want))
@@ -83,6 +86,7 @@ func cmpJSONArrays(t *testing.T, key string, want, have interface{}) {
 }
 
 func cmpJSONValues(t *testing.T, key string, want, have map[string]interface{}) {
+	t.Helper()
 	wantType, ok := want["type"].(string)
 	if !ok {
 		panic(fmt.Sprintf("'type' should be a string, but it is a %T", want["type"]))
@@ -126,6 +130,7 @@ func cmpJSONValues(t *testing.T, key string, want, have map[string]interface{})
 }
 
 func cmpAsStrings(t *testing.T, key string, want, have string) {
+	t.Helper()
 	if want != have {
 		t.Fatalf("Values for key '%s' don't match:\n"+
 			"  Expected:     %s\n"+
@@ -135,6 +140,7 @@ func cmpAsStrings(t *testing.T, key string, want, have string) {
 }
 
 func cmpFloats(t *testing.T, key string, want, have string) {
+	t.Helper()
 	// Special case for NaN, since NaN != NaN.
 	if strings.HasSuffix(want, "nan") || strings.HasSuffix(have, "nan") {
 		if want != have {
@@ -177,6 +183,7 @@ var layouts = map[string]string{
 }
 
 func cmpAsDatetimes(t *testing.T, key string, kind, want, have string) {
+	t.Helper()
 	layout, ok := layouts[kind]
 	if !ok {
 		panic("should never happen")
@@ -200,15 +207,6 @@ func cmpAsDatetimes(t *testing.T, key string, kind, want, have string) {
 	}
 }
 
-func cmpAsDatetimesLocal(t *testing.T, key string, want, have string) {
-	if datetimeRepl.Replace(want) != datetimeRepl.Replace(have) {
-		t.Fatalf("Values for key '%s' don't match:\n"+
-			"  Expected:     %v\n"+
-			"  Your encoder: %v",
-			key, want, have)
-	}
-}
-
 func kjoin(old, key string) string {
 	if len(old) == 0 {
 		return key
@@ -230,6 +228,7 @@ func isValue(m map[string]interface{}) bool {
 }
 
 func mismatch(t *testing.T, key string, wantType string, want, have interface{}) {
+	t.Helper()
 	t.Fatalf("Key '%s' is not an %s but %[4]T:\n"+
 		"  Expected:     %#[3]v\n"+
 		"  Your encoder: %#[4]v",
@@ -237,8 +236,9 @@ func mismatch(t *testing.T, key string, wantType string, want, have interface{})
 }
 
 func valMismatch(t *testing.T, key string, wantType, haveType string, want, have interface{}) {
+	t.Helper()
 	t.Fatalf("Key '%s' is not an %s but %s:\n"+
 		"  Expected:     %#[3]v\n"+
 		"  Your encoder: %#[4]v",
-		key, wantType, want, have)
+		key, wantType, haveType, want, have)
 }

internal/testsuite/parser.go

@@ -1,69 +0,0 @@
-package testsuite
-
-import (
-	"bytes"
-	"encoding/json"
-	"fmt"
-
-	"github.com/pelletier/go-toml/v2"
-)
-
-type parser struct{}
-
-func (p parser) Decode(input string) (output string, outputIsError bool, retErr error) {
-	defer func() {
-		if r := recover(); r != nil {
-			switch rr := r.(type) {
-			case error:
-				retErr = rr
-			default:
-				retErr = fmt.Errorf("%s", rr)
-			}
-		}
-	}()
-
-	var v interface{}
-
-	if err := toml.Unmarshal([]byte(input), &v); err != nil {
-		return err.Error(), true, nil
-	}
-
-	j, err := json.MarshalIndent(addTag("", v), "", "  ")
-	if err != nil {
-		return "", false, retErr
-	}
-
-	return string(j), false, retErr
-}
-
-func (p parser) Encode(input string) (output string, outputIsError bool, retErr error) {
-	defer func() {
-		if r := recover(); r != nil {
-			switch rr := r.(type) {
-			case error:
-				retErr = rr
-			default:
-				retErr = fmt.Errorf("%s", rr)
-			}
-		}
-	}()
-
-	var tmp interface{}
-	err := json.Unmarshal([]byte(input), &tmp)
-	if err != nil {
-		return "", false, err
-	}
-
-	rm, err := rmTag(tmp)
-	if err != nil {
-		return err.Error(), true, retErr
-	}
-
-	buf := new(bytes.Buffer)
-	err = toml.NewEncoder(buf).Encode(rm)
-	if err != nil {
-		return err.Error(), true, retErr
-	}
-
-	return buf.String(), false, retErr
-}

internal/testsuite/rm.go

@@ -4,10 +4,12 @@ import (
 	"fmt"
 	"strconv"
 	"time"
+
+	"github.com/pelletier/go-toml/v2"
 )
 
 // Remove JSON tags to a data structure as returned by toml-test.
-func rmTag(typedJson interface{}) (interface{}, error) {
+func rmTag(typedJSON interface{}) (interface{}, error) {
 	// Check if key is in the table m.
 	in := func(key string, m map[string]interface{}) bool {
 		_, ok := m[key]
@@ -15,8 +17,7 @@ func rmTag(typedJson interface{}) (interface{}, error) {
 	}
 
 	// Switch on the data type.
-	switch v := typedJson.(type) {
+	switch v := typedJSON.(type) {
-
 	// Object: this can either be a TOML table or a primitive with tags.
 	case map[string]interface{}:
 		// This value represents a primitive: remove the tags and return just
@@ -40,7 +41,7 @@ func rmTag(typedJson interface{}) (interface{}, error) {
 		}
 		return m, nil
 
-	// Array: remove tags from all itenm.
+	// Array: remove tags from all items.
 	case []interface{}:
 		a := make([]interface{}, len(v))
 		for i := range v {
@@ -54,7 +55,7 @@ func rmTag(typedJson interface{}) (interface{}, error) {
 	}
 
 	// The top level must be an object or array.
-	return nil, fmt.Errorf("unrecognized JSON format '%T'", typedJson)
+	return nil, fmt.Errorf("unrecognized JSON format '%T'", typedJSON)
 }
 
 // Return a primitive: read the "type" and convert the "value" to that.
@@ -76,14 +77,31 @@ func untag(typed map[string]interface{}) (interface{}, error) {
 			return nil, fmt.Errorf("untag: %w", err)
 		}
 		return f, nil
+
+		// toml.LocalDate{Year:2020, Month:12, Day:12}
 	case "datetime":
-		return parseTime(v, "2006-01-02T15:04:05.999999999Z07:00", false)
+		return time.Parse("2006-01-02T15:04:05.999999999Z07:00", v)
 	case "datetime-local":
-		return parseTime(v, "2006-01-02T15:04:05.999999999", true)
+		var t toml.LocalDateTime
+		err := t.UnmarshalText([]byte(v))
+		if err != nil {
+			return nil, fmt.Errorf("untag: %w", err)
+		}
+		return t, nil
 	case "date-local":
-		return parseTime(v, "2006-01-02", true)
+		var t toml.LocalDate
+		err := t.UnmarshalText([]byte(v))
+		if err != nil {
+			return nil, fmt.Errorf("untag: %w", err)
+		}
+		return t, nil
 	case "time-local":
-		return parseTime(v, "15:04:05.999999999", true)
+		var t toml.LocalTime
+		err := t.UnmarshalText([]byte(v))
+		if err != nil {
+			return nil, fmt.Errorf("untag: %w", err)
+		}
+		return t, nil
 	case "bool":
 		switch v {
 		case "true":
@@ -96,15 +114,3 @@ func untag(typed map[string]interface{}) (interface{}, error) {
 
 	return nil, fmt.Errorf("untag: unrecognized tag type %q", t)
 }
-
-func parseTime(v, format string, local bool) (t time.Time, err error) {
-	if local {
-		t, err = time.ParseInLocation(format, v, time.Local)
-	} else {
-		t, err = time.Parse(format, v)
-	}
-	if err != nil {
-		return time.Time{}, fmt.Errorf("Could not parse %q as a datetime: %w", v, err)
-	}
-	return t, nil
-}

internal/testsuite/testsuite.go

@@ -10,7 +10,7 @@ import (
 	"github.com/pelletier/go-toml/v2"
 )
 
-// Marshal is a helpfer function for calling toml.Marshal
+// Marshal is a helper function for calling toml.Marshal
 //
 // Only needed to avoid package import loops.
 func Marshal(v interface{}) ([]byte, error) {
@@ -27,7 +27,7 @@ func Unmarshal(data []byte, v interface{}) error {
 // ValueToTaggedJSON takes a data structure and returns the tagged JSON
 // representation.
 func ValueToTaggedJSON(doc interface{}) ([]byte, error) {
-	return json.MarshalIndent(addTag("", doc), "", "  ")
+	return json.MarshalIndent(addTag(doc), "", "  ")
 }
 
 // DecodeStdin is a helper function for the toml-test binary interface.  TOML input
@@ -37,14 +37,32 @@ func DecodeStdin() error {
 	var decoded map[string]interface{}
 
 	if err := toml.NewDecoder(os.Stdin).Decode(&decoded); err != nil {
-		return fmt.Errorf("Error decoding TOML: %s", err)
+		return fmt.Errorf("error decoding TOML: %w", err)
 	}
 
 	j := json.NewEncoder(os.Stdout)
 	j.SetIndent("", "  ")
-	if err := j.Encode(addTag("", decoded)); err != nil {
+	if err := j.Encode(addTag(decoded)); err != nil {
-		return fmt.Errorf("Error encoding JSON: %s", err)
+		return fmt.Errorf("error encoding JSON: %w", err)
 	}
 
 	return nil
 }
+
+// EncodeStdin is a helper function for the toml-test binary interface.  Tagged
+// JSON is read from STDIN and a resulting TOML representation is written to
+// STDOUT.
+func EncodeStdin() error {
+	var j interface{}
+	err := json.NewDecoder(os.Stdin).Decode(&j)
+	if err != nil {
+		return err
+	}
+
+	rm, err := rmTag(j)
+	if err != nil {
+		return fmt.Errorf("removing tags: %w", err)
+	}
+
+	return toml.NewEncoder(os.Stdout).Encode(rm)
+}

internal/tracker/key.go

@@ -1,8 +1,6 @@
 package tracker
 
-import (
+import "github.com/pelletier/go-toml/v2/unstable"
-	"github.com/pelletier/go-toml/v2/internal/ast"
-)
 
 // KeyTracker is a tracker that keeps track of the current Key as the AST is
 // walked.
@@ -11,19 +9,19 @@ type KeyTracker struct {
 }
 
 // UpdateTable sets the state of the tracker with the AST table node.
-func (t *KeyTracker) UpdateTable(node *ast.Node) {
+func (t *KeyTracker) UpdateTable(node *unstable.Node) {
 	t.reset()
 	t.Push(node)
 }
 
 // UpdateArrayTable sets the state of the tracker with the AST array table node.
-func (t *KeyTracker) UpdateArrayTable(node *ast.Node) {
+func (t *KeyTracker) UpdateArrayTable(node *unstable.Node) {
 	t.reset()
 	t.Push(node)
 }
 
 // Push the given key on the stack.
-func (t *KeyTracker) Push(node *ast.Node) {
+func (t *KeyTracker) Push(node *unstable.Node) {
 	it := node.Key()
 	for it.Next() {
 		t.k = append(t.k, string(it.Node().Data))
@@ -31,14 +29,14 @@ func (t *KeyTracker) Push(node *ast.Node) {
 }
 
 // Pop key from stack.
-func (t *KeyTracker) Pop(node *ast.Node) {
+func (t *KeyTracker) Pop(node *unstable.Node) {
 	it := node.Key()
 	for it.Next() {
 		t.k = t.k[:len(t.k)-1]
 	}
 }
 
-// Key returns the current key
+// Key returns the current key.
 func (t *KeyTracker) Key() []string {
 	k := make([]string, len(t.k))
 	copy(k, t.k)

internal/tracker/seen.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"sync"
 
-	"github.com/pelletier/go-toml/v2/internal/ast"
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 type keyKind uint8
@@ -57,7 +57,11 @@ type SeenTracker struct {
 	currentIdx int
 }
 
-var pool sync.Pool
+var pool = sync.Pool{
+	New: func() interface{} {
+		return &SeenTracker{}
+	},
+}
 
 func (s *SeenTracker) reset() {
 	// Always contains a root element at index 0.
@@ -149,24 +153,25 @@ func (s *SeenTracker) setExplicitFlag(parentIdx int) {
 
 // CheckExpression takes a top-level node and checks that it does not contain
 // keys that have been seen in previous calls, and validates that types are
-// consistent.
+// consistent. It returns true if it is the first time this node's key is seen.
-func (s *SeenTracker) CheckExpression(node *ast.Node) error {
+// Useful to clear array tables on first use.
+func (s *SeenTracker) CheckExpression(node *unstable.Node) (bool, error) {
 	if s.entries == nil {
 		s.reset()
 	}
 	switch node.Kind {
-	case ast.KeyValue:
+	case unstable.KeyValue:
 		return s.checkKeyValue(node)
-	case ast.Table:
+	case unstable.Table:
 		return s.checkTable(node)
-	case ast.ArrayTable:
+	case unstable.ArrayTable:
 		return s.checkArrayTable(node)
 	default:
 		panic(fmt.Errorf("this should not be a top level node type: %s", node.Kind))
 	}
 }
 
-func (s *SeenTracker) checkTable(node *ast.Node) error {
+func (s *SeenTracker) checkTable(node *unstable.Node) (bool, error) {
 	if s.currentIdx >= 0 {
 		s.setExplicitFlag(s.currentIdx)
 	}
@@ -192,7 +197,7 @@ func (s *SeenTracker) checkTable(node *ast.Node) error {
 		} else {
 			entry := s.entries[idx]
 			if entry.kind == valueKind {
-				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
+				return false, fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
 			}
 		}
 		parentIdx = idx
@@ -201,25 +206,27 @@ func (s *SeenTracker) checkTable(node *ast.Node) error {
 	k := it.Node().Data
 	idx := s.find(parentIdx, k)
 
+	first := false
 	if idx >= 0 {
 		kind := s.entries[idx].kind
 		if kind != tableKind {
-			return fmt.Errorf("toml: key %s should be a table, not a %s", string(k), kind)
+			return false, fmt.Errorf("toml: key %s should be a table, not a %s", string(k), kind)
 		}
 		if s.entries[idx].explicit {
-			return fmt.Errorf("toml: table %s already exists", string(k))
+			return false, fmt.Errorf("toml: table %s already exists", string(k))
 		}
 		s.entries[idx].explicit = true
 	} else {
 		idx = s.create(parentIdx, k, tableKind, true, false)
+		first = true
 	}
 
 	s.currentIdx = idx
 
-	return nil
+	return first, nil
 }
 
-func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
+func (s *SeenTracker) checkArrayTable(node *unstable.Node) (bool, error) {
 	if s.currentIdx >= 0 {
 		s.setExplicitFlag(s.currentIdx)
 	}
@@ -242,7 +249,7 @@ func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
 		} else {
 			entry := s.entries[idx]
 			if entry.kind == valueKind {
-				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
+				return false, fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
 			}
 		}
 
@@ -252,22 +259,23 @@ func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
 	k := it.Node().Data
 	idx := s.find(parentIdx, k)
 
-	if idx >= 0 {
+	firstTime := idx < 0
+	if firstTime {
+		idx = s.create(parentIdx, k, arrayTableKind, true, false)
+	} else {
 		kind := s.entries[idx].kind
 		if kind != arrayTableKind {
-			return fmt.Errorf("toml: key %s already exists as a %s,  but should be an array table", kind, string(k))
+			return false, fmt.Errorf("toml: key %s already exists as a %s,  but should be an array table", kind, string(k))
 		}
 		s.clear(idx)
-	} else {
-		idx = s.create(parentIdx, k, arrayTableKind, true, false)
 	}
 
 	s.currentIdx = idx
 
-	return nil
+	return firstTime, nil
 }
 
-func (s *SeenTracker) checkKeyValue(node *ast.Node) error {
+func (s *SeenTracker) checkKeyValue(node *unstable.Node) (bool, error) {
 	parentIdx := s.currentIdx
 	it := node.Key()
 
@@ -280,12 +288,13 @@ func (s *SeenTracker) checkKeyValue(node *ast.Node) error {
 			idx = s.create(parentIdx, k, tableKind, false, true)
 		} else {
 			entry := s.entries[idx]
-			if it.IsLast() {
+			switch {
-				return fmt.Errorf("toml: key %s is already defined", string(k))
+			case it.IsLast():
-			} else if entry.kind != tableKind {
+				return false, fmt.Errorf("toml: key %s is already defined", string(k))
-				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
+			case entry.kind != tableKind:
-			} else if entry.explicit {
+				return false, fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), entry.kind)
-				return fmt.Errorf("toml: cannot redefine table %s that has already been explicitly defined", string(k))
+			case entry.explicit:
+				return false, fmt.Errorf("toml: cannot redefine table %s that has already been explicitly defined", string(k))
 			}
 		}
 
@@ -297,51 +306,45 @@ func (s *SeenTracker) checkKeyValue(node *ast.Node) error {
 	value := node.Value()
 
 	switch value.Kind {
-	case ast.InlineTable:
+	case unstable.InlineTable:
 		return s.checkInlineTable(value)
-	case ast.Array:
+	case unstable.Array:
 		return s.checkArray(value)
+	default:
+		return false, nil
 	}
-
-	return nil
 }
 
-func (s *SeenTracker) checkArray(node *ast.Node) error {
+func (s *SeenTracker) checkArray(node *unstable.Node) (first bool, err error) {
 	it := node.Children()
 	for it.Next() {
 		n := it.Node()
-		switch n.Kind {
+		switch n.Kind { //nolint:exhaustive
-		case ast.InlineTable:
+		case unstable.InlineTable:
-			err := s.checkInlineTable(n)
+			first, err = s.checkInlineTable(n)
 			if err != nil {
-				return err
+				return false, err
 			}
-		case ast.Array:
+		case unstable.Array:
-			err := s.checkArray(n)
+			first, err = s.checkArray(n)
 			if err != nil {
-				return err
+				return false, err
 			}
 		}
 	}
-	return nil
+	return first, nil
 }
 
-func (s *SeenTracker) checkInlineTable(node *ast.Node) error {
+func (s *SeenTracker) checkInlineTable(node *unstable.Node) (first bool, err error) {
-	if pool.New == nil {
-		pool.New = func() interface{} {
-			return &SeenTracker{}
-		}
-	}
-
 	s = pool.Get().(*SeenTracker)
 	s.reset()
 
 	it := node.Children()
 	for it.Next() {
 		n := it.Node()
-		err := s.checkKeyValue(n)
+		first, err = s.checkKeyValue(n)
 		if err != nil {
-			return err
+			return false, err
 		}
 	}
 
@@ -352,5 +355,5 @@ func (s *SeenTracker) checkInlineTable(node *ast.Node) error {
 	// redefinition of its keys: check* functions cannot walk into
 	// a value.
 	pool.Put(s)
-	return nil
+	return first, nil
 }

internal/tracker/seen_test.go

@@ -1,10 +1,10 @@
 package tracker
 
 import (
+	"reflect"
 	"testing"
-	"unsafe"
 
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func TestEntrySize(t *testing.T) {
@@ -12,5 +12,10 @@ func TestEntrySize(t *testing.T) {
 	// performance of unmarshaling documents. Should only be increased with care
 	// and a very good reason.
 	maxExpectedEntrySize := 48
-	require.LessOrEqual(t, int(unsafe.Sizeof(entry{})), maxExpectedEntrySize)
+	entrySize := int(reflect.TypeOf(entry{}).Size())
+	assert.True(t,
+		entrySize <= maxExpectedEntrySize,
+		"Expected entry to be less than or equal to %d, got: %d",
+		maxExpectedEntrySize, entrySize,
+	)
 }

internal/tracker/tracker.go

@@ -1 +1,2 @@
+// Package tracker provides functions for keeping track of AST nodes.
 package tracker

localtime.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"strings"
 	"time"
+
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 // LocalDate represents a calendar day in no specific timezone.
@@ -43,7 +45,7 @@ func (d *LocalDate) UnmarshalText(b []byte) error {
 type LocalTime struct {
 	Hour       int // Hour of the day: [0; 24[
 	Minute     int // Minute of the hour: [0; 60[
-	Second     int // Second of the minute: [0; 60[
+	Second     int // Second of the minute: [0; 59]
 	Nanosecond int // Nanoseconds within the second:  [0, 1000000000[
 	Precision  int // Number of digits to display for Nanosecond.
 }
@@ -75,7 +77,7 @@ func (d LocalTime) MarshalText() ([]byte, error) {
 func (d *LocalTime) UnmarshalText(b []byte) error {
 	res, left, err := parseLocalTime(b)
 	if err == nil && len(left) != 0 {
-		err = newDecodeError(left, "extra characters")
+		err = unstable.NewParserError(left, "extra characters")
 	}
 	if err != nil {
 		return err
@@ -109,7 +111,7 @@ func (d LocalDateTime) MarshalText() ([]byte, error) {
 func (d *LocalDateTime) UnmarshalText(data []byte) error {
 	res, left, err := parseLocalDateTime(data)
 	if err == nil && len(left) != 0 {
-		err = newDecodeError(left, "extra characters")
+		err = unstable.NewParserError(left, "extra characters")
 	}
 	if err != nil {
 		return err

localtime_test.go

@@ -5,73 +5,73 @@ import (
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func TestLocalDate_AsTime(t *testing.T) {
 	d := toml.LocalDate{2021, 6, 8}
 	cast := d.AsTime(time.UTC)
-	require.Equal(t, time.Date(2021, time.June, 8, 0, 0, 0, 0, time.UTC), cast)
+	assert.Equal(t, time.Date(2021, time.June, 8, 0, 0, 0, 0, time.UTC), cast)
 }
 
 func TestLocalDate_String(t *testing.T) {
 	d := toml.LocalDate{2021, 6, 8}
-	require.Equal(t, "2021-06-08", d.String())
+	assert.Equal(t, "2021-06-08", d.String())
 }
 
 func TestLocalDate_MarshalText(t *testing.T) {
 	d := toml.LocalDate{2021, 6, 8}
 	b, err := d.MarshalText()
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, []byte("2021-06-08"), b)
+	assert.Equal(t, []byte("2021-06-08"), b)
 }
 
 func TestLocalDate_UnmarshalMarshalText(t *testing.T) {
 	d := toml.LocalDate{}
 	err := d.UnmarshalText([]byte("2021-06-08"))
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, toml.LocalDate{2021, 6, 8}, d)
+	assert.Equal(t, toml.LocalDate{2021, 6, 8}, d)
 
 	err = d.UnmarshalText([]byte("what"))
-	require.Error(t, err)
+	assert.Error(t, err)
 }
 
 func TestLocalTime_String(t *testing.T) {
 	d := toml.LocalTime{20, 12, 1, 2, 9}
-	require.Equal(t, "20:12:01.000000002", d.String())
+	assert.Equal(t, "20:12:01.000000002", d.String())
 	d = toml.LocalTime{20, 12, 1, 0, 0}
-	require.Equal(t, "20:12:01", d.String())
+	assert.Equal(t, "20:12:01", d.String())
 	d = toml.LocalTime{20, 12, 1, 0, 9}
-	require.Equal(t, "20:12:01.000000000", d.String())
+	assert.Equal(t, "20:12:01.000000000", d.String())
 	d = toml.LocalTime{20, 12, 1, 100, 0}
-	require.Equal(t, "20:12:01.0000001", d.String())
+	assert.Equal(t, "20:12:01.0000001", d.String())
 }
 
 func TestLocalTime_MarshalText(t *testing.T) {
 	d := toml.LocalTime{20, 12, 1, 2, 9}
 	b, err := d.MarshalText()
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, []byte("20:12:01.000000002"), b)
+	assert.Equal(t, []byte("20:12:01.000000002"), b)
 }
 
 func TestLocalTime_UnmarshalMarshalText(t *testing.T) {
 	d := toml.LocalTime{}
 	err := d.UnmarshalText([]byte("20:12:01.000000002"))
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, toml.LocalTime{20, 12, 1, 2, 9}, d)
+	assert.Equal(t, toml.LocalTime{20, 12, 1, 2, 9}, d)
 
 	err = d.UnmarshalText([]byte("what"))
-	require.Error(t, err)
+	assert.Error(t, err)
 
 	err = d.UnmarshalText([]byte("20:12:01.000000002 bad"))
-	require.Error(t, err)
+	assert.Error(t, err)
 }
 
 func TestLocalTime_RoundTrip(t *testing.T) {
 	var d struct{ A toml.LocalTime }
 	err := toml.Unmarshal([]byte("a=20:12:01.500"), &d)
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, "20:12:01.500", d.A.String())
+	assert.Equal(t, "20:12:01.500", d.A.String())
 }
 
 func TestLocalDateTime_AsTime(t *testing.T) {
@@ -80,7 +80,7 @@ func TestLocalDateTime_AsTime(t *testing.T) {
 		toml.LocalTime{20, 12, 1, 2, 9},
 	}
 	cast := d.AsTime(time.UTC)
-	require.Equal(t, time.Date(2021, time.June, 8, 20, 12, 1, 2, time.UTC), cast)
+	assert.Equal(t, time.Date(2021, time.June, 8, 20, 12, 1, 2, time.UTC), cast)
 }
 
 func TestLocalDateTime_String(t *testing.T) {
@@ -88,7 +88,7 @@ func TestLocalDateTime_String(t *testing.T) {
 		toml.LocalDate{2021, 6, 8},
 		toml.LocalTime{20, 12, 1, 2, 9},
 	}
-	require.Equal(t, "2021-06-08T20:12:01.000000002", d.String())
+	assert.Equal(t, "2021-06-08T20:12:01.000000002", d.String())
 }
 
 func TestLocalDateTime_MarshalText(t *testing.T) {
@@ -97,22 +97,22 @@ func TestLocalDateTime_MarshalText(t *testing.T) {
 		toml.LocalTime{20, 12, 1, 2, 9},
 	}
 	b, err := d.MarshalText()
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, []byte("2021-06-08T20:12:01.000000002"), b)
+	assert.Equal(t, []byte("2021-06-08T20:12:01.000000002"), b)
 }
 
 func TestLocalDateTime_UnmarshalMarshalText(t *testing.T) {
 	d := toml.LocalDateTime{}
 	err := d.UnmarshalText([]byte("2021-06-08 20:12:01.000000002"))
-	require.NoError(t, err)
+	assert.NoError(t, err)
-	require.Equal(t, toml.LocalDateTime{
+	assert.Equal(t, toml.LocalDateTime{
 		toml.LocalDate{2021, 6, 8},
 		toml.LocalTime{20, 12, 1, 2, 9},
 	}, d)
 
 	err = d.UnmarshalText([]byte("what"))
-	require.Error(t, err)
+	assert.Error(t, err)
 
 	err = d.UnmarshalText([]byte("2021-06-08 20:12:01.000000002 bad"))
-	require.Error(t, err)
+	assert.Error(t, err)
 }

marshaler.go

@@ -3,15 +3,19 @@ package toml
 import (
 	"bytes"
 	"encoding"
+	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
 	"math"
 	"reflect"
-	"sort"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
 	"unicode"
+
+	"github.com/pelletier/go-toml/v2/internal/characters"
 )
 
 // Marshal serializes a Go value as a TOML document.
@@ -35,10 +39,11 @@ type Encoder struct {
 	w io.Writer
 
 	// global settings
-	tablesInline    bool
+	tablesInline       bool
-	arraysMultiline bool
+	arraysMultiline    bool
-	indentSymbol    string
+	indentSymbol       string
-	indentTables    bool
+	indentTables       bool
+	marshalJSONNumbers bool
 }
 
 // NewEncoder returns a new Encoder that writes to w.
@@ -85,6 +90,17 @@ func (enc *Encoder) SetIndentTables(indent bool) *Encoder {
 	return enc
 }
 
+// SetMarshalJSONNumbers forces the encoder to serialize `json.Number` as a
+// float or integer instead of relying on TextMarshaler to emit a string.
+//
+// *Unstable:* This method does not follow the compatibility guarantees of
+// semver. It can be changed or removed without a new major version being
+// issued.
+func (enc *Encoder) SetMarshalJSONNumbers(indent bool) *Encoder {
+	enc.marshalJSONNumbers = indent
+	return enc
+}
+
 // Encode writes a TOML representation of v to the stream.
 //
 // If v cannot be represented to TOML it returns an error.
@@ -146,6 +162,11 @@ func (enc *Encoder) SetIndentTables(indent bool) *Encoder {
 //
 // The "omitempty" option prevents empty values or groups from being emitted.
 //
+// The "omitzero" option prevents zero values or groups from being emitted.
+//
+// The "commented" option prefixes the value and all its children with a comment
+// symbol.
+//
 // In addition to the "toml" tag struct tag, a "comment" tag can be used to emit
 // a TOML comment before the value being annotated. Comments are ignored inside
 // inline tables. For array tables, the comment is only present before the first
@@ -159,7 +180,7 @@ func (enc *Encoder) Encode(v interface{}) error {
 	ctx.inline = enc.tablesInline
 
 	if v == nil {
-		return fmt.Errorf("toml: cannot encode a nil interface")
+		return errors.New("toml: cannot encode a nil interface")
 	}
 
 	b, err := enc.encode(b, ctx, reflect.ValueOf(v))
@@ -178,6 +199,8 @@ func (enc *Encoder) Encode(v interface{}) error {
 type valueOptions struct {
 	multiline bool
 	omitempty bool
+	omitzero  bool
+	commented bool
 	comment   string
 }
 
@@ -203,6 +226,9 @@ type encoderCtx struct {
 	// Indentation level
 	indent int
 
+	// Prefix the current value with a comment.
+	commented bool
+
 	// Options coming from struct tags
 	options valueOptions
 }
@@ -243,10 +269,21 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 		return append(b, x.String()...), nil
 	case LocalDateTime:
 		return append(b, x.String()...), nil
+	case json.Number:
+		if enc.marshalJSONNumbers {
+			if x == "" { /// Useful zero value.
+				return append(b, "0"...), nil
+			} else if v, err := x.Int64(); err == nil {
+				return enc.encode(b, ctx, reflect.ValueOf(v))
+			} else if f, err := x.Float64(); err == nil {
+				return enc.encode(b, ctx, reflect.ValueOf(f))
+			}
+			return nil, fmt.Errorf("toml: unable to convert %q to int64 or float64", x)
+		}
 	}
 
 	hasTextMarshaler := v.Type().Implements(textMarshalerType)
-	if hasTextMarshaler || (v.CanAddr() && reflect.PtrTo(v.Type()).Implements(textMarshalerType)) {
+	if hasTextMarshaler || (v.CanAddr() && reflect.PointerTo(v.Type()).Implements(textMarshalerType)) {
 		if !hasTextMarshaler {
 			v = v.Addr()
 		}
@@ -271,11 +308,11 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 		return enc.encodeMap(b, ctx, v)
 	case reflect.Struct:
 		return enc.encodeStruct(b, ctx, v)
-	case reflect.Slice:
+	case reflect.Slice, reflect.Array:
 		return enc.encodeSlice(b, ctx, v)
 	case reflect.Interface:
 		if v.IsNil() {
-			return nil, fmt.Errorf("toml: encoding a nil interface is not supported")
+			return nil, errors.New("toml: encoding a nil interface is not supported")
 		}
 
 		return enc.encode(b, ctx, v.Elem())
@@ -292,28 +329,30 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 	case reflect.Float32:
 		f := v.Float()
 
-		if math.IsNaN(f) {
+		switch {
+		case math.IsNaN(f):
 			b = append(b, "nan"...)
-		} else if f > math.MaxFloat32 {
+		case f > math.MaxFloat32:
 			b = append(b, "inf"...)
-		} else if f < -math.MaxFloat32 {
+		case f < -math.MaxFloat32:
 			b = append(b, "-inf"...)
-		} else if math.Trunc(f) == f {
+		case math.Trunc(f) == f:
 			b = strconv.AppendFloat(b, f, 'f', 1, 32)
-		} else {
+		default:
 			b = strconv.AppendFloat(b, f, 'f', -1, 32)
 		}
 	case reflect.Float64:
 		f := v.Float()
-		if math.IsNaN(f) {
+		switch {
+		case math.IsNaN(f):
 			b = append(b, "nan"...)
-		} else if f > math.MaxFloat64 {
+		case f > math.MaxFloat64:
 			b = append(b, "inf"...)
-		} else if f < -math.MaxFloat64 {
+		case f < -math.MaxFloat64:
 			b = append(b, "-inf"...)
-		} else if math.Trunc(f) == f {
+		case math.Trunc(f) == f:
 			b = strconv.AppendFloat(b, f, 'f', 1, 64)
-		} else {
+		default:
 			b = strconv.AppendFloat(b, f, 'f', -1, 64)
 		}
 	case reflect.Bool:
@@ -350,14 +389,40 @@ func shouldOmitEmpty(options valueOptions, v reflect.Value) bool {
 	return options.omitempty && isEmptyValue(v)
 }
 
+func shouldOmitZero(options valueOptions, v reflect.Value) bool {
+	if !options.omitzero {
+		return false
+	}
+
+	// Check if the type implements isZeroer interface (has a custom IsZero method).
+	if v.Type().Implements(isZeroerType) {
+		return v.Interface().(isZeroer).IsZero()
+	}
+
+	// Check if pointer type implements isZeroer.
+	if reflect.PointerTo(v.Type()).Implements(isZeroerType) {
+		if v.CanAddr() {
+			return v.Addr().Interface().(isZeroer).IsZero()
+		}
+		// Create a temporary addressable copy to call the pointer receiver method.
+		pv := reflect.New(v.Type())
+		pv.Elem().Set(v)
+		return pv.Interface().(isZeroer).IsZero()
+	}
+
+	// Fall back to reflect's IsZero for types without custom IsZero method.
+	return v.IsZero()
+}
+
 func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v reflect.Value) ([]byte, error) {
 	var err error
 
 	if !ctx.inline {
 		b = enc.encodeComment(ctx.indent, options.comment, b)
+		b = enc.commented(ctx.commented, b)
+		b = enc.indent(ctx.indent, b)
 	}
 
-	b = enc.indent(ctx.indent, b)
 	b = enc.encodeKey(b, ctx.key)
 	b = append(b, " = "...)
 
@@ -376,6 +441,13 @@ func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v r
 	return b, nil
 }
 
+func (enc *Encoder) commented(commented bool, b []byte) []byte {
+	if commented {
+		return append(b, "# "...)
+	}
+	return b
+}
+
 func isEmptyValue(v reflect.Value) bool {
 	switch v.Kind() {
 	case reflect.Struct:
@@ -392,8 +464,9 @@ func isEmptyValue(v reflect.Value) bool {
 		return v.Float() == 0
 	case reflect.Interface, reflect.Ptr:
 		return v.IsNil()
+	default:
+		return false
 	}
-	return false
 }
 
 func isEmptyStruct(v reflect.Value) bool {
@@ -437,7 +510,7 @@ func (enc *Encoder) encodeString(b []byte, v string, options valueOptions) []byt
 func needsQuoting(v string) bool {
 	// TODO: vectorize
 	for _, b := range []byte(v) {
-		if b == '\'' || b == '\r' || b == '\n' || invalidAscii(b) {
+		if b == '\'' || b == '\r' || b == '\n' || characters.InvalidASCII(b) {
 			return true
 		}
 	}
@@ -475,12 +548,26 @@ func (enc *Encoder) encodeQuotedString(multiline bool, b []byte, v string) []byt
 		del = 0x7f
 	)
 
-	for _, r := range []byte(v) {
+	bv := []byte(v)
+	for i := 0; i < len(bv); i++ {
+		r := bv[i]
 		switch r {
 		case '\\':
 			b = append(b, `\\`...)
 		case '"':
-			b = append(b, `\"`...)
+			if multiline {
+				// Quotation marks do not need to be quoted in multiline strings unless
+				// it contains 3 consecutive. If 3+ quotes appear, quote all of them
+				// because it's visually better
+				if i+2 > len(bv) || bv[i+1] != '"' || bv[i+2] != '"' {
+					b = append(b, r)
+				} else {
+					b = append(b, `\"\"\"`...)
+					i += 2
+				}
+			} else {
+				b = append(b, `\"`...)
+			}
 		case '\b':
 			b = append(b, `\b`...)
 		case '\f':
@@ -517,13 +604,15 @@ func (enc *Encoder) encodeUnquotedKey(b []byte, v string) []byte {
 	return append(b, v...)
 }
 
-func (enc *Encoder) encodeTableHeader(ctx encoderCtx, b []byte) ([]byte, error) {
+func (enc *Encoder) encodeTableHeader(ctx encoderCtx, b []byte) []byte {
 	if len(ctx.parentKey) == 0 {
-		return b, nil
+		return b
 	}
 
 	b = enc.encodeComment(ctx.indent, ctx.options.comment, b)
 
+	b = enc.commented(ctx.commented, b)
+
 	b = enc.indent(ctx.indent, b)
 
 	b = append(b, '[')
@@ -537,10 +626,9 @@ func (enc *Encoder) encodeTableHeader(ctx encoderCtx, b []byte) ([]byte, error)
 
 	b = append(b, "]\n"...)
 
-	return b, nil
+	return b
 }
 
-//nolint:cyclop
 func (enc *Encoder) encodeKey(b []byte, k string) []byte {
 	needsQuotation := false
 	cannotUseLiteral := false
@@ -575,11 +663,38 @@ func (enc *Encoder) encodeKey(b []byte, k string) []byte {
 	}
 }
 
-func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
+func (enc *Encoder) keyToString(k reflect.Value) (string, error) {
-	if v.Type().Key().Kind() != reflect.String {
+	keyType := k.Type()
-		return nil, fmt.Errorf("toml: type %s is not supported as a map key", v.Type().Key().Kind())
+	if keyType.Implements(textMarshalerType) {
+		keyB, err := k.Interface().(encoding.TextMarshaler).MarshalText()
+		if err != nil {
+			return "", fmt.Errorf("toml: error marshalling key %v from text: %w", k, err)
+		}
+		return string(keyB), nil
 	}
 
+	switch keyType.Kind() {
+	case reflect.String:
+		return k.String(), nil
+
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		return strconv.FormatInt(k.Int(), 10), nil
+
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		return strconv.FormatUint(k.Uint(), 10), nil
+
+	case reflect.Float32:
+		return strconv.FormatFloat(k.Float(), 'f', -1, 32), nil
+
+	case reflect.Float64:
+		return strconv.FormatFloat(k.Float(), 'f', -1, 64), nil
+
+	default:
+		return "", fmt.Errorf("toml: type %s is not supported as a map key", keyType.Kind())
+	}
+}
+
+func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
 	var (
 		t                 table
 		emptyValueOptions valueOptions
@@ -587,11 +702,25 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 
 	iter := v.MapRange()
 	for iter.Next() {
-		k := iter.Key().String()
 		v := iter.Value()
 
-		if isNil(v) {
+		// Handle nil values: convert nil pointers to zero value,
-			continue
+		// skip nil interfaces and nil maps.
+		switch v.Kind() {
+		case reflect.Ptr:
+			if v.IsNil() {
+				v = reflect.Zero(v.Type().Elem())
+			}
+		case reflect.Interface, reflect.Map:
+			if v.IsNil() {
+				continue
+			}
+		default:
+		}
+
+		k, err := enc.keyToString(iter.Key())
+		if err != nil {
+			return nil, err
 		}
 
 		if willConvertToTableOrArrayTable(ctx, v) {
@@ -608,8 +737,8 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 }
 
 func sortEntriesByKey(e []entry) {
-	sort.Slice(e, func(i, j int) bool {
+	slices.SortFunc(e, func(a, b entry) int {
-		return e[i].Key < e[j].Key
+		return strings.Compare(a.Key, b.Key)
 	})
 }
 
@@ -672,11 +801,12 @@ func walkStruct(ctx encoderCtx, t *table, v reflect.Value) {
 			if fieldType.Anonymous {
 				if fieldType.Type.Kind() == reflect.Struct {
 					walkStruct(ctx, t, f)
+				} else if fieldType.Type.Kind() == reflect.Ptr && !f.IsNil() && f.Elem().Kind() == reflect.Struct {
+					walkStruct(ctx, t, f.Elem())
 				}
 				continue
-			} else {
-				k = fieldType.Name
 			}
+			k = fieldType.Name
 		}
 
 		if isNil(f) {
@@ -686,6 +816,8 @@ func walkStruct(ctx encoderCtx, t *table, v reflect.Value) {
 		options := valueOptions{
 			multiline: opts.multiline,
 			omitempty: opts.omitempty,
+			omitzero:  opts.omitzero,
+			commented: opts.commented,
 			comment:   fieldType.Tag.Get("comment"),
 		}
 
@@ -745,6 +877,8 @@ type tagOptions struct {
 	multiline bool
 	inline    bool
 	omitempty bool
+	omitzero  bool
+	commented bool
 }
 
 func parseTag(tag string) (string, tagOptions) {
@@ -756,7 +890,7 @@ func parseTag(tag string) (string, tagOptions) {
 	}
 
 	raw := tag[idx+1:]
-	tag = string(tag[:idx])
+	tag = tag[:idx]
 	for raw != "" {
 		var o string
 		i := strings.Index(raw, ",")
@@ -772,6 +906,10 @@ func parseTag(tag string) (string, tagOptions) {
 			opts.inline = true
 		case "omitempty":
 			opts.omitempty = true
+		case "omitzero":
+			opts.omitzero = true
+		case "commented":
+			opts.commented = true
 		}
 	}
 
@@ -788,10 +926,7 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 	}
 
 	if !ctx.skipTableHeader {
-		b, err = enc.encodeTableHeader(ctx, b)
+		b = enc.encodeTableHeader(ctx, b)
-		if err != nil {
-			return nil, err
-		}
 
 		if enc.indentTables && len(ctx.parentKey) > 0 {
 			ctx.indent++
@@ -804,11 +939,16 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		if shouldOmitEmpty(kv.Options, kv.Value) {
 			continue
 		}
+		if kv.Options.omitzero && shouldOmitZero(kv.Options, kv.Value) {
+			continue
+		}
 		hasNonEmptyKV = true
 
 		ctx.setKey(kv.Key)
+		ctx2 := ctx
+		ctx2.commented = kv.Options.commented || ctx2.commented
 
-		b, err = enc.encodeKv(b, ctx, kv.Options, kv.Value)
+		b, err = enc.encodeKv(b, ctx2, kv.Options, kv.Value)
 		if err != nil {
 			return nil, err
 		}
@@ -821,6 +961,9 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		if shouldOmitEmpty(table.Options, table.Value) {
 			continue
 		}
+		if table.Options.omitzero && shouldOmitZero(table.Options, table.Value) {
+			continue
+		}
 		if first {
 			first = false
 			if hasNonEmptyKV {
@@ -833,8 +976,10 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		ctx.setKey(table.Key)
 
 		ctx.options = table.Options
+		ctx2 := ctx
+		ctx2.commented = ctx2.commented || ctx.options.commented
 
-		b, err = enc.encode(b, ctx, table.Value)
+		b, err = enc.encode(b, ctx2, table.Value)
 		if err != nil {
 			return nil, err
 		}
@@ -853,6 +998,9 @@ func (enc *Encoder) encodeTableInline(b []byte, ctx encoderCtx, t table) ([]byte
 		if shouldOmitEmpty(kv.Options, kv.Value) {
 			continue
 		}
+		if kv.Options.omitzero && shouldOmitZero(kv.Options, kv.Value) {
+			continue
+		}
 
 		if first {
 			first = false
@@ -881,11 +1029,14 @@ func willConvertToTable(ctx encoderCtx, v reflect.Value) bool {
 	if !v.IsValid() {
 		return false
 	}
-	if v.Type() == timeType || v.Type().Implements(textMarshalerType) || (v.Kind() != reflect.Ptr && v.CanAddr() && reflect.PtrTo(v.Type()).Implements(textMarshalerType)) {
+	t := v.Type()
+	if t == timeType || t.Implements(textMarshalerType) {
+		return false
+	}
+	if v.Kind() != reflect.Ptr && v.CanAddr() && reflect.PointerTo(t).Implements(textMarshalerType) {
 		return false
 	}
 
-	t := v.Type()
 	switch t.Kind() {
 	case reflect.Map, reflect.Struct:
 		return !ctx.inline
@@ -912,7 +1063,7 @@ func willConvertToTableOrArrayTable(ctx encoderCtx, v reflect.Value) bool {
 		return willConvertToTableOrArrayTable(ctx, v.Elem())
 	}
 
-	if t.Kind() == reflect.Slice {
+	if t.Kind() == reflect.Slice || t.Kind() == reflect.Array {
 		if v.Len() == 0 {
 			// An empty slice should be a kv = [].
 			return false
@@ -952,6 +1103,13 @@ func (enc *Encoder) encodeSliceAsArrayTable(b []byte, ctx encoderCtx, v reflect.
 	ctx.shiftKey()
 
 	scratch := make([]byte, 0, 64)
+
+	scratch = enc.commented(ctx.commented, scratch)
+
+	if enc.indentTables {
+		scratch = enc.indent(ctx.indent, scratch)
+	}
+
 	scratch = append(scratch, "[["...)
 
 	for i, k := range ctx.parentKey {
@@ -967,6 +1125,10 @@ func (enc *Encoder) encodeSliceAsArrayTable(b []byte, ctx encoderCtx, v reflect.
 
 	b = enc.encodeComment(ctx.indent, ctx.options.comment, b)
 
+	if enc.indentTables {
+		ctx.indent++
+	}
+
 	for i := 0; i < v.Len(); i++ {
 		if i != 0 {
 			b = append(b, "\n"...)

ossfuzz/fuzz.go

@@ -0,0 +1,44 @@
+// Package ossfuzz provides a fuzzing target for OSS-Fuzz.
+package ossfuzz
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/pelletier/go-toml/v2"
+)
+
+// FuzzToml is the fuzzing target.
+func FuzzToml(data []byte) int {
+	if len(data) >= 2048 {
+		return 0
+	}
+
+	if strings.Contains(string(data), "nan") {
+		return 0
+	}
+
+	var v interface{}
+	err := toml.Unmarshal(data, &v)
+	if err != nil {
+		return 0
+	}
+
+	encoded, err := toml.Marshal(v)
+	if err != nil {
+		panic(fmt.Sprintf("failed to marshal unmarshaled document: %s", err))
+	}
+
+	var v2 interface{}
+	err = toml.Unmarshal(encoded, &v2)
+	if err != nil {
+		panic(fmt.Sprintf("failed round trip: %s", err))
+	}
+
+	if !reflect.DeepEqual(v, v2) {
+		panic(fmt.Sprintf("not equal: %#+v %#+v", v, v2))
+	}
+
+	return 1
+}

parser_test.go

@@ -1,450 +0,0 @@
-package toml
-
-import (
-	"strconv"
-	"strings"
-	"testing"
-
-	"github.com/pelletier/go-toml/v2/internal/ast"
-	"github.com/stretchr/testify/require"
-)
-
-//nolint:funlen
-func TestParser_AST_Numbers(t *testing.T) {
-	examples := []struct {
-		desc  string
-		input string
-		kind  ast.Kind
-		err   bool
-	}{
-		{
-			desc:  "integer just digits",
-			input: `1234`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "integer zero",
-			input: `0`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "integer sign",
-			input: `+99`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "integer hex uppercase",
-			input: `0xDEADBEEF`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "integer hex lowercase",
-			input: `0xdead_beef`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "integer octal",
-			input: `0o01234567`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "integer binary",
-			input: `0b11010110`,
-			kind:  ast.Integer,
-		},
-		{
-			desc:  "float zero",
-			input: `0.0`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float positive zero",
-			input: `+0.0`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float negative zero",
-			input: `-0.0`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float pi",
-			input: `3.1415`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float negative",
-			input: `-0.01`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float signed exponent",
-			input: `5e+22`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float exponent lowercase",
-			input: `1e06`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float exponent uppercase",
-			input: `-2E-2`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float fractional with exponent",
-			input: `6.626e-34`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "float underscores",
-			input: `224_617.445_991_228`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "inf",
-			input: `inf`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "inf negative",
-			input: `-inf`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "inf positive",
-			input: `+inf`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "nan",
-			input: `nan`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "nan negative",
-			input: `-nan`,
-			kind:  ast.Float,
-		},
-		{
-			desc:  "nan positive",
-			input: `+nan`,
-			kind:  ast.Float,
-		},
-	}
-
-	for _, e := range examples {
-		e := e
-		t.Run(e.desc, func(t *testing.T) {
-			p := parser{}
-			p.Reset([]byte(`A = ` + e.input))
-			p.NextExpression()
-			err := p.Error()
-			if e.err {
-				require.Error(t, err)
-			} else {
-				require.NoError(t, err)
-
-				expected := astNode{
-					Kind: ast.KeyValue,
-					Children: []astNode{
-						{Kind: e.kind, Data: []byte(e.input)},
-						{Kind: ast.Key, Data: []byte(`A`)},
-					},
-				}
-				compareNode(t, expected, p.Expression())
-			}
-		})
-	}
-}
-
-type (
-	astNode struct {
-		Kind     ast.Kind
-		Data     []byte
-		Children []astNode
-	}
-)
-
-func compareNode(t *testing.T, e astNode, n *ast.Node) {
-	t.Helper()
-	require.Equal(t, e.Kind, n.Kind)
-	require.Equal(t, e.Data, n.Data)
-
-	compareIterator(t, e.Children, n.Children())
-}
-
-func compareIterator(t *testing.T, expected []astNode, actual ast.Iterator) {
-	t.Helper()
-	idx := 0
-
-	for actual.Next() {
-		n := actual.Node()
-
-		if idx >= len(expected) {
-			t.Fatal("extra child in actual tree")
-		}
-		e := expected[idx]
-
-		compareNode(t, e, n)
-
-		idx++
-	}
-
-	if idx < len(expected) {
-		t.Fatal("missing children in actual", "idx =", idx, "expected =", len(expected))
-	}
-}
-
-//nolint:funlen
-func TestParser_AST(t *testing.T) {
-	examples := []struct {
-		desc  string
-		input string
-		ast   astNode
-		err   bool
-	}{
-		{
-			desc:  "simple string assignment",
-			input: `A = "hello"`,
-			ast: astNode{
-				Kind: ast.KeyValue,
-				Children: []astNode{
-					{
-						Kind: ast.String,
-						Data: []byte(`hello`),
-					},
-					{
-						Kind: ast.Key,
-						Data: []byte(`A`),
-					},
-				},
-			},
-		},
-		{
-			desc:  "simple bool assignment",
-			input: `A = true`,
-			ast: astNode{
-				Kind: ast.KeyValue,
-				Children: []astNode{
-					{
-						Kind: ast.Bool,
-						Data: []byte(`true`),
-					},
-					{
-						Kind: ast.Key,
-						Data: []byte(`A`),
-					},
-				},
-			},
-		},
-		{
-			desc:  "array of strings",
-			input: `A = ["hello", ["world", "again"]]`,
-			ast: astNode{
-				Kind: ast.KeyValue,
-				Children: []astNode{
-					{
-						Kind: ast.Array,
-						Children: []astNode{
-							{
-								Kind: ast.String,
-								Data: []byte(`hello`),
-							},
-							{
-								Kind: ast.Array,
-								Children: []astNode{
-									{
-										Kind: ast.String,
-										Data: []byte(`world`),
-									},
-									{
-										Kind: ast.String,
-										Data: []byte(`again`),
-									},
-								},
-							},
-						},
-					},
-					{
-						Kind: ast.Key,
-						Data: []byte(`A`),
-					},
-				},
-			},
-		},
-		{
-			desc:  "array of arrays of strings",
-			input: `A = ["hello", "world"]`,
-			ast: astNode{
-				Kind: ast.KeyValue,
-				Children: []astNode{
-					{
-						Kind: ast.Array,
-						Children: []astNode{
-							{
-								Kind: ast.String,
-								Data: []byte(`hello`),
-							},
-							{
-								Kind: ast.String,
-								Data: []byte(`world`),
-							},
-						},
-					},
-					{
-						Kind: ast.Key,
-						Data: []byte(`A`),
-					},
-				},
-			},
-		},
-		{
-			desc:  "inline table",
-			input: `name = { first = "Tom", last = "Preston-Werner" }`,
-			ast: astNode{
-				Kind: ast.KeyValue,
-				Children: []astNode{
-					{
-						Kind: ast.InlineTable,
-						Children: []astNode{
-							{
-								Kind: ast.KeyValue,
-								Children: []astNode{
-									{Kind: ast.String, Data: []byte(`Tom`)},
-									{Kind: ast.Key, Data: []byte(`first`)},
-								},
-							},
-							{
-								Kind: ast.KeyValue,
-								Children: []astNode{
-									{Kind: ast.String, Data: []byte(`Preston-Werner`)},
-									{Kind: ast.Key, Data: []byte(`last`)},
-								},
-							},
-						},
-					},
-					{
-						Kind: ast.Key,
-						Data: []byte(`name`),
-					},
-				},
-			},
-		},
-	}
-
-	for _, e := range examples {
-		e := e
-		t.Run(e.desc, func(t *testing.T) {
-			p := parser{}
-			p.Reset([]byte(e.input))
-			p.NextExpression()
-			err := p.Error()
-			if e.err {
-				require.Error(t, err)
-			} else {
-				require.NoError(t, err)
-				compareNode(t, e.ast, p.Expression())
-			}
-		})
-	}
-}
-
-func BenchmarkParseBasicStringWithUnicode(b *testing.B) {
-	p := &parser{}
-	b.Run("4", func(b *testing.B) {
-		input := []byte(`"\u1234\u5678\u9ABC\u1234\u5678\u9ABC"`)
-		b.ReportAllocs()
-		b.SetBytes(int64(len(input)))
-
-		for i := 0; i < b.N; i++ {
-			p.parseBasicString(input)
-		}
-	})
-	b.Run("8", func(b *testing.B) {
-		input := []byte(`"\u12345678\u9ABCDEF0\u12345678\u9ABCDEF0"`)
-		b.ReportAllocs()
-		b.SetBytes(int64(len(input)))
-
-		for i := 0; i < b.N; i++ {
-			p.parseBasicString(input)
-		}
-	})
-}
-
-func BenchmarkParseBasicStringsEasy(b *testing.B) {
-	p := &parser{}
-
-	for _, size := range []int{1, 4, 8, 16, 21} {
-		b.Run(strconv.Itoa(size), func(b *testing.B) {
-			input := []byte(`"` + strings.Repeat("A", size) + `"`)
-
-			b.ReportAllocs()
-			b.SetBytes(int64(len(input)))
-
-			for i := 0; i < b.N; i++ {
-				p.parseBasicString(input)
-			}
-		})
-	}
-}
-
-func TestParser_AST_DateTimes(t *testing.T) {
-	examples := []struct {
-		desc  string
-		input string
-		kind  ast.Kind
-		err   bool
-	}{
-		{
-			desc:  "offset-date-time with delim 'T' and UTC offset",
-			input: `2021-07-21T12:08:05Z`,
-			kind:  ast.DateTime,
-		},
-		{
-			desc:  "offset-date-time with space delim and +8hours offset",
-			input: `2021-07-21 12:08:05+08:00`,
-			kind:  ast.DateTime,
-		},
-		{
-			desc:  "local-date-time with nano second",
-			input: `2021-07-21T12:08:05.666666666`,
-			kind:  ast.LocalDateTime,
-		},
-		{
-			desc:  "local-date-time",
-			input: `2021-07-21T12:08:05`,
-			kind:  ast.LocalDateTime,
-		},
-		{
-			desc:  "local-date",
-			input: `2021-07-21`,
-			kind:  ast.LocalDate,
-		},
-	}
-
-	for _, e := range examples {
-		e := e
-		t.Run(e.desc, func(t *testing.T) {
-			p := parser{}
-			p.Reset([]byte(`A = ` + e.input))
-			p.NextExpression()
-			err := p.Error()
-			if e.err {
-				require.Error(t, err)
-			} else {
-				require.NoError(t, err)
-
-				expected := astNode{
-					Kind: ast.KeyValue,
-					Children: []astNode{
-						{Kind: e.kind, Data: []byte(e.input)},
-						{Kind: ast.Key, Data: []byte(`A`)},
-					},
-				}
-				compareNode(t, expected, p.Expression())
-			}
-		})
-	}
-}

strict.go

@@ -1,9 +1,8 @@
 package toml
 
 import (
-	"github.com/pelletier/go-toml/v2/internal/ast"
-	"github.com/pelletier/go-toml/v2/internal/danger"
 	"github.com/pelletier/go-toml/v2/internal/tracker"
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 type strict struct {
@@ -12,10 +11,13 @@ type strict struct {
 	// Tracks the current key being processed.
 	key tracker.KeyTracker
 
-	missing []decodeError
+	missing []unstable.ParserError
+
+	// Reference to the document for computing key ranges.
+	doc []byte
 }
 
-func (s *strict) EnterTable(node *ast.Node) {
+func (s *strict) EnterTable(node *unstable.Node) {
 	if !s.Enabled {
 		return
 	}
@@ -23,7 +25,7 @@ func (s *strict) EnterTable(node *ast.Node) {
 	s.key.UpdateTable(node)
 }
 
-func (s *strict) EnterArrayTable(node *ast.Node) {
+func (s *strict) EnterArrayTable(node *unstable.Node) {
 	if !s.Enabled {
 		return
 	}
@@ -31,7 +33,7 @@ func (s *strict) EnterArrayTable(node *ast.Node) {
 	s.key.UpdateArrayTable(node)
 }
 
-func (s *strict) EnterKeyValue(node *ast.Node) {
+func (s *strict) EnterKeyValue(node *unstable.Node) {
 	if !s.Enabled {
 		return
 	}
@@ -39,7 +41,7 @@ func (s *strict) EnterKeyValue(node *ast.Node) {
 	s.key.Push(node)
 }
 
-func (s *strict) ExitKeyValue(node *ast.Node) {
+func (s *strict) ExitKeyValue(node *unstable.Node) {
 	if !s.Enabled {
 		return
 	}
@@ -47,27 +49,27 @@ func (s *strict) ExitKeyValue(node *ast.Node) {
 	s.key.Pop(node)
 }
 
-func (s *strict) MissingTable(node *ast.Node) {
+func (s *strict) MissingTable(node *unstable.Node) {
 	if !s.Enabled {
 		return
 	}
 
-	s.missing = append(s.missing, decodeError{
+	s.missing = append(s.missing, unstable.ParserError{
-		highlight: keyLocation(node),
+		Highlight: s.keyLocation(node),
-		message:   "missing table",
+		Message:   "missing table",
-		key:       s.key.Key(),
+		Key:       s.key.Key(),
 	})
 }
 
-func (s *strict) MissingField(node *ast.Node) {
+func (s *strict) MissingField(node *unstable.Node) {
 	if !s.Enabled {
 		return
 	}
 
-	s.missing = append(s.missing, decodeError{
+	s.missing = append(s.missing, unstable.ParserError{
-		highlight: keyLocation(node),
+		Highlight: s.keyLocation(node),
-		message:   "missing field",
+		Message:   "missing field",
-		key:       s.key.Key(),
+		Key:       s.key.Key(),
 	})
 }
 
@@ -88,7 +90,7 @@ func (s *strict) Error(doc []byte) error {
 	return err
 }
 
-func keyLocation(node *ast.Node) []byte {
+func (s *strict) keyLocation(node *unstable.Node) []byte {
 	k := node.Key()
 
 	hasOne := k.Next()
@@ -96,12 +98,17 @@ func keyLocation(node *ast.Node) []byte {
 		panic("should not be called with empty key")
 	}
 
-	start := k.Node().Data
+	// Get the range from the first key to the last key.
-	end := k.Node().Data
+	firstRaw := k.Node().Raw
+	lastRaw := firstRaw
 
 	for k.Next() {
-		end = k.Node().Data
+		lastRaw = k.Node().Raw
 	}
 
-	return danger.BytesRange(start, end)
+	// Compute the slice from the document using the ranges.
+	start := firstRaw.Offset
+	end := lastRaw.Offset + lastRaw.Length
+
+	return s.doc[start:end]
 }

test-go-versions.sh

@@ -0,0 +1,597 @@
+#!/usr/bin/env bash
+
+set -uo pipefail
+
+# Colors for output
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+NC='\033[0m' # No Color
+
+# Go versions to test (1.11 through 1.26)
+GO_VERSIONS=(
+    "1.11"
+    "1.12"
+    "1.13"
+    "1.14"
+    "1.15"
+    "1.16"
+    "1.17"
+    "1.18"
+    "1.19"
+    "1.20"
+    "1.21"
+    "1.22"
+    "1.23"
+    "1.24"
+    "1.25"
+    "1.26"
+)
+
+# Default values
+PARALLEL=true
+VERBOSE=false
+OUTPUT_DIR="test-results"
+DOCKER_TIMEOUT="10m"
+
+usage() {
+    cat << EOF
+Usage: $0 [OPTIONS] [GO_VERSIONS...]
+
+Test go-toml across multiple Go versions using Docker containers.
+
+The script reports the lowest continuous supported Go version (where all subsequent 
+versions pass) and only exits with non-zero status if either of the two most recent 
+Go versions fail, indicating immediate attention is needed.
+
+Note: For Go versions < 1.21, the script automatically updates go.mod to match the 
+target version, but older versions may still fail due to missing standard library 
+features (e.g., the 'slices' package introduced in Go 1.21).
+
+OPTIONS:
+    -h, --help          Show this help message
+    -s, --sequential    Run tests sequentially instead of in parallel
+    -v, --verbose       Enable verbose output
+    -o, --output DIR    Output directory for test results (default: test-results)
+    -t, --timeout TIME  Docker timeout for each test (default: 10m)
+    --list              List available Go versions and exit
+
+ARGUMENTS:
+    GO_VERSIONS         Specific Go versions to test (default: all supported versions)
+                        Examples: 1.21 1.22 1.23
+
+EXAMPLES:
+    $0                          # Test all Go versions in parallel
+    $0 --sequential             # Test all Go versions sequentially
+    $0 1.21 1.22 1.23          # Test specific versions
+    $0 --verbose --output ./results 1.25 1.26  # Verbose output to custom directory
+
+EXIT CODES:
+    0                   Recent Go versions pass (good compatibility)
+    1                   Recent Go versions fail (needs attention) or script error
+
+EOF
+}
+
+log() {
+    echo -e "${BLUE}[$(date +'%H:%M:%S')]${NC} $*" >&2
+}
+
+log_success() {
+    echo -e "${GREEN}[$(date +'%H:%M:%S')] ✓${NC} $*" >&2
+}
+
+log_error() {
+    echo -e "${RED}[$(date +'%H:%M:%S')] ✗${NC} $*" >&2
+}
+
+log_warning() {
+    echo -e "${YELLOW}[$(date +'%H:%M:%S')] ⚠${NC} $*" >&2
+}
+
+# Parse command line arguments
+while [[ $# -gt 0 ]]; do
+    case $1 in
+        -h|--help)
+            usage
+            exit 0
+            ;;
+        -s|--sequential)
+            PARALLEL=false
+            shift
+            ;;
+        -v|--verbose)
+            VERBOSE=true
+            shift
+            ;;
+        -o|--output)
+            OUTPUT_DIR="$2"
+            shift 2
+            ;;
+        -t|--timeout)
+            DOCKER_TIMEOUT="$2"
+            shift 2
+            ;;
+        --list)
+            echo "Available Go versions:"
+            printf '%s\n' "${GO_VERSIONS[@]}"
+            exit 0
+            ;;
+        -*)
+            echo "Unknown option: $1" >&2
+            usage
+            exit 1
+            ;;
+        *)
+            # Remaining arguments are Go versions
+            break
+            ;;
+    esac
+done
+
+# If specific versions provided, use those instead of defaults
+if [[ $# -gt 0 ]]; then
+    GO_VERSIONS=("$@")
+fi
+
+# Validate Go versions
+for version in "${GO_VERSIONS[@]}"; do
+    if ! [[ "$version" =~ ^1\.(1[1-9]|2[0-6])$ ]]; then
+        log_error "Invalid Go version: $version. Supported versions: 1.11-1.26"
+        exit 1
+    fi
+done
+
+# Check if Docker is available
+if ! command -v docker &> /dev/null; then
+    log_error "Docker is required but not installed or not in PATH"
+    exit 1
+fi
+
+# Check if Docker daemon is running
+if ! docker info &> /dev/null; then
+    log_error "Docker daemon is not running"
+    exit 1
+fi
+
+# Create output directory
+mkdir -p "$OUTPUT_DIR"
+
+# Function to test a single Go version
+test_go_version() {
+    local go_version="$1"
+    local container_name="go-toml-test-${go_version}"
+    local result_file="${OUTPUT_DIR}/go-${go_version}.txt"
+    local dockerfile_content
+
+    log "Testing Go $go_version..."
+
+    # Create a temporary Dockerfile for this version
+    # For Go versions < 1.21, we need to update go.mod to match the Go version
+    local needs_go_mod_update=false
+    if [[ $(echo "$go_version 1.21" | tr ' ' '\n' | sort -V | head -n1) == "$go_version" && "$go_version" != "1.21" ]]; then
+        needs_go_mod_update=true
+    fi
+    
+    dockerfile_content="FROM golang:${go_version}-alpine
+
+# Install git (required for go mod)
+RUN apk add --no-cache git
+
+# Set working directory
+WORKDIR /app
+
+# Copy source code
+COPY . ."
+
+    # Add go.mod update step for older Go versions
+    if [[ "$needs_go_mod_update" == true ]]; then
+        dockerfile_content="$dockerfile_content
+
+# Update go.mod to match Go version (required for Go < 1.21)
+RUN if [ -f go.mod ]; then sed -i 's/^go [0-9]\\+\\.[0-9]\\+\\(\\.[0-9]\\+\\)\\?/go $go_version/' go.mod; fi
+
+# Note: Go versions < 1.21 may fail due to missing standard library packages (e.g., slices)
+# This is expected for projects that use Go 1.21+ features"
+    fi
+    
+    dockerfile_content="$dockerfile_content
+
+# Run tests
+CMD [\"sh\", \"-c\", \"go version && echo '--- Running go test ./... ---' && go test ./...\"]"
+
+    # Create temporary directory for this test
+    local temp_dir
+    temp_dir=$(mktemp -d)
+
+    # Copy source to temp directory (excluding test results and git)
+    rsync -a --exclude="$OUTPUT_DIR" --exclude=".git" --exclude="*.test" . "$temp_dir/"
+
+    # Create Dockerfile in temp directory
+    echo "$dockerfile_content" > "$temp_dir/Dockerfile"
+
+    # Build and run container
+    local exit_code=0
+    local output
+
+    if $VERBOSE; then
+        log "Building Docker image for Go $go_version..."
+    fi
+
+    # Capture both stdout and stderr, and the exit code
+    if output=$(cd "$temp_dir" && timeout "$DOCKER_TIMEOUT" docker build -t "$container_name" . 2>&1 && \
+                timeout "$DOCKER_TIMEOUT" docker run --rm "$container_name" 2>&1); then
+        log_success "Go $go_version: PASSED"
+        echo "PASSED" > "${result_file}.status"
+    else
+        exit_code=$?
+        log_error "Go $go_version: FAILED (exit code: $exit_code)"
+        echo "FAILED" > "${result_file}.status"
+    fi
+
+    # Save full output
+    echo "$output" > "$result_file"
+
+    # Clean up
+    docker rmi "$container_name" &> /dev/null || true
+    rm -rf "$temp_dir"
+
+    if $VERBOSE; then
+        echo "--- Go $go_version output ---"
+        echo "$output"
+        echo "--- End Go $go_version output ---"
+    fi
+
+    return $exit_code
+}
+
+# Function to run tests in parallel
+run_parallel() {
+    local pids=()
+    local failed_versions=()
+
+    log "Starting parallel tests for ${#GO_VERSIONS[@]} Go versions..."
+
+    # Start all tests in background
+    for version in "${GO_VERSIONS[@]}"; do
+        test_go_version "$version" &
+        pids+=($!)
+    done
+
+    # Wait for all tests to complete
+    for i in "${!pids[@]}"; do
+        local pid=${pids[$i]}
+        local version=${GO_VERSIONS[$i]}
+
+        if ! wait $pid; then
+            failed_versions+=("$version")
+        fi
+    done
+
+    return ${#failed_versions[@]}
+}
+
+# Function to run tests sequentially
+run_sequential() {
+    local failed_versions=()
+
+    log "Starting sequential tests for ${#GO_VERSIONS[@]} Go versions..."
+
+    for version in "${GO_VERSIONS[@]}"; do
+        if ! test_go_version "$version"; then
+            failed_versions+=("$version")
+        fi
+    done
+
+    return ${#failed_versions[@]}
+}
+
+# Main execution
+main() {
+    local start_time
+    start_time=$(date +%s)
+
+    log "Starting Go version compatibility tests..."
+    log "Testing versions: ${GO_VERSIONS[*]}"
+    log "Output directory: $OUTPUT_DIR"
+    log "Parallel execution: $PARALLEL"
+
+    local failed_count
+    if $PARALLEL; then
+        run_parallel
+        failed_count=$?
+    else
+        run_sequential
+        failed_count=$?
+    fi
+
+    local end_time
+    end_time=$(date +%s)
+    local duration=$((end_time - start_time))
+
+    # Collect results for display
+    local passed_versions=()
+    local failed_versions=()
+    local unknown_versions=()
+    local passed_count=0
+
+    for version in "${GO_VERSIONS[@]}"; do
+        local status_file="${OUTPUT_DIR}/go-${version}.txt.status"
+        if [[ -f "$status_file" ]]; then
+            local status
+            status=$(cat "$status_file")
+            if [[ "$status" == "PASSED" ]]; then
+                passed_versions+=("$version")
+                ((passed_count++))
+            else
+                failed_versions+=("$version")
+            fi
+        else
+            unknown_versions+=("$version")
+        fi
+    done
+
+    # Generate summary report
+    local summary_file="${OUTPUT_DIR}/summary.txt"
+    {
+        echo "Go Version Compatibility Test Summary"
+        echo "====================================="
+        echo "Date: $(date)"
+        echo "Duration: ${duration}s"
+        echo "Parallel: $PARALLEL"
+        echo ""
+        echo "Results:"
+
+        for version in "${GO_VERSIONS[@]}"; do
+            local status_file="${OUTPUT_DIR}/go-${version}.txt.status"
+            if [[ -f "$status_file" ]]; then
+                local status
+                status=$(cat "$status_file")
+                if [[ "$status" == "PASSED" ]]; then
+                    echo "  Go $version: ✓ PASSED"
+                else
+                    echo "  Go $version: ✗ FAILED"
+                fi
+            else
+                echo "  Go $version: ? UNKNOWN (no status file)"
+            fi
+        done
+
+        echo ""
+        echo "Summary: $passed_count/${#GO_VERSIONS[@]} versions passed"
+
+        if [[ $failed_count -gt 0 ]]; then
+            echo ""
+            echo "Failed versions details:"
+            for version in "${failed_versions[@]}"; do
+                echo ""
+                echo "--- Go $version (FAILED) ---"
+                local result_file="${OUTPUT_DIR}/go-${version}.txt"
+                if [[ -f "$result_file" ]]; then
+                    tail -n 30 "$result_file"
+                fi
+            done
+        fi
+    } > "$summary_file"
+
+        # Find lowest continuous supported version and check recent versions
+    local lowest_continuous_version=""
+    local recent_versions_failed=false
+    
+    # Sort versions to ensure proper order
+    local sorted_versions=()
+    for version in "${GO_VERSIONS[@]}"; do
+        sorted_versions+=("$version")
+    done
+    # Sort versions numerically (1.11, 1.12, ..., 1.25)
+    IFS=$'\n' sorted_versions=($(sort -V <<< "${sorted_versions[*]}"))
+    
+    # Find lowest continuous supported version (all versions from this point onwards pass)
+    for version in "${sorted_versions[@]}"; do
+        local status_file="${OUTPUT_DIR}/go-${version}.txt.status"
+        local all_subsequent_pass=true
+        
+        # Check if this version and all subsequent versions pass
+        local found_current=false
+        for check_version in "${sorted_versions[@]}"; do
+            if [[ "$check_version" == "$version" ]]; then
+                found_current=true
+            fi
+            
+            if [[ "$found_current" == true ]]; then
+                local check_status_file="${OUTPUT_DIR}/go-${check_version}.txt.status"
+                if [[ -f "$check_status_file" ]]; then
+                    local status
+                    status=$(cat "$check_status_file")
+                    if [[ "$status" != "PASSED" ]]; then
+                        all_subsequent_pass=false
+                        break
+                    fi
+                else
+                    all_subsequent_pass=false
+                    break
+                fi
+            fi
+        done
+        
+        if [[ "$all_subsequent_pass" == true ]]; then
+            lowest_continuous_version="$version"
+            break
+        fi
+    done
+    
+    # Check if the two most recent versions failed
+    local num_versions=${#sorted_versions[@]}
+    if [[ $num_versions -ge 2 ]]; then
+        local second_recent="${sorted_versions[$((num_versions-2))]}"
+        local most_recent="${sorted_versions[$((num_versions-1))]}"
+        
+        local second_recent_status_file="${OUTPUT_DIR}/go-${second_recent}.txt.status"
+        local most_recent_status_file="${OUTPUT_DIR}/go-${most_recent}.txt.status"
+        
+        local second_recent_failed=false
+        local most_recent_failed=false
+        
+        if [[ -f "$second_recent_status_file" ]]; then
+            local status
+            status=$(cat "$second_recent_status_file")
+            if [[ "$status" != "PASSED" ]]; then
+                second_recent_failed=true
+            fi
+        else
+            second_recent_failed=true
+        fi
+        
+        if [[ -f "$most_recent_status_file" ]]; then
+            local status
+            status=$(cat "$most_recent_status_file")
+            if [[ "$status" != "PASSED" ]]; then
+                most_recent_failed=true
+            fi
+        else
+            most_recent_failed=true
+        fi
+        
+        if [[ "$second_recent_failed" == true || "$most_recent_failed" == true ]]; then
+            recent_versions_failed=true
+        fi
+    elif [[ $num_versions -eq 1 ]]; then
+        # Only one version tested, check if it's the most recent and failed
+        local only_version="${sorted_versions[0]}"
+        local only_status_file="${OUTPUT_DIR}/go-${only_version}.txt.status"
+        
+        if [[ -f "$only_status_file" ]]; then
+            local status
+            status=$(cat "$only_status_file")
+            if [[ "$status" != "PASSED" ]]; then
+                recent_versions_failed=true
+            fi
+        else
+            recent_versions_failed=true
+        fi
+    fi
+    
+    # Display summary
+    echo ""
+    log "Test completed in ${duration}s"
+    log "Summary report: $summary_file"
+    
+    echo ""
+    echo "========================================"
+    echo "           FINAL RESULTS"
+    echo "========================================"
+    echo ""
+    
+    # Display passed versions
+    if [[ ${#passed_versions[@]} -gt 0 ]]; then
+        log_success "PASSED (${#passed_versions[@]}/${#GO_VERSIONS[@]}):"
+        # Sort passed versions for display
+        local sorted_passed=()
+        for version in "${sorted_versions[@]}"; do
+            for passed_version in "${passed_versions[@]}"; do
+                if [[ "$version" == "$passed_version" ]]; then
+                    sorted_passed+=("$version")
+                    break
+                fi
+            done
+        done
+        for version in "${sorted_passed[@]}"; do
+            echo -e "  ${GREEN}✓${NC} Go $version"
+        done
+        echo ""
+    fi
+    
+    # Display failed versions
+    if [[ ${#failed_versions[@]} -gt 0 ]]; then
+        log_error "FAILED (${#failed_versions[@]}/${#GO_VERSIONS[@]}):"
+        # Sort failed versions for display
+        local sorted_failed=()
+        for version in "${sorted_versions[@]}"; do
+            for failed_version in "${failed_versions[@]}"; do
+                if [[ "$version" == "$failed_version" ]]; then
+                    sorted_failed+=("$version")
+                    break
+                fi
+            done
+        done
+        for version in "${sorted_failed[@]}"; do
+            echo -e "  ${RED}✗${NC} Go $version"
+        done
+        echo ""
+        
+        # Show failure details
+        echo "========================================"
+        echo "         FAILURE DETAILS"
+        echo "========================================"
+        echo ""
+        
+        for version in "${sorted_failed[@]}"; do
+            echo -e "${RED}--- Go $version FAILURE LOGS (last 30 lines) ---${NC}"
+            local result_file="${OUTPUT_DIR}/go-${version}.txt"
+            if [[ -f "$result_file" ]]; then
+                tail -n 30 "$result_file" | sed 's/^/  /'
+            else
+                echo "  No log file found: $result_file"
+            fi
+            echo ""
+        done
+    fi
+    
+    # Display unknown versions
+    if [[ ${#unknown_versions[@]} -gt 0 ]]; then
+        log_warning "UNKNOWN (${#unknown_versions[@]}/${#GO_VERSIONS[@]}):"
+        for version in "${unknown_versions[@]}"; do
+            echo -e "  ${YELLOW}?${NC} Go $version (no status file)"
+        done
+        echo ""
+    fi
+    
+    echo "========================================"
+    echo "         COMPATIBILITY SUMMARY"
+    echo "========================================"
+    echo ""
+    
+    if [[ -n "$lowest_continuous_version" ]]; then
+        log_success "Lowest continuous supported version: Go $lowest_continuous_version"
+        echo "  (All versions from Go $lowest_continuous_version onwards pass)"
+    else
+        log_error "No continuous version support found"
+        echo "  (No version has all subsequent versions passing)"
+    fi
+    
+    echo ""
+    echo "========================================"
+    echo "Full detailed logs available in: $OUTPUT_DIR"
+    echo "========================================"
+    
+    # Determine exit code based on recent versions
+    if [[ "$recent_versions_failed" == true ]]; then
+        log_error "OVERALL RESULT: Recent Go versions failed - this needs attention!"
+        if [[ -n "$lowest_continuous_version" ]]; then
+            echo "Note: Continuous support starts from Go $lowest_continuous_version"
+        fi
+        exit 1
+    else
+        log_success "OVERALL RESULT: Recent Go versions pass - compatibility looks good!"
+        if [[ -n "$lowest_continuous_version" ]]; then
+            echo "Continuous support starts from Go $lowest_continuous_version"
+        fi
+        exit 0
+    fi
+}
+
+# Trap to clean up on exit
+cleanup() {
+    # Kill any remaining background processes
+    jobs -p | xargs -r kill 2>/dev/null || true
+
+    # Clean up any remaining Docker containers
+    docker ps -q --filter "name=go-toml-test-" | xargs -r docker stop 2>/dev/null || true
+    docker images -q --filter "reference=go-toml-test-*" | xargs -r docker rmi 2>/dev/null || true
+}
+
+trap cleanup EXIT
+
+# Run main function
+main

toml_testgen_support_test.go

@@ -1,15 +1,16 @@
-//go:generate go run ./cmd/tomltestgen/main.go -o toml_testgen_test.go
+//go:generate go run github.com/toml-lang/toml-test/cmd/toml-test@v1.6.0 -copy ./tests
+//go:generate go run ./cmd/tomltestgen/main.go -r v1.6.0 -o toml_testgen_test.go
 
-// This is a support file for toml_testgen_test.go
 package toml_test
 
 import (
 	"encoding/json"
+	"errors"
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 	"github.com/pelletier/go-toml/v2/internal/testsuite"
-	"github.com/stretchr/testify/require"
 )
 
 func testgenInvalid(t *testing.T, input string) {
@@ -38,21 +39,22 @@ func testgenValid(t *testing.T, input string, jsonRef string) {
 
 	err := testsuite.Unmarshal([]byte(input), &doc)
 	if err != nil {
-		if de, ok := err.(*toml.DecodeError); ok {
+		de := &toml.DecodeError{}
+		if errors.As(err, &de) {
 			t.Logf("%s\n%s", err, de)
 		}
 		t.Fatalf("failed parsing toml: %s", err)
 	}
 	j, err := testsuite.ValueToTaggedJSON(doc)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	var ref interface{}
 	err = json.Unmarshal([]byte(jsonRef), &ref)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	var actual interface{}
-	err = json.Unmarshal([]byte(j), &actual)
+	err = json.Unmarshal(j, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	testsuite.CmpJSON(t, "", ref, actual)
 }

types.go

@@ -6,9 +6,18 @@ import (
 	"time"
 )
 
-var timeType = reflect.TypeOf(time.Time{})
+// isZeroer is used to check if a type has a custom IsZero method.
-var textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
+// This allows custom types to define their own zero-value semantics.
-var textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
+type isZeroer interface {
-var mapStringInterfaceType = reflect.TypeOf(map[string]interface{}{})
+	IsZero() bool
-var sliceInterfaceType = reflect.TypeOf([]interface{}{})
+}
-var stringType = reflect.TypeOf("")
+
+var (
+	timeType               = reflect.TypeOf((*time.Time)(nil)).Elem()
+	textMarshalerType      = reflect.TypeOf((*encoding.TextMarshaler)(nil)).Elem()
+	textUnmarshalerType    = reflect.TypeOf((*encoding.TextUnmarshaler)(nil)).Elem()
+	isZeroerType           = reflect.TypeOf((*isZeroer)(nil)).Elem()
+	mapStringInterfaceType = reflect.TypeOf(map[string]interface{}(nil))
+	sliceInterfaceType     = reflect.TypeOf([]interface{}(nil))
+	stringType             = reflect.TypeOf("")
+)

unmarshaler.go

@@ -5,26 +5,23 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math"
 	"reflect"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
 
-	"github.com/pelletier/go-toml/v2/internal/ast"
-	"github.com/pelletier/go-toml/v2/internal/danger"
 	"github.com/pelletier/go-toml/v2/internal/tracker"
+	"github.com/pelletier/go-toml/v2/unstable"
 )
 
 // Unmarshal deserializes a TOML document into a Go value.
 //
 // It is a shortcut for Decoder.Decode() with the default options.
 func Unmarshal(data []byte, v interface{}) error {
-	p := parser{}
+	d := decoder{}
-	p.Reset(data)
+	d.p.Reset(data)
-	d := decoder{p: &p}
-
 	return d.FromParser(v)
 }
 
@@ -35,6 +32,9 @@ type Decoder struct {
 
 	// global settings
 	strict bool
+
+	// toggles unmarshaler interface
+	unmarshalerInterface bool
 }
 
 // NewDecoder creates a new Decoder that will read from r.
@@ -54,13 +54,36 @@ func (d *Decoder) DisallowUnknownFields() *Decoder {
 	return d
 }
 
+// EnableUnmarshalerInterface allows to enable unmarshaler interface.
+//
+// With this feature enabled, types implementing the unstable.Unmarshaler
+// interface can be decoded from any structure of the document. It allows types
+// that don't have a straightforward TOML representation to provide their own
+// decoding logic.
+//
+// The UnmarshalTOML method receives raw TOML bytes:
+//   - For single values: the raw value bytes (e.g., `"hello"` for a string)
+//   - For tables: all key-value lines belonging to that table
+//   - For inline tables/arrays: the raw bytes of the inline structure
+//
+// The unstable.RawMessage type can be used to capture raw TOML bytes for
+// later processing, similar to json.RawMessage.
+//
+// *Unstable:* This method does not follow the compatibility guarantees of
+// semver. It can be changed or removed without a new major version being
+// issued.
+func (d *Decoder) EnableUnmarshalerInterface() *Decoder {
+	d.unmarshalerInterface = true
+	return d
+}
+
 // Decode the whole content of r into v.
 //
 // By default, values in the document that don't exist in the target Go value
 // are ignored. See Decoder.DisallowUnknownFields() to change this behavior.
 //
 // When a TOML local date, time, or date-time is decoded into a time.Time, its
-// value is represented in time.Local timezone. Otherwise the approriate Local*
+// value is represented in time.Local timezone. Otherwise the appropriate Local*
 // structure is used. For time values, precision up to the nanosecond is
 // supported by truncating extra digits.
 //
@@ -96,26 +119,26 @@ func (d *Decoder) DisallowUnknownFields() *Decoder {
 //	Inline Table     -> same as Table
 //	Array of Tables  -> same as Array and Table
 func (d *Decoder) Decode(v interface{}) error {
-	b, err := ioutil.ReadAll(d.r)
+	b, err := io.ReadAll(d.r)
 	if err != nil {
 		return fmt.Errorf("toml: %w", err)
 	}
 
-	p := parser{}
-	p.Reset(b)
 	dec := decoder{
-		p: &p,
 		strict: strict{
 			Enabled: d.strict,
+			doc:     b,
 		},
+		unmarshalerInterface: d.unmarshalerInterface,
 	}
+	dec.p.Reset(b)
 
 	return dec.FromParser(v)
 }
 
 type decoder struct {
 	// Which parser instance in use for this decoding session.
-	p *parser
+	p unstable.Parser
 
 	// Flag indicating that the current expression is stashed.
 	// If set to true, calling nextExpr will not actually pull a new expression
@@ -127,6 +150,10 @@ type decoder struct {
 	// need to be skipped.
 	skipUntilTable bool
 
+	// Flag indicating that the current array/slice table should be cleared because
+	// it is the first encounter of an array table.
+	clearArrayTable bool
+
 	// Tracks position in Go arrays.
 	// This is used when decoding [[array tables]] into Go arrays. Given array
 	// tables are separate TOML expression, we need to keep track of where we
@@ -139,6 +166,9 @@ type decoder struct {
 	// Strict mode
 	strict strict
 
+	// Flag that enables/disables unmarshaler interface.
+	unmarshalerInterface bool
+
 	// Current context for the error.
 	errorContext *errorContext
 }
@@ -149,15 +179,19 @@ type errorContext struct {
 }
 
 func (d *decoder) typeMismatchError(toml string, target reflect.Type) error {
+	return fmt.Errorf("toml: %s", d.typeMismatchString(toml, target))
+}
+
+func (d *decoder) typeMismatchString(toml string, target reflect.Type) string {
 	if d.errorContext != nil && d.errorContext.Struct != nil {
 		ctx := d.errorContext
 		f := ctx.Struct.FieldByIndex(ctx.Field)
-		return fmt.Errorf("toml: cannot decode TOML %s into struct field %s.%s of type %s", toml, ctx.Struct, f.Name, f.Type)
+		return fmt.Sprintf("cannot decode TOML %s into struct field %s.%s of type %s", toml, ctx.Struct, f.Name, f.Type)
 	}
-	return fmt.Errorf("toml: cannot decode TOML %s into a Go value of type %s", toml, target)
+	return fmt.Sprintf("cannot decode TOML %s into a Go value of type %s", toml, target)
 }
 
-func (d *decoder) expr() *ast.Node {
+func (d *decoder) expr() *unstable.Node {
 	return d.p.Expression()
 }
 
@@ -197,7 +231,7 @@ func (d *decoder) FromParser(v interface{}) error {
 	}
 
 	if r.IsNil() {
-		return fmt.Errorf("toml: decoding pointer target cannot be nil")
+		return errors.New("toml: decoding pointer target cannot be nil")
 	}
 
 	r = r.Elem()
@@ -208,12 +242,12 @@ func (d *decoder) FromParser(v interface{}) error {
 
 	err := d.fromParser(r)
 	if err == nil {
-		return d.strict.Error(d.p.data)
+		return d.strict.Error(d.p.Data())
 	}
 
-	var e *decodeError
+	var e *unstable.ParserError
 	if errors.As(err, &e) {
-		return wrapDecodeError(d.p.data, e)
+		return wrapDecodeError(d.p.Data(), e)
 	}
 
 	return err
@@ -234,42 +268,44 @@ func (d *decoder) fromParser(root reflect.Value) error {
 Rules for the unmarshal code:
 
 - The stack is used to keep track of which values need to be set where.
-- handle* functions <=> switch on a given ast.Kind.
+- handle* functions <=> switch on a given unstable.Kind.
 - unmarshalX* functions need to unmarshal a node of kind X.
 - An "object" is either a struct or a map.
 */
 
-func (d *decoder) handleRootExpression(expr *ast.Node, v reflect.Value) error {
+func (d *decoder) handleRootExpression(expr *unstable.Node, v reflect.Value) error {
 	var x reflect.Value
 	var err error
+	var first bool // used for to clear array tables on first use
 
-	if !(d.skipUntilTable && expr.Kind == ast.KeyValue) {
+	if !d.skipUntilTable || expr.Kind != unstable.KeyValue {
-		err = d.seen.CheckExpression(expr)
+		first, err = d.seen.CheckExpression(expr)
 		if err != nil {
 			return err
 		}
 	}
 
 	switch expr.Kind {
-	case ast.KeyValue:
+	case unstable.KeyValue:
 		if d.skipUntilTable {
 			return nil
 		}
 		x, err = d.handleKeyValue(expr, v)
-	case ast.Table:
+	case unstable.Table:
 		d.skipUntilTable = false
 		d.strict.EnterTable(expr)
 		x, err = d.handleTable(expr.Key(), v)
-	case ast.ArrayTable:
+	case unstable.ArrayTable:
 		d.skipUntilTable = false
 		d.strict.EnterArrayTable(expr)
+		d.clearArrayTable = first
 		x, err = d.handleArrayTable(expr.Key(), v)
 	default:
 		panic(fmt.Errorf("parser should not permit expression of kind %s at document root", expr.Kind))
 	}
 
 	if d.skipUntilTable {
-		if expr.Kind == ast.Table || expr.Kind == ast.ArrayTable {
+		if expr.Kind == unstable.Table || expr.Kind == unstable.ArrayTable {
 			d.strict.MissingTable(expr)
 		}
 	} else if err == nil && x.IsValid() {
@@ -279,14 +315,14 @@ func (d *decoder) handleRootExpression(expr *ast.Node, v reflect.Value) error {
 	return err
 }
 
-func (d *decoder) handleArrayTable(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleArrayTable(key unstable.Iterator, v reflect.Value) (reflect.Value, error) {
 	if key.Next() {
 		return d.handleArrayTablePart(key, v)
 	}
 	return d.handleKeyValues(v)
 }
 
-func (d *decoder) handleArrayTableCollectionLast(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleArrayTableCollectionLast(key unstable.Iterator, v reflect.Value) (reflect.Value, error) {
 	switch v.Kind() {
 	case reflect.Interface:
 		elem := v.Elem()
@@ -303,6 +339,10 @@ func (d *decoder) handleArrayTableCollectionLast(key ast.Iterator, v reflect.Val
 				reflect.Copy(nelem, elem)
 				elem = nelem
 			}
+			if d.clearArrayTable && elem.Len() > 0 {
+				elem.SetLen(0)
+				d.clearArrayTable = false
+			}
 		}
 		return d.handleArrayTableCollectionLast(key, elem)
 	case reflect.Ptr:
@@ -321,6 +361,10 @@ func (d *decoder) handleArrayTableCollectionLast(key ast.Iterator, v reflect.Val
 
 		return v, nil
 	case reflect.Slice:
+		if d.clearArrayTable && v.Len() > 0 {
+			v.SetLen(0)
+			d.clearArrayTable = false
+		}
 		elemType := v.Type().Elem()
 		var elem reflect.Value
 		if elemType.Kind() == reflect.Interface {
@@ -339,13 +383,13 @@ func (d *decoder) handleArrayTableCollectionLast(key ast.Iterator, v reflect.Val
 	case reflect.Array:
 		idx := d.arrayIndex(true, v)
 		if idx >= v.Len() {
-			return v, fmt.Errorf("toml: cannot decode array table into %s at position %d", v.Type(), idx)
+			return v, fmt.Errorf("%w at position %d", d.typeMismatchError("array table", v.Type()), idx)
 		}
 		elem := v.Index(idx)
 		_, err := d.handleArrayTable(key, elem)
 		return v, err
 	default:
-		return reflect.Value{}, fmt.Errorf("toml: cannot decode array table into a %s", v.Type())
+		return reflect.Value{}, d.typeMismatchError("array table", v.Type())
 	}
 }
 
@@ -353,7 +397,7 @@ func (d *decoder) handleArrayTableCollectionLast(key ast.Iterator, v reflect.Val
 // evaluated like a normal key, but if it returns a collection, it also needs to
 // point to the last element of the collection. Unless it is the last part of
 // the key, then it needs to create a new element at the end.
-func (d *decoder) handleArrayTableCollection(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleArrayTableCollection(key unstable.Iterator, v reflect.Value) (reflect.Value, error) {
 	if key.IsLast() {
 		return d.handleArrayTableCollectionLast(key, v)
 	}
@@ -377,30 +421,54 @@ func (d *decoder) handleArrayTableCollection(key ast.Iterator, v reflect.Value)
 
 		return v, nil
 	case reflect.Slice:
-		elem := v.Index(v.Len() - 1)
+		// Create a new element when the slice is empty; otherwise operate on
+		// the last element.
+		var (
+			elem    reflect.Value
+			created bool
+		)
+		if v.Len() == 0 {
+			created = true
+			elemType := v.Type().Elem()
+			if elemType.Kind() == reflect.Interface {
+				elem = makeMapStringInterface()
+			} else {
+				elem = reflect.New(elemType).Elem()
+			}
+		} else {
+			elem = v.Index(v.Len() - 1)
+		}
+
 		x, err := d.handleArrayTable(key, elem)
 		if err != nil || d.skipUntilTable {
 			return reflect.Value{}, err
 		}
 		if x.IsValid() {
-			elem.Set(x)
+			if created {
+				elem = x
+			} else {
+				elem.Set(x)
+			}
 		}
 
+		if created {
+			return reflect.Append(v, elem), nil
+		}
 		return v, err
 	case reflect.Array:
 		idx := d.arrayIndex(false, v)
 		if idx >= v.Len() {
-			return v, fmt.Errorf("toml: cannot decode array table into %s at position %d", v.Type(), idx)
+			return v, fmt.Errorf("%w at position %d", d.typeMismatchError("array table", v.Type()), idx)
 		}
 		elem := v.Index(idx)
 		_, err := d.handleArrayTable(key, elem)
 		return v, err
+	default:
+		return d.handleArrayTable(key, v)
 	}
-
-	return d.handleArrayTable(key, v)
 }
 
-func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handlerFn, makeFn valueMakerFn) (reflect.Value, error) {
+func (d *decoder) handleKeyPart(key unstable.Iterator, v reflect.Value, nextFn handlerFn, makeFn valueMakerFn) (reflect.Value, error) {
 	var rv reflect.Value
 
 	// First, dispatch over v to make sure it is a valid object.
@@ -417,7 +485,10 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 		vt := v.Type()
 
 		// Create the key for the map element. Convert to key type.
-		mk := reflect.ValueOf(string(key.Node().Data)).Convert(vt.Key())
+		mk, err := d.keyFromData(vt.Key(), key.Node().Data)
+		if err != nil {
+			return reflect.Value{}, err
+		}
 
 		// If the map does not exist, create it.
 		if v.IsNil() {
@@ -428,7 +499,8 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 
 		mv := v.MapIndex(mk)
 		set := false
-		if !mv.IsValid() {
+		switch {
+		case !mv.IsValid():
 			// If there is no value in the map, create a new one according to
 			// the map type. If the element type is interface, create either a
 			// map[string]interface{} or a []interface{} depending on whether
@@ -441,13 +513,13 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 				mv = reflect.New(t).Elem()
 			}
 			set = true
-		} else if mv.Kind() == reflect.Interface {
+		case mv.Kind() == reflect.Interface:
 			mv = mv.Elem()
 			if !mv.IsValid() {
 				mv = makeFn()
 			}
 			set = true
-		} else if !mv.CanAddr() {
+		case !mv.CanAddr():
 			vt := v.Type()
 			t := vt.Elem()
 			oldmv := mv
@@ -518,7 +590,7 @@ func (d *decoder) handleKeyPart(key ast.Iterator, v reflect.Value, nextFn handle
 // HandleArrayTablePart navigates the Go structure v using the key v. It is
 // only used for the prefix (non-last) parts of an array-table. When
 // encountering a collection, it should go to the last element.
-func (d *decoder) handleArrayTablePart(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleArrayTablePart(key unstable.Iterator, v reflect.Value) (reflect.Value, error) {
 	var makeFn valueMakerFn
 	if key.IsLast() {
 		makeFn = makeSliceInterface
@@ -530,20 +602,30 @@ func (d *decoder) handleArrayTablePart(key ast.Iterator, v reflect.Value) (refle
 
 // HandleTable returns a reference when it has checked the next expression but
 // cannot handle it.
-func (d *decoder) handleTable(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleTable(key unstable.Iterator, v reflect.Value) (reflect.Value, error) {
 	if v.Kind() == reflect.Slice {
-		if v.Len() == 0 {
+		// For non-empty slices, work with the last element
-			return reflect.Value{}, newDecodeError(key.Node().Data, "cannot store a table in a slice")
+		if v.Len() > 0 {
+			elem := v.Index(v.Len() - 1)
+			x, err := d.handleTable(key, elem)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			if x.IsValid() {
+				elem.Set(x)
+			}
+			return reflect.Value{}, nil
 		}
-		elem := v.Index(v.Len() - 1)
+		// Empty slice - check if it implements Unmarshaler (e.g., RawMessage)
-		x, err := d.handleTable(key, elem)
+		// and we're at the end of the key path
-		if err != nil {
+		if d.unmarshalerInterface && !key.Next() {
-			return reflect.Value{}, err
+			if v.CanAddr() && v.Addr().CanInterface() {
+				if outi, ok := v.Addr().Interface().(unstable.Unmarshaler); ok {
+					return d.handleKeyValuesUnmarshaler(outi)
+				}
+			}
 		}
-		if x.IsValid() {
+		return reflect.Value{}, unstable.NewParserError(key.Node().Data, "cannot store a table in a slice")
-			elem.Set(x)
-		}
-		return reflect.Value{}, nil
 	}
 	if key.Next() {
 		// Still scoping the key
@@ -557,10 +639,28 @@ func (d *decoder) handleTable(key ast.Iterator, v reflect.Value) (reflect.Value,
 // Handle root expressions until the end of the document or the next
 // non-key-value.
 func (d *decoder) handleKeyValues(v reflect.Value) (reflect.Value, error) {
+	// Check if target implements Unmarshaler before processing key-values.
+	// This allows types to handle entire tables themselves.
+	if d.unmarshalerInterface {
+		vv := v
+		for vv.Kind() == reflect.Ptr {
+			if vv.IsNil() {
+				vv.Set(reflect.New(vv.Type().Elem()))
+			}
+			vv = vv.Elem()
+		}
+		if vv.CanAddr() && vv.Addr().CanInterface() {
+			if outi, ok := vv.Addr().Interface().(unstable.Unmarshaler); ok {
+				// Collect all key-value expressions for this table
+				return d.handleKeyValuesUnmarshaler(outi)
+			}
+		}
+	}
+
 	var rv reflect.Value
 	for d.nextExpr() {
 		expr := d.expr()
-		if expr.Kind != ast.KeyValue {
+		if expr.Kind != unstable.KeyValue {
 			// Stash the expression so that fromParser can just loop and use
 			// the right handler.
 			// We could just recurse ourselves here, but at least this gives a
@@ -569,7 +669,7 @@ func (d *decoder) handleKeyValues(v reflect.Value) (reflect.Value, error) {
 			break
 		}
 
-		err := d.seen.CheckExpression(expr)
+		_, err := d.seen.CheckExpression(expr)
 		if err != nil {
 			return reflect.Value{}, err
 		}
@@ -586,8 +686,43 @@ func (d *decoder) handleKeyValues(v reflect.Value) (reflect.Value, error) {
 	return rv, nil
 }
 
+// handleKeyValuesUnmarshaler collects all key-value expressions for a table
+// and passes them to the Unmarshaler as raw TOML bytes.
+func (d *decoder) handleKeyValuesUnmarshaler(u unstable.Unmarshaler) (reflect.Value, error) {
+	// Collect raw bytes from all key-value expressions for this table.
+	// We use the Raw field on each KeyValue expression to preserve the
+	// original formatting (whitespace, quoting style, etc.) from the document.
+	var buf []byte
+
+	for d.nextExpr() {
+		expr := d.expr()
+		if expr.Kind != unstable.KeyValue {
+			d.stashExpr()
+			break
+		}
+
+		_, err := d.seen.CheckExpression(expr)
+		if err != nil {
+			return reflect.Value{}, err
+		}
+
+		// Use the raw bytes from the original document to preserve formatting
+		if expr.Raw.Length > 0 {
+			raw := d.p.Raw(expr.Raw)
+			buf = append(buf, raw...)
+		}
+		buf = append(buf, '\n')
+	}
+
+	if err := u.UnmarshalTOML(buf); err != nil {
+		return reflect.Value{}, err
+	}
+
+	return reflect.Value{}, nil
+}
+
 type (
-	handlerFn    func(key ast.Iterator, v reflect.Value) (reflect.Value, error)
+	handlerFn    func(key unstable.Iterator, v reflect.Value) (reflect.Value, error)
 	valueMakerFn func() reflect.Value
 )
 
@@ -599,11 +734,11 @@ func makeSliceInterface() reflect.Value {
 	return reflect.MakeSlice(sliceInterfaceType, 0, 16)
 }
 
-func (d *decoder) handleTablePart(key ast.Iterator, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleTablePart(key unstable.Iterator, v reflect.Value) (reflect.Value, error) {
 	return d.handleKeyPart(key, v, d.handleTable, makeMapStringInterface)
 }
 
-func (d *decoder) tryTextUnmarshaler(node *ast.Node, v reflect.Value) (bool, error) {
+func (d *decoder) tryTextUnmarshaler(node *unstable.Node, v reflect.Value) (bool, error) {
 	// Special case for time, because we allow to unmarshal to it from
 	// different kind of AST nodes.
 	if v.Type() == timeType {
@@ -613,7 +748,7 @@ func (d *decoder) tryTextUnmarshaler(node *ast.Node, v reflect.Value) (bool, err
 	if v.CanAddr() && v.Addr().Type().Implements(textUnmarshalerType) {
 		err := v.Addr().Interface().(encoding.TextUnmarshaler).UnmarshalText(node.Data)
 		if err != nil {
-			return false, newDecodeError(d.p.Raw(node.Raw), "%w", err)
+			return false, unstable.NewParserError(d.p.Raw(node.Raw), "%w", err)
 		}
 
 		return true, nil
@@ -622,43 +757,58 @@ func (d *decoder) tryTextUnmarshaler(node *ast.Node, v reflect.Value) (bool, err
 	return false, nil
 }
 
-func (d *decoder) handleValue(value *ast.Node, v reflect.Value) error {
+func (d *decoder) handleValue(value *unstable.Node, v reflect.Value) error {
 	for v.Kind() == reflect.Ptr {
 		v = initAndDereferencePointer(v)
 	}
 
-	ok, err := d.tryTextUnmarshaler(value, v)
+	if d.unmarshalerInterface {
-	if ok || err != nil {
+		if v.CanAddr() && v.Addr().CanInterface() {
-		return err
+			if outi, ok := v.Addr().Interface().(unstable.Unmarshaler); ok {
+				// Pass raw bytes from the original document
+				return outi.UnmarshalTOML(d.p.Raw(value.Raw))
+			}
+		}
+	}
+
+	// Only try TextUnmarshaler for scalar types. For Array and InlineTable,
+	// fall through to struct/map unmarshaling to allow flexible unmarshaling
+	// where a type can implement UnmarshalText for string values but still
+	// be populated field-by-field from a table. See issue #974.
+	if value.Kind != unstable.Array && value.Kind != unstable.InlineTable {
+		ok, err := d.tryTextUnmarshaler(value, v)
+		if ok || err != nil {
+			return err
+		}
 	}
 
 	switch value.Kind {
-	case ast.String:
+	case unstable.String:
 		return d.unmarshalString(value, v)
-	case ast.Integer:
+	case unstable.Integer:
 		return d.unmarshalInteger(value, v)
-	case ast.Float:
+	case unstable.Float:
 		return d.unmarshalFloat(value, v)
-	case ast.Bool:
+	case unstable.Bool:
 		return d.unmarshalBool(value, v)
-	case ast.DateTime:
+	case unstable.DateTime:
 		return d.unmarshalDateTime(value, v)
-	case ast.LocalDate:
+	case unstable.LocalDate:
 		return d.unmarshalLocalDate(value, v)
-	case ast.LocalTime:
+	case unstable.LocalTime:
 		return d.unmarshalLocalTime(value, v)
-	case ast.LocalDateTime:
+	case unstable.LocalDateTime:
 		return d.unmarshalLocalDateTime(value, v)
-	case ast.InlineTable:
+	case unstable.InlineTable:
 		return d.unmarshalInlineTable(value, v)
-	case ast.Array:
+	case unstable.Array:
 		return d.unmarshalArray(value, v)
 	default:
 		panic(fmt.Errorf("handleValue not implemented for %s", value.Kind))
 	}
 }
 
-func (d *decoder) unmarshalArray(array *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalArray(array *unstable.Node, v reflect.Value) error {
 	switch v.Kind() {
 	case reflect.Slice:
 		if v.IsNil() {
@@ -729,7 +879,7 @@ func (d *decoder) unmarshalArray(array *ast.Node, v reflect.Value) error {
 	return nil
 }
 
-func (d *decoder) unmarshalInlineTable(itable *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalInlineTable(itable *unstable.Node, v reflect.Value) error {
 	// Make sure v is an initialized object.
 	switch v.Kind() {
 	case reflect.Map:
@@ -746,7 +896,7 @@ func (d *decoder) unmarshalInlineTable(itable *ast.Node, v reflect.Value) error
 		}
 		return d.unmarshalInlineTable(itable, elem)
 	default:
-		return newDecodeError(itable.Data, "cannot store inline table in Go type %s", v.Kind())
+		return unstable.NewParserError(d.p.Raw(itable.Raw), "cannot store inline table in Go type %s", v.Kind())
 	}
 
 	it := itable.Children()
@@ -765,70 +915,75 @@ func (d *decoder) unmarshalInlineTable(itable *ast.Node, v reflect.Value) error
 	return nil
 }
 
-func (d *decoder) unmarshalDateTime(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalDateTime(value *unstable.Node, v reflect.Value) error {
 	dt, err := parseDateTime(value.Data)
 	if err != nil {
 		return err
 	}
 
+	if v.Kind() != reflect.Interface && v.Type() != timeType {
+		return unstable.NewParserError(d.p.Raw(value.Raw), "%s", d.typeMismatchString("datetime", v.Type()))
+	}
 	v.Set(reflect.ValueOf(dt))
 	return nil
 }
 
-func (d *decoder) unmarshalLocalDate(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalLocalDate(value *unstable.Node, v reflect.Value) error {
 	ld, err := parseLocalDate(value.Data)
 	if err != nil {
 		return err
 	}
 
+	if v.Kind() != reflect.Interface && v.Type() != timeType {
+		return unstable.NewParserError(d.p.Raw(value.Raw), "%s", d.typeMismatchString("local date", v.Type()))
+	}
 	if v.Type() == timeType {
-		cast := ld.AsTime(time.Local)
+		v.Set(reflect.ValueOf(ld.AsTime(time.Local)))
-		v.Set(reflect.ValueOf(cast))
 		return nil
 	}
-
 	v.Set(reflect.ValueOf(ld))
-
 	return nil
 }
 
-func (d *decoder) unmarshalLocalTime(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalLocalTime(value *unstable.Node, v reflect.Value) error {
 	lt, rest, err := parseLocalTime(value.Data)
 	if err != nil {
 		return err
 	}
 
 	if len(rest) > 0 {
-		return newDecodeError(rest, "extra characters at the end of a local time")
+		return unstable.NewParserError(rest, "extra characters at the end of a local time")
 	}
 
+	if v.Kind() != reflect.Interface {
+		return unstable.NewParserError(d.p.Raw(value.Raw), "%s", d.typeMismatchString("local time", v.Type()))
+	}
 	v.Set(reflect.ValueOf(lt))
 	return nil
 }
 
-func (d *decoder) unmarshalLocalDateTime(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalLocalDateTime(value *unstable.Node, v reflect.Value) error {
 	ldt, rest, err := parseLocalDateTime(value.Data)
 	if err != nil {
 		return err
 	}
 
 	if len(rest) > 0 {
-		return newDecodeError(rest, "extra characters at the end of a local date time")
+		return unstable.NewParserError(rest, "extra characters at the end of a local date time")
 	}
 
+	if v.Kind() != reflect.Interface && v.Type() != timeType {
+		return unstable.NewParserError(d.p.Raw(value.Raw), "%s", d.typeMismatchString("local datetime", v.Type()))
+	}
 	if v.Type() == timeType {
-		cast := ldt.AsTime(time.Local)
+		v.Set(reflect.ValueOf(ldt.AsTime(time.Local)))
-
-		v.Set(reflect.ValueOf(cast))
 		return nil
 	}
-
 	v.Set(reflect.ValueOf(ldt))
-
 	return nil
 }
 
-func (d *decoder) unmarshalBool(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalBool(value *unstable.Node, v reflect.Value) error {
 	b := value.Data[0] == 't'
 
 	switch v.Kind() {
@@ -837,13 +992,13 @@ func (d *decoder) unmarshalBool(value *ast.Node, v reflect.Value) error {
 	case reflect.Interface:
 		v.Set(reflect.ValueOf(b))
 	default:
-		return newDecodeError(value.Data, "cannot assign boolean to a %t", b)
+		return unstable.NewParserError(value.Data, "cannot assign boolean to a %t", b)
 	}
 
 	return nil
 }
 
-func (d *decoder) unmarshalFloat(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalFloat(value *unstable.Node, v reflect.Value) error {
 	f, err := parseFloat(value.Data)
 	if err != nil {
 		return err
@@ -854,13 +1009,13 @@ func (d *decoder) unmarshalFloat(value *ast.Node, v reflect.Value) error {
 		v.SetFloat(f)
 	case reflect.Float32:
 		if f > math.MaxFloat32 {
-			return newDecodeError(value.Data, "number %f does not fit in a float32", f)
+			return unstable.NewParserError(value.Data, "number %f does not fit in a float32", f)
 		}
 		v.SetFloat(f)
 	case reflect.Interface:
 		v.Set(reflect.ValueOf(f))
 	default:
-		return newDecodeError(value.Data, "float cannot be assigned to %s", v.Kind())
+		return unstable.NewParserError(value.Data, "float cannot be assigned to %s", v.Kind())
 	}
 
 	return nil
@@ -879,14 +1034,20 @@ const (
 // compile time, so it is computed during initialization.
 var maxUint int64 = math.MaxInt64
 
-func init() {
+func init() { //nolint:gochecknoinits
 	m := uint64(^uint(0))
+	// #nosec G115
 	if m < uint64(maxUint) {
 		maxUint = int64(m)
 	}
 }
 
-func (d *decoder) unmarshalInteger(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalInteger(value *unstable.Node, v reflect.Value) error {
+	kind := v.Kind()
+	if kind == reflect.Float32 || kind == reflect.Float64 {
+		return d.unmarshalFloat(value, v)
+	}
+
 	i, err := parseInteger(value.Data)
 	if err != nil {
 		return err
@@ -894,7 +1055,7 @@ func (d *decoder) unmarshalInteger(value *ast.Node, v reflect.Value) error {
 
 	var r reflect.Value
 
-	switch v.Kind() {
+	switch kind {
 	case reflect.Int64:
 		v.SetInt(i)
 		return nil
@@ -955,7 +1116,7 @@ func (d *decoder) unmarshalInteger(value *ast.Node, v reflect.Value) error {
 	case reflect.Interface:
 		r = reflect.ValueOf(i)
 	default:
-		return d.typeMismatchError("integer", v.Type())
+		return unstable.NewParserError(d.p.Raw(value.Raw), "%s", d.typeMismatchString("integer", v.Type()))
 	}
 
 	if !r.Type().AssignableTo(v.Type()) {
@@ -967,20 +1128,20 @@ func (d *decoder) unmarshalInteger(value *ast.Node, v reflect.Value) error {
 	return nil
 }
 
-func (d *decoder) unmarshalString(value *ast.Node, v reflect.Value) error {
+func (d *decoder) unmarshalString(value *unstable.Node, v reflect.Value) error {
 	switch v.Kind() {
 	case reflect.String:
 		v.SetString(string(value.Data))
 	case reflect.Interface:
 		v.Set(reflect.ValueOf(string(value.Data)))
 	default:
-		return newDecodeError(d.p.Raw(value.Raw), "cannot store TOML string into a Go %s", v.Kind())
+		return unstable.NewParserError(d.p.Raw(value.Raw), "%s", d.typeMismatchString("string", v.Type()))
 	}
 
 	return nil
 }
 
-func (d *decoder) handleKeyValue(expr *ast.Node, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleKeyValue(expr *unstable.Node, v reflect.Value) (reflect.Value, error) {
 	d.strict.EnterKeyValue(expr)
 
 	v, err := d.handleKeyValueInner(expr.Key(), expr.Value(), v)
@@ -994,7 +1155,7 @@ func (d *decoder) handleKeyValue(expr *ast.Node, v reflect.Value) (reflect.Value
 	return v, err
 }
 
-func (d *decoder) handleKeyValueInner(key ast.Iterator, value *ast.Node, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) handleKeyValueInner(key unstable.Iterator, value *unstable.Node, v reflect.Value) (reflect.Value, error) {
 	if key.Next() {
 		// Still scoping the key
 		return d.handleKeyValuePart(key, value, v)
@@ -1004,7 +1165,63 @@ func (d *decoder) handleKeyValueInner(key ast.Iterator, value *ast.Node, v refle
 	return reflect.Value{}, d.handleValue(value, v)
 }
 
-func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflect.Value) (reflect.Value, error) {
+func (d *decoder) keyFromData(keyType reflect.Type, data []byte) (reflect.Value, error) {
+	switch {
+	case stringType.AssignableTo(keyType):
+		return reflect.ValueOf(string(data)), nil
+
+	case stringType.ConvertibleTo(keyType):
+		return reflect.ValueOf(string(data)).Convert(keyType), nil
+
+	case keyType.Implements(textUnmarshalerType):
+		mk := reflect.New(keyType.Elem())
+		if err := mk.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+			return reflect.Value{}, fmt.Errorf("toml: error unmarshalling key type %s from text: %w", stringType, err)
+		}
+		return mk, nil
+
+	case reflect.PointerTo(keyType).Implements(textUnmarshalerType):
+		mk := reflect.New(keyType)
+		if err := mk.Interface().(encoding.TextUnmarshaler).UnmarshalText(data); err != nil {
+			return reflect.Value{}, fmt.Errorf("toml: error unmarshalling key type %s from text: %w", stringType, err)
+		}
+		return mk.Elem(), nil
+	}
+
+	switch keyType.Kind() {
+	case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+		key, err := strconv.ParseInt(string(data), 10, 64)
+		if err != nil {
+			return reflect.Value{}, fmt.Errorf("toml: error parsing key of type %s from integer: %w", stringType, err)
+		}
+		return reflect.ValueOf(key).Convert(keyType), nil
+	case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+		key, err := strconv.ParseUint(string(data), 10, 64)
+		if err != nil {
+			return reflect.Value{}, fmt.Errorf("toml: error parsing key of type %s from unsigned integer: %w", stringType, err)
+		}
+		return reflect.ValueOf(key).Convert(keyType), nil
+
+	case reflect.Float32:
+		key, err := strconv.ParseFloat(string(data), 32)
+		if err != nil {
+			return reflect.Value{}, fmt.Errorf("toml: error parsing key of type %s from float: %w", stringType, err)
+		}
+		return reflect.ValueOf(float32(key)), nil
+
+	case reflect.Float64:
+		key, err := strconv.ParseFloat(string(data), 64)
+		if err != nil {
+			return reflect.Value{}, fmt.Errorf("toml: error parsing key of type %s from float: %w", stringType, err)
+		}
+		return reflect.ValueOf(float64(key)), nil
+
+	default:
+		return reflect.Value{}, fmt.Errorf("toml: cannot convert map key of type %s to expected type %s", stringType, keyType)
+	}
+}
+
+func (d *decoder) handleKeyValuePart(key unstable.Iterator, value *unstable.Node, v reflect.Value) (reflect.Value, error) {
 	// contains the replacement for v
 	var rv reflect.Value
 
@@ -1014,16 +1231,9 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 	case reflect.Map:
 		vt := v.Type()
 
-		mk := reflect.ValueOf(string(key.Node().Data))
+		mk, err := d.keyFromData(vt.Key(), key.Node().Data)
-		mkt := stringType
+		if err != nil {
-
+			return reflect.Value{}, err
-		keyType := vt.Key()
-		if !mkt.AssignableTo(keyType) {
-			if !mkt.ConvertibleTo(keyType) {
-				return reflect.Value{}, fmt.Errorf("toml: cannot convert map key of type %s to expected type %s", mkt, keyType)
-			}
-
-			mk = mk.Convert(keyType)
 		}
 
 		// If the map does not exist, create it.
@@ -1034,15 +1244,9 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 
 		mv := v.MapIndex(mk)
 		set := false
-		if !mv.IsValid() {
+		if !mv.IsValid() || key.IsLast() {
 			set = true
 			mv = reflect.New(v.Type().Elem()).Elem()
-		} else {
-			if key.IsLast() {
-				var x interface{}
-				mv = reflect.ValueOf(&x).Elem()
-				set = true
-			}
 		}
 
 		nv, err := d.handleKeyValueInner(key, value, mv)
@@ -1060,6 +1264,18 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 	case reflect.Struct:
 		path, found := structFieldPath(v, string(key.Node().Data))
 		if !found {
+			// If no matching struct field is found but the target implements the
+			// unstable.Unmarshaler interface (and it is enabled), delegate the
+			// decoding of this value to the custom unmarshaler.
+			if d.unmarshalerInterface {
+				if v.CanAddr() && v.Addr().CanInterface() {
+					if outi, ok := v.Addr().Interface().(unstable.Unmarshaler); ok {
+						// Pass raw bytes from the original document
+						return reflect.Value{}, outi.UnmarshalTOML(d.p.Raw(value.Raw))
+					}
+				}
+			}
+			// Otherwise, keep previous behavior and skip until the next table.
 			d.skipUntilTable = true
 			break
 		}
@@ -1072,6 +1288,19 @@ func (d *decoder) handleKeyValuePart(key ast.Iterator, value *ast.Node, v reflec
 		d.errorContext.Field = path
 
 		f := fieldByIndex(v, path)
+
+		if !f.CanAddr() {
+			// If the field is not addressable, need to take a slower path and
+			// make a copy of the struct itself to a new location.
+			nvp := reflect.New(v.Type())
+			nvp.Elem().Set(v)
+			v = nvp.Elem()
+			_, err := d.handleKeyValuePart(key, value, v)
+			if err != nil {
+				return reflect.Value{}, err
+			}
+			return nvp.Elem(), nil
+		}
 		x, err := d.handleKeyValueInner(key, value, f)
 		if err != nil {
 			return reflect.Value{}, err
@@ -1137,10 +1366,10 @@ func initAndDereferencePointer(v reflect.Value) reflect.Value {
 
 // Same as reflect.Value.FieldByIndex, but creates pointers if needed.
 func fieldByIndex(v reflect.Value, path []int) reflect.Value {
-	for i, x := range path {
+	for _, x := range path {
 		v = v.Field(x)
 
-		if i < len(path)-1 && v.Kind() == reflect.Pointer {
+		if v.Kind() == reflect.Ptr {
 			if v.IsNil() {
 				v.Set(reflect.New(v.Type().Elem()))
 			}
@@ -1152,13 +1381,13 @@ func fieldByIndex(v reflect.Value, path []int) reflect.Value {
 
 type fieldPathsMap = map[string][]int
 
-var globalFieldPathsCache atomic.Value // map[danger.TypeID]fieldPathsMap
+var globalFieldPathsCache atomic.Value // map[reflect.Type]fieldPathsMap
 
 func structFieldPath(v reflect.Value, name string) ([]int, bool) {
 	t := v.Type()
 
-	cache, _ := globalFieldPathsCache.Load().(map[danger.TypeID]fieldPathsMap)
+	cache, _ := globalFieldPathsCache.Load().(map[reflect.Type]fieldPathsMap)
-	fieldPaths, ok := cache[danger.MakeTypeID(t)]
+	fieldPaths, ok := cache[t]
 
 	if !ok {
 		fieldPaths = map[string][]int{}
@@ -1169,8 +1398,8 @@ func structFieldPath(v reflect.Value, name string) ([]int, bool) {
 			fieldPaths[strings.ToLower(name)] = path
 		})
 
-		newCache := make(map[danger.TypeID]fieldPathsMap, len(cache)+1)
+		newCache := make(map[reflect.Type]fieldPathsMap, len(cache)+1)
-		newCache[danger.MakeTypeID(t)] = fieldPaths
+		newCache[t] = fieldPaths
 		for k, v := range cache {
 			newCache[k] = v
 		}
@@ -1194,7 +1423,9 @@ func forEachField(t reflect.Type, path []int, do func(name string, path []int))
 			continue
 		}
 
-		fieldPath := append(path, i)
+		fieldPath := make([]int, 0, len(path)+1)
+		fieldPath = append(fieldPath, path...)
+		fieldPath = append(fieldPath, i)
 		fieldPath = fieldPath[:len(fieldPath):len(fieldPath)]
 
 		name := f.Tag.Get("toml")
@@ -1208,7 +1439,7 @@ func forEachField(t reflect.Type, path []int, do func(name string, path []int))
 
 		if f.Anonymous && name == "" {
 			t2 := f.Type
-			if t2.Kind() == reflect.Pointer {
+			if t2.Kind() == reflect.Ptr {
 				t2 = t2.Elem()
 			}
 

unstable/ast.go

@@ -0,0 +1,149 @@
+package unstable
+
+import (
+	"errors"
+	"fmt"
+)
+
+// Iterator over a sequence of nodes.
+//
+// Starts uninitialized, you need to call Next() first.
+//
+// For example:
+//
+//	it := n.Children()
+//	for it.Next() {
+//		n := it.Node()
+//		// do something with n
+//	}
+type Iterator struct {
+	nodes   *[]Node
+	idx     int32
+	started bool
+}
+
+// Next moves the iterator forward and returns true if points to a
+// node, false otherwise.
+func (c *Iterator) Next() bool {
+	if c.nodes == nil {
+		return false
+	}
+	nodes := *c.nodes
+	if !c.started {
+		c.started = true
+	} else {
+		idx := c.idx
+		if idx >= 0 && int(idx) < len(nodes) {
+			c.idx = nodes[idx].next
+		}
+	}
+	return c.idx >= 0 && int(c.idx) < len(nodes)
+}
+
+// IsLast returns true if the current node of the iterator is the last
+// one.  Subsequent calls to Next() will return false.
+func (c *Iterator) IsLast() bool {
+	return c.nodes == nil || c.idx < 0 || (*c.nodes)[c.idx].next < 0
+}
+
+// Node returns a pointer to the node pointed at by the iterator.
+func (c *Iterator) Node() *Node {
+	if c.nodes == nil || c.idx < 0 {
+		return nil
+	}
+	n := &(*c.nodes)[c.idx]
+	n.nodes = c.nodes
+	return n
+}
+
+// Node in a TOML expression AST.
+//
+// Depending on Kind, its sequence of children should be interpreted
+// differently.
+//
+//   - Array have one child per element in the array.
+//   - InlineTable have one child per key-value in the table (each of kind
+//     InlineTable).
+//   - KeyValue have at least two children. The first one is the value. The rest
+//     make a potentially dotted key.
+//   - Table and ArrayTable's children represent a dotted key (same as
+//     KeyValue, but without the first node being the value).
+//
+// When relevant, Raw describes the range of bytes this node is referring to in
+// the input document. Use Parser.Raw() to retrieve the actual bytes.
+type Node struct {
+	Kind Kind
+	Raw  Range  // Raw bytes from the input.
+	Data []byte // Node value (either allocated or referencing the input).
+
+	// Absolute indices into the backing nodes slice. -1 means none.
+	next  int32
+	child int32
+
+	// Reference to the backing nodes slice for navigation.
+	nodes *[]Node
+}
+
+// Range of bytes in the document.
+type Range struct {
+	Offset uint32
+	Length uint32
+}
+
+// Next returns a pointer to the next node, or nil if there is no next node.
+func (n *Node) Next() *Node {
+	if n.next < 0 {
+		return nil
+	}
+	next := &(*n.nodes)[n.next]
+	next.nodes = n.nodes
+	return next
+}
+
+// Child returns a pointer to the first child node of this node. Other children
+// can be accessed calling Next on the first child.  Returns nil if this Node
+// has no child.
+func (n *Node) Child() *Node {
+	if n.child < 0 {
+		return nil
+	}
+	child := &(*n.nodes)[n.child]
+	child.nodes = n.nodes
+	return child
+}
+
+// Valid returns true if the node's kind is set (not to Invalid).
+func (n *Node) Valid() bool {
+	return n != nil
+}
+
+// Key returns the children nodes making the Key on a supported node. Panics
+// otherwise.  They are guaranteed to be all be of the Kind Key. A simple key
+// would return just one element.
+func (n *Node) Key() Iterator {
+	switch n.Kind {
+	case KeyValue:
+		child := n.child
+		if child < 0 {
+			panic(errors.New("KeyValue should have at least two children"))
+		}
+		valueNode := &(*n.nodes)[child]
+		return Iterator{nodes: n.nodes, idx: valueNode.next}
+	case Table, ArrayTable:
+		return Iterator{nodes: n.nodes, idx: n.child}
+	default:
+		panic(fmt.Errorf("Key() is not supported on a %s", n.Kind))
+	}
+}
+
+// Value returns a pointer to the value node of a KeyValue.
+// Guaranteed to be non-nil.  Panics if not called on a KeyValue node,
+// or if the Children are malformed.
+func (n *Node) Value() *Node {
+	return n.Child()
+}
+
+// Children returns an iterator over a node's children.
+func (n *Node) Children() Iterator {
+	return Iterator{nodes: n.nodes, idx: n.child}
+}

unstable/benchmark_test.go

@@ -1,16 +1,18 @@
-package toml
+package unstable
 
 import (
 	"bytes"
 	"testing"
 )
 
-var valid10Ascii = []byte("1234567890")
+var (
-var valid10Utf8 = []byte("日本語a")
+	valid10ASCII = []byte("1234567890")
-var valid1kUtf8 = bytes.Repeat([]byte("0123456789日本語日本語日本語日abcdefghijklmnopqrstuvwx"), 16)
+	valid10Utf8  = []byte("日本語a")
-var valid1MUtf8 = bytes.Repeat(valid1kUtf8, 1024)
+	valid1kUtf8  = bytes.Repeat([]byte("0123456789日本語日本語日本語日abcdefghijklmnopqrstuvwx"), 16)
-var valid1kAscii = bytes.Repeat([]byte("012345678998jhjklasDJKLAAdjdfjsdklfjdslkabcdefghijklmnopqrstuvwx"), 16)
+	valid1MUtf8  = bytes.Repeat(valid1kUtf8, 1024)
-var valid1MAscii = bytes.Repeat(valid1kAscii, 1024)
+	valid1kASCII = bytes.Repeat([]byte("012345678998jhjklasDJKLAAdjdfjsdklfjdslkabcdefghijklmnopqrstuvwx"), 16)
+	valid1MASCII = bytes.Repeat(valid1kASCII, 1024)
+)
 
 func BenchmarkScanComments(b *testing.B) {
 	wrap := func(x []byte) []byte {
@@ -18,9 +20,9 @@ func BenchmarkScanComments(b *testing.B) {
 	}
 
 	inputs := map[string][]byte{
-		"10Valid":     wrap(valid10Ascii),
+		"10Valid":     wrap(valid10ASCII),
-		"1kValid":     wrap(valid1kAscii),
+		"1kValid":     wrap(valid1kASCII),
-		"1MValid":     wrap(valid1MAscii),
+		"1MValid":     wrap(valid1MASCII),
 		"10ValidUtf8": wrap(valid10Utf8),
 		"1kValidUtf8": wrap(valid1kUtf8),
 		"1MValidUtf8": wrap(valid1MUtf8),
@@ -33,7 +35,7 @@ func BenchmarkScanComments(b *testing.B) {
 			b.ResetTimer()
 
 			for i := 0; i < b.N; i++ {
-				scanComment(input)
+				_, _, _ = scanComment(input)
 			}
 		})
 	}
@@ -45,9 +47,9 @@ func BenchmarkParseLiteralStringValid(b *testing.B) {
 	}
 
 	inputs := map[string][]byte{
-		"10Valid":     wrap(valid10Ascii),
+		"10Valid":     wrap(valid10ASCII),
-		"1kValid":     wrap(valid1kAscii),
+		"1kValid":     wrap(valid1kASCII),
-		"1MValid":     wrap(valid1MAscii),
+		"1MValid":     wrap(valid1MASCII),
 		"10ValidUtf8": wrap(valid10Utf8),
 		"1kValidUtf8": wrap(valid1kUtf8),
 		"1MValidUtf8": wrap(valid1MUtf8),
@@ -55,7 +57,7 @@ func BenchmarkParseLiteralStringValid(b *testing.B) {
 
 	for name, input := range inputs {
 		b.Run(name, func(b *testing.B) {
-			p := parser{}
+			p := Parser{}
 			b.SetBytes(int64(len(input)))
 			b.ReportAllocs()
 			b.ResetTimer()
@@ -63,7 +65,7 @@ func BenchmarkParseLiteralStringValid(b *testing.B) {
 			for i := 0; i < b.N; i++ {
 				_, _, _, err := p.parseLiteralString(input)
 				if err != nil {
-					panic(err)
+					b.Error(err)
 				}
 			}
 		})

unstable/builder.go

@@ -0,0 +1,64 @@
+package unstable
+
+// root contains a full AST.
+//
+// It is immutable once constructed with Builder.
+type root struct {
+	nodes []Node
+}
+
+func (r *root) at(idx reference) *Node {
+	return &r.nodes[idx]
+}
+
+type reference int
+
+const invalidReference reference = -1
+
+func (r reference) Valid() bool {
+	return r != invalidReference
+}
+
+type builder struct {
+	tree    root
+	lastIdx int
+}
+
+func (b *builder) NodeAt(ref reference) *Node {
+	n := b.tree.at(ref)
+	n.nodes = &b.tree.nodes
+	return n
+}
+
+func (b *builder) Reset() {
+	b.tree.nodes = b.tree.nodes[:0]
+	b.lastIdx = 0
+}
+
+func (b *builder) Push(n Node) reference {
+	b.lastIdx = len(b.tree.nodes)
+	n.next = -1
+	n.child = -1
+	b.tree.nodes = append(b.tree.nodes, n)
+	return reference(b.lastIdx)
+}
+
+func (b *builder) PushAndChain(n Node) reference {
+	newIdx := len(b.tree.nodes)
+	n.next = -1
+	n.child = -1
+	b.tree.nodes = append(b.tree.nodes, n)
+	if b.lastIdx >= 0 {
+		b.tree.nodes[b.lastIdx].next = int32(newIdx) //nolint:gosec // TOML ASTs are small
+	}
+	b.lastIdx = newIdx
+	return reference(b.lastIdx)
+}
+
+func (b *builder) AttachChild(parent reference, child reference) {
+	b.tree.nodes[parent].child = int32(child) //nolint:gosec // TOML ASTs are small
+}
+
+func (b *builder) Chain(from reference, to reference) {
+	b.tree.nodes[from].next = int32(to) //nolint:gosec // TOML ASTs are small
+}

unstable/doc.go

@@ -0,0 +1,3 @@
+// Package unstable provides APIs that do not meet the backward compatibility
+// guarantees yet.
+package unstable

unstable/kind.go

@@ -1,35 +1,49 @@
-package ast
+package unstable
 
 import "fmt"
 
+// Kind represents the type of TOML structure contained in a given Node.
 type Kind int
 
 const (
-	// meta
+	// Invalid represents an invalid meta node.
 	Invalid Kind = iota
+	// Comment represents a comment meta node.
 	Comment
+	// Key represents a key meta node.
 	Key
 
-	// top level structures
+	// Table represents a top-level table.
 	Table
+	// ArrayTable represents a top-level array table.
 	ArrayTable
+	// KeyValue represents a top-level key value.
 	KeyValue
 
-	// containers values
+	// Array represents an array container value.
 	Array
+	// InlineTable represents an inline table container value.
 	InlineTable
 
-	// values
+	// String represents a string value.
 	String
+	// Bool represents a boolean value.
 	Bool
+	// Float represents a floating point value.
 	Float
+	// Integer represents an integer value.
 	Integer
+	// LocalDate represents a a local date value.
 	LocalDate
+	// LocalTime represents a local time value.
 	LocalTime
+	// LocalDateTime represents a local date/time value.
 	LocalDateTime
+	// DateTime represents a data/time value.
 	DateTime
 )
 
+// String implementation of fmt.Stringer.
 func (k Kind) String() string {
 	switch k {
 	case Invalid:

unstable/parser.go

@@ -1,50 +1,133 @@
-package toml
+package unstable
 
 import (
 	"bytes"
+	"fmt"
+	"reflect"
 	"unicode"
 
-	"github.com/pelletier/go-toml/v2/internal/ast"
+	"github.com/pelletier/go-toml/v2/internal/characters"
-	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
-type parser struct {
+// ParserError describes an error relative to the content of the document.
-	builder ast.Builder
+//
-	ref     ast.Reference
+// It cannot outlive the instance of Parser it refers to, and may cause panics
-	data    []byte
+// if the parser is reset.
-	left    []byte
+type ParserError struct {
-	err     error
+	Highlight []byte
-	first   bool
+	Message   string
+	Key       []string // optional
 }
 
-func (p *parser) Range(b []byte) ast.Range {
+// Error is the implementation of the error interface.
-	return ast.Range{
+func (e *ParserError) Error() string {
-		Offset: uint32(danger.SubsliceOffset(p.data, b)),
+	return e.Message
-		Length: uint32(len(b)),
+}
+
+// NewParserError is a convenience function to create a ParserError
+//
+// Warning: Highlight needs to be a subslice of Parser.data, so only slices
+// returned by Parser.Raw are valid candidates.
+func NewParserError(highlight []byte, format string, args ...interface{}) error {
+	return &ParserError{
+		Highlight: highlight,
+		Message:   fmt.Errorf(format, args...).Error(),
 	}
 }
 
-func (p *parser) Raw(raw ast.Range) []byte {
+// Parser scans over a TOML-encoded document and generates an iterative AST.
+//
+// To prime the Parser, first reset it with the contents of a TOML document.
+// Then, process all top-level expressions sequentially. See Example.
+//
+// Don't forget to check Error() after you're done parsing.
+//
+// Each top-level expression needs to be fully processed before calling
+// NextExpression() again. Otherwise, calls to various Node methods may panic if
+// the parser has moved on the next expression.
+//
+// For performance reasons, go-toml doesn't make a copy of the input bytes to
+// the parser. Make sure to copy all the bytes you need to outlive the slice
+// given to the parser.
+type Parser struct {
+	data    []byte
+	builder builder
+	ref     reference
+	left    []byte
+	err     error
+	first   bool
+
+	KeepComments bool
+}
+
+// Data returns the slice provided to the last call to Reset.
+func (p *Parser) Data() []byte {
+	return p.data
+}
+
+// Range returns a range description that corresponds to a given slice of the
+// input. If the argument is not a subslice of the parser input, this function
+// panics.
+func (p *Parser) Range(b []byte) Range {
+	return Range{
+		Offset: uint32(subsliceOffset(p.data, b)), //nolint:gosec // TOML documents are small
+		Length: uint32(len(b)),                    //nolint:gosec // TOML documents are small
+	}
+}
+
+// rangeOfToken computes the Range of a token given the remaining bytes after the token.
+// This is used when the token was extracted from the beginning of some position,
+// and 'rest' is what remains after the token.
+func (p *Parser) rangeOfToken(token, rest []byte) Range {
+	offset := len(p.data) - len(token) - len(rest)
+	return Range{Offset: uint32(offset), Length: uint32(len(token))} //nolint:gosec // TOML documents are small
+}
+
+// subsliceOffset returns the byte offset of subslice b within data.
+// b must share the same backing array as data (any subslice of data).
+func subsliceOffset(data, b []byte) int {
+	if len(b) == 0 {
+		return 0
+	}
+
+	dataPtr := reflect.ValueOf(data).Pointer()
+	bPtr := reflect.ValueOf(b).Pointer()
+
+	offset := int(bPtr - dataPtr)
+	if offset < 0 || offset > len(data) {
+		panic("subslice is not within data")
+	}
+	return offset
+}
+
+// Raw returns the slice corresponding to the bytes in the given range.
+func (p *Parser) Raw(raw Range) []byte {
 	return p.data[raw.Offset : raw.Offset+raw.Length]
 }
 
-func (p *parser) Reset(b []byte) {
+// Reset brings the parser to its initial state for a given input. It wipes an
+// reuses internal storage to reduce allocation.
+func (p *Parser) Reset(b []byte) {
 	p.builder.Reset()
-	p.ref = ast.InvalidReference
+	p.ref = invalidReference
 	p.data = b
 	p.left = b
 	p.err = nil
 	p.first = true
 }
 
-//nolint:cyclop
+// NextExpression parses the next top-level expression. If an expression was
-func (p *parser) NextExpression() bool {
+// successfully parsed, it returns true. If the parser is at the end of the
+// document or an error occurred, it returns false.
+//
+// Retrieve the parsed expression with Expression().
+func (p *Parser) NextExpression() bool {
 	if len(p.left) == 0 || p.err != nil {
 		return false
 	}
 
 	p.builder.Reset()
-	p.ref = ast.InvalidReference
+	p.ref = invalidReference
 
 	for {
 		if len(p.left) == 0 || p.err != nil {
@@ -73,15 +156,54 @@ func (p *parser) NextExpression() bool {
 	}
 }
 
-func (p *parser) Expression() *ast.Node {
+// Expression returns a pointer to the node representing the last successfully
+// parsed expression.
+func (p *Parser) Expression() *Node {
 	return p.builder.NodeAt(p.ref)
 }
 
-func (p *parser) Error() error {
+// Error returns any error that has occurred during parsing.
+func (p *Parser) Error() error {
 	return p.err
 }
 
-func (p *parser) parseNewline(b []byte) ([]byte, error) {
+// Position describes a position in the input.
+type Position struct {
+	// Number of bytes from the beginning of the input.
+	Offset int
+	// Line number, starting at 1.
+	Line int
+	// Column number, starting at 1.
+	Column int
+}
+
+// Shape describes the position of a range in the input.
+type Shape struct {
+	Start Position
+	End   Position
+}
+
+// Shape returns the shape of the given range in the input.  Will
+// panic if the range is not a subslice of the input.
+func (p *Parser) Shape(r Range) Shape {
+	return Shape{
+		Start: p.positionAt(int(r.Offset)),
+		End:   p.positionAt(int(r.Offset + r.Length)),
+	}
+}
+
+// positionAt returns the position at the given byte offset in the document.
+func (p *Parser) positionAt(offset int) Position {
+	lead := p.data[:offset]
+
+	return Position{
+		Offset: offset,
+		Line:   bytes.Count(lead, []byte{'\n'}) + 1,
+		Column: len(lead) - bytes.LastIndex(lead, []byte{'\n'}),
+	}
+}
+
+func (p *Parser) parseNewline(b []byte) ([]byte, error) {
 	if b[0] == '\n' {
 		return b[1:], nil
 	}
@@ -91,14 +213,27 @@ func (p *parser) parseNewline(b []byte) ([]byte, error) {
 		return rest, err
 	}
 
-	return nil, newDecodeError(b[0:1], "expected newline but got %#U", b[0])
+	return nil, NewParserError(b[0:1], "expected newline but got %#U", b[0])
 }
 
-func (p *parser) parseExpression(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseComment(b []byte) (reference, []byte, error) {
+	ref := invalidReference
+	data, rest, err := scanComment(b)
+	if p.KeepComments && err == nil {
+		ref = p.builder.Push(Node{
+			Kind: Comment,
+			Raw:  p.rangeOfToken(data, rest),
+			Data: data,
+		})
+	}
+	return ref, rest, err
+}
+
+func (p *Parser) parseExpression(b []byte) (reference, []byte, error) {
 	// expression =  ws [ comment ]
 	// expression =/ ws keyval ws [ comment ]
 	// expression =/ ws table ws [ comment ]
-	ref := ast.InvalidReference
+	ref := invalidReference
 
 	b = p.parseWhitespace(b)
 
@@ -107,7 +242,7 @@ func (p *parser) parseExpression(b []byte) (ast.Reference, []byte, error) {
 	}
 
 	if b[0] == '#' {
-		_, rest, err := scanComment(b)
+		ref, rest, err := p.parseComment(b)
 		return ref, rest, err
 	}
 
@@ -129,14 +264,17 @@ func (p *parser) parseExpression(b []byte) (ast.Reference, []byte, error) {
 	b = p.parseWhitespace(b)
 
 	if len(b) > 0 && b[0] == '#' {
-		_, rest, err := scanComment(b)
+		cref, rest, err := p.parseComment(b)
+		if cref != invalidReference {
+			p.builder.Chain(ref, cref)
+		}
 		return ref, rest, err
 	}
 
 	return ref, b, nil
 }
 
-func (p *parser) parseTable(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseTable(b []byte) (reference, []byte, error) {
 	// table = std-table / array-table
 	if len(b) > 1 && b[1] == '[' {
 		return p.parseArrayTable(b)
@@ -145,12 +283,12 @@ func (p *parser) parseTable(b []byte) (ast.Reference, []byte, error) {
 	return p.parseStdTable(b)
 }
 
-func (p *parser) parseArrayTable(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseArrayTable(b []byte) (reference, []byte, error) {
 	// array-table = array-table-open key array-table-close
 	// array-table-open  = %x5B.5B ws  ; [[ Double left square bracket
 	// array-table-close = ws %x5D.5D  ; ]] Double right square bracket
-	ref := p.builder.Push(ast.Node{
+	ref := p.builder.Push(Node{
-		Kind: ast.ArrayTable,
+		Kind: ArrayTable,
 	})
 
 	b = b[2:]
@@ -174,12 +312,12 @@ func (p *parser) parseArrayTable(b []byte) (ast.Reference, []byte, error) {
 	return ref, b, err
 }
 
-func (p *parser) parseStdTable(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseStdTable(b []byte) (reference, []byte, error) {
 	// std-table = std-table-open key std-table-close
 	// std-table-open  = %x5B ws     ; [ Left square bracket
 	// std-table-close = ws %x5D     ; ] Right square bracket
-	ref := p.builder.Push(ast.Node{
+	ref := p.builder.Push(Node{
-		Kind: ast.Table,
+		Kind: Table,
 	})
 
 	b = b[1:]
@@ -199,15 +337,18 @@ func (p *parser) parseStdTable(b []byte) (ast.Reference, []byte, error) {
 	return ref, b, err
 }
 
-func (p *parser) parseKeyval(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseKeyval(b []byte) (reference, []byte, error) {
 	// keyval = key keyval-sep val
-	ref := p.builder.Push(ast.Node{
+	// Track the start position for Raw range
-		Kind: ast.KeyValue,
+	startB := b
+
+	ref := p.builder.Push(Node{
+		Kind: KeyValue,
 	})
 
 	key, b, err := p.parseKey(b)
 	if err != nil {
-		return ast.InvalidReference, nil, err
+		return invalidReference, nil, err
 	}
 
 	// keyval-sep = ws %x3D ws ; =
@@ -215,12 +356,12 @@ func (p *parser) parseKeyval(b []byte) (ast.Reference, []byte, error) {
 	b = p.parseWhitespace(b)
 
 	if len(b) == 0 {
-		return ast.InvalidReference, nil, newDecodeError(b, "expected = after a key, but the document ends there")
+		return invalidReference, nil, NewParserError(startB[:len(startB)-len(b)], "expected = after a key, but the document ends there")
 	}
 
 	b, err = expect('=', b)
 	if err != nil {
-		return ast.InvalidReference, nil, err
+		return invalidReference, nil, err
 	}
 
 	b = p.parseWhitespace(b)
@@ -233,16 +374,21 @@ func (p *parser) parseKeyval(b []byte) (ast.Reference, []byte, error) {
 	p.builder.Chain(valRef, key)
 	p.builder.AttachChild(ref, valRef)
 
+	// Set Raw to span the entire key-value expression.
+	// Access the node directly in the slice to avoid the write barrier
+	// that NodeAt's nodes-pointer setup would trigger.
+	p.builder.tree.nodes[ref].Raw = p.rangeOfToken(startB[:len(startB)-len(b)], b)
+
 	return ref, b, err
 }
 
 //nolint:cyclop,funlen
-func (p *parser) parseVal(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseVal(b []byte) (reference, []byte, error) {
 	// val = string / boolean / array / inline-table / date-time / float / integer
-	ref := ast.InvalidReference
+	ref := invalidReference
 
 	if len(b) == 0 {
-		return ref, nil, newDecodeError(b, "expected value, not eof")
+		return ref, nil, NewParserError(b, "expected value, not eof")
 	}
 
 	var err error
@@ -259,9 +405,9 @@ func (p *parser) parseVal(b []byte) (ast.Reference, []byte, error) {
 		}
 
 		if err == nil {
-			ref = p.builder.Push(ast.Node{
+			ref = p.builder.Push(Node{
-				Kind: ast.String,
+				Kind: String,
-				Raw:  p.Range(raw),
+				Raw:  p.rangeOfToken(raw, b),
 				Data: v,
 			})
 		}
@@ -277,9 +423,9 @@ func (p *parser) parseVal(b []byte) (ast.Reference, []byte, error) {
 		}
 
 		if err == nil {
-			ref = p.builder.Push(ast.Node{
+			ref = p.builder.Push(Node{
-				Kind: ast.String,
+				Kind: String,
-				Raw:  p.Range(raw),
+				Raw:  p.rangeOfToken(raw, b),
 				Data: v,
 			})
 		}
@@ -287,22 +433,22 @@ func (p *parser) parseVal(b []byte) (ast.Reference, []byte, error) {
 		return ref, b, err
 	case 't':
 		if !scanFollowsTrue(b) {
-			return ref, nil, newDecodeError(atmost(b, 4), "expected 'true'")
+			return ref, nil, NewParserError(atmost(b, 4), "expected 'true'")
 		}
 
-		ref = p.builder.Push(ast.Node{
+		ref = p.builder.Push(Node{
-			Kind: ast.Bool,
+			Kind: Bool,
 			Data: b[:4],
 		})
 
 		return ref, b[4:], nil
 	case 'f':
 		if !scanFollowsFalse(b) {
-			return ref, nil, newDecodeError(atmost(b, 5), "expected 'false'")
+			return ref, nil, NewParserError(atmost(b, 5), "expected 'false'")
 		}
 
-		ref = p.builder.Push(ast.Node{
+		ref = p.builder.Push(Node{
-			Kind: ast.Bool,
+			Kind: Bool,
 			Data: b[:5],
 		})
 
@@ -324,7 +470,7 @@ func atmost(b []byte, n int) []byte {
 	return b[:n]
 }
 
-func (p *parser) parseLiteralString(b []byte) ([]byte, []byte, []byte, error) {
+func (p *Parser) parseLiteralString(b []byte) ([]byte, []byte, []byte, error) {
 	v, rest, err := scanLiteralString(b)
 	if err != nil {
 		return nil, nil, nil, err
@@ -333,19 +479,20 @@ func (p *parser) parseLiteralString(b []byte) ([]byte, []byte, []byte, error) {
 	return v, v[1 : len(v)-1], rest, nil
 }
 
-func (p *parser) parseInlineTable(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseInlineTable(b []byte) (reference, []byte, error) {
 	// inline-table = inline-table-open [ inline-table-keyvals ] inline-table-close
 	// inline-table-open  = %x7B ws     ; {
 	// inline-table-close = ws %x7D     ; }
 	// inline-table-sep   = ws %x2C ws  ; , Comma
 	// inline-table-keyvals = keyval [ inline-table-sep inline-table-keyvals ]
-	parent := p.builder.Push(ast.Node{
+	parent := p.builder.Push(Node{
-		Kind: ast.InlineTable,
+		Kind: InlineTable,
+		Raw:  p.rangeOfToken(b[:1], b[1:]),
 	})
 
 	first := true
 
-	var child ast.Reference
+	var child reference
 
 	b = b[1:]
 
@@ -356,7 +503,7 @@ func (p *parser) parseInlineTable(b []byte) (ast.Reference, []byte, error) {
 		b = p.parseWhitespace(b)
 
 		if len(b) == 0 {
-			return parent, nil, newDecodeError(previousB[:1], "inline table is incomplete")
+			return parent, nil, NewParserError(previousB[:1], "inline table is incomplete")
 		}
 
 		if b[0] == '}' {
@@ -371,7 +518,7 @@ func (p *parser) parseInlineTable(b []byte) (ast.Reference, []byte, error) {
 			b = p.parseWhitespace(b)
 		}
 
-		var kv ast.Reference
+		var kv reference
 
 		kv, b, err = p.parseKeyval(b)
 		if err != nil {
@@ -394,7 +541,7 @@ func (p *parser) parseInlineTable(b []byte) (ast.Reference, []byte, error) {
 }
 
 //nolint:funlen,cyclop
-func (p *parser) parseValArray(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseValArray(b []byte) (reference, []byte, error) {
 	// array = array-open [ array-values ] ws-comment-newline array-close
 	// array-open =  %x5B ; [
 	// array-close = %x5D ; ]
@@ -405,23 +552,39 @@ func (p *parser) parseValArray(b []byte) (ast.Reference, []byte, error) {
 	arrayStart := b
 	b = b[1:]
 
-	parent := p.builder.Push(ast.Node{
+	parent := p.builder.Push(Node{
-		Kind: ast.Array,
+		Kind: Array,
 	})
 
+	// First indicates whether the parser is looking for the first element
+	// (non-comment) of the array.
 	first := true
 
-	var lastChild ast.Reference
+	lastChild := invalidReference
+
+	addChild := func(valueRef reference) {
+		if lastChild == invalidReference {
+			p.builder.AttachChild(parent, valueRef)
+		} else {
+			p.builder.Chain(lastChild, valueRef)
+		}
+		lastChild = valueRef
+	}
 
 	var err error
 	for len(b) > 0 {
-		b, err = p.parseOptionalWhitespaceCommentNewline(b)
+		var cref reference
+		cref, b, err = p.parseOptionalWhitespaceCommentNewline(b)
 		if err != nil {
 			return parent, nil, err
 		}
 
+		if cref != invalidReference {
+			addChild(cref)
+		}
+
 		if len(b) == 0 {
-			return parent, nil, newDecodeError(arrayStart[:1], "array is incomplete")
+			return parent, nil, NewParserError(arrayStart[:1], "array is incomplete")
 		}
 
 		if b[0] == ']' {
@@ -430,16 +593,19 @@ func (p *parser) parseValArray(b []byte) (ast.Reference, []byte, error) {
 
 		if b[0] == ',' {
 			if first {
-				return parent, nil, newDecodeError(b[0:1], "array cannot start with comma")
+				return parent, nil, NewParserError(b[0:1], "array cannot start with comma")
 			}
 			b = b[1:]
 
-			b, err = p.parseOptionalWhitespaceCommentNewline(b)
+			cref, b, err = p.parseOptionalWhitespaceCommentNewline(b)
 			if err != nil {
 				return parent, nil, err
 			}
+			if cref != invalidReference {
+				addChild(cref)
+			}
 		} else if !first {
-			return parent, nil, newDecodeError(b[0:1], "array elements must be separated by commas")
+			return parent, nil, NewParserError(b[0:1], "array elements must be separated by commas")
 		}
 
 		// TOML allows trailing commas in arrays.
@@ -447,23 +613,22 @@ func (p *parser) parseValArray(b []byte) (ast.Reference, []byte, error) {
 			break
 		}
 
-		var valueRef ast.Reference
+		var valueRef reference
 		valueRef, b, err = p.parseVal(b)
 		if err != nil {
 			return parent, nil, err
 		}
 
-		if first {
+		addChild(valueRef)
-			p.builder.AttachChild(parent, valueRef)
-		} else {
-			p.builder.Chain(lastChild, valueRef)
-		}
-		lastChild = valueRef
 
-		b, err = p.parseOptionalWhitespaceCommentNewline(b)
+		cref, b, err = p.parseOptionalWhitespaceCommentNewline(b)
 		if err != nil {
 			return parent, nil, err
 		}
+		if cref != invalidReference {
+			addChild(cref)
+		}
+
 		first = false
 	}
 
@@ -472,15 +637,35 @@ func (p *parser) parseValArray(b []byte) (ast.Reference, []byte, error) {
 	return parent, rest, err
 }
 
-func (p *parser) parseOptionalWhitespaceCommentNewline(b []byte) ([]byte, error) {
+func (p *Parser) parseOptionalWhitespaceCommentNewline(b []byte) (reference, []byte, error) {
+	rootCommentRef := invalidReference
+	latestCommentRef := invalidReference
+
+	addComment := func(ref reference) {
+		switch {
+		case rootCommentRef == invalidReference:
+			rootCommentRef = ref
+		case latestCommentRef == invalidReference:
+			p.builder.AttachChild(rootCommentRef, ref)
+			latestCommentRef = ref
+		default:
+			p.builder.Chain(latestCommentRef, ref)
+			latestCommentRef = ref
+		}
+	}
+
 	for len(b) > 0 {
 		var err error
 		b = p.parseWhitespace(b)
 
 		if len(b) > 0 && b[0] == '#' {
-			_, b, err = scanComment(b)
+			var ref reference
+			ref, b, err = p.parseComment(b)
 			if err != nil {
-				return nil, err
+				return invalidReference, nil, err
+			}
+			if ref != invalidReference {
+				addComment(ref)
 			}
 		}
 
@@ -491,17 +676,17 @@ func (p *parser) parseOptionalWhitespaceCommentNewline(b []byte) ([]byte, error)
 		if b[0] == '\n' || b[0] == '\r' {
 			b, err = p.parseNewline(b)
 			if err != nil {
-				return nil, err
+				return invalidReference, nil, err
 			}
 		} else {
 			break
 		}
 	}
 
-	return b, nil
+	return rootCommentRef, b, nil
 }
 
-func (p *parser) parseMultilineLiteralString(b []byte) ([]byte, []byte, []byte, error) {
+func (p *Parser) parseMultilineLiteralString(b []byte) ([]byte, []byte, []byte, error) {
 	token, rest, err := scanMultilineLiteralString(b)
 	if err != nil {
 		return nil, nil, nil, err
@@ -520,7 +705,7 @@ func (p *parser) parseMultilineLiteralString(b []byte) ([]byte, []byte, []byte,
 }
 
 //nolint:funlen,gocognit,cyclop
-func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, error) {
+func (p *Parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, error) {
 	// ml-basic-string = ml-basic-string-delim [ newline ] ml-basic-body
 	// ml-basic-string-delim
 	// ml-basic-string-delim = 3quotation-mark
@@ -551,11 +736,11 @@ func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, er
 
 	if !escaped {
 		str := token[startIdx:endIdx]
-		verr := utf8TomlValidAlreadyEscaped(str)
+		highlight := characters.Utf8TomlValidAlreadyEscaped(str)
-		if verr.Zero() {
+		if len(highlight) == 0 {
 			return token, str, rest, nil
 		}
-		return nil, nil, nil, newDecodeError(str[verr.Index:verr.Index+verr.Size], "invalid UTF-8")
+		return nil, nil, nil, NewParserError(highlight, "invalid UTF-8")
 	}
 
 	var builder bytes.Buffer
@@ -591,7 +776,7 @@ func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, er
 				i += j
 				for ; i < len(token)-3; i++ {
 					c := token[i]
-					if !(c == '\n' || c == '\r' || c == ' ' || c == '\t') {
+					if c != '\n' && c != '\r' && c != ' ' && c != '\t' {
 						i--
 						break
 					}
@@ -635,13 +820,13 @@ func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, er
 				builder.WriteRune(x)
 				i += 8
 			default:
-				return nil, nil, nil, newDecodeError(token[i:i+1], "invalid escaped character %#U", c)
+				return nil, nil, nil, NewParserError(token[i:i+1], "invalid escaped character %#U", c)
 			}
 			i++
 		} else {
-			size := utf8ValidNext(token[i:])
+			size := characters.Utf8ValidNext(token[i:])
 			if size == 0 {
-				return nil, nil, nil, newDecodeError(token[i:i+1], "invalid character %#U", c)
+				return nil, nil, nil, NewParserError(token[i:i+1], "invalid character %#U", c)
 			}
 			builder.Write(token[i : i+size])
 			i += size
@@ -651,7 +836,7 @@ func (p *parser) parseMultilineBasicString(b []byte) ([]byte, []byte, []byte, er
 	return token, builder.Bytes(), rest, nil
 }
 
-func (p *parser) parseKey(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseKey(b []byte) (reference, []byte, error) {
 	// key = simple-key / dotted-key
 	// simple-key = quoted-key / unquoted-key
 	//
@@ -662,12 +847,12 @@ func (p *parser) parseKey(b []byte) (ast.Reference, []byte, error) {
 	// dot-sep   = ws %x2E ws  ; . Period
 	raw, key, b, err := p.parseSimpleKey(b)
 	if err != nil {
-		return ast.InvalidReference, nil, err
+		return invalidReference, nil, err
 	}
 
-	ref := p.builder.Push(ast.Node{
+	ref := p.builder.Push(Node{
-		Kind: ast.Key,
+		Kind: Key,
-		Raw:  p.Range(raw),
+		Raw:  p.rangeOfToken(raw, b),
 		Data: key,
 	})
 
@@ -681,9 +866,9 @@ func (p *parser) parseKey(b []byte) (ast.Reference, []byte, error) {
 				return ref, nil, err
 			}
 
-			p.builder.PushAndChain(ast.Node{
+			p.builder.PushAndChain(Node{
-				Kind: ast.Key,
+				Kind: Key,
-				Raw:  p.Range(raw),
+				Raw:  p.rangeOfToken(raw, b),
 				Data: key,
 			})
 		} else {
@@ -694,9 +879,9 @@ func (p *parser) parseKey(b []byte) (ast.Reference, []byte, error) {
 	return ref, b, nil
 }
 
-func (p *parser) parseSimpleKey(b []byte) (raw, key, rest []byte, err error) {
+func (p *Parser) parseSimpleKey(b []byte) (raw, key, rest []byte, err error) {
 	if len(b) == 0 {
-		return nil, nil, nil, newDecodeError(b, "expected key but found none")
+		return nil, nil, nil, NewParserError(b, "expected key but found none")
 	}
 
 	// simple-key = quoted-key / unquoted-key
@@ -711,12 +896,12 @@ func (p *parser) parseSimpleKey(b []byte) (raw, key, rest []byte, err error) {
 		key, rest = scanUnquotedKey(b)
 		return key, key, rest, nil
 	default:
-		return nil, nil, nil, newDecodeError(b[0:1], "invalid character at start of key: %c", b[0])
+		return nil, nil, nil, NewParserError(b[0:1], "invalid character at start of key: %c", b[0])
 	}
 }
 
 //nolint:funlen,cyclop
-func (p *parser) parseBasicString(b []byte) ([]byte, []byte, []byte, error) {
+func (p *Parser) parseBasicString(b []byte) ([]byte, []byte, []byte, error) {
 	// basic-string = quotation-mark *basic-char quotation-mark
 	// quotation-mark = %x22            ; "
 	// basic-char = basic-unescaped / escaped
@@ -744,11 +929,11 @@ func (p *parser) parseBasicString(b []byte) ([]byte, []byte, []byte, error) {
 	// validate the string and return a direct reference to the buffer.
 	if !escaped {
 		str := token[startIdx:endIdx]
-		verr := utf8TomlValidAlreadyEscaped(str)
+		highlight := characters.Utf8TomlValidAlreadyEscaped(str)
-		if verr.Zero() {
+		if len(highlight) == 0 {
 			return token, str, rest, nil
 		}
-		return nil, nil, nil, newDecodeError(str[verr.Index:verr.Index+verr.Size], "invalid UTF-8")
+		return nil, nil, nil, NewParserError(highlight, "invalid UTF-8")
 	}
 
 	i := startIdx
@@ -795,13 +980,13 @@ func (p *parser) parseBasicString(b []byte) ([]byte, []byte, []byte, error) {
 				builder.WriteRune(x)
 				i += 8
 			default:
-				return nil, nil, nil, newDecodeError(token[i:i+1], "invalid escaped character %#U", c)
+				return nil, nil, nil, NewParserError(token[i:i+1], "invalid escaped character %#U", c)
 			}
 			i++
 		} else {
-			size := utf8ValidNext(token[i:])
+			size := characters.Utf8ValidNext(token[i:])
 			if size == 0 {
-				return nil, nil, nil, newDecodeError(token[i:i+1], "invalid character %#U", c)
+				return nil, nil, nil, NewParserError(token[i:i+1], "invalid character %#U", c)
 			}
 			builder.Write(token[i : i+size])
 			i += size
@@ -813,13 +998,13 @@ func (p *parser) parseBasicString(b []byte) ([]byte, []byte, []byte, error) {
 
 func hexToRune(b []byte, length int) (rune, error) {
 	if len(b) < length {
-		return -1, newDecodeError(b, "unicode point needs %d character, not %d", length, len(b))
+		return -1, NewParserError(b, "unicode point needs %d character, not %d", length, len(b))
 	}
 	b = b[:length]
 
 	var r uint32
 	for i, c := range b {
-		d := uint32(0)
+		var d uint32
 		switch {
 		case '0' <= c && c <= '9':
 			d = uint32(c - '0')
@@ -828,19 +1013,19 @@ func hexToRune(b []byte, length int) (rune, error) {
 		case 'A' <= c && c <= 'F':
 			d = uint32(c - 'A' + 10)
 		default:
-			return -1, newDecodeError(b[i:i+1], "non-hex character")
+			return -1, NewParserError(b[i:i+1], "non-hex character")
 		}
 		r = r*16 + d
 	}
 
 	if r > unicode.MaxRune || 0xD800 <= r && r < 0xE000 {
-		return -1, newDecodeError(b, "escape sequence is invalid Unicode code point")
+		return -1, NewParserError(b, "escape sequence is invalid Unicode code point")
 	}
 
 	return rune(r), nil
 }
 
-func (p *parser) parseWhitespace(b []byte) []byte {
+func (p *Parser) parseWhitespace(b []byte) []byte {
 	// ws = *wschar
 	// wschar =  %x20  ; Space
 	// wschar =/ %x09  ; Horizontal tab
@@ -850,25 +1035,27 @@ func (p *parser) parseWhitespace(b []byte) []byte {
 }
 
 //nolint:cyclop
-func (p *parser) parseIntOrFloatOrDateTime(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) parseIntOrFloatOrDateTime(b []byte) (reference, []byte, error) {
 	switch b[0] {
 	case 'i':
 		if !scanFollowsInf(b) {
-			return ast.InvalidReference, nil, newDecodeError(atmost(b, 3), "expected 'inf'")
+			return invalidReference, nil, NewParserError(atmost(b, 3), "expected 'inf'")
 		}
 
-		return p.builder.Push(ast.Node{
+		return p.builder.Push(Node{
-			Kind: ast.Float,
+			Kind: Float,
 			Data: b[:3],
+			Raw:  p.rangeOfToken(b[:3], b[3:]),
 		}), b[3:], nil
 	case 'n':
 		if !scanFollowsNan(b) {
-			return ast.InvalidReference, nil, newDecodeError(atmost(b, 3), "expected 'nan'")
+			return invalidReference, nil, NewParserError(atmost(b, 3), "expected 'nan'")
 		}
 
-		return p.builder.Push(ast.Node{
+		return p.builder.Push(Node{
-			Kind: ast.Float,
+			Kind: Float,
 			Data: b[:3],
+			Raw:  p.rangeOfToken(b[:3], b[3:]),
 		}), b[3:], nil
 	case '+', '-':
 		return p.scanIntOrFloat(b)
@@ -898,7 +1085,7 @@ func (p *parser) parseIntOrFloatOrDateTime(b []byte) (ast.Reference, []byte, err
 	return p.scanIntOrFloat(b)
 }
 
-func (p *parser) scanDateTime(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) scanDateTime(b []byte) (reference, []byte, error) {
 	// scans for contiguous characters in [0-9T:Z.+-], and up to one space if
 	// followed by a digit.
 	hasDate := false
@@ -921,7 +1108,7 @@ byteLoop:
 			}
 		case c == 'T' || c == 't' || c == ':' || c == '.':
 			hasTime = true
-		case c == '+' || c == '-' || c == 'Z' || c == 'z':
+		case c == '+' || c == 'Z' || c == 'z':
 			hasTz = true
 		case c == ' ':
 			if !seenSpace && i+1 < len(b) && isDigit(b[i+1]) {
@@ -941,30 +1128,30 @@ byteLoop:
 		}
 	}
 
-	var kind ast.Kind
+	var kind Kind
 
 	if hasTime {
 		if hasDate {
 			if hasTz {
-				kind = ast.DateTime
+				kind = DateTime
 			} else {
-				kind = ast.LocalDateTime
+				kind = LocalDateTime
 			}
 		} else {
-			kind = ast.LocalTime
+			kind = LocalTime
 		}
 	} else {
-		kind = ast.LocalDate
+		kind = LocalDate
 	}
 
-	return p.builder.Push(ast.Node{
+	return p.builder.Push(Node{
 		Kind: kind,
 		Data: b[:i],
 	}), b[i:], nil
 }
 
 //nolint:funlen,gocognit,cyclop
-func (p *parser) scanIntOrFloat(b []byte) (ast.Reference, []byte, error) {
+func (p *Parser) scanIntOrFloat(b []byte) (reference, []byte, error) {
 	i := 0
 
 	if len(b) > 2 && b[0] == '0' && b[1] != '.' && b[1] != 'e' && b[1] != 'E' {
@@ -990,9 +1177,10 @@ func (p *parser) scanIntOrFloat(b []byte) (ast.Reference, []byte, error) {
 			}
 		}
 
-		return p.builder.Push(ast.Node{
+		return p.builder.Push(Node{
-			Kind: ast.Integer,
+			Kind: Integer,
 			Data: b[:i],
+			Raw:  p.rangeOfToken(b[:i], b[i:]),
 		}), b[i:], nil
 	}
 
@@ -1013,42 +1201,45 @@ func (p *parser) scanIntOrFloat(b []byte) (ast.Reference, []byte, error) {
 
 		if c == 'i' {
 			if scanFollowsInf(b[i:]) {
-				return p.builder.Push(ast.Node{
+				return p.builder.Push(Node{
-					Kind: ast.Float,
+					Kind: Float,
 					Data: b[:i+3],
+					Raw:  p.rangeOfToken(b[:i+3], b[i+3:]),
 				}), b[i+3:], nil
 			}
 
-			return ast.InvalidReference, nil, newDecodeError(b[i:i+1], "unexpected character 'i' while scanning for a number")
+			return invalidReference, nil, NewParserError(b[i:i+1], "unexpected character 'i' while scanning for a number")
 		}
 
 		if c == 'n' {
 			if scanFollowsNan(b[i:]) {
-				return p.builder.Push(ast.Node{
+				return p.builder.Push(Node{
-					Kind: ast.Float,
+					Kind: Float,
 					Data: b[:i+3],
+					Raw:  p.rangeOfToken(b[:i+3], b[i+3:]),
 				}), b[i+3:], nil
 			}
 
-			return ast.InvalidReference, nil, newDecodeError(b[i:i+1], "unexpected character 'n' while scanning for a number")
+			return invalidReference, nil, NewParserError(b[i:i+1], "unexpected character 'n' while scanning for a number")
 		}
 
 		break
 	}
 
 	if i == 0 {
-		return ast.InvalidReference, b, newDecodeError(b, "incomplete number")
+		return invalidReference, b, NewParserError(b, "incomplete number")
 	}
 
-	kind := ast.Integer
+	kind := Integer
 
 	if isFloat {
-		kind = ast.Float
+		kind = Float
 	}
 
-	return p.builder.Push(ast.Node{
+	return p.builder.Push(Node{
 		Kind: kind,
 		Data: b[:i],
+		Raw:  p.rangeOfToken(b[:i], b[i:]),
 	}), b[i:], nil
 }
 
@@ -1075,11 +1266,11 @@ func isValidBinaryRune(r byte) bool {
 
 func expect(x byte, b []byte) ([]byte, error) {
 	if len(b) == 0 {
-		return nil, newDecodeError(b, "expected character %c but the document ended here", x)
+		return nil, NewParserError(b, "expected character %c but the document ended here", x)
 	}
 
 	if b[0] != x {
-		return nil, newDecodeError(b[0:1], "expected character %c", x)
+		return nil, NewParserError(b[0:1], "expected character %c", x)
 	}
 
 	return b[1:], nil

unstable/parser_range_test.go

@@ -0,0 +1,36 @@
+package unstable
+
+import (
+	"errors"
+	"testing"
+)
+
+// Regression test for https://github.com/pelletier/go-toml/issues/1047:
+// Parser.Range must use the real slice offset, not len(data)-len(slice).
+func TestParser_Range_HighlightAfterComment(t *testing.T) {
+	input := []byte("# comment\n= \"value\"")
+
+	var p Parser
+	p.Reset(input)
+	for p.NextExpression() {
+	}
+	err := p.Error()
+	if err == nil {
+		t.Fatal("expected an error")
+	}
+
+	var perr *ParserError
+	if !errors.As(err, &perr) {
+		t.Fatalf("expected *ParserError, got %T", err)
+	}
+
+	r := p.Range(perr.Highlight)
+	shape := p.Shape(r)
+
+	if r.Offset != 10 {
+		t.Errorf("Range offset: got %d, want 10", r.Offset)
+	}
+	if shape.Start.Line != 2 || shape.Start.Column != 1 {
+		t.Errorf("position: got %d:%d, want 2:1", shape.Start.Line, shape.Start.Column)
+	}
+}

unstable/parser_test.go

@@ -0,0 +1,697 @@
+package unstable
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+	"testing"
+
+	"github.com/pelletier/go-toml/v2/internal/assert"
+)
+
+func TestParser_AST_Numbers(t *testing.T) {
+	examples := []struct {
+		desc  string
+		input string
+		kind  Kind
+		err   bool
+	}{
+		{
+			desc:  "integer just digits",
+			input: `1234`,
+			kind:  Integer,
+		},
+		{
+			desc:  "integer zero",
+			input: `0`,
+			kind:  Integer,
+		},
+		{
+			desc:  "integer sign",
+			input: `+99`,
+			kind:  Integer,
+		},
+		{
+			desc:  "integer hex uppercase",
+			input: `0xDEADBEEF`,
+			kind:  Integer,
+		},
+		{
+			desc:  "integer hex lowercase",
+			input: `0xdead_beef`,
+			kind:  Integer,
+		},
+		{
+			desc:  "integer octal",
+			input: `0o01234567`,
+			kind:  Integer,
+		},
+		{
+			desc:  "integer binary",
+			input: `0b11010110`,
+			kind:  Integer,
+		},
+		{
+			desc:  "float zero",
+			input: `0.0`,
+			kind:  Float,
+		},
+		{
+			desc:  "float positive zero",
+			input: `+0.0`,
+			kind:  Float,
+		},
+		{
+			desc:  "float negative zero",
+			input: `-0.0`,
+			kind:  Float,
+		},
+		{
+			desc:  "float pi",
+			input: `3.1415`,
+			kind:  Float,
+		},
+		{
+			desc:  "float negative",
+			input: `-0.01`,
+			kind:  Float,
+		},
+		{
+			desc:  "float signed exponent",
+			input: `5e+22`,
+			kind:  Float,
+		},
+		{
+			desc:  "float exponent lowercase",
+			input: `1e06`,
+			kind:  Float,
+		},
+		{
+			desc:  "float exponent uppercase",
+			input: `-2E-2`,
+			kind:  Float,
+		},
+		{
+			desc:  "float fractional with exponent",
+			input: `6.626e-34`,
+			kind:  Float,
+		},
+		{
+			desc:  "float underscores",
+			input: `224_617.445_991_228`,
+			kind:  Float,
+		},
+		{
+			desc:  "inf",
+			input: `inf`,
+			kind:  Float,
+		},
+		{
+			desc:  "inf negative",
+			input: `-inf`,
+			kind:  Float,
+		},
+		{
+			desc:  "inf positive",
+			input: `+inf`,
+			kind:  Float,
+		},
+		{
+			desc:  "nan",
+			input: `nan`,
+			kind:  Float,
+		},
+		{
+			desc:  "nan negative",
+			input: `-nan`,
+			kind:  Float,
+		},
+		{
+			desc:  "nan positive",
+			input: `+nan`,
+			kind:  Float,
+		},
+	}
+
+	for _, e := range examples {
+		e := e
+		t.Run(e.desc, func(t *testing.T) {
+			p := Parser{}
+			p.Reset([]byte(`A = ` + e.input))
+			p.NextExpression()
+			err := p.Error()
+			if e.err {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+
+				expected := astNode{
+					Kind: KeyValue,
+					Children: []astNode{
+						{Kind: e.kind, Data: []byte(e.input)},
+						{Kind: Key, Data: []byte(`A`)},
+					},
+				}
+				compareNode(t, expected, p.Expression())
+			}
+		})
+	}
+}
+
+type (
+	astNode struct {
+		Kind     Kind
+		Data     []byte
+		Children []astNode
+	}
+)
+
+func compareNode(t *testing.T, e astNode, n *Node) {
+	t.Helper()
+	assert.Equal(t, e.Kind, n.Kind)
+	assert.Equal(t, e.Data, n.Data)
+
+	compareIterator(t, e.Children, n.Children())
+}
+
+func compareIterator(t *testing.T, expected []astNode, actual Iterator) {
+	t.Helper()
+	idx := 0
+
+	for actual.Next() {
+		n := actual.Node()
+
+		if idx >= len(expected) {
+			t.Fatal("extra child in actual tree")
+		}
+		e := expected[idx]
+
+		compareNode(t, e, n)
+
+		idx++
+	}
+
+	if idx < len(expected) {
+		t.Fatal("missing children in actual", "idx =", idx, "expected =", len(expected))
+	}
+}
+
+//nolint:funlen
+func TestParser_AST(t *testing.T) {
+	examples := []struct {
+		desc  string
+		input string
+		ast   astNode
+		err   bool
+	}{
+		{
+			desc:  "simple string assignment",
+			input: `A = "hello"`,
+			ast: astNode{
+				Kind: KeyValue,
+				Children: []astNode{
+					{
+						Kind: String,
+						Data: []byte(`hello`),
+					},
+					{
+						Kind: Key,
+						Data: []byte(`A`),
+					},
+				},
+			},
+		},
+		{
+			desc:  "simple bool assignment",
+			input: `A = true`,
+			ast: astNode{
+				Kind: KeyValue,
+				Children: []astNode{
+					{
+						Kind: Bool,
+						Data: []byte(`true`),
+					},
+					{
+						Kind: Key,
+						Data: []byte(`A`),
+					},
+				},
+			},
+		},
+		{
+			desc:  "array of strings",
+			input: `A = ["hello", ["world", "again"]]`,
+			ast: astNode{
+				Kind: KeyValue,
+				Children: []astNode{
+					{
+						Kind: Array,
+						Children: []astNode{
+							{
+								Kind: String,
+								Data: []byte(`hello`),
+							},
+							{
+								Kind: Array,
+								Children: []astNode{
+									{
+										Kind: String,
+										Data: []byte(`world`),
+									},
+									{
+										Kind: String,
+										Data: []byte(`again`),
+									},
+								},
+							},
+						},
+					},
+					{
+						Kind: Key,
+						Data: []byte(`A`),
+					},
+				},
+			},
+		},
+		{
+			desc:  "array of arrays of strings",
+			input: `A = ["hello", "world"]`,
+			ast: astNode{
+				Kind: KeyValue,
+				Children: []astNode{
+					{
+						Kind: Array,
+						Children: []astNode{
+							{
+								Kind: String,
+								Data: []byte(`hello`),
+							},
+							{
+								Kind: String,
+								Data: []byte(`world`),
+							},
+						},
+					},
+					{
+						Kind: Key,
+						Data: []byte(`A`),
+					},
+				},
+			},
+		},
+		{
+			desc:  "inline table",
+			input: `name = { first = "Tom", last = "Preston-Werner" }`,
+			ast: astNode{
+				Kind: KeyValue,
+				Children: []astNode{
+					{
+						Kind: InlineTable,
+						Children: []astNode{
+							{
+								Kind: KeyValue,
+								Children: []astNode{
+									{Kind: String, Data: []byte(`Tom`)},
+									{Kind: Key, Data: []byte(`first`)},
+								},
+							},
+							{
+								Kind: KeyValue,
+								Children: []astNode{
+									{Kind: String, Data: []byte(`Preston-Werner`)},
+									{Kind: Key, Data: []byte(`last`)},
+								},
+							},
+						},
+					},
+					{
+						Kind: Key,
+						Data: []byte(`name`),
+					},
+				},
+			},
+		},
+	}
+
+	for _, e := range examples {
+		e := e
+		t.Run(e.desc, func(t *testing.T) {
+			p := Parser{}
+			p.Reset([]byte(e.input))
+			p.NextExpression()
+			err := p.Error()
+			if e.err {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+				compareNode(t, e.ast, p.Expression())
+			}
+		})
+	}
+}
+
+func BenchmarkParseBasicStringWithUnicode(b *testing.B) {
+	p := &Parser{}
+	b.Run("4", func(b *testing.B) {
+		input := []byte(`"\u1234\u5678\u9ABC\u1234\u5678\u9ABC"`)
+		b.ReportAllocs()
+		b.SetBytes(int64(len(input)))
+
+		for i := 0; i < b.N; i++ {
+			_, _, _, _ = p.parseBasicString(input)
+		}
+	})
+	b.Run("8", func(b *testing.B) {
+		input := []byte(`"\u12345678\u9ABCDEF0\u12345678\u9ABCDEF0"`)
+		b.ReportAllocs()
+		b.SetBytes(int64(len(input)))
+
+		for i := 0; i < b.N; i++ {
+			_, _, _, _ = p.parseBasicString(input)
+		}
+	})
+}
+
+func BenchmarkParseBasicStringsEasy(b *testing.B) {
+	p := &Parser{}
+
+	for _, size := range []int{1, 4, 8, 16, 21} {
+		b.Run(strconv.Itoa(size), func(b *testing.B) {
+			input := []byte(`"` + strings.Repeat("A", size) + `"`)
+
+			b.ReportAllocs()
+			b.SetBytes(int64(len(input)))
+
+			for i := 0; i < b.N; i++ {
+				_, _, _, _ = p.parseBasicString(input)
+			}
+		})
+	}
+}
+
+func TestParser_AST_DateTimes(t *testing.T) {
+	examples := []struct {
+		desc  string
+		input string
+		kind  Kind
+		err   bool
+	}{
+		{
+			desc:  "offset-date-time with delim 'T' and UTC offset",
+			input: `2021-07-21T12:08:05Z`,
+			kind:  DateTime,
+		},
+		{
+			desc:  "offset-date-time with space delim and +8hours offset",
+			input: `2021-07-21 12:08:05+08:00`,
+			kind:  DateTime,
+		},
+		{
+			desc:  "local-date-time with nano second",
+			input: `2021-07-21T12:08:05.666666666`,
+			kind:  LocalDateTime,
+		},
+		{
+			desc:  "local-date-time",
+			input: `2021-07-21T12:08:05`,
+			kind:  LocalDateTime,
+		},
+		{
+			desc:  "local-date",
+			input: `2021-07-21`,
+			kind:  LocalDate,
+		},
+	}
+
+	for _, e := range examples {
+		e := e
+		t.Run(e.desc, func(t *testing.T) {
+			p := Parser{}
+			p.Reset([]byte(`A = ` + e.input))
+			p.NextExpression()
+			err := p.Error()
+			if e.err {
+				assert.Error(t, err)
+			} else {
+				assert.NoError(t, err)
+
+				expected := astNode{
+					Kind: KeyValue,
+					Children: []astNode{
+						{Kind: e.kind, Data: []byte(e.input)},
+						{Kind: Key, Data: []byte(`A`)},
+					},
+				}
+				compareNode(t, expected, p.Expression())
+			}
+		})
+	}
+}
+
+// This example demonstrates how to parse a TOML document and preserving
+// comments.  Comments are stored in the AST as Comment nodes. This example
+// displays the structure of the full AST generated by the parser using the
+// following structure:
+//
+//  1. Each root-level expression is separated by three dashes.
+//  2. Bytes associated to a node are displayed in square brackets.
+//  3. Siblings have the same indentation.
+//  4. Children of a node are indented one level.
+func ExampleParser_comments() {
+	doc := `# Top of the document comment.
+# Optional, any amount of lines.
+
+# Above table.
+[table] # Next to table.
+# Above simple value.
+key = "value" # Next to simple value.
+# Below simple value.
+
+# Some comment alone.
+
+# Multiple comments, on multiple lines.
+
+# Above inline table.
+name = { first = "Tom", last = "Preston-Werner" } # Next to inline table.
+# Below inline table.
+
+# Above array.
+array = [ 1, 2, 3 ] # Next to one-line array.
+# Below array.
+
+# Above multi-line array.
+key5 = [ # Next to start of inline array.
+  # Second line before array content.
+  1, # Next to first element.
+  # After first element.
+  # Before second element.
+  2,
+  3, # Next to last element
+  # After last element.
+] # Next to end of array.
+# Below multi-line array.
+
+# Before array table.
+[[products]] # Next to array table.
+# After array table.
+`
+
+	var printGeneric func(*Parser, int, *Node)
+	printGeneric = func(p *Parser, indent int, e *Node) {
+		if e == nil {
+			return
+		}
+		s := p.Shape(e.Raw)
+		x := fmt.Sprintf("%d:%d->%d:%d (%d->%d)", s.Start.Line, s.Start.Column, s.End.Line, s.End.Column, s.Start.Offset, s.End.Offset)
+		fmt.Printf("%-25s | %s%s [%s]\n", x, strings.Repeat("  ", indent), e.Kind, e.Data)
+		printGeneric(p, indent+1, e.Child())
+		printGeneric(p, indent, e.Next())
+	}
+
+	printTree := func(p *Parser) {
+		for p.NextExpression() {
+			e := p.Expression()
+			fmt.Println("---")
+			printGeneric(p, 0, e)
+		}
+		if err := p.Error(); err != nil {
+			panic(err)
+		}
+	}
+
+	p := &Parser{
+		KeepComments: true,
+	}
+	p.Reset([]byte(doc))
+	printTree(p)
+
+	// Output:
+	// ---
+	// 1:1->1:31 (0->30)         | Comment [# Top of the document comment.]
+	// ---
+	// 2:1->2:33 (31->63)        | Comment [# Optional, any amount of lines.]
+	// ---
+	// 4:1->4:15 (65->79)        | Comment [# Above table.]
+	// ---
+	// 1:1->1:1 (0->0)           | Table []
+	// 5:2->5:7 (81->86)         |   Key [table]
+	// 5:9->5:25 (88->104)       | Comment [# Next to table.]
+	// ---
+	// 6:1->6:22 (105->126)      | Comment [# Above simple value.]
+	// ---
+	// 7:1->7:14 (127->140)      | KeyValue []
+	// 7:7->7:14 (133->140)      |   String [value]
+	// 7:1->7:4 (127->130)       |   Key [key]
+	// 7:15->7:38 (141->164)     | Comment [# Next to simple value.]
+	// ---
+	// 8:1->8:22 (165->186)      | Comment [# Below simple value.]
+	// ---
+	// 10:1->10:22 (188->209)    | Comment [# Some comment alone.]
+	// ---
+	// 12:1->12:40 (211->250)    | Comment [# Multiple comments, on multiple lines.]
+	// ---
+	// 14:1->14:22 (252->273)    | Comment [# Above inline table.]
+	// ---
+	// 15:1->15:50 (274->323)    | KeyValue []
+	// 15:8->15:9 (281->282)     |   InlineTable []
+	// 15:10->15:23 (283->296)   |     KeyValue []
+	// 15:18->15:23 (291->296)   |       String [Tom]
+	// 15:10->15:15 (283->288)   |       Key [first]
+	// 15:25->15:48 (298->321)   |     KeyValue []
+	// 15:32->15:48 (305->321)   |       String [Preston-Werner]
+	// 15:25->15:29 (298->302)   |       Key [last]
+	// 15:1->15:5 (274->278)     |   Key [name]
+	// 15:51->15:74 (324->347)   | Comment [# Next to inline table.]
+	// ---
+	// 16:1->16:22 (348->369)    | Comment [# Below inline table.]
+	// ---
+	// 18:1->18:15 (371->385)    | Comment [# Above array.]
+	// ---
+	// 19:1->19:20 (386->405)    | KeyValue []
+	// 1:1->1:1 (0->0)           |   Array []
+	// 19:11->19:12 (396->397)   |     Integer [1]
+	// 19:14->19:15 (399->400)   |     Integer [2]
+	// 19:17->19:18 (402->403)   |     Integer [3]
+	// 19:1->19:6 (386->391)     |   Key [array]
+	// 19:21->19:46 (406->431)   | Comment [# Next to one-line array.]
+	// ---
+	// 20:1->20:15 (432->446)    | Comment [# Below array.]
+	// ---
+	// 22:1->22:26 (448->473)    | Comment [# Above multi-line array.]
+	// ---
+	// 23:1->31:2 (474->694)     | KeyValue []
+	// 1:1->1:1 (0->0)           |   Array []
+	// 23:10->23:42 (483->515)   |     Comment [# Next to start of inline array.]
+	// 24:3->24:38 (518->553)    |       Comment [# Second line before array content.]
+	// 25:3->25:4 (556->557)     |     Integer [1]
+	// 25:6->25:30 (559->583)    |     Comment [# Next to first element.]
+	// 26:3->26:25 (586->608)    |       Comment [# After first element.]
+	// 27:3->27:27 (611->635)    |       Comment [# Before second element.]
+	// 28:3->28:4 (638->639)     |     Integer [2]
+	// 29:3->29:4 (643->644)     |     Integer [3]
+	// 29:6->29:28 (646->668)    |     Comment [# Next to last element]
+	// 30:3->30:24 (671->692)    |       Comment [# After last element.]
+	// 23:1->23:5 (474->478)     |   Key [key5]
+	// 31:3->31:26 (695->718)    | Comment [# Next to end of array.]
+	// ---
+	// 32:1->32:26 (719->744)    | Comment [# Below multi-line array.]
+	// ---
+	// 34:1->34:22 (746->767)    | Comment [# Before array table.]
+	// ---
+	// 1:1->1:1 (0->0)           | ArrayTable []
+	// 35:3->35:11 (770->778)    |   Key [products]
+	// 35:14->35:36 (781->803)   | Comment [# Next to array table.]
+	// ---
+	// 36:1->36:21 (804->824)    | Comment [# After array table.]
+}
+
+func TestIterator_IsLast(t *testing.T) {
+	// Test IsLast on an iterator with multiple elements using public Parser API
+	doc := `array = [1, 2, 3]`
+	p := Parser{}
+	p.Reset([]byte(doc))
+	p.NextExpression()
+
+	e := p.Expression()
+	arr := e.Value() // The array node
+
+	it := arr.Children()
+	count := 0
+	lastCount := 0
+	for it.Next() {
+		count++
+		if it.IsLast() {
+			lastCount++
+		}
+	}
+
+	assert.Equal(t, 3, count)
+	assert.Equal(t, 1, lastCount)
+}
+
+func TestNodeChaining(t *testing.T) {
+	// Test that sibling nodes are correctly chained via Next()
+	// This exercises the internal PushAndChain functionality through public APIs
+	doc := `a.b.c = 1`
+	p := Parser{}
+	p.Reset([]byte(doc))
+	p.NextExpression()
+
+	e := p.Expression()
+	// KeyValue has children: value, then key parts (a, b, c)
+	keyIt := e.Key()
+
+	// Collect all key parts by following the iterator
+	var keys []string
+	for keyIt.Next() {
+		keys = append(keys, string(keyIt.Node().Data))
+	}
+
+	assert.Equal(t, []string{"a", "b", "c"}, keys)
+}
+
+func TestMultipleExpressions(t *testing.T) {
+	// Test parsing multiple top-level expressions
+	// This exercises root iteration through public APIs
+	doc := `
+key1 = "value1"
+key2 = "value2"
+key3 = "value3"
+`
+	p := Parser{}
+	p.Reset([]byte(doc))
+
+	var keys []string
+	for p.NextExpression() {
+		e := p.Expression()
+		keyIt := e.Key()
+		keyIt.Next()
+		keys = append(keys, string(keyIt.Node().Data))
+	}
+
+	assert.NoError(t, p.Error())
+	assert.Equal(t, []string{"key1", "key2", "key3"}, keys)
+}
+
+func ExampleParser() {
+	doc := `
+	hello = "world"
+	value = 42
+	`
+	p := Parser{}
+	p.Reset([]byte(doc))
+	for p.NextExpression() {
+		e := p.Expression()
+		fmt.Printf("Expression: %s\n", e.Kind)
+		value := e.Value()
+		it := e.Key()
+		k := it.Node() // shortcut: we know there is no dotted key in the example
+		fmt.Printf("%s -> (%s) %s\n", k.Data, value.Kind, value.Data)
+	}
+
+	// Output:
+	// Expression: KeyValue
+	// hello -> (String) world
+	// Expression: KeyValue
+	// value -> (Integer) 42
+}

unstable/scanner.go

@@ -1,4 +1,6 @@
-package toml
+package unstable
+
+import "github.com/pelletier/go-toml/v2/internal/characters"
 
 func scanFollows(b []byte, pattern string) bool {
 	n := len(pattern)
@@ -54,16 +56,16 @@ func scanLiteralString(b []byte) ([]byte, []byte, error) {
 		case '\'':
 			return b[:i+1], b[i+1:], nil
 		case '\n', '\r':
-			return nil, nil, newDecodeError(b[i:i+1], "literal strings cannot have new lines")
+			return nil, nil, NewParserError(b[i:i+1], "literal strings cannot have new lines")
 		}
-		size := utf8ValidNext(b[i:])
+		size := characters.Utf8ValidNext(b[i:])
 		if size == 0 {
-			return nil, nil, newDecodeError(b[i:i+1], "invalid character")
+			return nil, nil, NewParserError(b[i:i+1], "invalid character")
 		}
 		i += size
 	}
 
-	return nil, nil, newDecodeError(b[len(b):], "unterminated literal string")
+	return nil, nil, NewParserError(b[len(b):], "unterminated literal string")
 }
 
 func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
@@ -98,39 +100,39 @@ func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
 				i++
 
 				if i < len(b) && b[i] == '\'' {
-					return nil, nil, newDecodeError(b[i-3:i+1], "''' not allowed in multiline literal string")
+					return nil, nil, NewParserError(b[i-3:i+1], "''' not allowed in multiline literal string")
 				}
 
 				return b[:i], b[i:], nil
 			}
 		case '\r':
 			if len(b) < i+2 {
-				return nil, nil, newDecodeError(b[len(b):], `need a \n after \r`)
+				return nil, nil, NewParserError(b[len(b):], `need a \n after \r`)
 			}
 			if b[i+1] != '\n' {
-				return nil, nil, newDecodeError(b[i:i+2], `need a \n after \r`)
+				return nil, nil, NewParserError(b[i:i+2], `need a \n after \r`)
 			}
 			i += 2 // skip the \n
 			continue
 		}
-		size := utf8ValidNext(b[i:])
+		size := characters.Utf8ValidNext(b[i:])
 		if size == 0 {
-			return nil, nil, newDecodeError(b[i:i+1], "invalid character")
+			return nil, nil, NewParserError(b[i:i+1], "invalid character")
 		}
 		i += size
 	}
 
-	return nil, nil, newDecodeError(b[len(b):], `multiline literal string not terminated by '''`)
+	return nil, nil, NewParserError(b[len(b):], `multiline literal string not terminated by '''`)
 }
 
 func scanWindowsNewline(b []byte) ([]byte, []byte, error) {
 	const lenCRLF = 2
 	if len(b) < lenCRLF {
-		return nil, nil, newDecodeError(b, "windows new line expected")
+		return nil, nil, NewParserError(b, "windows new line expected")
 	}
 
 	if b[1] != '\n' {
-		return nil, nil, newDecodeError(b, `windows new line should be \r\n`)
+		return nil, nil, NewParserError(b, `windows new line should be \r\n`)
 	}
 
 	return b[:lenCRLF], b[lenCRLF:], nil
@@ -149,7 +151,6 @@ func scanWhitespace(b []byte) ([]byte, []byte) {
 	return b, b[len(b):]
 }
 
-//nolint:unparam
 func scanComment(b []byte) ([]byte, []byte, error) {
 	// comment-start-symbol = %x23 ; #
 	// non-ascii = %x80-D7FF / %xE000-10FFFF
@@ -165,11 +166,11 @@ func scanComment(b []byte) ([]byte, []byte, error) {
 			if i+1 < len(b) && b[i+1] == '\n' {
 				return b[:i+1], b[i+1:], nil
 			}
-			return nil, nil, newDecodeError(b[i:i+1], "invalid character in comment")
+			return nil, nil, NewParserError(b[i:i+1], "invalid character in comment")
 		}
-		size := utf8ValidNext(b[i:])
+		size := characters.Utf8ValidNext(b[i:])
 		if size == 0 {
-			return nil, nil, newDecodeError(b[i:i+1], "invalid character in comment")
+			return nil, nil, NewParserError(b[i:i+1], "invalid character in comment")
 		}
 
 		i += size
@@ -192,17 +193,17 @@ func scanBasicString(b []byte) ([]byte, bool, []byte, error) {
 		case '"':
 			return b[:i+1], escaped, b[i+1:], nil
 		case '\n', '\r':
-			return nil, escaped, nil, newDecodeError(b[i:i+1], "basic strings cannot have new lines")
+			return nil, escaped, nil, NewParserError(b[i:i+1], "basic strings cannot have new lines")
 		case '\\':
 			if len(b) < i+2 {
-				return nil, escaped, nil, newDecodeError(b[i:i+1], "need a character after \\")
+				return nil, escaped, nil, NewParserError(b[i:i+1], "need a character after \\")
 			}
 			escaped = true
 			i++ // skip the next character
 		}
 	}
 
-	return nil, escaped, nil, newDecodeError(b[len(b):], `basic string not terminated by "`)
+	return nil, escaped, nil, NewParserError(b[len(b):], `basic string not terminated by "`)
 }
 
 func scanMultilineBasicString(b []byte) ([]byte, bool, []byte, error) {
@@ -243,27 +244,27 @@ func scanMultilineBasicString(b []byte) ([]byte, bool, []byte, error) {
 				i++
 
 				if i < len(b) && b[i] == '"' {
-					return nil, escaped, nil, newDecodeError(b[i-3:i+1], `""" not allowed in multiline basic string`)
+					return nil, escaped, nil, NewParserError(b[i-3:i+1], `""" not allowed in multiline basic string`)
 				}
 
 				return b[:i], escaped, b[i:], nil
 			}
 		case '\\':
 			if len(b) < i+2 {
-				return nil, escaped, nil, newDecodeError(b[len(b):], "need a character after \\")
+				return nil, escaped, nil, NewParserError(b[len(b):], "need a character after \\")
 			}
 			escaped = true
 			i++ // skip the next character
 		case '\r':
 			if len(b) < i+2 {
-				return nil, escaped, nil, newDecodeError(b[len(b):], `need a \n after \r`)
+				return nil, escaped, nil, NewParserError(b[len(b):], `need a \n after \r`)
 			}
 			if b[i+1] != '\n' {
-				return nil, escaped, nil, newDecodeError(b[i:i+2], `need a \n after \r`)
+				return nil, escaped, nil, NewParserError(b[i:i+2], `need a \n after \r`)
 			}
 			i++ // skip the \n
 		}
 	}
 
-	return nil, escaped, nil, newDecodeError(b[len(b):], `multiline basic string not terminated by """`)
+	return nil, escaped, nil, NewParserError(b[len(b):], `multiline basic string not terminated by """`)
 }

unstable/unmarshaler.go

@@ -0,0 +1,32 @@
+package unstable
+
+// Unmarshaler is implemented by types that can unmarshal a TOML
+// description of themselves. The input is a valid TOML document
+// containing the relevant portion of the parsed document.
+//
+// For tables (including split tables defined in multiple places),
+// the data contains the raw key-value bytes from the original document
+// with adjusted table headers to be relative to the unmarshaling target.
+type Unmarshaler interface {
+	UnmarshalTOML(data []byte) error
+}
+
+// RawMessage is a raw encoded TOML value. It implements Unmarshaler
+// and can be used to delay TOML decoding or capture raw content.
+//
+// Example usage:
+//
+//	type Config struct {
+//	    Plugin RawMessage `toml:"plugin"`
+//	}
+//
+//	var cfg Config
+//	toml.NewDecoder(r).EnableUnmarshalerInterface().Decode(&cfg)
+//	// cfg.Plugin now contains the raw TOML bytes for [plugin]
+type RawMessage []byte
+
+// UnmarshalTOML implements Unmarshaler.
+func (m *RawMessage) UnmarshalTOML(data []byte) error {
+	*m = append((*m)[0:0], data...)
+	return nil
+}