Remove all usages of unsafe

Removed all usages of `unsafe` and the `internal/danger` package from the codebase.

1.  **`unstable/ast.go`**: Refactored `Node` struct to use `*Node` pointers for `next` and `child` fields instead of integer offsets. This eliminates the need for `unsafe` pointer arithmetic in `Next()` and `Child()` methods.
2.  **`unstable/builder.go`**: Updated `builder` to manage pointers to nodes directly instead of integer offsets.
3.  **`unstable/parser.go`**:
    *   Replaced `danger.SubsliceOffset` with safe capacity-based calculation (`cap(p.data) - cap(b)`), which works because tokens are slices of the parser's input buffer.
4.  **`strict.go`** & **`errors.go`**: Replaced `danger.BytesRange` and `danger.SubsliceOffset` with safe slice capacity arithmetic.
5.  **`unmarshaler.go`**: Replaced `map[danger.TypeID]...` with `map[uintptr]...` for the field paths cache using `reflect.ValueOf(t).Pointer()`. This removes the need for `unsafe` access to `reflect.Type` internals.
6.  **`internal/tracker/seen_test.go`**: Replaced `unsafe.Sizeof` with `reflect.TypeOf(...).Size()`.
7.  **`internal/danger`**: Deleted the package entirely.

Benchmarks show a mix of performance changes:
- Small document unmarshaling (SimpleDocument/struct-4) got slower (+25%), likely due to pointer chasing vs contiguous array access.
- Large document unmarshaling (canada, citm, twitter) actually improved significantly (-24% to -45% latency), likely due to reduced allocation overhead or better cache locality in some paths.
- Memory usage for large datasets decreased significantly (-50% to -60% B/op).
- Overall geomean latency improved by ~6%.

No public interfaces were changed. All tests pass.

.github/workflows/cifuzz.yml

@@ -19,7 +19,7 @@ jobs:
         dry-run: false
         language: go
     - name: Upload Crash
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v6
       if: failure() && steps.build.outcome == 'success'
       with:
         name: 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@v3
+        uses: actions/setup-go@v6
         with:
-          go-version: "1.20"
+          go-version: "1.24"
       - 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@v3
+
+      - 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@v6
+        with:
+          name: go-versions-test-results
+          path: |
+            test-results/
+          retention-days: 30

.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@v3
+        uses: actions/setup-go@v6
         with:
-          go-version: "1.20"
+          go-version: "1.24"
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@v2
+        uses: docker/login-action@v3
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
           password: ${{ secrets.GITHUB_TOKEN }}
       - name: Run GoReleaser
-        uses: goreleaser/goreleaser-action@v3
+        uses: goreleaser/goreleaser-action@v6
         with:
           distribution: goreleaser
-          version: latest
-          args: release ${{ inputs.args }} --rm-dist
+          version: '~> v2'
+          args: release ${{ inputs.args }} --clean
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/workflow.yml

@@ -11,22 +11,22 @@ jobs:
   build:
     strategy:
       matrix:
-        os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest']
-        go: [ '1.19', '1.20' ]
+        os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest', 'macos-14' ]
+        go: [ '1.23', '1.24' ]
     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@v3
+        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

.goreleaser.yaml

@@ -1,3 +1,4 @@
+version: 2
 before:
   hooks:
     - go mod tidy
@@ -18,6 +19,7 @@ builds:
       - linux_amd64
       - linux_arm64
       - linux_arm
+      - linux_riscv64
       - windows_amd64
       - windows_arm64
       - windows_arm
@@ -37,6 +39,7 @@ builds:
       - linux_amd64
       - linux_arm64
       - linux_arm
+      - linux_riscv64
       - windows_amd64
       - windows_arm64
       - windows_arm
@@ -55,6 +58,7 @@ builds:
     targets:
       - linux_amd64
       - linux_arm64
+      - linux_riscv64
       - linux_arm
       - windows_amd64
       - windows_arm64
@@ -109,7 +113,7 @@ 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 +1,57 @@
+# 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`
+
+### 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.
-2. Generate release notes using [`gh`][gh]. Example:
-```
-$ gh api -X POST \
-  -F tag_name='v2.0.0-beta.5' \
-  -F target_commitish='v2' \
-  -F previous_tag_name='v2.0.0-beta.4' \
-  --jq '.body' \
-  repos/pelletier/go-toml/releases/generate-notes
-```
-3. Look for "Other changes". That would indicate a pull request not labeled
-   properly. Tweak labels and pull request titles until changelog looks good for
-   users.
-4. [Draft new release][new-release].
-5. Fill tag and target with the same value used to generate the changelog.
-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.
+1. Decide on the next version number. Use semver. Review commits since last
+   version to assess.
+2. Tag release. For example:
+   ```
+   git checkout v2
+   git pull
+   git tag v2.2.0
+   git push --tags
+   ```
+3. CI automatically builds a draft GitHub release. Review it and edit as
+   necessary. Look for "Other changes". That would indicate a pull request not
+   labeled properly. Tweak labels and pull request titles until changelog looks
+   good for users.
+4. Check "create discussion" box, in the "Releases" category.
+5. If new version is an alpha or beta only, check pre-release box.
+
 
 [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"
-3| key2 = "missing2"
- | ~~~~ missing field
-4| key3 = "missing3"
-5| key4 = "value4"
+1| [server]
+2| path = 100
+ |        ~~~ cannot decode TOML integer into struct field toml_test.Server.Path of type string
+3| port = 50
 ```
 
 [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
-      Name    string
-      Tags    []string
+	Version int
+	Name    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,
-      Name:    "go-toml",
-      Tags:    []string{"go", "toml"},
+	Version: 2,
+	Name:    "go-toml",
+	Tags:    []string{"go", "toml"},
 }
 
 b, err := toml.Marshal(cfg)
 if err != nil {
-      panic(err)
+	panic(err)
 }
 fmt.Println(string(b))
 
@@ -156,17 +235,17 @@ the AST level. See https://pkg.go.dev/github.com/pelletier/go-toml/v2/unstable.
 Execution time speedup compared to other Go TOML libraries:
 
 <table>
-    <thead>
-        <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/ReferenceFile/map-2</td><td>1.7x</td><td>1.8x</td></tr>
-        <tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>2.5x</td></tr>
-        <tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.9x</td></tr>
-        <tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.9x</td></tr>
-        <tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.4x</td><td>5.3x</td></tr>
-     </tbody>
+	<thead>
+		<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>2.2x</td></tr>
+		<tr><td>Marshal/ReferenceFile/map-2</td><td>1.7x</td><td>2.1x</td></tr>
+		<tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>3.0x</td></tr>
+		<tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.7x</td></tr>
+		<tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.7x</td></tr>
+		<tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.6x</td><td>5.1x</td></tr>
+	 </tbody>
 </table>
 <details><summary>See more</summary>
 <p>The table above has the results of the most common use-cases. The table below
@@ -174,22 +253,22 @@ contains the results of all benchmarks, including unrealistic ones. It is
 provided for completeness.</p>
 
 <table>
-    <thead>
-        <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/struct-2</td><td>2.7x</td><td>4.2x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.5x</td><td>3.1x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>6.2x</td><td>3.9x</td></tr>
-        <tr><td>UnmarshalDataset/example-2</td><td>3.1x</td><td>3.5x</td></tr>
-        <tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>3.1x</td></tr>
-        <tr><td>UnmarshalDataset/twitter-2</td><td>2.5x</td><td>2.6x</td></tr>
-        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.1x</td><td>2.2x</td></tr>
-        <tr><td>UnmarshalDataset/canada-2</td><td>1.6x</td><td>1.3x</td></tr>
-        <tr><td>UnmarshalDataset/config-2</td><td>4.3x</td><td>3.2x</td></tr>
-        <tr><td>[Geo mean]</td><td>2.7x</td><td>2.8x</td></tr>
-     </tbody>
+	<thead>
+		<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>2.7x</td></tr>
+		<tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>3.8x</td></tr>
+		<tr><td>Unmarshal/SimpleDocument/map-2</td><td>3.8x</td><td>3.0x</td></tr>
+		<tr><td>Unmarshal/SimpleDocument/struct-2</td><td>5.6x</td><td>4.1x</td></tr>
+		<tr><td>UnmarshalDataset/example-2</td><td>3.0x</td><td>3.2x</td></tr>
+		<tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>2.9x</td></tr>
+		<tr><td>UnmarshalDataset/twitter-2</td><td>2.6x</td><td>2.7x</td></tr>
+		<tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.2x</td><td>2.3x</td></tr>
+		<tr><td>UnmarshalDataset/canada-2</td><td>1.8x</td><td>1.5x</td></tr>
+		<tr><td>UnmarshalDataset/config-2</td><td>4.1x</td><td>2.9x</td></tr>
+		<tr><td>geomean</td><td>2.7x</td><td>2.8x</td></tr>
+	 </tbody>
 </table>
 <p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>
 </details>
@@ -214,24 +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
-    $ tomljson --help
-    ```
+	```
+	$ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
+	$ tomljson --help
+	```
 
  * `jsontoml`: Reads a JSON file and outputs a TOML representation.
 
-    ```
-    $ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
-    $ jsontoml --help
-    ```
+	```
+	$ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
+	$ jsontoml --help
+	```
 
  * `tomll`: Lints and reformats a TOML file.
 
-    ```
-    $ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
-    $ tomll --help
-    ```
+	```
+	$ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
+	$ tomll --help
+	```
 
 ### Docker image
 
@@ -242,7 +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
 
@@ -274,16 +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{
-    B: "Before",
-  },
+	A: inner{
+		B: "Before",
+	},
 }
 
 data := `
@@ -322,7 +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)
@@ -497,27 +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.
@@ -553,10 +625,11 @@ complete solutions exist out there.
 
 ## Versioning
 
-Go-toml follows [Semantic Versioning](https://semver.org). The supported version
-of [TOML](https://github.com/toml-lang/toml) is indicated at the beginning of
-this document. The last two major versions of Go are supported
-(see [Go Release Policy](https://golang.org/doc/devel/release.html#policy)).
+Expect for parts explicitly marked otherwise, go-toml follows [Semantic
+Versioning](https://semver.org). The supported version of
+[TOML](https://github.com/toml-lang/toml) is indicated at the beginning of this
+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

@@ -3,13 +3,13 @@ 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 {
@@ -35,11 +35,11 @@ func TestUnmarshalDatasetCode(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)
-			require.Equal(t, len(b), tc.jsonLen)
+			assert.NoError(t, err)
+			assert.Equal(t, len(b), tc.jsonLen)
 		})
 	}
 }
@@ -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()
 
 	gz, err := gzip.NewReader(f)
-	require.NoError(tb, err)
+	assert.NoError(tb, err)
 
-	buf, err := ioutil.ReadAll(gz)
-	require.NoError(tb, err)
+	buf, err := io.ReadAll(gz)
+	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) {
@@ -59,7 +59,7 @@ func BenchmarkUnmarshal(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)
 		}
@@ -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)
 		}
@@ -344,11 +344,11 @@ type benchmarkDoc struct {
 }
 
 func TestUnmarshalReferenceFile(t *testing.T) {
-	bytes, err := ioutil.ReadFile("benchmark.toml")
-	require.NoError(t, err)
+	bytes, err := os.ReadFile("benchmark.toml")
+	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
@@ -151,7 +152,7 @@ bench() {
     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
-        mktemp --suffix=-$1;
+    if mktemp --version &> /dev/null; then
+	# GNU
+        mktemp --suffix=-$1
     else
-        mktemp -t $1;
+	# BSD
+	mktemp -t $1
     fi
 }
 
@@ -183,12 +186,14 @@ 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
     ])
 # move geomean to the end
 results.append(results[0])
@@ -259,10 +264,10 @@ 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-encoder/gotoml-test-encoder.go

@@ -0,0 +1,30 @@
+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 < toml-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/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func TestConvert(t *testing.T) {
 	examples := []struct {
-		name     string
-		input    string
-		expected string
-		errors   bool
+		name          string
+		input         string
+		expected      string
+		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

@@ -7,8 +7,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 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())

cmd/tomll/main_test.go

@@ -5,8 +5,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 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

@@ -7,17 +7,13 @@
 package main
 
 import (
-	"archive/zip"
 	"bytes"
 	"flag"
 	"fmt"
 	"go/format"
-	"io"
-	"io/ioutil"
 	"log"
-	"net/http"
 	"os"
-	"regexp"
+	"path/filepath"
 	"strconv"
 	"strings"
 	"text/template"
@@ -64,30 +60,6 @@ const srcTemplate = "// Generated by tomltestgen for toml-test ref {{.Ref}} on {
 	"}\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 := ""
 	nextUpper := true
@@ -107,19 +79,6 @@ func kebabToCamel(kebab string) string {
 	return camel
 }
 
-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 {
 	return strconv.Quote(input)
 }
@@ -138,61 +97,59 @@ 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 {
-		zipFilesMap[f.Name] = f
+		log.Printf("> [%s] %s\n", "invalid", name)
+
+		tomlContent, err := os.ReadFile(f)
+		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)`)
-	for _, f := range zipReader.File {
-		groups := testFileRegexp.FindStringSubmatch(f.Name)
-		if len(groups) > 0 {
-			name := kebabToCamel(groups[3])
-			testType := groups[2]
+	dirContent, _ = filepath.Glob("tests/valid/**/*.toml")
+	for _, f := range dirContent {
+		filename := strings.TrimPrefix(f, "tests/valid/")
+		name := kebabToCamel(strings.TrimSuffix(filename, ".toml"))
+		name = strings.ReplaceAll(name, ".", "_")
 
-			log.Printf("> [%s] %s\n", testType, name)
+		log.Printf("> [%s] %s\n", "valid", name)
 
-			tomlContent := readFileFromZip(f)
-
-			switch testType {
-			case "invalid":
-				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))
-			}
+		tomlContent, err := os.ReadFile(f)
+		if err != nil {
+			fmt.Printf("failed reading test file: %s\n", err)
+			os.Exit(1)
 		}
+
+		filename = strings.TrimSuffix(f, ".toml")
+		jsonContent, err := os.ReadFile(filename + ".json")
+		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 +159,7 @@ 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 +173,7 @@ func main() {
 		return
 	}
 
-	err = os.WriteFile(*out, outputBytes, 0644)
+	err = os.WriteFile(*out, outputBytes, 0o644)
 	if err != nil {
 		panic(err)
 	}

decode.go

@@ -318,7 +318,7 @@ 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, unstable.NewParserError(b, "float integer part cannot have leading zeroes")
 	}
 

errors.go

@@ -5,7 +5,6 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/pelletier/go-toml/v2/internal/danger"
 	"github.com/pelletier/go-toml/v2/unstable"
 )
 
@@ -54,6 +53,17 @@ func (s *StrictMissingError) String() string {
 	return buf.String()
 }
 
+// Unwrap returns wrapped decode errors
+//
+// Implements errors.Join() interface.
+func (s *StrictMissingError) Unwrap() []error {
+	var errs []error
+	for i := range s.Errors {
+		errs = append(errs, &s.Errors[i])
+	}
+	return errs
+}
+
 type Key []string
 
 // Error returns the error message contained in the DecodeError.
@@ -78,7 +88,7 @@ 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.
@@ -88,7 +98,7 @@ func (e *DecodeError) Key() Key {
 //
 //nolint:funlen
 func wrapDecodeError(document []byte, de *unstable.ParserError) *DecodeError {
-	offset := danger.SubsliceOffset(document, de.Highlight)
+	offset := cap(document) - cap(de.Highlight)
 
 	errMessage := de.Error()
 	errLine, errColumn := positionAtEnd(document[:offset])

errors_test.go

@@ -7,8 +7,8 @@ import (
 	"strings"
 	"testing"
 
+	"github.com/pelletier/go-toml/v2/internal/assert"
 	"github.com/pelletier/go-toml/v2/unstable"
-	"github.com/stretchr/testify/assert"
 )
 
 //nolint:funlen
@@ -205,6 +205,21 @@ func TestDecodeError_Accessors(t *testing.T) {
 	assert.Equal(t, "bar", e.String())
 }
 
+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

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

@@ -1,19 +1,16 @@
-//go:build go1.18 || go1.19 || go1.20
-// +build go1.18 go1.19 go1.20
-
 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)
 	}
@@ -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
-
-require github.com/stretchr/testify v1.8.1
+go 1.21.0

go.sum

@@ -1,17 +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/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
-github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
-github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
-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 +1,135 @@
+package assert
+
+import (
+	"bytes"
+	"fmt"
+	"reflect"
+	"strings"
+	"testing"
+)
+
+// True asserts that an expression is true.
+func True(t testing.TB, ok bool, msgAndArgs ...any) {
+	if ok {
+		return
+	}
+	t.Helper()
+	t.Fatal(formatMsgAndArgs("Expected expression to be true", msgAndArgs...))
+}
+
+// False asserts that an expression is false.
+func False(t testing.TB, ok bool, msgAndArgs ...any) {
+	if !ok {
+		return
+	}
+	t.Helper()
+	t.Fatal(formatMsgAndArgs("Expected expression to be false", msgAndArgs...))
+}
+
+// Equal asserts that "expected" and "actual" are equal.
+func Equal[T any](t testing.TB, expected, actual T, msgAndArgs ...any) {
+	if objectsAreEqual(expected, actual) {
+		return
+	}
+	t.Helper()
+	msg := formatMsgAndArgs("Expected values to be equal:", msgAndArgs...)
+	t.Fatalf("%s\n%s", msg, diff(expected, actual))
+}
+
+// Error asserts that an error is not nil.
+func Error(t testing.TB, err error, msgAndArgs ...any) {
+	if err != nil {
+		return
+	}
+	t.Helper()
+	t.Fatal(formatMsgAndArgs("Expected an error", msgAndArgs...))
+}
+
+// NoError asserts that an error is nil.
+func NoError(t testing.TB, err error, msgAndArgs ...any) {
+	if err == nil {
+		return
+	}
+	t.Helper()
+	msg := formatMsgAndArgs("Unexpected error:", msgAndArgs...)
+	t.Fatalf("%s\n%+v", msg, err)
+}
+
+// Panics asserts that the given function panics.
+func Panics(t testing.TB, fn func(), msgAndArgs ...any) {
+	t.Helper()
+	defer func() {
+		if recover() == nil {
+			msg := formatMsgAndArgs("Expected function to panic", msgAndArgs...)
+			t.Fatal(msg)
+		}
+	}()
+	fn()
+}
+
+// Zero asserts that a value is its zero value.
+func Zero[T any](t testing.TB, value T, msgAndArgs ...any) {
+	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
+	}
+	t.Helper()
+	msg := formatMsgAndArgs("Expected zero value but got:", msgAndArgs...)
+	t.Fatalf("%s\n%v", msg, value)
+}
+
+func NotZero[T any](t testing.TB, value T, msgAndArgs ...any) {
+	var zero T
+	if !objectsAreEqual(value, zero) {
+		val := reflect.ValueOf(value)
+		if !((val.Kind() == reflect.Slice || val.Kind() == reflect.Map || val.Kind() == reflect.Array) && val.Len() == 0) {
+			return
+		}
+	}
+	t.Helper()
+	msg := formatMsgAndArgs("Unexpected zero value:", msgAndArgs...)
+	t.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 +1,184 @@
+package assert
+
+import (
+	"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(t testing.TB) {
+		Panics(t, invalidMessage)
+	})
+	assertFail(t, "Non-fmt message value", func(t testing.TB) {
+		True(t, false, "example %s", "message")
+	})
+}
+
+func TestTrue(t *testing.T) {
+	assertOk(t, "Succeed", func(t testing.TB) {
+		True(t, 1 > 0)
+	})
+	assertFail(t, "Fail", func(t testing.TB) {
+		True(t, 1 < 0)
+	})
+}
+
+func TestFalse(t *testing.T) {
+	assertOk(t, "Succeed", func(t testing.TB) {
+		False(t, 1 < 0)
+	})
+	assertFail(t, "Fail", func(t testing.TB) {
+		False(t, 1 > 0)
+	})
+}
+
+func TestEqual(t *testing.T) {
+	assertOk(t, "Nil", func(t testing.TB) {
+		Equal(t, interface{}(nil), interface{}(nil))
+	})
+	assertOk(t, "Identical structs", func(t testing.TB) {
+		Equal(t, Data{"expected", 1234}, Data{"expected", 1234})
+	})
+	assertFail(t, "Different structs", func(t testing.TB) {
+		Equal(t, Data{"expected", 1234}, Data{"actual", 1234})
+	})
+	assertOk(t, "Identical numbers", func(t testing.TB) {
+		Equal(t, 1234, 1234)
+	})
+	assertFail(t, "Identical numbers", func(t testing.TB) {
+		Equal(t, 1234, 1324)
+	})
+	assertOk(t, "Zero-length byte arrays", func(t testing.TB) {
+		Equal(t, []byte(nil), []byte(""))
+	})
+	assertOk(t, "Identical byte arrays", func(t testing.TB) {
+		Equal(t, []byte{1, 2, 3, 4}, []byte{1, 2, 3, 4})
+	})
+	assertFail(t, "Different byte arrays", func(t testing.TB) {
+		Equal(t, []byte{1, 2, 3, 4}, []byte{1, 3, 2, 4})
+	})
+	assertOk(t, "Identical strings", func(t testing.TB) {
+		Equal(t, "example", "example")
+	})
+	assertFail(t, "Identical strings", func(t testing.TB) {
+		Equal(t, "example", "elpmaxe")
+	})
+}
+
+func TestError(t *testing.T) {
+	assertOk(t, "Error", func(t testing.TB) {
+		Error(t, fmt.Errorf("example"))
+	})
+	assertFail(t, "Nil", func(t testing.TB) {
+		Error(t, nil)
+	})
+}
+
+func TestNoError(t *testing.T) {
+	assertFail(t, "Error", func(t testing.TB) {
+		NoError(t, fmt.Errorf("example"))
+	})
+	assertOk(t, "Nil", func(t testing.TB) {
+		NoError(t, nil)
+	})
+}
+
+func TestPanics(t *testing.T) {
+	willPanic := func() { panic("example") }
+	wontPanic := func() {}
+	assertOk(t, "Will panic", func(t testing.TB) {
+		Panics(t, willPanic)
+	})
+	assertFail(t, "Won't panic", func(t testing.TB) {
+		Panics(t, wontPanic)
+	})
+}
+
+func TestZero(t *testing.T) {
+	assertOk(t, "Empty struct", func(t testing.TB) {
+		Zero(t, Data{})
+	})
+	assertFail(t, "Non-empty struct", func(t testing.TB) {
+		Zero(t, Data{Label: "example"})
+	})
+	assertOk(t, "Nil slice", func(t testing.TB) {
+		var slice []int
+		Zero(t, slice)
+	})
+	assertFail(t, "Non-empty slice", func(t testing.TB) {
+		slice := []int{1, 2, 3, 4}
+		Zero(t, slice)
+	})
+	assertOk(t, "Zero-length slice", func(t testing.TB) {
+		slice := []int{}
+		Zero(t, slice)
+	})
+}
+
+func TestNotZero(t *testing.T) {
+	assertFail(t, "Empty struct", func(t testing.TB) {
+		zero := Data{}
+		NotZero(t, zero)
+	})
+	assertOk(t, "Non-empty struct", func(t testing.TB) {
+		notZero := Data{Label: "example"}
+		NotZero(t, notZero)
+	})
+	assertFail(t, "Nil slice", func(t testing.TB) {
+		var slice []int
+		NotZero(t, slice)
+	})
+	assertFail(t, "Zero-length slice", func(t testing.TB) {
+		slice := []int{}
+		NotZero(t, slice)
+	})
+	assertOk(t, "Non-empty slice", func(t testing.TB) {
+		slice := []int{1, 2, 3, 4}
+		NotZero(t, 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(t 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(t 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/cli/cli.go

@@ -6,7 +6,6 @@ import (
 	"flag"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 
 	"github.com/pelletier/go-toml/v2"
@@ -23,7 +22,7 @@ type Program struct {
 }
 
 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))
 }
@@ -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)
 	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(), 0600)
 }

internal/cli/cli_test.go

@@ -4,15 +4,13 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"os"
 	"path"
 	"strings"
 	"testing"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func processMain(args []string, input io.Reader, stdout, stderr io.Writer, f ConvertFn) int {
@@ -30,8 +28,8 @@ func TestProcessMainStdin(t *testing.T) {
 	})
 
 	assert.Equal(t, 0, exit)
-	assert.Empty(t, stdout.String())
-	assert.Empty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.Zero(t, stderr.String())
 }
 
 func TestProcessMainStdinErr(t *testing.T) {
@@ -44,8 +42,8 @@ func TestProcessMainStdinErr(t *testing.T) {
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
-	assert.NotEmpty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.NotZero(t, stderr.String())
 }
 
 func TestProcessMainStdinDecodeErr(t *testing.T) {
@@ -59,16 +57,16 @@ func TestProcessMainStdinDecodeErr(t *testing.T) {
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
-	assert.Contains(t, stderr.String(), "error occurred at")
+	assert.Zero(t, stdout.String())
+	assert.True(t, strings.Contains(stderr.String(), "error occurred at"))
 }
 
 func TestProcessMainFileExists(t *testing.T) {
-	tmpfile, err := ioutil.TempFile("", "example")
-	require.NoError(t, err)
+	tmpfile, err := os.CreateTemp("", "example")
+	assert.NoError(t, err)
 	defer os.Remove(tmpfile.Name())
 	_, err = tmpfile.Write([]byte(`some data`))
-	require.NoError(t, err)
+	assert.NoError(t, err)
 
 	stdout := new(bytes.Buffer)
 	stderr := new(bytes.Buffer)
@@ -78,8 +76,8 @@ func TestProcessMainFileExists(t *testing.T) {
 	})
 
 	assert.Equal(t, 0, exit)
-	assert.Empty(t, stdout.String())
-	assert.Empty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.Zero(t, stderr.String())
 }
 
 func TestProcessMainFileDoesNotExist(t *testing.T) {
@@ -91,22 +89,22 @@ func TestProcessMainFileDoesNotExist(t *testing.T) {
 	})
 
 	assert.Equal(t, -1, exit)
-	assert.Empty(t, stdout.String())
-	assert.NotEmpty(t, stderr.String())
+	assert.Zero(t, stdout.String())
+	assert.NotZero(t, stderr.String())
 }
 
 func TestProcessMainFilesInPlace(t *testing.T) {
-	dir, err := ioutil.TempDir("", "")
-	require.NoError(t, err)
+	dir, err := os.MkdirTemp("", "")
+	assert.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)
-	require.NoError(t, err)
-	err = ioutil.WriteFile(path2, []byte("content 2"), 0600)
-	require.NoError(t, err)
+	err = os.WriteFile(path1, []byte("content 1"), 0600)
+	assert.NoError(t, err)
+	err = os.WriteFile(path2, []byte("content 2"), 0600)
+	assert.NoError(t, err)
 
 	p := Program{
 		Fn:      dummyFileFn,
@@ -115,15 +113,15 @@ 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)
-	require.NoError(t, err)
-	require.Equal(t, "1", string(v1))
+	v1, err := os.ReadFile(path1)
+	assert.NoError(t, err)
+	assert.Equal(t, "1", string(v1))
 
-	v2, err := ioutil.ReadFile(path2)
-	require.NoError(t, err)
-	require.Equal(t, "2", string(v2))
+	v2, err := os.ReadFile(path2)
+	assert.NoError(t, err)
+	assert.Equal(t, "2", string(v2))
 }
 
 func TestProcessMainFilesInPlaceErrRead(t *testing.T) {
@@ -134,18 +132,18 @@ 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("", "")
-	require.NoError(t, err)
+	dir, err := os.MkdirTemp("", "")
+	assert.NoError(t, err)
 	defer os.RemoveAll(dir)
 
 	path1 := path.Join(dir, "file1")
 
-	err = ioutil.WriteFile(path1, []byte("content 1"), 0600)
-	require.NoError(t, err)
+	err = os.WriteFile(path1, []byte("content 1"), 0600)
+	assert.NoError(t, err)
 
 	p := Program{
 		Fn:      func(io.Reader, io.Writer) error { return fmt.Errorf("oh no") },
@@ -154,15 +152,15 @@ func TestProcessMainFilesInPlaceFailFn(t *testing.T) {
 
 	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)
-	require.NoError(t, err)
-	require.Equal(t, "content 1", string(v1))
+	v1, err := os.ReadFile(path1)
+	assert.NoError(t, err)
+	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

@@ -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) {
@@ -107,13 +107,13 @@ name = 'List.Second'
 `
 
 	result, err := toml.Marshal(docData)
-	require.NoError(t, err)
-	require.Equal(t, marshalTestToml, string(result))
+	assert.NoError(t, err)
+	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
@@ -128,7 +128,7 @@ String2 = 'Two'
 String2 = 'Three'
 `
 
-	require.Equal(t, string(expected), string(result))
+	assert.Equal(t, string(expected), string(result))
 
 }
 
@@ -153,7 +153,7 @@ 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 +164,7 @@ stringlist = []
 [map]
 `
 
-	require.Equal(t, string(expected), string(result))
+	assert.Equal(t, string(expected), string(result))
 }
 
 type textMarshaler struct {
@@ -187,13 +187,13 @@ 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

@@ -16,8 +16,7 @@ import (
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 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)
-	require.Equal(t, basicTestData, result)
+	assert.NoError(t, err)
+	assert.Equal(t, basicTestData, result)
 }
 
 type quotedKeyMarshalTestStruct struct {
@@ -300,7 +299,7 @@ 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 +339,7 @@ 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 +455,7 @@ 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 +503,7 @@ 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)
 }
 
@@ -540,7 +539,7 @@ 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)
 }
 
@@ -834,7 +833,7 @@ 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)
 		})
 	}
@@ -963,7 +962,7 @@ 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) {
@@ -1090,7 +1089,7 @@ func TestUnmarshalCheckConversionFloatInt(t *testing.T) {
 	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)
 		})
 	}
 }
@@ -1125,7 +1124,7 @@ 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)
 		})
 	}
 }
@@ -1745,7 +1744,7 @@ Age = 23
 	}
 	actual := OuterStruct{}
 	err := toml.Unmarshal(doc, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, actual)
 }
 
@@ -1830,7 +1829,7 @@ InnerField = "After4"
 	}
 
 	err := toml.Unmarshal(doc, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, actual)
 }
 
@@ -1879,7 +1878,7 @@ 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"},
@@ -1930,7 +1929,7 @@ func TestUnmarshalMixedTypeSlice(t *testing.T) {
 		},
 	}
 	err := toml.Unmarshal(doc, &actual)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 	assert.Equal(t, expected, actual)
 }
 
@@ -1939,7 +1938,7 @@ 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"},
@@ -1998,8 +1997,13 @@ func TestDecoderStrict(t *testing.T) {
 	}
 
 	err := strictDecoder(input).Decode(&doc)
-	require.Error(t, err)
-	require.IsType(t, &toml.StrictMissingError{}, err)
+	assert.Error(t, err)
+
+	assert.Equal(t,
+		reflect.TypeOf(err), reflect.TypeOf(&toml.StrictMissingError{}),
+		"Expected a *toml.StrictMissingError, got: %v", reflect.TypeOf(err),
+	)
+
 	se := err.(*toml.StrictMissingError)
 
 	keys := []toml.Key{}
@@ -2015,10 +2019,10 @@ 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)
@@ -2036,7 +2040,7 @@ func TestDecoderStrictValid(t *testing.T) {
 	}
 
 	err := strictDecoder(input).Decode(&doc)
-	require.NoError(t, err)
+	assert.NoError(t, err)
 }
 
 type docUnmarshalTOML struct {
@@ -2087,7 +2091,7 @@ 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)
 }
@@ -2153,7 +2157,7 @@ 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)
@@ -2223,7 +2227,10 @@ 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"])
@@ -2276,7 +2283,7 @@ func (c *Custom) UnmarshalTOML(v interface{}) error {
 	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 {
@@ -2314,7 +2321,7 @@ type config437 struct {
 	} `toml:"HTTP"`
 }
 
-func TestGithubIssue437(t *testing.T) {
+func TestGitHubIssue437(t *testing.T) {
 	t.Skipf("unmarshalTOML not implemented")
 	src := `
 [HTTP]

internal/testsuite/rm.go

@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"strconv"
 	"time"
+
+	"github.com/pelletier/go-toml/v2"
 )
 
 // Remove JSON tags to a data structure as returned by toml-test.
@@ -40,7 +42,7 @@ 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 {
@@ -76,14 +78,31 @@ 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":

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) {
@@ -48,3 +48,21 @@ func DecodeStdin() error {
 
 	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/seen.go

@@ -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.
@@ -149,8 +153,9 @@ 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.
-func (s *SeenTracker) CheckExpression(node *unstable.Node) error {
+// consistent. It returns true if it is the first time this node's key is seen.
+// Useful to clear array tables on first use.
+func (s *SeenTracker) CheckExpression(node *unstable.Node) (bool, error) {
 	if s.entries == nil {
 		s.reset()
 	}
@@ -166,7 +171,7 @@ func (s *SeenTracker) CheckExpression(node *unstable.Node) error {
 	}
 }
 
-func (s *SeenTracker) checkTable(node *unstable.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 *unstable.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 *unstable.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 *unstable.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 *unstable.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 *unstable.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 *unstable.Node) error {
+func (s *SeenTracker) checkKeyValue(node *unstable.Node) (bool, error) {
 	parentIdx := s.currentIdx
 	it := node.Key()
 
@@ -281,11 +289,11 @@ func (s *SeenTracker) checkKeyValue(node *unstable.Node) error {
 		} else {
 			entry := s.entries[idx]
 			if it.IsLast() {
-				return fmt.Errorf("toml: key %s is already defined", string(k))
+				return false, fmt.Errorf("toml: key %s is already defined", string(k))
 			} else if entry.kind != tableKind {
-				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)
 			} else if entry.explicit {
-				return fmt.Errorf("toml: cannot redefine table %s that has already been explicitly defined", string(k))
+				return false, fmt.Errorf("toml: cannot redefine table %s that has already been explicitly defined", string(k))
 			}
 		}
 
@@ -303,45 +311,39 @@ func (s *SeenTracker) checkKeyValue(node *unstable.Node) error {
 		return s.checkArray(value)
 	}
 
-	return nil
+	return false, nil
 }
 
-func (s *SeenTracker) checkArray(node *unstable.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 {
 		case unstable.InlineTable:
-			err := s.checkInlineTable(n)
+			first, err = s.checkInlineTable(n)
 			if err != nil {
-				return err
+				return false, err
 			}
 		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 *unstable.Node) error {
-	if pool.New == nil {
-		pool.New = func() interface{} {
-			return &SeenTracker{}
-		}
-	}
-
+func (s *SeenTracker) checkInlineTable(node *unstable.Node) (first bool, err error) {
 	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 +354,5 @@ func (s *SeenTracker) checkInlineTable(node *unstable.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 +12,9 @@ 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)
+	assert.True(t,
+		int(reflect.TypeOf(entry{}).Size()) <= maxExpectedEntrySize,
+		"Expected entry to be less than or equal to %d, got: %d",
+		maxExpectedEntrySize, int(reflect.TypeOf(entry{}).Size()),
+	)
 }

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)
-	require.Equal(t, []byte("2021-06-08"), b)
+	assert.NoError(t, err)
+	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)
-	require.Equal(t, toml.LocalDate{2021, 6, 8}, d)
+	assert.NoError(t, err)
+	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)
-	require.Equal(t, []byte("20:12:01.000000002"), b)
+	assert.NoError(t, err)
+	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)
-	require.Equal(t, toml.LocalTime{20, 12, 1, 2, 9}, d)
+	assert.NoError(t, err)
+	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)
-	require.Equal(t, "20:12:01.500", d.A.String())
+	assert.NoError(t, err)
+	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)
-	require.Equal(t, []byte("2021-06-08T20:12:01.000000002"), b)
+	assert.NoError(t, err)
+	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)
-	require.Equal(t, toml.LocalDateTime{
+	assert.NoError(t, err)
+	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

@@ -3,11 +3,12 @@ package toml
 import (
 	"bytes"
 	"encoding"
+	"encoding/json"
 	"fmt"
 	"io"
 	"math"
 	"reflect"
-	"sort"
+	"slices"
 	"strconv"
 	"strings"
 	"time"
@@ -37,10 +38,11 @@ type Encoder struct {
 	w io.Writer
 
 	// global settings
-	tablesInline    bool
-	arraysMultiline bool
-	indentSymbol    string
-	indentTables    bool
+	tablesInline       bool
+	arraysMultiline    bool
+	indentSymbol       string
+	indentTables       bool
+	marshalJsonNumbers bool
 }
 
 // NewEncoder returns a new Encoder that writes to w.
@@ -87,6 +89,17 @@ 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.
@@ -148,6 +161,11 @@ 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
@@ -180,6 +198,8 @@ func (enc *Encoder) Encode(v interface{}) error {
 type valueOptions struct {
 	multiline bool
 	omitempty bool
+	omitzero  bool
+	commented bool
 	comment   string
 }
 
@@ -205,6 +225,9 @@ type encoderCtx struct {
 	// Indentation level
 	indent int
 
+	// Prefix the current value with a comment.
+	commented bool
+
 	// Options coming from struct tags
 	options valueOptions
 }
@@ -245,10 +268,22 @@ 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))
+			} else {
+				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()
 		}
@@ -273,7 +308,7 @@ 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() {
@@ -352,11 +387,16 @@ func shouldOmitEmpty(options valueOptions, v reflect.Value) bool {
 	return options.omitempty && isEmptyValue(v)
 }
 
+func shouldOmitZero(options valueOptions, v reflect.Value) bool {
+	return options.omitzero && 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)
 	}
 
@@ -378,6 +418,13 @@ 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:
@@ -477,12 +524,26 @@ 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':
@@ -526,6 +587,8 @@ func (enc *Encoder) encodeTableHeader(ctx encoderCtx, b []byte) ([]byte, error)
 
 	b = enc.encodeComment(ctx.indent, ctx.options.comment, b)
 
+	b = enc.commented(ctx.commented, b)
+
 	b = enc.indent(ctx.indent, b)
 
 	b = append(b, '[')
@@ -577,11 +640,35 @@ func (enc *Encoder) encodeKey(b []byte, k string) []byte {
 	}
 }
 
-func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
-	if v.Type().Key().Kind() != reflect.String {
-		return nil, fmt.Errorf("toml: type %s is not supported as a map key", v.Type().Key().Kind())
-	}
+func (enc *Encoder) keyToString(k reflect.Value) (string, error) {
+	keyType := k.Type()
+	switch {
+	case keyType.Kind() == reflect.String:
+		return k.String(), nil
 
+	case 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
+
+	case keyType.Kind() == reflect.Int || keyType.Kind() == reflect.Int8 || keyType.Kind() == reflect.Int16 || keyType.Kind() == reflect.Int32 || keyType.Kind() == reflect.Int64:
+		return strconv.FormatInt(k.Int(), 10), nil
+
+	case keyType.Kind() == reflect.Uint || keyType.Kind() == reflect.Uint8 || keyType.Kind() == reflect.Uint16 || keyType.Kind() == reflect.Uint32 || keyType.Kind() == reflect.Uint64:
+		return strconv.FormatUint(k.Uint(), 10), nil
+
+	case keyType.Kind() == reflect.Float32:
+		return strconv.FormatFloat(k.Float(), 'f', -1, 32), nil
+
+	case keyType.Kind() == reflect.Float64:
+		return strconv.FormatFloat(k.Float(), 'f', -1, 64), nil
+	}
+	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
@@ -589,13 +676,17 @@ 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) {
 			continue
 		}
 
+		k, err := enc.keyToString(iter.Key())
+		if err != nil {
+			return nil, err
+		}
+
 		if willConvertToTableOrArrayTable(ctx, v) {
 			t.pushTable(k, v, emptyValueOptions)
 		} else {
@@ -610,8 +701,8 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 }
 
 func sortEntriesByKey(e []entry) {
-	sort.Slice(e, func(i, j int) bool {
-		return e[i].Key < e[j].Key
+	slices.SortFunc(e, func(a, b entry) int {
+		return strings.Compare(a.Key, b.Key)
 	})
 }
 
@@ -674,6 +765,8 @@ 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 {
@@ -688,6 +781,8 @@ 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"),
 		}
 
@@ -747,6 +842,8 @@ type tagOptions struct {
 	multiline bool
 	inline    bool
 	omitempty bool
+	omitzero  bool
+	commented bool
 }
 
 func parseTag(tag string) (string, tagOptions) {
@@ -758,7 +855,7 @@ 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, ",")
@@ -774,6 +871,10 @@ func parseTag(tag string) (string, tagOptions) {
 			opts.inline = true
 		case "omitempty":
 			opts.omitempty = true
+		case "omitzero":
+			opts.omitzero = true
+		case "commented":
+			opts.commented = true
 		}
 	}
 
@@ -806,11 +907,16 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		if shouldOmitEmpty(kv.Options, kv.Value) {
 			continue
 		}
+		if 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
 		}
@@ -823,6 +929,9 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		if shouldOmitEmpty(table.Options, table.Value) {
 			continue
 		}
+		if shouldOmitZero(table.Options, table.Value) {
+			continue
+		}
 		if first {
 			first = false
 			if hasNonEmptyKV {
@@ -835,8 +944,10 @@ 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
 		}
@@ -855,6 +966,9 @@ func (enc *Encoder) encodeTableInline(b []byte, ctx encoderCtx, t table) ([]byte
 		if shouldOmitEmpty(kv.Options, kv.Value) {
 			continue
 		}
+		if shouldOmitZero(kv.Options, kv.Value) {
+			continue
+		}
 
 		if first {
 			first = false
@@ -883,7 +997,7 @@ 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)) {
+	if v.Type() == timeType || v.Type().Implements(textMarshalerType) || (v.Kind() != reflect.Ptr && v.CanAddr() && reflect.PointerTo(v.Type()).Implements(textMarshalerType)) {
 		return false
 	}
 
@@ -914,7 +1028,7 @@ 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
@@ -954,6 +1068,13 @@ 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 {
@@ -969,6 +1090,10 @@ 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 +1,42 @@
+package ossfuzz
+
+import (
+	"fmt"
+	"reflect"
+	"strings"
+
+	"github.com/pelletier/go-toml/v2"
+)
+
+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
+}

strict.go

@@ -1,7 +1,6 @@
 package toml
 
 import (
-	"github.com/pelletier/go-toml/v2/internal/danger"
 	"github.com/pelletier/go-toml/v2/internal/tracker"
 	"github.com/pelletier/go-toml/v2/unstable"
 )
@@ -103,5 +102,5 @@ func keyLocation(node *unstable.Node) []byte {
 		end = k.Node().Data
 	}
 
-	return danger.BytesRange(start, end)
+	return start[:cap(start)-cap(end)+len(end)]
 }

test-go-versions.sh

@@ -0,0 +1,596 @@
+#!/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 1.25)
+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"
+)
+
+# 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
+    $0 --verbose --output ./results 1.24 1.25  # Verbose output to custom directory
+
+EXIT CODES:
+    0                   Recent Go versions pass (good compatibility)
+    1                   Recent Go versions fail (needs attention) or script error
+
+EOF
+}
+
+log() {
+    echo -e "${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[0-5])$ ]]; then
+        log_error "Invalid Go version: $version. Supported versions: 1.11-1.25"
+        exit 1
+    fi
+done
+
+# Check if Docker is available
+if ! command -v docker &> /dev/null; then
+    log_error "Docker is required but not installed or not in PATH"
+    exit 1
+fi
+
+# Check if Docker daemon is running
+if ! docker info &> /dev/null; then
+    log_error "Docker daemon is not running"
+    exit 1
+fi
+
+# Create output directory
+mkdir -p "$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

@@ -1,4 +1,5 @@
-//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
@@ -8,8 +9,8 @@ import (
 	"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) {
@@ -44,15 +45,15 @@ func testgenValid(t *testing.T, input string, jsonRef string) {
 		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)
-	require.NoError(t, err)
+	err = json.Unmarshal(j, &actual)
+	assert.NoError(t, err)
 
 	testsuite.CmpJSON(t, "", ref, actual)
 }

unmarshaler.go

@@ -5,14 +5,13 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math"
 	"reflect"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
 
-	"github.com/pelletier/go-toml/v2/internal/danger"
 	"github.com/pelletier/go-toml/v2/internal/tracker"
 	"github.com/pelletier/go-toml/v2/unstable"
 )
@@ -21,10 +20,8 @@ import (
 //
 // It is a shortcut for Decoder.Decode() with the default options.
 func Unmarshal(data []byte, v interface{}) error {
-	p := unstable.Parser{}
-	p.Reset(data)
-	d := decoder{p: &p}
-
+	d := decoder{}
+	d.p.Reset(data)
 	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.
@@ -54,6 +54,24 @@ 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.
+//
+// Currently, types can only decode from a single value. Tables and array tables
+// are not supported.
+//
+// *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
@@ -96,26 +114,25 @@ 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 := unstable.Parser{}
-	p.Reset(b)
 	dec := decoder{
-		p: &p,
 		strict: strict{
 			Enabled: d.strict,
 		},
+		unmarshalerInterface: d.unmarshalerInterface,
 	}
+	dec.p.Reset(b)
 
 	return dec.FromParser(v)
 }
 
 type decoder struct {
 	// Which parser instance in use for this decoding session.
-	p *unstable.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 +144,10 @@ 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 +160,9 @@ type decoder struct {
 	// Strict mode
 	strict strict
 
+	// Flag that enables/disables unmarshaler interface.
+	unmarshalerInterface bool
+
 	// Current context for the error.
 	errorContext *errorContext
 }
@@ -149,12 +173,16 @@ 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() *unstable.Node {
@@ -242,9 +270,10 @@ Rules for the unmarshal code:
 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 == unstable.KeyValue) {
-		err = d.seen.CheckExpression(expr)
+		first, err = d.seen.CheckExpression(expr)
 		if err != nil {
 			return err
 		}
@@ -263,6 +292,7 @@ func (d *decoder) handleRootExpression(expr *unstable.Node, v reflect.Value) err
 	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))
@@ -303,6 +333,10 @@ func (d *decoder) handleArrayTableCollectionLast(key unstable.Iterator, v reflec
 				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 +355,10 @@ func (d *decoder) handleArrayTableCollectionLast(key unstable.Iterator, v reflec
 
 		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 {
@@ -377,15 +415,39 @@ func (d *decoder) handleArrayTableCollection(key unstable.Iterator, v reflect.Va
 
 		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)
@@ -417,7 +479,10 @@ func (d *decoder) handleKeyPart(key unstable.Iterator, v reflect.Value, nextFn h
 		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() {
@@ -569,7 +634,7 @@ 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
 		}
@@ -627,6 +692,14 @@ func (d *decoder) handleValue(value *unstable.Node, v reflect.Value) error {
 		v = initAndDereferencePointer(v)
 	}
 
+	if d.unmarshalerInterface {
+		if v.CanAddr() && v.Addr().CanInterface() {
+			if outi, ok := v.Addr().Interface().(unstable.Unmarshaler); ok {
+				return outi.UnmarshalTOML(value)
+			}
+		}
+	}
+
 	ok, err := d.tryTextUnmarshaler(value, v)
 	if ok || err != nil {
 		return err
@@ -960,7 +1033,7 @@ func (d *decoder) unmarshalInteger(value *unstable.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()) {
@@ -979,7 +1052,7 @@ func (d *decoder) unmarshalString(value *unstable.Node, v reflect.Value) error {
 	case reflect.Interface:
 		v.Set(reflect.ValueOf(string(value.Data)))
 	default:
-		return unstable.NewParserError(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
@@ -1009,6 +1082,58 @@ func (d *decoder) handleKeyValueInner(key unstable.Iterator, value *unstable.Nod
 	return reflect.Value{}, d.handleValue(value, v)
 }
 
+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
+
+	case keyType.Kind() == reflect.Int || keyType.Kind() == reflect.Int8 || keyType.Kind() == reflect.Int16 || keyType.Kind() == reflect.Int32 || keyType.Kind() == 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 keyType.Kind() == reflect.Uint || keyType.Kind() == reflect.Uint8 || keyType.Kind() == reflect.Uint16 || keyType.Kind() == reflect.Uint32 || keyType.Kind() == 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 keyType.Kind() == 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 keyType.Kind() == 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
+	}
+	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
@@ -1019,16 +1144,9 @@ func (d *decoder) handleKeyValuePart(key unstable.Iterator, value *unstable.Node
 	case reflect.Map:
 		vt := v.Type()
 
-		mk := reflect.ValueOf(string(key.Node().Data))
-		mkt := stringType
-
-		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)
+		mk, err := d.keyFromData(vt.Key(), key.Node().Data)
+		if err != nil {
+			return reflect.Value{}, err
 		}
 
 		// If the map does not exist, create it.
@@ -1059,6 +1177,17 @@ func (d *decoder) handleKeyValuePart(key unstable.Iterator, value *unstable.Node
 	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 {
+						return reflect.Value{}, outi.UnmarshalTOML(value)
+					}
+				}
+			}
+			// Otherwise, keep previous behavior and skip until the next table.
 			d.skipUntilTable = true
 			break
 		}
@@ -1071,6 +1200,19 @@ func (d *decoder) handleKeyValuePart(key unstable.Iterator, value *unstable.Node
 		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
@@ -1136,10 +1278,10 @@ 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.Ptr {
+		if v.Kind() == reflect.Ptr {
 			if v.IsNil() {
 				v.Set(reflect.New(v.Type().Elem()))
 			}
@@ -1151,13 +1293,22 @@ 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[uintptr]fieldPathsMap
 
 func structFieldPath(v reflect.Value, name string) ([]int, bool) {
 	t := v.Type()
+	// reflect.Type is an interface. We want to use the address of the underlying
+	// rtype as the key.
+	// This avoids using the interface as map key, which is slower.
+	//
+	// In the future this should be replaced by t.Pointer() if it becomes available.
+	//
+	// v.Type() returns a reflect.Type interface.
+	// reflect.ValueOf(t).Pointer() returns the address of the rtype.
+	tid := reflect.ValueOf(t).Pointer()
 
-	cache, _ := globalFieldPathsCache.Load().(map[danger.TypeID]fieldPathsMap)
-	fieldPaths, ok := cache[danger.MakeTypeID(t)]
+	cache, _ := globalFieldPathsCache.Load().(map[uintptr]fieldPathsMap)
+	fieldPaths, ok := cache[tid]
 
 	if !ok {
 		fieldPaths = map[string][]int{}
@@ -1168,8 +1319,8 @@ func structFieldPath(v reflect.Value, name string) ([]int, bool) {
 			fieldPaths[strings.ToLower(name)] = path
 		})
 
-		newCache := make(map[danger.TypeID]fieldPathsMap, len(cache)+1)
-		newCache[danger.MakeTypeID(t)] = fieldPaths
+		newCache := make(map[uintptr]fieldPathsMap, len(cache)+1)
+		newCache[tid] = fieldPaths
 		for k, v := range cache {
 			newCache[k] = v
 		}

unstable/ast.go

@@ -2,9 +2,6 @@ package unstable
 
 import (
 	"fmt"
-	"unsafe"
-
-	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
 // Iterator over a sequence of nodes.
@@ -37,7 +34,7 @@ func (c *Iterator) Next() bool {
 // 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.node.next == 0
+	return c.node.next == nil
 }
 
 // Node returns a pointer to the node pointed at by the iterator.
@@ -65,11 +62,9 @@ type Node struct {
 	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
+	// References to other nodes.
+	next  *Node // nil if last element
+	child *Node // nil if no child
 }
 
 // Range of bytes in the document.
@@ -80,24 +75,14 @@ type Range struct {
 
 // 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
-	}
-	ptr := unsafe.Pointer(n)
-	size := unsafe.Sizeof(Node{})
-	return (*Node)(danger.Stride(ptr, size, n.next))
+	return n.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 an nil if this Node
+// 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
-	}
-	ptr := unsafe.Pointer(n)
-	size := unsafe.Sizeof(Node{})
-	return (*Node)(danger.Stride(ptr, size, n.child))
+	return n.child
 }
 
 // Valid returns true if the node's kind is set (not to Invalid).

unstable/builder.go

@@ -4,68 +4,118 @@ package unstable
 //
 // It is immutable once constructed with Builder.
 type root struct {
-	nodes []Node
+	first *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
+	return Iterator{node: r.first}
 }
 
-func (r *root) at(idx reference) *Node {
-	return &r.nodes[idx]
+type reference struct {
+	*Node
 }
 
-type reference int
-
-const invalidReference reference = -1
+var invalidReference = reference{}
 
 func (r reference) Valid() bool {
-	return r != invalidReference
+	return r.Node != nil
 }
 
 type builder struct {
-	tree    root
-	lastIdx int
+	// chunks of nodes. Pointers to nodes are stable because we only append
+	// to the last chunk, and chunks are allocated with fixed capacity.
+	chunks [][]Node
+	// current chunk index
+	chunkIdx int
+
+	// root node of the tree
+	root root
+
+	// last pushed node (for chaining)
+	last *Node
 }
 
+const initialChunkSize = 16
+const maxChunkSize = 2048
+
 func (b *builder) Tree() *root {
-	return &b.tree
+	return &b.root
 }
 
 func (b *builder) NodeAt(ref reference) *Node {
-	return b.tree.at(ref)
+	return ref.Node
 }
 
 func (b *builder) Reset() {
-	b.tree.nodes = b.tree.nodes[:0]
-	b.lastIdx = 0
+	b.chunkIdx = 0
+	for i := range b.chunks {
+		b.chunks[i] = b.chunks[i][:0]
+	}
+	b.root.first = nil
+	b.last = nil
+}
+
+func (b *builder) ensureCapacity() {
+	if b.chunkIdx >= len(b.chunks) {
+		size := initialChunkSize
+		if len(b.chunks) > 0 {
+			lastCap := cap(b.chunks[len(b.chunks)-1])
+			size = lastCap * 2
+			if size > maxChunkSize {
+				size = maxChunkSize
+			}
+		}
+		b.chunks = append(b.chunks, make([]Node, 0, size))
+	}
+	if len(b.chunks[b.chunkIdx]) == cap(b.chunks[b.chunkIdx]) {
+		b.chunkIdx++
+		if b.chunkIdx >= len(b.chunks) {
+			size := initialChunkSize
+			if len(b.chunks) > 0 {
+				lastCap := cap(b.chunks[len(b.chunks)-1])
+				size = lastCap * 2
+				if size > maxChunkSize {
+					size = maxChunkSize
+				}
+			}
+			b.chunks = append(b.chunks, make([]Node, 0, size))
+		}
+	}
+}
+
+func (b *builder) push(n Node) *Node {
+	b.ensureCapacity()
+	chunk := &b.chunks[b.chunkIdx]
+	*chunk = append(*chunk, n)
+	return &(*chunk)[len(*chunk)-1]
 }
 
 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)
+	ptr := b.push(n)
+	if b.root.first == nil {
+		b.root.first = ptr
+	}
+	b.last = ptr
+	return reference{ptr}
 }
 
 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
+	ptr := b.push(n)
+	if b.root.first == nil {
+		b.root.first = ptr
 	}
-	b.lastIdx = newIdx
-	return reference(b.lastIdx)
+	if b.last != nil {
+		b.last.next = ptr
+	}
+	b.last = ptr
+	return reference{ptr}
 }
 
 func (b *builder) AttachChild(parent reference, child reference) {
-	b.tree.nodes[parent].child = int(child) - int(parent)
+	parent.child = child.Node
 }
 
 func (b *builder) Chain(from reference, to reference) {
-	b.tree.nodes[from].next = int(to) - int(from)
+	from.next = to.Node
 }

unstable/parser.go

@@ -6,7 +6,6 @@ import (
 	"unicode"
 
 	"github.com/pelletier/go-toml/v2/internal/characters"
-	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
 // ParserError describes an error relative to the content of the document.
@@ -49,8 +48,6 @@ func NewParserError(highlight []byte, format string, args ...interface{}) error
 // 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.
-//
-// The parser doesn't provide nodes for comments yet, nor for whitespace.
 type Parser struct {
 	data    []byte
 	builder builder
@@ -58,6 +55,8 @@ type Parser struct {
 	left    []byte
 	err     error
 	first   bool
+
+	KeepComments bool
 }
 
 // Data returns the slice provided to the last call to Reset.
@@ -70,7 +69,7 @@ func (p *Parser) Data() []byte {
 // panics.
 func (p *Parser) Range(b []byte) Range {
 	return Range{
-		Offset: uint32(danger.SubsliceOffset(p.data, b)),
+		Offset: uint32(cap(p.data) - cap(b)),
 		Length: uint32(len(b)),
 	}
 }
@@ -142,6 +141,44 @@ func (p *Parser) Error() error {
 	return p.err
 }
 
+// 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
+}
+
+func (p *Parser) position(b []byte) Position {
+	offset := cap(p.data) - cap(b)
+
+	lead := p.data[:offset]
+
+	return Position{
+		Offset: offset,
+		Line:   bytes.Count(lead, []byte{'\n'}) + 1,
+		Column: len(lead) - bytes.LastIndex(lead, []byte{'\n'}),
+	}
+}
+
+// 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 {
+	raw := p.Raw(r)
+	return Shape{
+		Start: p.position(raw),
+		End:   p.position(raw[r.Length:]),
+	}
+}
+
 func (p *Parser) parseNewline(b []byte) ([]byte, error) {
 	if b[0] == '\n' {
 		return b[1:], nil
@@ -155,6 +192,19 @@ func (p *Parser) parseNewline(b []byte) ([]byte, error) {
 	return nil, NewParserError(b[0:1], "expected newline but got %#U", b[0])
 }
 
+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.Range(data),
+			Data: data,
+		})
+	}
+	return ref, rest, err
+}
+
 func (p *Parser) parseExpression(b []byte) (reference, []byte, error) {
 	// expression =  ws [ comment ]
 	// expression =/ ws keyval ws [ comment ]
@@ -168,7 +218,7 @@ func (p *Parser) parseExpression(b []byte) (reference, []byte, error) {
 	}
 
 	if b[0] == '#' {
-		_, rest, err := scanComment(b)
+		ref, rest, err := p.parseComment(b)
 		return ref, rest, err
 	}
 
@@ -190,7 +240,10 @@ func (p *Parser) parseExpression(b []byte) (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
 	}
 
@@ -471,17 +524,33 @@ func (p *Parser) parseValArray(b []byte) (reference, []byte, error) {
 		Kind: Array,
 	})
 
+	// First indicates whether the parser is looking for the first element
+	// (non-comment) of the array.
 	first := true
 
-	var lastChild 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)
+		cref := invalidReference
+		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, NewParserError(arrayStart[:1], "array is incomplete")
 		}
@@ -496,10 +565,13 @@ func (p *Parser) parseValArray(b []byte) (reference, []byte, error) {
 			}
 			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, NewParserError(b[0:1], "array elements must be separated by commas")
 		}
@@ -515,17 +587,16 @@ func (p *Parser) parseValArray(b []byte) (reference, []byte, error) {
 			return parent, nil, err
 		}
 
-		if first {
-			p.builder.AttachChild(parent, valueRef)
-		} else {
-			p.builder.Chain(lastChild, valueRef)
-		}
-		lastChild = valueRef
+		addChild(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
 	}
 
@@ -534,15 +605,34 @@ func (p *Parser) parseValArray(b []byte) (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) {
+		if rootCommentRef == invalidReference {
+			rootCommentRef = ref
+		} else if latestCommentRef == invalidReference {
+			p.builder.AttachChild(rootCommentRef, ref)
+			latestCommentRef = ref
+		} else {
+			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)
 			}
 		}
 
@@ -553,14 +643,14 @@ 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) {
@@ -922,6 +1012,7 @@ func (p *Parser) parseIntOrFloatOrDateTime(b []byte) (reference, []byte, error)
 		return p.builder.Push(Node{
 			Kind: Float,
 			Data: b[:3],
+			Raw:  p.Range(b[:3]),
 		}), b[3:], nil
 	case 'n':
 		if !scanFollowsNan(b) {
@@ -931,6 +1022,7 @@ func (p *Parser) parseIntOrFloatOrDateTime(b []byte) (reference, []byte, error)
 		return p.builder.Push(Node{
 			Kind: Float,
 			Data: b[:3],
+			Raw:  p.Range(b[:3]),
 		}), b[3:], nil
 	case '+', '-':
 		return p.scanIntOrFloat(b)
@@ -983,7 +1075,7 @@ 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]) {
@@ -1055,6 +1147,7 @@ func (p *Parser) scanIntOrFloat(b []byte) (reference, []byte, error) {
 		return p.builder.Push(Node{
 			Kind: Integer,
 			Data: b[:i],
+			Raw:  p.Range(b[:i]),
 		}), b[i:], nil
 	}
 
@@ -1078,6 +1171,7 @@ func (p *Parser) scanIntOrFloat(b []byte) (reference, []byte, error) {
 				return p.builder.Push(Node{
 					Kind: Float,
 					Data: b[:i+3],
+					Raw:  p.Range(b[:i+3]),
 				}), b[i+3:], nil
 			}
 
@@ -1089,6 +1183,7 @@ func (p *Parser) scanIntOrFloat(b []byte) (reference, []byte, error) {
 				return p.builder.Push(Node{
 					Kind: Float,
 					Data: b[:i+3],
+					Raw:  p.Range(b[:i+3]),
 				}), b[i+3:], nil
 			}
 
@@ -1111,6 +1206,7 @@ func (p *Parser) scanIntOrFloat(b []byte) (reference, []byte, error) {
 	return p.builder.Push(Node{
 		Kind: kind,
 		Data: b[:i],
+		Raw:  p.Range(b[:i]),
 	}), b[i:], nil
 }
 

unstable/parser_test.go

@@ -6,7 +6,7 @@ import (
 	"strings"
 	"testing"
 
-	"github.com/stretchr/testify/require"
+	"github.com/pelletier/go-toml/v2/internal/assert"
 )
 
 func TestParser_AST_Numbers(t *testing.T) {
@@ -141,9 +141,9 @@ func TestParser_AST_Numbers(t *testing.T) {
 			p.NextExpression()
 			err := p.Error()
 			if e.err {
-				require.Error(t, err)
+				assert.Error(t, err)
 			} else {
-				require.NoError(t, err)
+				assert.NoError(t, err)
 
 				expected := astNode{
 					Kind: KeyValue,
@@ -168,8 +168,8 @@ type (
 
 func compareNode(t *testing.T, e astNode, n *Node) {
 	t.Helper()
-	require.Equal(t, e.Kind, n.Kind)
-	require.Equal(t, e.Data, n.Data)
+	assert.Equal(t, e.Kind, n.Kind)
+	assert.Equal(t, e.Data, n.Data)
 
 	compareIterator(t, e.Children, n.Children())
 }
@@ -341,9 +341,9 @@ func TestParser_AST(t *testing.T) {
 			p.NextExpression()
 			err := p.Error()
 			if e.err {
-				require.Error(t, err)
+				assert.Error(t, err)
 			} else {
-				require.NoError(t, err)
+				assert.NoError(t, err)
 				compareNode(t, e.ast, p.Expression())
 			}
 		})
@@ -431,9 +431,9 @@ func TestParser_AST_DateTimes(t *testing.T) {
 			p.NextExpression()
 			err := p.Error()
 			if e.err {
-				require.Error(t, err)
+				assert.Error(t, err)
 			} else {
-				require.NoError(t, err)
+				assert.NoError(t, err)
 
 				expected := astNode{
 					Kind: KeyValue,
@@ -448,6 +448,163 @@ func TestParser_AST_DateTimes(t *testing.T) {
 	}
 }
 
+// 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.]
+	// ---
+	// 1:1->1:1 (0->0)           | 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.]
+	// ---
+	// 1:1->1:1 (0->0)           | KeyValue []
+	// 15:8->15:9 (281->282)     |   InlineTable []
+	// 1:1->1:1 (0->0)           |     KeyValue []
+	// 15:18->15:23 (291->296)   |       String [Tom]
+	// 15:10->15:15 (283->288)   |       Key [first]
+	// 1:1->1:1 (0->0)           |     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.]
+	// ---
+	// 1:1->1:1 (0->0)           | 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.]
+	// ---
+	// 1:1->1:1 (0->0)           | 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 ExampleParser() {
 	doc := `
 	hello = "world"

unstable/scanner.go

@@ -151,7 +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

unstable/unmarshaler.go

@@ -0,0 +1,7 @@
+package unstable
+
+// The Unmarshaler interface may be implemented by types to customize their
+// behavior when being unmarshaled from a TOML document.
+type Unmarshaler interface {
+	UnmarshalTOML(value *Node) error
+}