Bump testing to go 1.23 (#961)

Signed-off-by: Daniel Weiße <dw@edgeless.systems>

.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@v4
       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@v4
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL
-      uses: github/codeql-action/init@v2
+      uses: github/codeql-action/init@v3
       with:
         languages: ${{ matrix.language }}
         # If you wish to specify custom queries, you can do so here or in a config file.
@@ -50,7 +50,7 @@ jobs:
     # 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@v3
 
     # 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@v3

.github/workflows/coverage.yml

@@ -9,12 +9,12 @@ jobs:
     runs-on: "ubuntu-latest"
     name: report
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Setup go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v5
         with:
-          go-version: "1.20"
+          go-version: "1.23"
       - name: Run tests with coverage
         run: ./ci.sh coverage -d "${GITHUB_BASE_REF-HEAD}"

.github/workflows/release.yml

@@ -16,24 +16,24 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Set up Go
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v5
         with:
-          go-version: "1.20"
+          go-version: "1.23"
       - 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
+          version: '~> v2'
-          args: release ${{ inputs.args }} --rm-dist
+          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']
+        os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest', 'macos-14' ]
-        go: [ '1.19', '1.20' ]
+        go: [ '1.22', '1.23' ]
     runs-on: ${{ matrix.os }}
     name: ${{ matrix.go }}/${{ matrix.os }}
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
           fetch-depth: 0
       - name: Setup go ${{ matrix.go }}
-        uses: actions/setup-go@v3
+        uses: actions/setup-go@v5
         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

@@ -4,3 +4,4 @@ cmd/tomll/tomll
 cmd/tomljson/tomljson
 cmd/tomltestgen/tomltestgen
 dist
+tests/

.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

CONTRIBUTING.md

@@ -165,25 +165,22 @@ Checklist:
 
 ### New release
 
-1. Decide on the next version number. Use semver.
+1. Decide on the next version number. Use semver. Review commits since last
-2. Generate release notes using [`gh`][gh]. Example:
+   version to assess.
+2. Tag release. For example:
 ```
-$ gh api -X POST \
+git checkout v2
-  -F tag_name='v2.0.0-beta.5' \
+git pull
-  -F target_commitish='v2' \
+git tag v2.2.0
-  -F previous_tag_name='v2.0.0-beta.4' \
+git push --tags
-  --jq '.body' \
-  repos/pelletier/go-toml/releases/generate-notes
 ```
-3. Look for "Other changes". That would indicate a pull request not labeled
+3. CI automatically builds a draft Github release. Review it and edit as
-   properly. Tweak labels and pull request titles until changelog looks good for
+   necessary. Look for "Other changes". That would indicate a pull request not
-   users.
+   labeled properly. Tweak labels and pull request titles until changelog looks
-4. [Draft new release][new-release].
+   good for users.
-5. Fill tag and target with the same value used to generate the changelog.
+4. Check "create discussion" box, in the "Releases" category.
-6. Set title to the new tag value.
+5. If new version is an alpha or beta only, check pre-release box.
-7. Paste the generated changelog.
+
-8. Check "create discussion", in the "Releases" category.
-9. Check pre-release if new version is an alpha or beta.
 
 [issues-tracker]: https://github.com/pelletier/go-toml/issues
 [bug-report]: https://github.com/pelletier/go-toml/issues/new?template=bug_report.md

LICENSE

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

README.md

@@ -45,16 +45,15 @@ to check for typos. [See example in the documentation][strict].
 
 ### Contextualized errors
 
-When most decoding errors occur, go-toml returns [`DecodeError`][decode-err]),
+When most decoding errors occur, go-toml returns [`DecodeError`][decode-err],
 which contains a human readable contextualized version of the error. For
 example:
 
 ```
-2| key1 = "value1"
+1| [server]
-3| key2 = "missing2"
+2| path = 100
- | ~~~~ missing field
+ |        ~~~ cannot decode TOML integer into struct field toml_test.Server.Path of type string
-4| key3 = "missing3"
+3| port = 50
-5| key4 = "value4"
 ```
 
 [decode-err]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#DecodeError
@@ -73,15 +72,35 @@ representation.
 [tlt]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalTime
 [tldt]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalDateTime
 
+### Commented config
+
+Since TOML is often used for configuration files, go-toml can emit documents
+annotated with [comments and commented-out values][comments-example]. For
+example, it can generate the following file:
+
+```toml
+# Host IP to connect to.
+host = '127.0.0.1'
+# Port of the remote server.
+port = 4242
+
+# Encryption parameters (optional)
+# [TLS]
+# cipher = 'AEAD-AES128-GCM-SHA256'
+# version = 'TLS 1.3'
+```
+
+[comments-example]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#example-Marshal-Commented
+
 ## Getting started
 
 Given the following struct, let's see how to read it and write it as TOML:
 
 ```go
 type MyConfig struct {
-      Version int
+	Version int
-      Name    string
+	Name    string
-      Tags    []string
+	Tags    []string
 }
 ```
 
@@ -100,7 +119,7 @@ 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)
@@ -121,14 +140,14 @@ as a TOML document:
 
 ```go
 cfg := MyConfig{
-      Version: 2,
+	Version: 2,
-      Name:    "go-toml",
+	Name:    "go-toml",
-      Tags:    []string{"go", "toml"},
+	Tags:    []string{"go", "toml"},
 }
 
 b, err := toml.Marshal(cfg)
 if err != nil {
-      panic(err)
+	panic(err)
 }
 fmt.Println(string(b))
 
@@ -156,17 +175,17 @@ 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>
+	<thead>
-        <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
+		<tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
-    </thead>
+	</thead>
-    <tbody>
+	<tbody>
-        <tr><td>Marshal/HugoFrontMatter-2</td><td>1.9x</td><td>1.9x</td></tr>
+		<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>1.8x</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>2.5x</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>2.9x</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>2.9x</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>4.4x</td><td>5.3x</td></tr>
+		<tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.6x</td><td>5.1x</td></tr>
-     </tbody>
+	 </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 +193,22 @@ contains the results of all benchmarks, including unrealistic ones. It is
 provided for completeness.</p>
 
 <table>
-    <thead>
+	<thead>
-        <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
+		<tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
-    </thead>
+	</thead>
-    <tbody>
+	<tbody>
-        <tr><td>Marshal/SimpleDocument/map-2</td><td>1.8x</td><td>2.9x</td></tr>
+		<tr><td>Marshal/SimpleDocument/map-2</td><td>1.8x</td><td>2.7x</td></tr>
-        <tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>4.2x</td></tr>
+		<tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>3.8x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.5x</td><td>3.1x</td></tr>
+		<tr><td>Unmarshal/SimpleDocument/map-2</td><td>3.8x</td><td>3.0x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>6.2x</td><td>3.9x</td></tr>
+		<tr><td>Unmarshal/SimpleDocument/struct-2</td><td>5.6x</td><td>4.1x</td></tr>
-        <tr><td>UnmarshalDataset/example-2</td><td>3.1x</td><td>3.5x</td></tr>
+		<tr><td>UnmarshalDataset/example-2</td><td>3.0x</td><td>3.2x</td></tr>
-        <tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>3.1x</td></tr>
+		<tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>2.9x</td></tr>
-        <tr><td>UnmarshalDataset/twitter-2</td><td>2.5x</td><td>2.6x</td></tr>
+		<tr><td>UnmarshalDataset/twitter-2</td><td>2.6x</td><td>2.7x</td></tr>
-        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.1x</td><td>2.2x</td></tr>
+		<tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.2x</td><td>2.3x</td></tr>
-        <tr><td>UnmarshalDataset/canada-2</td><td>1.6x</td><td>1.3x</td></tr>
+		<tr><td>UnmarshalDataset/canada-2</td><td>1.8x</td><td>1.5x</td></tr>
-        <tr><td>UnmarshalDataset/config-2</td><td>4.3x</td><td>3.2x</td></tr>
+		<tr><td>UnmarshalDataset/config-2</td><td>4.1x</td><td>2.9x</td></tr>
-        <tr><td>[Geo mean]</td><td>2.7x</td><td>2.8x</td></tr>
+		<tr><td>geomean</td><td>2.7x</td><td>2.8x</td></tr>
-     </tbody>
+	 </tbody>
 </table>
 <p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>
 </details>
@@ -214,24 +233,24 @@ Go-toml provides three handy command line tools:
 
  * `tomljson`: Reads a TOML file and outputs its JSON representation.
 
-    ```
+	```
-    $ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
+	$ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
-    $ tomljson --help
+	$ tomljson --help
-    ```
+	```
 
  * `jsontoml`: Reads a JSON file and outputs a TOML representation.
 
-    ```
+	```
-    $ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
+	$ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
-    $ jsontoml --help
+	$ jsontoml --help
-    ```
+	```
 
  * `tomll`: Lints and reformats a TOML file.
 
-    ```
+	```
-    $ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
+	$ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
-    $ tomll --help
+	$ tomll --help
-    ```
+	```
 
 ### Docker image
 
@@ -242,7 +261,7 @@ 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 +293,16 @@ element in the interface to decode the object. For example:
 
 ```go
 type inner struct {
-  B interface{}
+	B interface{}
 }
 type doc struct {
-  A interface{}
+	A interface{}
 }
 
 d := doc{
-  A: inner{
+	A: inner{
-    B: "Before",
+		B: "Before",
-  },
+	},
 }
 
 data := `
@@ -322,7 +341,7 @@ 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 +516,20 @@ 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 +565,11 @@ complete solutions exist out there.
 
 ## Versioning
 
-Go-toml follows [Semantic Versioning](https://semver.org). The supported version
+Expect for parts explicitly marked otherwise, go-toml follows [Semantic
-of [TOML](https://github.com/toml-lang/toml) is indicated at the beginning of
+Versioning](https://semver.org). The supported version of
-this document. The last two major versions of Go are supported
+[TOML](https://github.com/toml-lang/toml) is indicated at the beginning of this
-(see [Go Release Policy](https://golang.org/doc/devel/release.html#policy)).
+document. The last two major versions of Go are supported (see [Go Release
+Policy](https://golang.org/doc/devel/release.html#policy)).
 
 ## License
 

SECURITY.md

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

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
+    if mktemp --version &> /dev/null; then
-        mktemp --suffix=-$1;
+	# 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

@@ -11,10 +11,11 @@ import (
 
 func TestConvert(t *testing.T) {
 	examples := []struct {
-		name     string
+		name          string
-		input    string
+		input         string
-		expected string
+		expected      string
-		errors   bool
+		errors        bool
+		useJsonNumber bool
 	}{
 		{
 			name: "valid json",
@@ -26,6 +27,19 @@ func TestConvert(t *testing.T) {
 }`,
 			expected: `[mytoml]
 a = 42.0
+`,
+		},
+		{
+			name:          "use json number",
+			useJsonNumber: true,
+			input: `
+{
+  "mytoml": {
+    "a": 42
+  }
+}`,
+			expected: `[mytoml]
+a = 42
 `,
 		},
 		{
@@ -37,6 +51,7 @@ 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)

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 +97,57 @@ 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"))
 
-	for _, f := range zipReader.File {
+		log.Printf("> [%s] %s\n", "invalid", name)
-		zipFilesMap[f.Name] = f
+
+		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)`)
+	dirContent, _ = filepath.Glob("tests/valid/**/*.toml")
-	for _, f := range zipReader.File {
+	for _, f := range dirContent {
-		groups := testFileRegexp.FindStringSubmatch(f.Name)
+		filename := strings.TrimPrefix(f, "tests/valid/")
-		if len(groups) > 0 {
+		name := kebabToCamel(strings.TrimSuffix(filename, ".toml"))
-			name := kebabToCamel(groups[3])
-			testType := groups[2]
 
-			log.Printf("> [%s] %s\n", testType, name)
+		log.Printf("> [%s] %s\n", "valid", name)
 
-			tomlContent := readFileFromZip(f)
+		tomlContent, err := os.ReadFile(f)
-
+		if err != nil {
-			switch testType {
+			fmt.Printf("failed reading test file: %s\n", err)
-			case "invalid":
+			os.Exit(1)
-				collection.Invalid = append(collection.Invalid, invalid{
-					Name:  name,
-					Input: tomlContent,
-				})
-				collection.Count++
-			case "valid":
-				baseFilePath := groups[1]
-				jsonFilePath := baseFilePath + ".json"
-				jsonContent := readFileFromZip(zipFilesMap[jsonFilePath])
-
-				collection.Valid = append(collection.Valid, valid{
-					Name:    name,
-					Input:   tomlContent,
-					JsonRef: jsonContent,
-				})
-				collection.Count++
-			default:
-				panic(fmt.Sprintf("unknown test type: %s", testType))
-			}
 		}
+
+		filename = strings.TrimSuffix(f, ".toml")
+		jsonContent, err := os.ReadFile(filename + ".json")
+		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 +157,7 @@ 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 +171,7 @@ 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")
 	}
 

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}
+}

fuzz_test.go

@@ -1,6 +1,3 @@
-//go:build go1.18 || go1.19 || go1.20
-// +build go1.18 go1.19 go1.20
-
 package toml_test
 
 import (

go.mod

@@ -1,5 +1,11 @@
 module github.com/pelletier/go-toml/v2
 
-go 1.16
+go 1.21.0
 
-require github.com/stretchr/testify v1.8.1
+require github.com/stretchr/testify v1.9.0
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,17 +1,10 @@
-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/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
-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/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.
@@ -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

@@ -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.
+// consistent. It returns true if it is the first time this node's key is seen.
-func (s *SeenTracker) CheckExpression(node *unstable.Node) error {
+// Useful to clear array tables on first use.
+func (s *SeenTracker) CheckExpression(node *unstable.Node) (bool, error) {
 	if s.entries == nil {
 		s.reset()
 	}
@@ -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 {
+func (s *SeenTracker) checkInlineTable(node *unstable.Node) (first bool, err error) {
-	if pool.New == nil {
-		pool.New = func() interface{} {
-			return &SeenTracker{}
-		}
-	}
-
 	s = pool.Get().(*SeenTracker)
 	s.reset()
 
 	it := node.Children()
 	for it.Next() {
 		n := it.Node()
-		err := s.checkKeyValue(n)
+		first, err = s.checkKeyValue(n)
 		if err != nil {
-			return err
+			return false, err
 		}
 	}
 
@@ -352,5 +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
 }

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
+	tablesInline       bool
-	arraysMultiline bool
+	arraysMultiline    bool
-	indentSymbol    string
+	indentSymbol       string
-	indentTables    bool
+	indentTables       bool
+	marshalJsonNumbers bool
 }
 
 // NewEncoder returns a new Encoder that writes to w.
@@ -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 +161,9 @@ func (enc *Encoder) SetIndentTables(indent bool) *Encoder {
 //
 // The "omitempty" option prevents empty 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 +196,7 @@ func (enc *Encoder) Encode(v interface{}) error {
 type valueOptions struct {
 	multiline bool
 	omitempty bool
+	commented bool
 	comment   string
 }
 
@@ -205,6 +222,9 @@ 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 +265,22 @@ 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 +305,7 @@ 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() {
@@ -357,6 +389,7 @@ func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v r
 
 	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 +411,13 @@ 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:
@@ -526,6 +566,8 @@ 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 +619,35 @@ func (enc *Encoder) encodeKey(b []byte, k string) []byte {
 	}
 }
 
-func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
+func (enc *Encoder) keyToString(k reflect.Value) (string, error) {
-	if v.Type().Key().Kind() != reflect.String {
+	keyType := k.Type()
-		return nil, fmt.Errorf("toml: type %s is not supported as a map key", v.Type().Key().Kind())
+	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 +655,17 @@ 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 +680,8 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 }
 
 func sortEntriesByKey(e []entry) {
-	sort.Slice(e, func(i, j int) bool {
+	slices.SortFunc(e, func(a, b entry) int {
-		return e[i].Key < e[j].Key
+		return strings.Compare(a.Key, b.Key)
 	})
 }
 
@@ -674,6 +744,8 @@ 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 +760,7 @@ func walkStruct(ctx encoderCtx, t *table, v reflect.Value) {
 		options := valueOptions{
 			multiline: opts.multiline,
 			omitempty: opts.omitempty,
+			commented: opts.commented,
 			comment:   fieldType.Tag.Get("comment"),
 		}
 
@@ -747,6 +820,7 @@ type tagOptions struct {
 	multiline bool
 	inline    bool
 	omitempty bool
+	commented bool
 }
 
 func parseTag(tag string) (string, tagOptions) {
@@ -774,6 +848,8 @@ func parseTag(tag string) (string, tagOptions) {
 			opts.inline = true
 		case "omitempty":
 			opts.omitempty = true
+		case "commented":
+			opts.commented = true
 		}
 	}
 
@@ -809,8 +885,10 @@ func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, erro
 		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
 		}
@@ -835,8 +913,10 @@ 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
 		}
@@ -883,7 +963,7 @@ 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 +994,7 @@ 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 +1034,13 @@ 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 +1056,10 @@ 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"...)

marshaler_test.go

@@ -15,6 +15,21 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type marshalTextKey struct {
+	A string
+	B string
+}
+
+func (k marshalTextKey) MarshalText() ([]byte, error) {
+	return []byte(k.A + "-" + k.B), nil
+}
+
+type marshalBadTextKey struct{}
+
+func (k marshalBadTextKey) MarshalText() ([]byte, error) {
+	return nil, fmt.Errorf("error")
+}
+
 func TestMarshal(t *testing.T) {
 	someInt := 42
 
@@ -97,6 +112,53 @@ also = 'that'
 a = 'test'
 `,
 		},
+		{
+			desc: `map with text key`,
+			v: map[marshalTextKey]string{
+				{A: "a", B: "1"}: "value 1",
+				{A: "a", B: "2"}: "value 2",
+				{A: "b", B: "1"}: "value 3",
+			},
+			expected: `a-1 = 'value 1'
+a-2 = 'value 2'
+b-1 = 'value 3'
+`,
+		},
+		{
+			desc: `table with text key`,
+			v: map[marshalTextKey]map[string]string{
+				{A: "a", B: "1"}: {"value": "foo"},
+			},
+			expected: `[a-1]
+value = 'foo'
+`,
+		},
+		{
+			desc: `map with ptr text key`,
+			v: map[*marshalTextKey]string{
+				{A: "a", B: "1"}: "value 1",
+				{A: "a", B: "2"}: "value 2",
+				{A: "b", B: "1"}: "value 3",
+			},
+			expected: `a-1 = 'value 1'
+a-2 = 'value 2'
+b-1 = 'value 3'
+`,
+		},
+		{
+			desc: `map with bad text key`,
+			v: map[marshalBadTextKey]string{
+				{}: "value 1",
+			},
+			err: true,
+		},
+		{
+			desc: `map with bad ptr text key`,
+			v: map[*marshalBadTextKey]string{
+				{}: "value 1",
+			},
+			err: true,
+		},
 		{
 			desc: "simple string array",
 			v: map[string][]string{
@@ -144,6 +206,45 @@ a = 'test'
 
 [[top]]
 'map2.1' = 'v2.1'
+`,
+		},
+		{
+			desc: "fixed size string array",
+			v: map[string][3]string{
+				"array": {"one", "two", "three"},
+			},
+			expected: `array = ['one', 'two', 'three']
+`,
+		},
+		{
+			desc: "fixed size nested string arrays",
+			v: map[string][2][2]string{
+				"array": {{"one", "two"}, {"three"}},
+			},
+			expected: `array = [['one', 'two'], ['three', '']]
+`,
+		},
+		{
+			desc: "mixed strings and fixed size nested string arrays",
+			v: map[string][]interface{}{
+				"array": {"a string", [2]string{"one", "two"}, "last"},
+			},
+			expected: `array = ['a string', ['one', 'two'], 'last']
+`,
+		},
+		{
+			desc: "fixed size array of maps",
+			v: map[string][2]map[string]string{
+				"ftop": {
+					{"map1.1": "v1.1"},
+					{"map2.1": "v2.1"},
+				},
+			},
+			expected: `[[ftop]]
+'map1.1' = 'v1.1'
+
+[[ftop]]
+'map2.1' = 'v2.1'
 `,
 		},
 		{
@@ -483,13 +584,74 @@ inner = 42
 			expected: `[parent]
 [parent."in\ner"]
 foo = 42
+`,
+		},
+		{
+			desc: "int map key",
+			v:    map[int]interface{}{1: "a"},
+			expected: `1 = 'a'
+`,
+		},
+		{
+			desc: "int8 map key",
+			v:    map[int8]interface{}{1: "a"},
+			expected: `1 = 'a'
+`,
+		},
+		{
+			desc: "int64 map key",
+			v:    map[int64]interface{}{1: "a"},
+			expected: `1 = 'a'
+`,
+		},
+		{
+			desc: "uint map key",
+			v:    map[uint]interface{}{1: "a"},
+			expected: `1 = 'a'
+`,
+		},
+		{
+			desc: "uint8 map key",
+			v:    map[uint8]interface{}{1: "a"},
+			expected: `1 = 'a'
+`,
+		},
+		{
+			desc: "uint64 map key",
+			v:    map[uint64]interface{}{1: "a"},
+			expected: `1 = 'a'
+`,
+		},
+		{
+			desc: "float32 map key",
+			v: map[float32]interface{}{
+				1.1:    "a",
+				1.0020: "b",
+			},
+			expected: `'1.002' = 'b'
+'1.1' = 'a'
+`,
+		},
+		{
+			desc: "float64 map key",
+			v: map[float64]interface{}{
+				1.1:    "a",
+				1.0020: "b",
+			},
+			expected: `'1.002' = 'b'
+'1.1' = 'a'
 `,
 		},
 		{
 			desc: "invalid map key",
-			v:    map[int]interface{}{},
+			v:    map[struct{ int }]interface{}{{1}: "a"},
 			err:  true,
 		},
+		{
+			desc:     "invalid map key but empty",
+			v:        map[struct{ int }]interface{}{},
+			expected: "",
+		},
 		{
 			desc: "unhandled type",
 			v: struct {
@@ -842,6 +1004,29 @@ func TestEncoderSetIndentSymbol(t *testing.T) {
 	assert.Equal(t, expected, w.String())
 }
 
+func TestEncoderSetMarshalJsonNumbers(t *testing.T) {
+	var w strings.Builder
+	enc := toml.NewEncoder(&w)
+	enc.SetMarshalJsonNumbers(true)
+	err := enc.Encode(map[string]interface{}{
+		"A": json.Number("1.1"),
+		"B": json.Number("42e-3"),
+		"C": json.Number("42"),
+		"D": json.Number("0"),
+		"E": json.Number("0.0"),
+		"F": json.Number(""),
+	})
+	require.NoError(t, err)
+	expected := `A = 1.1
+B = 0.042
+C = 42
+D = 0
+E = 0.0
+F = 0
+`
+	assert.Equal(t, expected, w.String())
+}
+
 func TestEncoderOmitempty(t *testing.T) {
 	type doc struct {
 		String  string            `toml:",omitempty,multiline"`
@@ -1095,6 +1280,45 @@ randomize = true
 	require.Equal(t, expected, buf.String())
 }
 
+func TestMarhsalIssue888(t *testing.T) {
+	type Thing struct {
+		FieldA string `comment:"my field A"`
+		FieldB string `comment:"my field B"`
+	}
+
+	type Cfg struct {
+		Custom []Thing `comment:"custom config"`
+	}
+
+	buf := new(bytes.Buffer)
+
+	config := Cfg{
+		Custom: []Thing{
+			{FieldA: "field a 1", FieldB: "field b 1"},
+			{FieldA: "field a 2", FieldB: "field b 2"},
+		},
+	}
+
+	encoder := toml.NewEncoder(buf).SetIndentTables(true)
+	encoder.Encode(config)
+
+	expected := `# custom config
+[[Custom]]
+  # my field A
+  FieldA = 'field a 1'
+  # my field B
+  FieldB = 'field b 1'
+
+[[Custom]]
+  # my field A
+  FieldA = 'field a 2'
+  # my field B
+  FieldB = 'field b 2'
+`
+
+	require.Equal(t, expected, buf.String())
+}
+
 func TestMarshalNestedAnonymousStructs(t *testing.T) {
 	type Embedded struct {
 		Value string `toml:"value" json:"value"`
@@ -1159,6 +1383,38 @@ value = ''
 	require.Equal(t, expected, string(result))
 }
 
+func TestMarshalNestedAnonymousStructs_PointerEmbedded(t *testing.T) {
+	type Embedded struct {
+		Value   string  `toml:"value" json:"value"`
+		Omitted string  `toml:"omitted,omitempty"`
+		Ptr     *string `toml:"ptr"`
+	}
+
+	type Named struct {
+		Value string `toml:"value" json:"value"`
+	}
+
+	type Doc struct {
+		*Embedded
+		*Named    `toml:"named" json:"named"`
+		Anonymous struct {
+			*Embedded
+			Value *string `toml:"value" json:"value"`
+		} `toml:"anonymous,omitempty" json:"anonymous,omitempty"`
+	}
+
+	doc := &Doc{
+		Embedded: &Embedded{Value: "foo"},
+	}
+
+	expected := `value = 'foo'
+`
+
+	result, err := toml.Marshal(doc)
+	require.NoError(t, err)
+	require.Equal(t, expected, string(result))
+}
+
 func TestLocalTime(t *testing.T) {
 	v := map[string]toml.LocalTime{
 		"a": {
@@ -1192,7 +1448,7 @@ func TestMarshalUint64Overflow(t *testing.T) {
 
 func TestIndentWithInlineTable(t *testing.T) {
 	x := map[string][]map[string]string{
-		"one": []map[string]string{
+		"one": {
 			{"0": "0"},
 			{"1": "1"},
 		},
@@ -1211,6 +1467,131 @@ func TestIndentWithInlineTable(t *testing.T) {
 	assert.Equal(t, expected, buf.String())
 }
 
+type C3 struct {
+	Value  int   `toml:",commented"`
+	Values []int `toml:",commented"`
+}
+
+type C2 struct {
+	Int       int64
+	String    string
+	ArrayInts []int
+	Structs   []C3
+}
+
+type C1 struct {
+	Int       int64  `toml:",commented"`
+	String    string `toml:",commented"`
+	ArrayInts []int  `toml:",commented"`
+	Structs   []C3   `toml:",commented"`
+}
+
+type Commented struct {
+	Int    int64  `toml:",commented"`
+	String string `toml:",commented"`
+
+	C1 C1
+	C2 C2 `toml:",commented"` // same as C1, but commented at top level
+}
+
+func TestMarshalCommented(t *testing.T) {
+	c := Commented{
+		Int:    42,
+		String: "root",
+
+		C1: C1{
+			Int:       11,
+			String:    "C1",
+			ArrayInts: []int{1, 2, 3},
+			Structs: []C3{
+				{Value: 100},
+				{Values: []int{4, 5, 6}},
+			},
+		},
+		C2: C2{
+			Int:       22,
+			String:    "C2",
+			ArrayInts: []int{1, 2, 3},
+			Structs: []C3{
+				{Value: 100},
+				{Values: []int{4, 5, 6}},
+			},
+		},
+	}
+
+	out, err := toml.Marshal(c)
+	require.NoError(t, err)
+
+	expected := `# Int = 42
+# String = 'root'
+
+[C1]
+# Int = 11
+# String = 'C1'
+# ArrayInts = [1, 2, 3]
+
+# [[C1.Structs]]
+# Value = 100
+# Values = []
+
+# [[C1.Structs]]
+# Value = 0
+# Values = [4, 5, 6]
+
+# [C2]
+# Int = 22
+# String = 'C2'
+# ArrayInts = [1, 2, 3]
+
+# [[C2.Structs]]
+# Value = 100
+# Values = []
+
+# [[C2.Structs]]
+# Value = 0
+# Values = [4, 5, 6]
+`
+
+	require.Equal(t, expected, string(out))
+}
+
+func TestMarshalIndentedCustomTypeArray(t *testing.T) {
+	c := struct {
+		Nested struct {
+			NestedArray []struct {
+				Value int
+			}
+		}
+	}{
+		Nested: struct {
+			NestedArray []struct {
+				Value int
+			}
+		}{
+			NestedArray: []struct {
+				Value int
+			}{
+				{Value: 1},
+				{Value: 2},
+			},
+		},
+	}
+
+	expected := `[Nested]
+  [[Nested.NestedArray]]
+    Value = 1
+
+  [[Nested.NestedArray]]
+    Value = 2
+`
+
+	var buf bytes.Buffer
+	enc := toml.NewEncoder(&buf)
+	enc.SetIndentTables(true)
+	require.NoError(t, enc.Encode(c))
+	require.Equal(t, expected, buf.String())
+}
+
 func ExampleMarshal() {
 	type MyConfig struct {
 		Version int
@@ -1235,3 +1616,160 @@ func ExampleMarshal() {
 	// Name = 'go-toml'
 	// Tags = ['go', 'toml']
 }
+
+// Example that uses the 'commented' field tag option to generate an example
+// configuration file that has commented out sections (example from
+// go-graphite/graphite-clickhouse).
+func ExampleMarshal_commented() {
+	type Common struct {
+		Listen               string        `toml:"listen"                     comment:"general listener"`
+		PprofListen          string        `toml:"pprof-listen"               comment:"listener to serve /debug/pprof requests. '-pprof' argument overrides it"`
+		MaxMetricsPerTarget  int           `toml:"max-metrics-per-target"     comment:"limit numbers of queried metrics per target in /render requests, 0 or negative = unlimited"`
+		MemoryReturnInterval time.Duration `toml:"memory-return-interval"     comment:"daemon will return the freed memory to the OS when it>0"`
+	}
+
+	type Costs struct {
+		Cost       *int           `toml:"cost"        comment:"default cost (for wildcarded equalence or matched with regex, or if no value cost set)"`
+		ValuesCost map[string]int `toml:"values-cost" comment:"cost with some value (for equalence without wildcards) (additional tuning, usually not needed)"`
+	}
+
+	type ClickHouse struct {
+		URL string `toml:"url" comment:"default url, see https://clickhouse.tech/docs/en/interfaces/http. Can be overwritten with query-params"`
+
+		RenderMaxQueries        int               `toml:"render-max-queries" comment:"Max queries to render queiries"`
+		RenderConcurrentQueries int               `toml:"render-concurrent-queries" comment:"Concurrent queries to render queiries"`
+		TaggedCosts             map[string]*Costs `toml:"tagged-costs,commented"`
+		TreeTable               string            `toml:"tree-table,commented"`
+		ReverseTreeTable        string            `toml:"reverse-tree-table,commented"`
+		DateTreeTable           string            `toml:"date-tree-table,commented"`
+		DateTreeTableVersion    int               `toml:"date-tree-table-version,commented"`
+		TreeTimeout             time.Duration     `toml:"tree-timeout,commented"`
+		TagTable                string            `toml:"tag-table,commented"`
+		ExtraPrefix             string            `toml:"extra-prefix"             comment:"add extra prefix (directory in graphite) for all metrics, w/o trailing dot"`
+		ConnectTimeout          time.Duration     `toml:"connect-timeout"          comment:"TCP connection timeout"`
+		DataTableLegacy         string            `toml:"data-table,commented"`
+		RollupConfLegacy        string            `toml:"rollup-conf,commented"`
+		MaxDataPoints           int               `toml:"max-data-points"          comment:"max points per metric when internal-aggregation=true"`
+		InternalAggregation     bool              `toml:"internal-aggregation"     comment:"ClickHouse-side aggregation, see doc/aggregation.md"`
+	}
+
+	type Tags struct {
+		Rules      string `toml:"rules"`
+		Date       string `toml:"date"`
+		ExtraWhere string `toml:"extra-where"`
+		InputFile  string `toml:"input-file"`
+		OutputFile string `toml:"output-file"`
+	}
+
+	type Config struct {
+		Common     Common     `toml:"common"`
+		ClickHouse ClickHouse `toml:"clickhouse"`
+		Tags       Tags       `toml:"tags,commented"`
+	}
+
+	cfg := &Config{
+		Common: Common{
+			Listen:               ":9090",
+			PprofListen:          "",
+			MaxMetricsPerTarget:  15000, // This is arbitrary value to protect CH from overload
+			MemoryReturnInterval: 0,
+		},
+		ClickHouse: ClickHouse{
+			URL:                 "http://localhost:8123?cancel_http_readonly_queries_on_client_close=1",
+			ExtraPrefix:         "",
+			ConnectTimeout:      time.Second,
+			DataTableLegacy:     "",
+			RollupConfLegacy:    "auto",
+			MaxDataPoints:       1048576,
+			InternalAggregation: true,
+		},
+		Tags: Tags{},
+	}
+
+	out, err := toml.Marshal(cfg)
+	if err != nil {
+		panic(err)
+	}
+	err = toml.Unmarshal(out, &cfg)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println(string(out))
+
+	// Output:
+	// [common]
+	// # general listener
+	// listen = ':9090'
+	// # listener to serve /debug/pprof requests. '-pprof' argument overrides it
+	// pprof-listen = ''
+	// # limit numbers of queried metrics per target in /render requests, 0 or negative = unlimited
+	// max-metrics-per-target = 15000
+	// # daemon will return the freed memory to the OS when it>0
+	// memory-return-interval = 0
+	//
+	// [clickhouse]
+	// # default url, see https://clickhouse.tech/docs/en/interfaces/http. Can be overwritten with query-params
+	// url = 'http://localhost:8123?cancel_http_readonly_queries_on_client_close=1'
+	// # Max queries to render queiries
+	// render-max-queries = 0
+	// # Concurrent queries to render queiries
+	// render-concurrent-queries = 0
+	// # tree-table = ''
+	// # reverse-tree-table = ''
+	// # date-tree-table = ''
+	// # date-tree-table-version = 0
+	// # tree-timeout = 0
+	// # tag-table = ''
+	// # add extra prefix (directory in graphite) for all metrics, w/o trailing dot
+	// extra-prefix = ''
+	// # TCP connection timeout
+	// connect-timeout = 1000000000
+	// # data-table = ''
+	// # rollup-conf = 'auto'
+	// # max points per metric when internal-aggregation=true
+	// max-data-points = 1048576
+	// # ClickHouse-side aggregation, see doc/aggregation.md
+	// internal-aggregation = true
+	//
+	// # [tags]
+	// # rules = ''
+	// # date = ''
+	// # extra-where = ''
+	// # input-file = ''
+	// # output-file = ''
+}
+
+func TestReadmeComments(t *testing.T) {
+	type TLS struct {
+		Cipher  string `toml:"cipher"`
+		Version string `toml:"version"`
+	}
+	type Config struct {
+		Host string `toml:"host" comment:"Host IP to connect to."`
+		Port int    `toml:"port" comment:"Port of the remote server."`
+		Tls  TLS    `toml:"TLS,commented" comment:"Encryption parameters (optional)"`
+	}
+	example := Config{
+		Host: "127.0.0.1",
+		Port: 4242,
+		Tls: TLS{
+			Cipher:  "AEAD-AES128-GCM-SHA256",
+			Version: "TLS 1.3",
+		},
+	}
+	out, err := toml.Marshal(example)
+	require.NoError(t, err)
+
+	expected := `# 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'
+`
+	require.Equal(t, expected, string(out))
+}

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
+}

toml_testgen_support_test.go

@@ -1,3 +1,4 @@
+//go:generate go run github.com/toml-lang/toml-test/cmd/toml-test@master -copy ./tests
 //go:generate go run ./cmd/tomltestgen/main.go -o toml_testgen_test.go
 
 // This is a support file for toml_testgen_test.go

unmarshaler.go

@@ -5,9 +5,9 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"math"
 	"reflect"
+	"strconv"
 	"strings"
 	"sync/atomic"
 	"time"
@@ -21,10 +21,8 @@ import (
 //
 // It is a shortcut for Decoder.Decode() with the default options.
 func Unmarshal(data []byte, v interface{}) error {
-	p := unstable.Parser{}
+	d := decoder{}
-	p.Reset(data)
+	d.p.Reset(data)
-	d := decoder{p: &p}
-
 	return d.FromParser(v)
 }
 
@@ -35,6 +33,9 @@ type Decoder struct {
 
 	// global settings
 	strict bool
+
+	// toggles unmarshaler interface
+	unmarshalerInterface bool
 }
 
 // NewDecoder creates a new Decoder that will read from r.
@@ -54,6 +55,24 @@ 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 straightfoward 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 +115,25 @@ 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 +145,10 @@ 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 +161,9 @@ type decoder struct {
 	// Strict mode
 	strict strict
 
+	// Flag that enables/disables unmarshaler interface.
+	unmarshalerInterface bool
+
 	// Current context for the error.
 	errorContext *errorContext
 }
@@ -149,12 +174,16 @@ 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 +271,10 @@ 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 +293,7 @@ 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 +334,10 @@ 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 +356,10 @@ 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 {
@@ -417,7 +456,10 @@ 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 +611,7 @@ 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 +669,14 @@ 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 +1010,7 @@ 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), d.typeMismatchString("integer", v.Type()))
 	}
 
 	if !r.Type().AssignableTo(v.Type()) {
@@ -979,7 +1029,7 @@ 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), d.typeMismatchString("string", v.Type()))
 	}
 
 	return nil
@@ -1009,6 +1059,58 @@ 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 +1121,9 @@ func (d *decoder) handleKeyValuePart(key unstable.Iterator, value *unstable.Node
 	case reflect.Map:
 		vt := v.Type()
 
-		mk := reflect.ValueOf(string(key.Node().Data))
+		mk, err := d.keyFromData(vt.Key(), key.Node().Data)
-		mkt := stringType
+		if err != nil {
-
+			return reflect.Value{}, err
-		keyType := vt.Key()
-		if !mkt.AssignableTo(keyType) {
-			if !mkt.ConvertibleTo(keyType) {
-				return reflect.Value{}, fmt.Errorf("toml: cannot convert map key of type %s to expected type %s", mkt, keyType)
-			}
-
-			mk = mk.Convert(keyType)
 		}
 
 		// If the map does not exist, create it.
@@ -1071,6 +1166,19 @@ 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 +1244,10 @@ 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()))
 			}

unmarshaler_test.go

@@ -12,10 +12,32 @@ import (
 	"time"
 
 	"github.com/pelletier/go-toml/v2"
+	"github.com/pelletier/go-toml/v2/unstable"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
+type unmarshalTextKey struct {
+	A string
+	B string
+}
+
+func (k *unmarshalTextKey) UnmarshalText(text []byte) error {
+	parts := strings.Split(string(text), "-")
+	if len(parts) != 2 {
+		return fmt.Errorf("invalid text key: %s", text)
+	}
+	k.A = parts[0]
+	k.B = parts[1]
+	return nil
+}
+
+type unmarshalBadTextKey struct{}
+
+func (k *unmarshalBadTextKey) UnmarshalText(text []byte) error {
+	return fmt.Errorf("error")
+}
+
 func ExampleDecoder_DisallowUnknownFields() {
 	type S struct {
 		Key1 string
@@ -69,7 +91,6 @@ func ExampleUnmarshal() {
 	fmt.Println("version:", cfg.Version)
 	fmt.Println("name:", cfg.Name)
 	fmt.Println("tags:", cfg.Tags)
-
 	// Output:
 	// version: 2
 	// name: go-toml
@@ -184,7 +205,6 @@ func TestUnmarshal_Floats(t *testing.T) {
 		testFn   func(t *testing.T, v float64)
 		err      bool
 	}{
-
 		{
 			desc:     "float pi",
 			input:    `3.1415`,
@@ -220,6 +240,11 @@ func TestUnmarshal_Floats(t *testing.T) {
 			input:    `0E0`,
 			expected: 0.0,
 		},
+		{
+			desc:     "float zero without decimals",
+			input:    `0`,
+			expected: 0.0,
+		},
 		{
 			desc:     "float fractional with exponent",
 			input:    `6.626e-34`,
@@ -315,6 +340,7 @@ func TestUnmarshal(t *testing.T) {
 		target   interface{}
 		expected interface{}
 		err      bool
+		assert   func(t *testing.T, test test)
 	}
 	examples := []struct {
 		skip  bool
@@ -350,6 +376,96 @@ func TestUnmarshal(t *testing.T) {
 				}
 			},
 		},
+		{
+			desc:  "kv text key",
+			input: `a-1 = "foo"`,
+			gen: func() test {
+				type doc = map[unmarshalTextKey]string
+
+				return test{
+					target:   &doc{},
+					expected: &doc{{A: "a", B: "1"}: "foo"},
+				}
+			},
+		},
+		{
+			desc: "table text key",
+			input: `["a-1"]
+foo = "bar"`,
+			gen: func() test {
+				type doc = map[unmarshalTextKey]map[string]string
+
+				return test{
+					target:   &doc{},
+					expected: &doc{{A: "a", B: "1"}: map[string]string{"foo": "bar"}},
+				}
+			},
+		},
+		{
+			desc:  "kv ptr text key",
+			input: `a-1 = "foo"`,
+			gen: func() test {
+				type doc = map[*unmarshalTextKey]string
+
+				return test{
+					target:   &doc{},
+					expected: &doc{{A: "a", B: "1"}: "foo"},
+					assert: func(t *testing.T, test test) {
+						// Despite the documentation:
+						//     Pointer variable equality is determined based on the equality of the
+						// 		 referenced values (as opposed to the memory addresses).
+						// assert.Equal does not work properly with maps with pointer keys
+						// https://github.com/stretchr/testify/issues/1143
+						expected := make(map[unmarshalTextKey]string)
+						for k, v := range *(test.expected.(*doc)) {
+							expected[*k] = v
+						}
+						got := make(map[unmarshalTextKey]string)
+						for k, v := range *(test.target.(*doc)) {
+							got[*k] = v
+						}
+						assert.Equal(t, expected, got)
+					},
+				}
+			},
+		},
+		{
+			desc:  "kv bad text key",
+			input: `a-1 = "foo"`,
+			gen: func() test {
+				type doc = map[unmarshalBadTextKey]string
+
+				return test{
+					target: &doc{},
+					err:    true,
+				}
+			},
+		},
+		{
+			desc:  "kv bad ptr text key",
+			input: `a-1 = "foo"`,
+			gen: func() test {
+				type doc = map[*unmarshalBadTextKey]string
+
+				return test{
+					target: &doc{},
+					err:    true,
+				}
+			},
+		},
+		{
+			desc: "table bad text key",
+			input: `["a-1"]
+foo = "bar"`,
+			gen: func() test {
+				type doc = map[unmarshalBadTextKey]map[string]string
+
+				return test{
+					target: &doc{},
+					err:    true,
+				}
+			},
+		},
 		{
 			desc:  "time.time with negative zone",
 			input: `a = 1979-05-27T00:32:00-07:00 `, // space intentional
@@ -723,8 +839,10 @@ huey = 'dewey'
 
 				return test{
 					target: &doc{},
-					expected: &doc{A: []interface{}{"0", "1", "2", "3", "4", "5", "6",
+					expected: &doc{A: []interface{}{
-						"7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17"}},
+						"0", "1", "2", "3", "4", "5", "6",
+						"7", "8", "9", "10", "11", "12", "13", "14", "15", "16", "17",
+					}},
 				}
 			},
 		},
@@ -1166,6 +1284,64 @@ B = "data"`,
 				}
 			},
 		},
+		{
+			desc: "array table into maps with pointer on last key",
+			input: `[[foo]]
+			bar = "hello"`,
+			gen: func() test {
+				type doc struct {
+					Foo **[]interface{}
+				}
+				x := &[]interface{}{
+					map[string]interface{}{
+						"bar": "hello",
+					},
+				}
+				return test{
+					target: &doc{},
+					expected: &doc{
+						Foo: &x,
+					},
+				}
+			},
+		},
+		{
+			desc: "array table into maps with pointer on intermediate key",
+			input: `[[foo.foo2]]
+			bar = "hello"`,
+			gen: func() test {
+				type doc struct {
+					Foo **map[string]interface{}
+				}
+				x := &map[string]interface{}{
+					"foo2": []interface{}{
+						map[string]interface{}{
+							"bar": "hello",
+						},
+					},
+				}
+				return test{
+					target: &doc{},
+					expected: &doc{
+						Foo: &x,
+					},
+				}
+			},
+		},
+		{
+			desc: "array table into maps with pointer on last key with invalid leaf type",
+			input: `[[foo]]
+			bar = "hello"`,
+			gen: func() test {
+				type doc struct {
+					Foo **[]map[string]int
+				}
+				return test{
+					target: &doc{},
+					err:    true,
+				}
+			},
+		},
 		{
 			desc:  "unexported struct fields are ignored",
 			input: `foo = "bar"`,
@@ -1757,6 +1933,150 @@ B = "data"`,
 				}
 			},
 		},
+		{
+			desc:  "into map of int to string",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[int]string{},
+					expected: &map[int]string{1: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of int8 to string",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[int8]string{},
+					expected: &map[int8]string{1: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of int64 to string",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[int64]string{},
+					expected: &map[int64]string{1: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of uint to string",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[uint]string{},
+					expected: &map[uint]string{1: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of uint8 to string",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[uint8]string{},
+					expected: &map[uint8]string{1: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of uint64 to string",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[uint64]string{},
+					expected: &map[uint64]string{1: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of uint with invalid key",
+			input: `-1 = "a"`,
+			gen: func() test {
+				return test{
+					target: &map[uint]string{},
+					err:    true,
+				}
+			},
+		},
+		{
+			desc:  "into map of float64 to string",
+			input: `'1.01' = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[float64]string{},
+					expected: &map[float64]string{1.01: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of float64 with invalid key",
+			input: `key = "a"`,
+			gen: func() test {
+				return test{
+					target: &map[float64]string{},
+					err:    true,
+				}
+			},
+		},
+		{
+			desc:  "into map of float32 to string",
+			input: `'1.01' = "a"`,
+			gen: func() test {
+				return test{
+					target:   &map[float32]string{},
+					expected: &map[float32]string{1.01: "a"},
+					assert: func(t *testing.T, test test) {
+						assert.Equal(t, test.expected, test.target)
+					},
+				}
+			},
+		},
+		{
+			desc:  "into map of float32 with invalid key",
+			input: `key = "a"`,
+			gen: func() test {
+				return test{
+					target: &map[float32]string{},
+					err:    true,
+				}
+			},
+		},
+		{
+			desc:  "invalid map key type",
+			input: `1 = "a"`,
+			gen: func() test {
+				return test{
+					target: &map[struct{ int }]string{},
+					err:    true,
+				}
+			},
+		},
 	}
 
 	for _, e := range examples {
@@ -1777,7 +2097,11 @@ B = "data"`,
 				require.Error(t, err)
 			} else {
 				require.NoError(t, err)
-				assert.Equal(t, test.expected, test.target)
+				if test.assert != nil {
+					test.assert(t, test)
+				} else {
+					assert.Equal(t, test.expected, test.target)
+				}
 			}
 		})
 	}
@@ -1860,6 +2184,68 @@ func TestUnmarshalErrors(t *testing.T) {
 	require.Equal(t, "toml: cannot decode TOML integer into struct field toml_test.mystruct.Bar of type string", err.Error())
 }
 
+func TestUnmarshalStringInvalidStructField(t *testing.T) {
+	type Server struct {
+		Path string
+		Port int
+	}
+
+	type Cfg struct {
+		Server Server
+	}
+
+	var cfg Cfg
+
+	data := `[server]
+path = "/my/path"
+port = "bad"
+`
+
+	file := strings.NewReader(data)
+	err := toml.NewDecoder(file).Decode(&cfg)
+	require.Error(t, err)
+
+	x := err.(*toml.DecodeError)
+	require.Equal(t, "toml: cannot decode TOML string into struct field toml_test.Server.Port of type int", x.Error())
+	expected := `1| [server]
+2| path = "/my/path"
+3| port = "bad"
+ |        ~~~~~ cannot decode TOML string into struct field toml_test.Server.Port of type int`
+
+	require.Equal(t, expected, x.String())
+}
+
+func TestUnmarshalIntegerInvalidStructField(t *testing.T) {
+	type Server struct {
+		Path string
+		Port int
+	}
+
+	type Cfg struct {
+		Server Server
+	}
+
+	var cfg Cfg
+
+	data := `[server]
+path = 100
+port = 50
+`
+
+	file := strings.NewReader(data)
+	err := toml.NewDecoder(file).Decode(&cfg)
+	require.Error(t, err)
+
+	x := err.(*toml.DecodeError)
+	require.Equal(t, "toml: cannot decode TOML integer into struct field toml_test.Server.Path of type string", x.Error())
+	expected := `1| [server]
+2| path = 100
+ |        ~~~ cannot decode TOML integer into struct field toml_test.Server.Path of type string
+3| port = 50`
+
+	require.Equal(t, expected, x.String())
+}
+
 func TestUnmarshalInvalidTarget(t *testing.T) {
 	x := "foo"
 	err := toml.Unmarshal([]byte{}, x)
@@ -2402,7 +2788,7 @@ func TestIssue772(t *testing.T) {
 		FileHandling `toml:"filehandling"`
 	}
 
-	var defaultConfigFile = []byte(`
+	defaultConfigFile := []byte(`
 		[filehandling]
 		pattern = "reach-masterdev-"`)
 
@@ -2487,6 +2873,162 @@ func TestIssue851(t *testing.T) {
 	require.Equal(t, map[string]string{"a": "1", "b": "2"}, target.Params)
 }
 
+func TestIssue866(t *testing.T) {
+	type Pipeline struct {
+		Mapping map[string]struct {
+			Req [][]string `toml:"req"`
+			Res [][]string `toml:"res"`
+		} `toml:"mapping"`
+	}
+
+	type Pipelines struct {
+		PipelineMapping map[string]*Pipeline `toml:"pipelines"`
+	}
+
+	badToml := `
+[pipelines.register]
+mapping.inst.req = [
+    ["param1", "value1"],
+]
+mapping.inst.res = [
+    ["param2", "value2"],
+]
+`
+
+	pipelines := new(Pipelines)
+	if err := toml.NewDecoder(bytes.NewBufferString(badToml)).DisallowUnknownFields().Decode(pipelines); err != nil {
+		t.Fatal(err)
+	}
+	if pipelines.PipelineMapping["register"].Mapping["inst"].Req[0][0] != "param1" {
+		t.Fatal("unmarshal failed with mismatch value")
+	}
+
+	goodTooToml := `
+[pipelines.register]
+mapping.inst.req = [
+    ["param1", "value1"],
+]
+`
+
+	pipelines = new(Pipelines)
+	if err := toml.NewDecoder(bytes.NewBufferString(goodTooToml)).DisallowUnknownFields().Decode(pipelines); err != nil {
+		t.Fatal(err)
+	}
+	if pipelines.PipelineMapping["register"].Mapping["inst"].Req[0][0] != "param1" {
+		t.Fatal("unmarshal failed with mismatch value")
+	}
+
+	goodToml := `
+[pipelines.register.mapping.inst]
+req = [
+    ["param1", "value1"],
+]
+res = [
+    ["param2", "value2"],
+]
+`
+
+	pipelines = new(Pipelines)
+	if err := toml.NewDecoder(bytes.NewBufferString(goodToml)).DisallowUnknownFields().Decode(pipelines); err != nil {
+		t.Fatal(err)
+	}
+	if pipelines.PipelineMapping["register"].Mapping["inst"].Req[0][0] != "param1" {
+		t.Fatal("unmarshal failed with mismatch value")
+	}
+}
+
+func TestIssue915(t *testing.T) {
+	type blah struct {
+		A string `toml:"a"`
+	}
+
+	type config struct {
+		Fizz string `toml:"fizz"`
+		blah `toml:"blah"`
+	}
+
+	b := []byte(`
+fizz = "abc"
+blah.a = "def"`)
+	var cfg config
+	err := toml.Unmarshal(b, &cfg)
+	require.NoError(t, err)
+
+	require.Equal(t, "abc", cfg.Fizz)
+	require.Equal(t, "def", cfg.blah.A)
+	require.Equal(t, "def", cfg.A)
+}
+
+func TestIssue931(t *testing.T) {
+	type item struct {
+		Name string
+	}
+
+	type items struct {
+		Slice []item
+	}
+
+	its := items{[]item{{"a"}, {"b"}}}
+
+	b := []byte(`
+	[[Slice]]
+  Name = 'c'
+
+[[Slice]]
+  Name = 'd'
+	`)
+
+	toml.Unmarshal(b, &its)
+	require.Equal(t, items{[]item{{"c"}, {"d"}}}, its)
+}
+
+func TestIssue931Interface(t *testing.T) {
+	type items struct {
+		Slice interface{}
+	}
+
+	type item = map[string]interface{}
+
+	its := items{[]interface{}{item{"Name": "a"}, item{"Name": "b"}}}
+
+	b := []byte(`
+	[[Slice]]
+  Name = 'c'
+
+[[Slice]]
+  Name = 'd'
+	`)
+
+	toml.Unmarshal(b, &its)
+	require.Equal(t, items{[]interface{}{item{"Name": "c"}, item{"Name": "d"}}}, its)
+}
+
+func TestIssue931SliceInterface(t *testing.T) {
+	type items struct {
+		Slice []interface{}
+	}
+
+	type item = map[string]interface{}
+
+	its := items{
+		[]interface{}{
+			item{"Name": "a"},
+			item{"Name": "b"},
+		},
+	}
+
+	b := []byte(`
+	[[Slice]]
+  Name = 'c'
+
+[[Slice]]
+  Name = 'd'
+	`)
+
+	toml.Unmarshal(b, &its)
+	require.Equal(t, items{[]interface{}{item{"Name": "c"}, item{"Name": "d"}}}, its)
+}
+
 func TestUnmarshalDecodeErrors(t *testing.T) {
 	examples := []struct {
 		desc string
@@ -2955,7 +3497,7 @@ func TestOmitEmpty(t *testing.T) {
 		X []elem `toml:",inline"`
 	}
 
-	d := doc{X: []elem{elem{
+	d := doc{X: []elem{{
 		Foo: "test",
 		Inner: inner{
 			V: "alue",
@@ -3322,3 +3864,138 @@ func TestUnmarshalEmbedNonString(t *testing.T) {
 	require.NoError(t, err)
 	require.Nil(t, d.Foo)
 }
+
+func TestUnmarshal_Nil(t *testing.T) {
+	type Foo struct {
+		Foo *Foo `toml:"foo,omitempty"`
+		Bar *Foo `toml:"bar,omitempty"`
+	}
+
+	examples := []struct {
+		desc     string
+		input    string
+		expected string
+		err      bool
+	}{
+		{
+			desc:     "empty",
+			input:    ``,
+			expected: ``,
+		},
+		{
+			desc: "simplest",
+			input: `
+            [foo]
+            [foo.foo]
+            `,
+			expected: "[foo]\n[foo.foo]\n",
+		},
+	}
+
+	for _, ex := range examples {
+		e := ex
+		t.Run(e.desc, func(t *testing.T) {
+			foo := Foo{}
+			err := toml.Unmarshal([]byte(e.input), &foo)
+			if e.err {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+				j, err := toml.Marshal(foo)
+				require.NoError(t, err)
+				assert.Equal(t, e.expected, string(j))
+			}
+		})
+	}
+}
+
+type CustomUnmarshalerKey struct {
+	A int64
+}
+
+func (k *CustomUnmarshalerKey) UnmarshalTOML(value *unstable.Node) error {
+	item, err := strconv.ParseInt(string(value.Data), 10, 64)
+	if err != nil {
+		return fmt.Errorf("error converting to int64, %v", err)
+	}
+	k.A = item
+	return nil
+}
+
+func TestUnmarshal_CustomUnmarshaler(t *testing.T) {
+	type MyConfig struct {
+		Unmarshalers []CustomUnmarshalerKey `toml:"unmarshalers"`
+		Foo          *string                `toml:"foo,omitempty"`
+	}
+
+	examples := []struct {
+		desc                        string
+		disableUnmarshalerInterface bool
+		input                       string
+		expected                    MyConfig
+		err                         bool
+	}{
+		{
+			desc:     "empty",
+			input:    ``,
+			expected: MyConfig{Unmarshalers: []CustomUnmarshalerKey{}, Foo: nil},
+		},
+		{
+			desc:  "simple",
+			input: `unmarshalers = [1,2,3]`,
+			expected: MyConfig{
+				Unmarshalers: []CustomUnmarshalerKey{
+					{A: 1},
+					{A: 2},
+					{A: 3},
+				},
+				Foo: nil,
+			},
+		},
+		{
+			desc: "unmarshal string and custom unmarshaler",
+			input: `unmarshalers = [1,2,3]
+foo = "bar"`,
+			expected: MyConfig{
+				Unmarshalers: []CustomUnmarshalerKey{
+					{A: 1},
+					{A: 2},
+					{A: 3},
+				},
+				Foo: func(v string) *string {
+					return &v
+				}("bar"),
+			},
+		},
+		{
+			desc:                        "simple example, but unmarshaler interface disabled",
+			disableUnmarshalerInterface: true,
+			input:                       `unmarshalers = [1,2,3]`,
+			err:                         true,
+		},
+	}
+
+	for _, ex := range examples {
+		e := ex
+		t.Run(e.desc, func(t *testing.T) {
+			foo := MyConfig{}
+
+			decoder := toml.NewDecoder(bytes.NewReader([]byte(e.input)))
+			if !ex.disableUnmarshalerInterface {
+				decoder.EnableUnmarshalerInterface()
+			}
+			err := decoder.Decode(&foo)
+
+			if e.err {
+				require.Error(t, err)
+			} else {
+				require.NoError(t, err)
+				require.Equal(t, len(foo.Unmarshalers), len(e.expected.Unmarshalers))
+				for i := 0; i < len(foo.Unmarshalers); i++ {
+					require.Equal(t, foo.Unmarshalers[i], e.expected.Unmarshalers[i])
+				}
+				require.Equal(t, foo.Foo, e.expected.Foo)
+			}
+		})
+	}
+}

unstable/parser.go

@@ -49,8 +49,6 @@ 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 +56,8 @@ type Parser struct {
 	left    []byte
 	err     error
 	first   bool
+
+	KeepComments bool
 }
 
 // Data returns the slice provided to the last call to Reset.
@@ -142,6 +142,44 @@ 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 := danger.SubsliceOffset(p.data, 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 +193,19 @@ 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 +219,7 @@ 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 +241,10 @@ 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 +525,33 @@ 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 +566,13 @@ 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 +588,16 @@ func (p *Parser) parseValArray(b []byte) (reference, []byte, error) {
 			return parent, nil, err
 		}
 
-		if first {
+		addChild(valueRef)
-			p.builder.AttachChild(parent, valueRef)
-		} else {
-			p.builder.Chain(lastChild, valueRef)
-		}
-		lastChild = valueRef
 
-		b, err = p.parseOptionalWhitespaceCommentNewline(b)
+		cref, b, err = p.parseOptionalWhitespaceCommentNewline(b)
 		if err != nil {
 			return parent, nil, err
 		}
+		if cref != invalidReference {
+			addChild(cref)
+		}
+
 		first = false
 	}
 
@@ -534,15 +606,34 @@ 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 +644,14 @@ 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 +1013,7 @@ 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 +1023,7 @@ 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)
@@ -1055,6 +1148,7 @@ 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 +1172,7 @@ 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 +1184,7 @@ 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 +1207,7 @@ 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

@@ -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
+}