Fix unmarshaling of nested non-exported struct (#917)

Fixes #915

.github/workflows/codeql-analysis.yml

@@ -35,7 +35,7 @@ jobs:
 
     steps:
     - name: Checkout repository
-      uses: actions/checkout@v3
+      uses: actions/checkout@v4
 
     # Initializes the CodeQL tools for scanning.
     - name: Initialize CodeQL

.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@v4
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - name: Run tests with coverage
         run: ./ci.sh coverage -d "${GITHUB_BASE_REF-HEAD}"

.github/workflows/release.yml

@@ -16,15 +16,15 @@ 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@v4
         with:
-          go-version: "1.20"
+          go-version: "1.21"
       - name: Login to GitHub Container Registry
-        uses: docker/login-action@v2
+        uses: docker/login-action@v3
         with:
           registry: ghcr.io
           username: ${{ github.actor }}

.github/workflows/workflow.yml

@@ -12,11 +12,11 @@ jobs:
     strategy:
       matrix:
         os: [ 'ubuntu-latest', 'windows-latest', 'macos-latest' ]
-        go: [ '1.19', '1.20' ]
+        go: [ '1.20', '1.21' ]
     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 }}

.gitignore

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

.goreleaser.yaml

@@ -18,6 +18,7 @@ builds:
       - linux_amd64
       - linux_arm64
       - linux_arm
+      - linux_riscv64
       - windows_amd64
       - windows_arm64
       - windows_arm
@@ -37,6 +38,7 @@ builds:
       - linux_amd64
       - linux_arm64
       - linux_arm
+      - linux_riscv64
       - windows_amd64
       - windows_arm64
       - windows_arm
@@ -55,6 +57,7 @@ builds:
     targets:
       - linux_amd64
       - linux_arm64
+      - linux_riscv64
       - linux_arm
       - windows_amd64
       - windows_arm64

LICENSE

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

README.md

@@ -45,16 +45,15 @@ to check for typos. [See example in the documentation][strict].
 
 ### Contextualized errors
 
-When most decoding errors occur, go-toml returns [`DecodeError`][decode-err]),
+When most decoding errors occur, go-toml returns [`DecodeError`][decode-err],
 which contains a human readable contextualized version of the error. For
 example:
 
 ```
-2| key1 = "value1"
-3| key2 = "missing2"
- | ~~~~ missing field
-4| key3 = "missing3"
-5| key4 = "value4"
+1| [server]
+2| path = 100
+ |        ~~~ cannot decode TOML integer into struct field toml_test.Server.Path of type string
+3| port = 50
 ```
 
 [decode-err]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#DecodeError
@@ -73,6 +72,26 @@ 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:
@@ -160,12 +179,12 @@ Execution time speedup compared to other Go TOML libraries:
         <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
     </thead>
     <tbody>
-        <tr><td>Marshal/HugoFrontMatter-2</td><td>1.9x</td><td>1.9x</td></tr>
-        <tr><td>Marshal/ReferenceFile/map-2</td><td>1.7x</td><td>1.8x</td></tr>
-        <tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>2.5x</td></tr>
-        <tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.9x</td></tr>
-        <tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.9x</td></tr>
-        <tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.4x</td><td>5.3x</td></tr>
+        <tr><td>Marshal/HugoFrontMatter-2</td><td>1.9x</td><td>2.2x</td></tr>
+        <tr><td>Marshal/ReferenceFile/map-2</td><td>1.7x</td><td>2.1x</td></tr>
+        <tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>3.0x</td></tr>
+        <tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.7x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.7x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.6x</td><td>5.1x</td></tr>
      </tbody>
 </table>
 <details><summary>See more</summary>
@@ -178,17 +197,17 @@ provided for completeness.</p>
         <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
     </thead>
     <tbody>
-        <tr><td>Marshal/SimpleDocument/map-2</td><td>1.8x</td><td>2.9x</td></tr>
-        <tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>4.2x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.5x</td><td>3.1x</td></tr>
-        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>6.2x</td><td>3.9x</td></tr>
-        <tr><td>UnmarshalDataset/example-2</td><td>3.1x</td><td>3.5x</td></tr>
-        <tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>3.1x</td></tr>
-        <tr><td>UnmarshalDataset/twitter-2</td><td>2.5x</td><td>2.6x</td></tr>
-        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.1x</td><td>2.2x</td></tr>
-        <tr><td>UnmarshalDataset/canada-2</td><td>1.6x</td><td>1.3x</td></tr>
-        <tr><td>UnmarshalDataset/config-2</td><td>4.3x</td><td>3.2x</td></tr>
-        <tr><td>[Geo mean]</td><td>2.7x</td><td>2.8x</td></tr>
+        <tr><td>Marshal/SimpleDocument/map-2</td><td>1.8x</td><td>2.7x</td></tr>
+        <tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>3.8x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/map-2</td><td>3.8x</td><td>3.0x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/struct-2</td><td>5.6x</td><td>4.1x</td></tr>
+        <tr><td>UnmarshalDataset/example-2</td><td>3.0x</td><td>3.2x</td></tr>
+        <tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>2.9x</td></tr>
+        <tr><td>UnmarshalDataset/twitter-2</td><td>2.6x</td><td>2.7x</td></tr>
+        <tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.2x</td><td>2.3x</td></tr>
+        <tr><td>UnmarshalDataset/canada-2</td><td>1.8x</td><td>1.5x</td></tr>
+        <tr><td>UnmarshalDataset/config-2</td><td>4.1x</td><td>2.9x</td></tr>
+        <tr><td>geomean</td><td>2.7x</td><td>2.8x</td></tr>
      </tbody>
 </table>
 <p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>
@@ -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.

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

@@ -77,7 +77,7 @@ cover() {
 
     pushd "$dir"
     go test -covermode=atomic  -coverpkg=./... -coverprofile=coverage.out.tmp ./...
-    cat coverage.out.tmp | grep -v fuzz | 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
@@ -152,7 +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
@@ -161,10 +161,12 @@ bench() {
 }
 
 fmktemp() {
-    if mktemp --version|grep GNU >/dev/null; then
-        mktemp --suffix=-$1;
+    if mktemp --version &> /dev/null; then
+	# GNU
+        mktemp --suffix=-$1
     else
-        mktemp -t $1;
+	# BSD
+	mktemp -t $1
     fi
 }
 
@@ -184,12 +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])
@@ -260,10 +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/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 {
-		zipFilesMap[f.Name] = f
+		log.Printf("> [%s] %s\n", "invalid", name)
+
+		tomlContent, err := os.ReadFile(f)
+		if err != nil {
+			fmt.Printf("failed to read test file: %s\n", err)
+			os.Exit(1)
 		}
 
-	testFileRegexp := regexp.MustCompile(`([^/]+/tests/(valid|invalid)/(.+))\.(toml)`)
-	for _, f := range zipReader.File {
-		groups := testFileRegexp.FindStringSubmatch(f.Name)
-		if len(groups) > 0 {
-			name := kebabToCamel(groups[3])
-			testType := groups[2]
-
-			log.Printf("> [%s] %s\n", testType, name)
-
-			tomlContent := readFileFromZip(f)
-
-			switch testType {
-			case "invalid":
 		collection.Invalid = append(collection.Invalid, invalid{
 			Name:  name,
-					Input: tomlContent,
+			Input: string(tomlContent),
 		})
 		collection.Count++
-			case "valid":
-				baseFilePath := groups[1]
-				jsonFilePath := baseFilePath + ".json"
-				jsonContent := readFileFromZip(zipFilesMap[jsonFilePath])
+	}
+
+	dirContent, _ = filepath.Glob("tests/valid/**/*.toml")
+	for _, f := range dirContent {
+		filename := strings.TrimPrefix(f, "tests/valid/")
+		name := kebabToCamel(strings.TrimSuffix(filename, ".toml"))
+
+		log.Printf("> [%s] %s\n", "valid", name)
+
+		tomlContent, err := os.ReadFile(f)
+		if err != nil {
+			fmt.Printf("failed reading test file: %s\n", err)
+			os.Exit(1)
+		}
+
+		filename = strings.TrimSuffix(f, ".toml")
+		jsonContent, err := os.ReadFile(filename + ".json")
+		if err != nil {
+			fmt.Printf("failed reading validation json: %s\n", err)
+			os.Exit(1)
+		}
 
 		collection.Valid = append(collection.Valid, valid{
 			Name:    name,
-					Input:   tomlContent,
-					JsonRef: jsonContent,
+			Input:   string(tomlContent),
+			JsonRef: string(jsonContent),
 		})
 		collection.Count++
-			default:
-				panic(fmt.Sprintf("unknown test type: %s", testType))
-			}
-		}
 	}
 
 	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")
 	}
 

fuzz_test.go

@@ -1,5 +1,5 @@
-//go:build go1.18 || go1.19 || go1.20
-// +build go1.18 go1.19 go1.20
+//go:build go1.18 || go1.19 || go1.20 || go1.21
+// +build go1.18 go1.19 go1.20 go1.21
 
 package toml_test
 

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)
+}

marshaler.go

@@ -148,6 +148,9 @@ 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 +183,7 @@ func (enc *Encoder) Encode(v interface{}) error {
 type valueOptions struct {
 	multiline bool
 	omitempty bool
+	commented bool
 	comment   string
 }
 
@@ -205,6 +209,9 @@ type encoderCtx struct {
 	// Indentation level
 	indent int
 
+	// Prefix the current value with a comment.
+	commented bool
+
 	// Options coming from struct tags
 	options valueOptions
 }
@@ -357,6 +364,7 @@ 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 +386,13 @@ 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 +541,8 @@ 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, '[')
@@ -704,6 +721,7 @@ 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"),
 		}
 
@@ -763,6 +781,7 @@ type tagOptions struct {
 	multiline bool
 	inline    bool
 	omitempty bool
+	commented bool
 }
 
 func parseTag(tag string) (string, tagOptions) {
@@ -790,6 +809,8 @@ func parseTag(tag string) (string, tagOptions) {
 			opts.inline = true
 		case "omitempty":
 			opts.omitempty = true
+		case "commented":
+			opts.commented = true
 		}
 	}
 
@@ -825,8 +846,10 @@ 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
 		}
@@ -851,8 +874,10 @@ 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
 		}
@@ -970,6 +995,9 @@ func (enc *Encoder) encodeSliceAsArrayTable(b []byte, ctx encoderCtx, v reflect.
 	ctx.shiftKey()
 
 	scratch := make([]byte, 0, 64)
+
+	scratch = enc.commented(ctx.commented, scratch)
+
 	scratch = append(scratch, "[["...)
 
 	for i, k := range ctx.parentKey {
@@ -985,6 +1013,10 @@ 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

@@ -1201,6 +1201,45 @@ 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"`
@@ -1298,7 +1337,7 @@ 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"},
 		},
@@ -1317,6 +1356,94 @@ 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 ExampleMarshal() {
 	type MyConfig struct {
 		Version int
@@ -1341,3 +1468,161 @@ 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

@@ -1,5 +1,5 @@
-//go:build go1.18 || go1.19 || go1.20
-// +build go1.18 go1.19 go1.20
+//go:build go1.18 || go1.19 || go1.20 || go1.21
+// +build go1.18 go1.19 go1.20 go1.21
 
 package ossfuzz
 

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

@@ -149,12 +149,16 @@ 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 {
@@ -963,7 +967,7 @@ 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()) {
@@ -982,7 +986,7 @@ 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
@@ -1093,9 +1097,9 @@ func (d *decoder) handleKeyValuePart(key unstable.Iterator, value *unstable.Node
 
 		f := fieldByIndex(v, path)
 
-		if !f.CanSet() {
-			// If the field is not settable, need to take a slower path and make a copy of
-			// the struct itself to a new location.
+		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()

unmarshaler_test.go

@@ -240,6 +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`,
@@ -2043,6 +2048,68 @@ 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)
@@ -2734,6 +2801,28 @@ res = [
 	}
 }
 
+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 TestUnmarshalDecodeErrors(t *testing.T) {
 	examples := []struct {
 		desc string

unstable/parser.go

@@ -1013,6 +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) {
@@ -1022,6 +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)
@@ -1146,6 +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
 	}
 
@@ -1169,6 +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
 			}
 
@@ -1180,6 +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
 			}
 
@@ -1202,6 +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

@@ -569,9 +569,9 @@ key5 = [ # Next to start of inline array.
 	// ---
 	// 1:1->1:1 (0->0)           | KeyValue []
 	// 1:1->1:1 (0->0)           |   Array []
-	// 1:1->1:1 (0->0)           |     Integer [1]
-	// 1:1->1:1 (0->0)           |     Integer [2]
-	// 1:1->1:1 (0->0)           |     Integer [3]
+	// 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.]
 	// ---
@@ -583,12 +583,12 @@ key5 = [ # Next to start of inline array.
 	// 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.]
-	// 1:1->1:1 (0->0)           |     Integer [1]
+	// 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.]
-	// 1:1->1:1 (0->0)           |     Integer [2]
-	// 1:1->1:1 (0->0)           |     Integer [3]
+	// 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]