AST Tweaks (#551)

* Use pointers instead of copying around ast.Node

Node is a 56B struct that is constantly in the hot path. Passing nodes
around by copy had a cost that started to add up. This change replaces
them by pointers. Using unsafe pointer arithmetic and converting
sibling/child indexes to relative offsets, it removes the need to carry
around a pointer to the root of the tree. This saves 8B per Node. This
space will be used to store an extra []byte slice to provide contextual
error handling on all nodes, including the ones whose data is different
than the raw input (for example: strings with escaped characters), while
staying under the size of a cache line.

* Remove conditional

* Add Raw to track range in data for parsed values

* Simplify reference tracking

.gitattributes

@@ -0,0 +1,3 @@
+* text=auto
+
+benchmark/benchmark.toml text eol=lf

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,5 +1,19 @@
-**Issue:** add link to pelletier/go-toml issue here
+<!--
+
+Thank you for your pull request!
+
+Please read the Code changes section of the CONTRIBUTING.md file,
+and make sure you have followed the instructions.
+
+https://github.com/pelletier/go-toml/blob/v2/CONTRIBUTING.md#code-changes
+
+-->
 
 Explanation of what this pull request does.
 
-More detailed description of the decisions being made and the reasons why (if the patch is non-trivial).
+More detailed description of the decisions being made and the reasons why (if
+the patch is non-trivial).
+
+---
+
+Paste `benchstat` results here

.github/workflows/coverage.yml

@@ -0,0 +1,20 @@
+name: coverage
+on:
+  pull_request:
+    branches:
+      - v2
+
+jobs:
+  report:
+    runs-on: "ubuntu-latest"
+    name: report
+    steps:
+      - uses: actions/checkout@master
+        with:
+          fetch-depth: 0
+      - name: Setup go
+        uses: actions/setup-go@master
+        with:
+          go-version: 1.16
+      - name: Run tests with coverage
+        run: ./ci.sh coverage -d "${GITHUB_BASE_REF-HEAD}"

.github/workflows/workflow.yml

@@ -23,6 +23,3 @@ jobs:
           go-version: ${{ matrix.go }}
       - name: Run unit tests
         run: go test -race ./...
-      - name: Run benchmark tests
-        run: go test -race ./...
-        working-directory: benchmark

.golangci.toml

@@ -4,6 +4,9 @@ golangci-lint-version =  "1.39.0"
 [linters-settings.wsl]
 allow-assign-and-anything = true
 
+[linters-settings.exhaustive]
+default-signifies-exhaustive = true
+
 [linters]
 disable-all = true
 enable = [
@@ -18,13 +21,13 @@ enable = [
     "errcheck",
     "errorlint",
     "exhaustive",
-    "exhaustivestruct",
+    # "exhaustivestruct",
     "exportloopref",
     "forbidigo",
-    "forcetypeassert",
+    # "forcetypeassert",
     "funlen",
     "gci",
-    "gochecknoglobals",
+    # "gochecknoglobals",
     "gochecknoinits",
     "gocognit",
     "goconst",
@@ -32,7 +35,7 @@ enable = [
     "gocyclo",
     "godot",
     "godox",
-    "goerr113",
+    # "goerr113",
     "gofmt",
     "gofumpt",
     "goheader",
@@ -45,7 +48,7 @@ enable = [
     "gosec",
     "gosimple",
     "govet",
-    "ifshort",
+    # "ifshort",
     "importas",
     "ineffassign",
     "lll",
@@ -54,10 +57,10 @@ enable = [
     "nakedret",
     "nestif",
     "nilerr",
-    "nlreturn",
+    # "nlreturn",
     "noctx",
     "nolintlint",
-    "paralleltest",
+    #"paralleltest",
     "prealloc",
     "predeclared",
     "revive",
@@ -76,6 +79,6 @@ enable = [
     "varcheck",
     "wastedassign",
     "whitespace",
-    "wrapcheck",
-    "wsl"
+    # "wrapcheck",
+    # "wsl"
 ]

CONTRIBUTING.md

@@ -1,74 +1,74 @@
-## Contributing
+# Contributing
 
 Thank you for your interest in go-toml! We appreciate you considering
 contributing to go-toml!
 
-The main goal is the project is to provide an easy-to-use TOML
-implementation for Go that gets the job done and gets out of your way –
-dealing with TOML is probably not the central piece of your project.
+The main goal is the project is to provide an easy-to-use and efficient TOML
+implementation for Go that gets the job done and gets out of your way – dealing
+with TOML is probably not the central piece of your project.
 
-As the single maintainer of go-toml, time is scarce. All help, big or
-small, is more than welcomed!
+As the single maintainer of go-toml, time is scarce. All help, big or small, is
+more than welcomed!
 
-### Ask questions
+## Ask questions
 
-Any question you may have, somebody else might have it too. Always feel
-free to ask them on the [issues tracker][issues-tracker].  We will try to
-answer them as clearly and quickly as possible, time permitting.
+Any question you may have, somebody else might have it too. Always feel free to
+ask them on the [discussion board][discussions]. We will try to answer them as
+clearly and quickly as possible, time permitting.
 
 Asking questions also helps us identify areas where the documentation needs
 improvement, or new features that weren't envisioned before. Sometimes, a
-seemingly innocent question leads to the fix of a bug. Don't hesitate and
-ask away!
+seemingly innocent question leads to the fix of a bug. Don't hesitate and ask
+away!
 
-### Improve the documentation
+[discussions]: https://github.com/pelletier/go-toml/discussions
 
-The best way to share your knowledge and experience with go-toml is to
-improve the documentation. Fix a typo, clarify an interface, add an
-example, anything goes!
+## Improve the documentation
 
-The documentation is present in the [README][readme] and thorough the
-source code. On release, it gets updated on [pkg.go.dev][pkg.go.dev]. To make a
-change to the documentation, create a pull request with your proposed
-changes. For simple changes like that, the easiest way to go is probably
-the "Fork this project and edit the file" button on Github, displayed at
-the top right of the file. Unless it's a trivial change (for example a
-typo), provide a little bit of context in your pull request description or
-commit message.
+The best way to share your knowledge and experience with go-toml is to improve
+the documentation. Fix a typo, clarify an interface, add an example, anything
+goes!
 
-### Report a bug
+The documentation is present in the [README][readme] and thorough the source
+code. On release, it gets updated on [pkg.go.dev][pkg.go.dev]. To make a change
+to the documentation, create a pull request with your proposed changes. For
+simple changes like that, the easiest way to go is probably the "Fork this
+project and edit the file" button on Github, displayed at the top right of the
+file. Unless it's a trivial change (for example a typo), provide a little bit of
+context in your pull request description or commit message.
 
-Found a bug! Sorry to hear that :(. Help us and other track them down and
-fix by reporting it. [File a new bug report][bug-report] on the [issues
-tracker][issues-tracker]. The template should provide enough guidance on
-what to include. When in doubt: add more details! By reducing ambiguity and
-providing more information, it decreases back and forth and saves everyone
-time.
+## Report a bug
 
-### Code changes
+Found a bug! Sorry to hear that :(. Help us and other track them down and fix by
+reporting it. [File a new bug report][bug-report] on the [issues
+tracker][issues-tracker]. The template should provide enough guidance on what to
+include. When in doubt: add more details! By reducing ambiguity and providing
+more information, it decreases back and forth and saves everyone time.
+
+## Code changes
 
 Want to contribute a patch? Very happy to hear that!
 
 First, some high-level rules:
 
-* A short proposal with some POC code is better than a lengthy piece of
-  text with no code. Code speaks louder than words.
-* No backward-incompatible patch will be accepted unless discussed.
-  Sometimes it's hard, and Go's lack of versioning by default does not
-  help, but we try not to break people's programs unless we absolutely have
+- A short proposal with some POC code is better than a lengthy piece of text
+  with no code. Code speaks louder than words. That being said, bigger changes
+  should probably start with a [discussion][discussions].
+- No backward-incompatible patch will be accepted unless discussed. Sometimes
+  it's hard, but we try not to break people's programs unless we absolutely have
   to.
-* If you are writing a new feature or extending an existing one, make sure
-  to write some documentation.
-* Bug fixes need to be accompanied with regression tests.
-* New code needs to be tested.
-* Your commit messages need to explain why the change is needed, even if
-  already included in the PR description.
+- If you are writing a new feature or extending an existing one, make sure to
+  write some documentation.
+- Bug fixes need to be accompanied with regression tests.
+- New code needs to be tested.
+- Your commit messages need to explain why the change is needed, even if already
+  included in the PR description.
 
-It does sound like a lot, but those best practices are here to save time
-overall and continuously improve the quality of the project, which is
-something everyone benefits from.
+It does sound like a lot, but those best practices are here to save time overall
+and continuously improve the quality of the project, which is something everyone
+benefits from.
 
-#### Get started
+### Get started
 
 The fairly standard code contribution process looks like that:
 
@@ -76,42 +76,92 @@ The fairly standard code contribution process looks like that:
 2. Make your changes, commit on any branch you like.
 3. [Open up a pull request][pull-request]
 4. Review, potential ask for changes.
-5. Merge. You're in!
+5. Merge.
 
 Feel free to ask for help! You can create draft pull requests to gather
 some early feedback!
 
-#### Run the tests
+### Run the tests
 
-You can run tests for go-toml using Go's test tool: `go test ./...`.
-When creating a pull requests, all tests will be ran on Linux on a few Go
-versions (Travis CI), and on Windows using the latest Go version
-(AppVeyor).
+You can run tests for go-toml using Go's test tool: `go test -race ./...`.
 
-#### Style
+During the pull request process, all tests will be ran on Linux, Windows, and
+MacOS on the last two versions of Go.
 
-Try to look around and follow the same format and structure as the rest of
-the code. We enforce using `go fmt` on the whole code base.
+However, given GitHub's new policy to _not_ run Actions on pull requests until a
+maintainer clicks on button, it is highly recommended that you run them locally
+as you make changes.
+
+### Check coverage
+
+We use `go tool cover` to compute test coverage. Most code editors have a way to
+run and display code coverage, but at the end of the day, we do this:
+
+```
+go test -covermode=atomic -coverprofile=coverage.out
+go tool cover -func=coverage.out
+```
+
+and verify that the overall percentage of tested code does not go down. This is
+a requirement. As a rule of thumb, all lines of code touched by your changes
+should be covered. On Unix you can use `./ci.sh coverage -d v2` to check if your
+code lowers the coverage.
+
+### Verify performance
+
+Go-toml aims to stay efficient. We rely on a set of scenarios executed with Go's
+builtin benchmark systems. Because of their noisy nature, containers provided by
+Github Actions cannot be reliably used for benchmarking. As a result, you are
+responsible for checking that your changes do not incur a performance penalty.
+You can run their following to execute benchmarks:
+
+```
+go test ./... -bench=. -count=10
+```
+
+Benchmark results should be compared against each other with
+[benchstat][benchstat]. Typical flow looks like this:
+
+1. On the `v2` branch, run `go test ./... -bench=. -count 10` and save output to
+   a file (for example `old.txt`).
+2. Make some code changes.
+3. Run `go test ....` again, and save the output to an other file (for example
+   `new.txt`).
+4. Run `benchstat old.txt new.txt` to check that time/op does not go up in any
+   test.
+
+On Unix you can use `./ci.sh benchmark -d v2` to verify how your code impacts
+performance.
+
+It is highly encouraged to add the benchstat results to your pull request
+description. Pull requests that lower performance will receive more scrutiny.
+
+[benchstat]: https://pkg.go.dev/golang.org/x/perf/cmd/benchstat
+
+### Style
+
+Try to look around and follow the same format and structure as the rest of the
+code. We enforce using `go fmt` on the whole code base.
 
 ---
 
-### Maintainers-only
+## Maintainers-only
 
-#### Merge pull request
+### Merge pull request
 
 Checklist:
 
-* Passing CI.
-* Does not introduce backward-incompatible changes (unless discussed).
-* Has relevant doc changes.
-* Has relevant unit tests.
+- Passing CI.
+- Does not introduce backward-incompatible changes (unless discussed).
+- Has relevant doc changes.
+- Benchstat does not show performance regression.
 
 1. Merge using "squash and merge".
 2. Make sure to edit the commit message to keep all the useful information
    nice and clean.
 3. Make sure the commit title is clear and contains the PR number (#123).
 
-#### New release
+### New release
 
 1. Go to [releases][releases]. Click on "X commits to master since this
    release".

README.md

@@ -1,57 +1,409 @@
-# go-toml V2
+# go-toml v2
 
-Development branch. Use at your own risk.
+Go library for the [TOML](https://toml.io/en/) format.
 
-[👉 Discussion on github](https://github.com/pelletier/go-toml/discussions/471).
+This library supports [TOML v1.0.0](https://toml.io/en/v1.0.0).
 
-* `toml.Unmarshal()` should work as well as v1.
+## Development status
 
-## Must do
+This is the upcoming major version of go-toml. It is currently in active
+development. As of release v2.0.0-beta.1, the library has reached feature parity
+with v1, and fixes a lot known bugs and performance issues along the way.
 
-### Unmarshal
+If you do not need the advanced document editing features of v1, you are
+encouraged to try out this version.
 
-- [x] Unmarshal into maps.
-- [x] Support Array Tables.
-- [x] Unmarshal into pointers.
-- [x] Support Date / times.
-- [x] Support struct tags annotations.
-- [x] Support Arrays.
-- [x] Support Unmarshaler interface.
-- [x] Original go-toml unmarshal tests pass.
-- [x] Benchmark!
-- [x] Abstract AST.
-- [x] Original go-toml testgen tests pass.
-- [x] Track file position (line, column) for errors.
-- [ ] Strict mode.
-- [ ] Document Unmarshal / Decode
+[👉 Roadmap for v2](https://github.com/pelletier/go-toml/discussions/506)
 
-### Marshal
+[🐞 Bug Reports](https://github.com/pelletier/go-toml/issues)
 
-- [x] Minimal implementation
-- [x] Multiline strings
-- [ ] Multiline arrays
-- [ ] `inline` tag for tables
-- [ ] Optional indentation
-- [ ] Option to pick default quotes
+[💬 Anything else](https://github.com/pelletier/go-toml/discussions)
 
-### Document
+## Documentation
 
-- [ ] Gather requirements and design API.
+Full API, examples, and implementation notes are available in the Go documentation.
 
-## Ideas
+[![Go Reference](https://pkg.go.dev/badge/github.com/pelletier/go-toml/v2.svg)](https://pkg.go.dev/github.com/pelletier/go-toml/v2)
 
-- [ ] Allow types to implement a `ASTUnmarshaler` interface to unmarshal
-      straight from the AST?
-- [x] Rewrite AST to use a single array as storage instead of one allocation per
-      node.
-- [ ] Provide "minimal allocations" option that uses `unsafe` to reuse the input
-      byte array as storage for strings.
-- [x] Cache reflection operations per type.
-- [ ] Optimize tracker pass.
+## Import
 
-## Differences with v1
+```go
+import "github.com/pelletier/go-toml/v2"
+```
 
-* [unmarshal](https://github.com/pelletier/go-toml/discussions/488)
+## Features
+
+### Stdlib behavior
+
+As much as possible, this library is designed to behave similarly as the
+standard library's `encoding/json`.
+
+### Performance
+
+While go-toml favors usability, it is written with performance in mind. Most
+operations should not be shockingly slow. See [benchmarks](#benchmarks).
+
+### Strict mode
+
+`Decoder` can be set to "strict mode", which makes it error when some parts of
+the TOML document was not prevent in the target structure. This is a great way
+to check for typos. [See example in the documentation][strict].
+
+[strict]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#example-Decoder.SetStrict
+
+### Contextualized errors
+
+When 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"
+```
+
+[decode-err]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#DecodeError
+
+### Local date and time support
+
+TOML supports native [local date/times][ldt]. It allows to represent a given
+date, time, or date-time without relation to a timezone or offset. To support
+this use-case, go-toml provides [`LocalDate`][tld], [`LocalTime`][tlt], and
+[`LocalDateTime`][tldt]. Those types can be transformed to and from `time.Time`,
+making them convenient yet unambiguous structures for their respective TOML
+representation.
+
+[ldt]: https://toml.io/en/v1.0.0#local-date-time
+[tld]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalDate
+[tlt]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalTime
+[tldt]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#LocalDateTime
+
+## Getting started
+
+Given the following struct, let's see how to read it and write it as TOML:
+
+```go
+type MyConfig struct {
+      Version int
+      Name    string
+      Tags    []string
+}
+```
+
+### Unmarshaling
+
+[`Unmarshal`][unmarshal] reads a TOML document and fills a Go structure with its
+content. For example:
+
+```go
+doc := `
+version = 2
+name = "go-toml"
+tags = ["go", "toml"]
+`
+
+var cfg MyConfig
+err := toml.Unmarshal([]byte(doc), &cfg)
+if err != nil {
+      panic(err)
+}
+fmt.Println("version:", cfg.Version)
+fmt.Println("name:", cfg.Name)
+fmt.Println("tags:", cfg.Tags)
+
+// Output:
+// version: 2
+// name: go-toml
+// tags: [go toml]
+```
+
+[unmarshal]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#Unmarshal
+
+### Marshaling
+
+[`Marshal`][marshal] is the opposite of Unmarshal: it represents a Go structure
+as a TOML document:
+
+```go
+cfg := MyConfig{
+      Version: 2,
+      Name:    "go-toml",
+      Tags:    []string{"go", "toml"},
+}
+
+b, err := toml.Marshal(cfg)
+if err != nil {
+      panic(err)
+}
+fmt.Println(string(b))
+
+// Output:
+// Version = 2
+// Name = 'go-toml'
+// Tags = ['go', 'toml']
+```
+
+[marshal]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#Marshal
+
+## Benchmarks
+
+Execution time speedup compared to other Go TOML libraries:
+
+<table>
+    <thead>
+        <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
+    </thead>
+    <tbody>
+        <tr><td>Marshal/HugoFrontMatter</td><td>2.0x</td><td>2.0x</td></tr>
+        <tr><td>Marshal/ReferenceFile/map</td><td>1.8x</td><td>2.0x</td></tr>
+        <tr><td>Marshal/ReferenceFile/struct</td><td>2.7x</td><td>2.7x</td></tr>
+        <tr><td>Unmarshal/HugoFrontMatter</td><td>3.0x</td><td>2.6x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/map</td><td>3.0x</td><td>3.1x</td></tr>
+        <tr><td>Unmarshal/ReferenceFile/struct</td><td>5.9x</td><td>6.6x</td></tr>
+     </tbody>
+</table>
+<details><summary>See more</summary>
+<p>The table above has the results of the most common use-cases. The table below
+contains the results of all benchmarks, including unrealistic ones. It is
+provided for completeness.</p>
+
+<table>
+    <thead>
+        <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
+    </thead>
+    <tbody>
+        <tr><td>Marshal/SimpleDocument/map</td><td>1.7x</td><td>2.1x</td></tr>
+        <tr><td>Marshal/SimpleDocument/struct</td><td>2.6x</td><td>2.9x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/map</td><td>4.1x</td><td>2.9x</td></tr>
+        <tr><td>Unmarshal/SimpleDocument/struct</td><td>6.3x</td><td>4.1x</td></tr>
+        <tr><td>UnmarshalDataset/example</td><td>3.5x</td><td>2.4x</td></tr>
+        <tr><td>UnmarshalDataset/code</td><td>2.2x</td><td>2.8x</td></tr>
+        <tr><td>UnmarshalDataset/twitter</td><td>2.8x</td><td>2.1x</td></tr>
+        <tr><td>UnmarshalDataset/citm_catalog</td><td>2.3x</td><td>1.5x</td></tr>
+        <tr><td>UnmarshalDataset/config</td><td>4.2x</td><td>3.2x</td></tr>
+        <tr><td>[Geo mean]</td><td>3.0x</td><td>2.7x</td></tr>
+     </tbody>
+</table>
+<p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>
+</details>
+
+## Migrating from v1
+
+This section describes the differences between v1 and v2, with some pointers on
+how to get the original behavior when possible.
+
+### Decoding / Unmarshal
+
+#### Automatic field name guessing
+
+When unmarshaling to a struct, if a key in the TOML document does not exactly
+match the name of a struct field or any of the `toml`-tagged field, v1 tries
+multiple variations of the key ([code][v1-keys]).
+
+V2 instead does a case-insensitive matching, like `encoding/json`.
+
+This could impact you if you are relying on casing to differentiate two fields,
+and one of them is a not using the `toml` struct tag. The recommended solution
+is to be specific about tag names for those fields using the `toml` struct tag.
+
+[v1-keys]: https://github.com/pelletier/go-toml/blob/a2e52561804c6cd9392ebf0048ca64fe4af67a43/marshal.go#L775-L781
+
+#### Ignore preexisting value in interface
+
+When decoding into a non-nil `interface{}`, go-toml v1 uses the type of the
+element in the interface to decode the object. For example:
+
+```go
+type inner struct {
+  B interface{}
+}
+type doc struct {
+  A interface{}
+}
+
+d := doc{
+  A: inner{
+    B: "Before",
+  },
+}
+
+data := `
+[A]
+B = "After"
+`
+
+toml.Unmarshal([]byte(data), &d)
+fmt.Printf("toml v1: %#v\n", d)
+
+// toml v1: main.doc{A:main.inner{B:"After"}}
+```
+
+In this case, field `A` is of type `interface{}`, containing a `inner` struct.
+V1 sees that type and uses it when decoding the object.
+
+When decoding an object into an `interface{}`, V2 instead disregards whatever
+value the `interface{}` may contain and replaces it with a
+`map[string]interface{}`. With the same data structure as above, here is what
+the result looks like:
+
+```go
+toml.Unmarshal([]byte(data), &d)
+fmt.Printf("toml v2: %#v\n", d)
+
+// toml v2: main.doc{A:map[string]interface {}{"B":"After"}}
+```
+
+This is to match `encoding/json`'s behavior. There is no way to make the v2
+decoder behave like v1.
+
+#### Values out of array bounds ignored
+
+When decoding into an array, v1 returns an error when the number of elements
+contained in the doc is superior to the capacity of the array. For example:
+
+```go
+type doc struct {
+  A [2]string
+}
+d := doc{}
+err := toml.Unmarshal([]byte(`A = ["one", "two", "many"]`), &d)
+fmt.Println(err)
+
+// (1, 1): unmarshal: TOML array length (3) exceeds destination array length (2)
+```
+
+In the same situation, v2 ignores the last value:
+
+```go
+err := toml.Unmarshal([]byte(`A = ["one", "two", "many"]`), &d)
+fmt.Println("err:", err, "d:", d)
+// err: <nil> d: {[one two]}
+```
+
+This is to match `encoding/json`'s behavior. There is no way to make the v2
+decoder behave like v1.
+
+#### Support for `toml.Unmarshaler` has been dropped
+
+This method was not widely used, poorly defined, and added a lot of complexity.
+A similar effect can be achieved by implementing the `encoding.TextUnmarshaler`
+interface and use strings.
+
+#### Support for `default` struct tag has been dropped
+
+This feature adds complexity and a poorly defined API for an effect that can be
+accomplished outside of the library.
+
+It does not seem like other format parsers in Go support that feature (the
+project referenced in the original ticket #202 has not been updated since 2017).
+Given that go-toml v2 should not touch values not in the document, the same
+effect can be achieved by pre-filling the struct with defaults (libraries like
+[go-defaults][go-defaults] can help). Also, string representation is not well
+defined for all types: it creates issues like #278.
+
+The recommended replacement is pre-filling the struct before unmarshaling.
+
+[go-defaults]: https://github.com/mcuadros/go-defaults
+
+### Encoding / Marshal
+
+#### Default struct fields order
+
+V1 emits struct fields order alphabetically by default. V2 struct fields are
+emitted in order they are defined. For example:
+
+```go
+type S struct {
+	B string
+	A string
+}
+
+data := S{
+	B: "B",
+	A: "A",
+}
+
+b, _ := tomlv1.Marshal(data)
+fmt.Println("v1:\n" + string(b))
+
+b, _ = tomlv2.Marshal(data)
+fmt.Println("v2:\n" + string(b))
+
+// Output:
+// v1:
+// A = "A"
+// B = "B"
+
+// v2:
+// B = 'B'
+// A = 'A'
+```
+
+There is no way to make v2 encoder behave like v1. A workaround could be to
+manually sort the fields alphabetically in the struct definition.
+
+#### No indentation by default
+
+V1 automatically indents content of tables by default. V2 does not. However the
+same behavior can be obtained using [`Encoder.SetIndentTables`][sit]. For example:
+
+```go
+data := map[string]interface{}{
+	"table": map[string]string{
+		"key": "value",
+	},
+}
+
+b, _ := tomlv1.Marshal(data)
+fmt.Println("v1:\n" + string(b))
+
+b, _ = tomlv2.Marshal(data)
+fmt.Println("v2:\n" + string(b))
+
+buf := bytes.Buffer{}
+enc := tomlv2.NewEncoder(&buf)
+enc.SetIndentTables(true)
+enc.Encode(data)
+fmt.Println("v2 Encoder:\n" + string(buf.Bytes()))
+
+// Output:
+// v1:
+//
+// [table]
+//   key = "value"
+//
+// v2:
+// [table]
+// key = 'value'
+//
+//
+// v2 Encoder:
+// [table]
+//   key = 'value'
+```
+
+[sit]: https://pkg.go.dev/github.com/pelletier/go-toml/v2#Encoder.SetIndentTables
+
+#### Keys and strings are single quoted
+
+V1 always uses double quotes (`"`) around strings and keys that cannot be
+represented bare (unquoted). V2 uses single quotes instead by default (`'`),
+unless a character cannot be represented, then falls back to double quotes.
+
+There is no way to make v2 encoder behave like v1.
+
+#### `TextMarshaler` emits as a string, not TOML
+
+Types that implement [`encoding.TextMarshaler`][tm] can emit arbitrary TOML in
+v1. The encoder would append the result to the output directly. In v2 the result
+is wrapped in a string. As a result, this interface cannot be implemented by the
+root object.
+
+There is no way to make v2 encoder behave like v1.
+
+[tm]: https://golang.org/pkg/encoding/#TextMarshaler
 
 ## License
 

benchmark/bench_datasets_test.go

@@ -8,6 +8,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/pelletier/go-toml/v2"
 	"github.com/stretchr/testify/require"
 )
 
@@ -30,65 +31,50 @@ var bench_inputs = []struct {
 
 func TestUnmarshalDatasetCode(t *testing.T) {
 	for _, tc := range bench_inputs {
-		buf := fixture(t, tc.name)
 		t.Run(tc.name, func(t *testing.T) {
-			for _, r := range runners {
-				if r.name == "bs" && tc.name == "canada" {
-					t.Skip("skipping: burntsushi can't handle mixed arrays")
-				}
+			buf := fixture(t, tc.name)
 
-				t.Run(r.name, func(t *testing.T) {
-					var v interface{}
-					check(t, r.unmarshal(buf, &v))
+			var v interface{}
+			require.NoError(t, toml.Unmarshal(buf, &v))
 
-					b, err := json.Marshal(v)
-					check(t, err)
-					require.Equal(t, len(b), tc.jsonLen)
-				})
-			}
+			b, err := json.Marshal(v)
+			require.NoError(t, err)
+			require.Equal(t, len(b), tc.jsonLen)
 		})
 	}
 }
 
 func BenchmarkUnmarshalDataset(b *testing.B) {
 	for _, tc := range bench_inputs {
-		buf := fixture(b, tc.name)
 		b.Run(tc.name, func(b *testing.B) {
-			bench(b, func(r runner, b *testing.B) {
-				if r.name == "bs" && tc.name == "canada" {
-					b.Skip("skipping: burntsushi can't handle mixed arrays")
-				}
-
-				b.SetBytes(int64(len(buf)))
-				b.ReportAllocs()
-				b.ResetTimer()
-				for i := 0; i < b.N; i++ {
-					var v interface{}
-					check(b, r.unmarshal(buf, &v))
-				}
-			})
+			buf := fixture(b, tc.name)
+			b.SetBytes(int64(len(buf)))
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				var v interface{}
+				require.NoError(b, toml.Unmarshal(buf, &v))
+			}
 		})
 	}
 }
 
 // fixture returns the uncompressed contents of path.
 func fixture(tb testing.TB, path string) []byte {
-	f, err := os.Open(filepath.Join("testdata", path+".toml.gz"))
-	check(tb, err)
+	tb.Helper()
+
+	file := path + ".toml.gz"
+	f, err := os.Open(filepath.Join("testdata", file))
+	if os.IsNotExist(err) {
+		tb.Skip("benchmark fixture not found:", file)
+	}
+	require.NoError(tb, err)
 	defer f.Close()
 
 	gz, err := gzip.NewReader(f)
-	check(tb, err)
+	require.NoError(tb, err)
 
 	buf, err := ioutil.ReadAll(gz)
-	check(tb, err)
-
+	require.NoError(tb, err)
 	return buf
 }
-
-func check(tb testing.TB, err error) {
-	if err != nil {
-		tb.Helper()
-		tb.Fatal(err)
-	}
-}

benchmark/benchmark.toml

@@ -186,7 +186,7 @@ key3 = 1979-05-27T00:32:00.999999-07:00
 key1 = [ 1, 2, 3 ]
 key2 = [ "red", "yellow", "green" ]
 key3 = [ [ 1, 2 ], [3, 4, 5] ]
-#key4 = [ [ 1, 2 ], ["a", "b", "c"] ] # this is ok
+key4 = [ [ 1, 2 ], ["a", "b", "c"] ] # this is ok
 
 # Arrays can also be multiline. So in addition to ignoring whitespace, arrays
 # also ignore newlines between the brackets.  Terminating commas are ok before

benchmark/benchmark_test.go

@@ -1,43 +1,103 @@
 package benchmark_test
 
 import (
+	"bytes"
 	"io/ioutil"
 	"testing"
 	"time"
 
-	tomlbs "github.com/BurntSushi/toml"
-	tomlv1 "github.com/pelletier/go-toml-v1"
 	"github.com/pelletier/go-toml/v2"
 	"github.com/stretchr/testify/require"
 )
 
-type runner struct {
-	name      string
-	unmarshal func([]byte, interface{}) error
-}
+func TestUnmarshalSimple(t *testing.T) {
+	doc := []byte(`A = "hello"`)
+	d := struct {
+		A string
+	}{}
 
-var runners = []runner{
-	{"v2", toml.Unmarshal},
-	{"v1", tomlv1.Unmarshal},
-	{"bs", tomlbs.Unmarshal},
-}
-
-func bench(b *testing.B, f func(r runner, b *testing.B)) {
-	for _, r := range runners {
-		b.Run(r.name, func(b *testing.B) {
-			f(r, b)
-		})
+	err := toml.Unmarshal(doc, &d)
+	if err != nil {
+		panic(err)
 	}
 }
 
-func BenchmarkUnmarshalSimple(b *testing.B) {
-	bench(b, func(r runner, b *testing.B) {
-		d := struct {
-			A string
-		}{}
+func BenchmarkUnmarshal(b *testing.B) {
+	b.Run("SimpleDocument", func(b *testing.B) {
 		doc := []byte(`A = "hello"`)
+
+		b.Run("struct", func(b *testing.B) {
+			b.SetBytes(int64(len(doc)))
+			b.ReportAllocs()
+			b.ResetTimer()
+
+			for i := 0; i < b.N; i++ {
+				d := struct {
+					A string
+				}{}
+
+				err := toml.Unmarshal(doc, &d)
+				if err != nil {
+					panic(err)
+				}
+			}
+		})
+
+		b.Run("map", func(b *testing.B) {
+			b.SetBytes(int64(len(doc)))
+			b.ReportAllocs()
+			b.ResetTimer()
+
+			for i := 0; i < b.N; i++ {
+				d := map[string]interface{}{}
+				err := toml.Unmarshal(doc, &d)
+				if err != nil {
+					panic(err)
+				}
+			}
+		})
+	})
+
+	b.Run("ReferenceFile", func(b *testing.B) {
+		bytes, err := ioutil.ReadFile("benchmark.toml")
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		b.Run("struct", func(b *testing.B) {
+			b.SetBytes(int64(len(bytes)))
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				d := benchmarkDoc{}
+				err := toml.Unmarshal(bytes, &d)
+				if err != nil {
+					panic(err)
+				}
+			}
+		})
+
+		b.Run("map", func(b *testing.B) {
+			b.SetBytes(int64(len(bytes)))
+			b.ReportAllocs()
+			b.ResetTimer()
+			for i := 0; i < b.N; i++ {
+				d := map[string]interface{}{}
+				err := toml.Unmarshal(bytes, &d)
+				if err != nil {
+					panic(err)
+				}
+			}
+		})
+	})
+
+	b.Run("HugoFrontMatter", func(b *testing.B) {
+		b.SetBytes(int64(len(hugoFrontMatterbytes)))
+		b.ReportAllocs()
+		b.ResetTimer()
 		for i := 0; i < b.N; i++ {
-			err := r.unmarshal(doc, &d)
+			d := map[string]interface{}{}
+			err := toml.Unmarshal(hugoFrontMatterbytes, &d)
 			if err != nil {
 				panic(err)
 			}
@@ -45,6 +105,137 @@ func BenchmarkUnmarshalSimple(b *testing.B) {
 	})
 }
 
+func marshal(v interface{}) ([]byte, error) {
+	var b bytes.Buffer
+	enc := toml.NewEncoder(&b)
+	err := enc.Encode(v)
+	return b.Bytes(), err
+}
+
+func BenchmarkMarshal(b *testing.B) {
+	b.Run("SimpleDocument", func(b *testing.B) {
+		doc := []byte(`A = "hello"`)
+
+		b.Run("struct", func(b *testing.B) {
+			d := struct {
+				A string
+			}{}
+
+			err := toml.Unmarshal(doc, &d)
+			if err != nil {
+				panic(err)
+			}
+
+			b.ReportAllocs()
+			b.ResetTimer()
+
+			var out []byte
+
+			for i := 0; i < b.N; i++ {
+				out, err = marshal(d)
+				if err != nil {
+					panic(err)
+				}
+			}
+
+			b.SetBytes(int64(len(out)))
+		})
+
+		b.Run("map", func(b *testing.B) {
+			d := map[string]interface{}{}
+			err := toml.Unmarshal(doc, &d)
+			if err != nil {
+				panic(err)
+			}
+
+			b.ReportAllocs()
+			b.ResetTimer()
+
+			var out []byte
+
+			for i := 0; i < b.N; i++ {
+				out, err = marshal(d)
+				if err != nil {
+					panic(err)
+				}
+			}
+
+			b.SetBytes(int64(len(out)))
+		})
+	})
+
+	b.Run("ReferenceFile", func(b *testing.B) {
+		bytes, err := ioutil.ReadFile("benchmark.toml")
+		if err != nil {
+			b.Fatal(err)
+		}
+
+		b.Run("struct", func(b *testing.B) {
+			d := benchmarkDoc{}
+			err := toml.Unmarshal(bytes, &d)
+			if err != nil {
+				panic(err)
+			}
+			b.ReportAllocs()
+			b.ResetTimer()
+
+			var out []byte
+
+			for i := 0; i < b.N; i++ {
+				out, err = marshal(d)
+				if err != nil {
+					panic(err)
+				}
+			}
+
+			b.SetBytes(int64(len(out)))
+		})
+
+		b.Run("map", func(b *testing.B) {
+			d := map[string]interface{}{}
+			err := toml.Unmarshal(bytes, &d)
+			if err != nil {
+				panic(err)
+			}
+
+			b.ReportAllocs()
+			b.ResetTimer()
+
+			var out []byte
+			for i := 0; i < b.N; i++ {
+				out, err = marshal(d)
+				if err != nil {
+					panic(err)
+				}
+			}
+
+			b.SetBytes(int64(len(out)))
+		})
+	})
+
+	b.Run("HugoFrontMatter", func(b *testing.B) {
+		d := map[string]interface{}{}
+		err := toml.Unmarshal(hugoFrontMatterbytes, &d)
+		if err != nil {
+			panic(err)
+		}
+
+		b.ReportAllocs()
+		b.ResetTimer()
+
+		var out []byte
+
+		for i := 0; i < b.N; i++ {
+			out, err = marshal(d)
+			if err != nil {
+				panic(err)
+			}
+		}
+
+		b.SetBytes(int64(len(out)))
+	})
+}
+
 type benchmarkDoc struct {
 	Table struct {
 		Key      string
@@ -58,7 +249,7 @@ type benchmarkDoc struct {
 			}
 			Point struct {
 				X int64
-				U int64
+				Y int64
 			}
 		}
 	}
@@ -131,6 +322,7 @@ type benchmarkDoc struct {
 		Key2 []string
 		Key3 [][]int64
 		// TODO: Key4 not supported by go-toml's Unmarshal
+		Key4 []interface{}
 		Key5 []int64
 		Key6 []int64
 	}
@@ -142,38 +334,321 @@ type benchmarkDoc struct {
 	Fruit []struct {
 		Name     string
 		Physical struct {
-			Color   string
-			Shape   string
-			Variety []struct {
-				Name string
-			}
+			Color string
+			Shape string
+		}
+		Variety []struct {
+			Name string
 		}
 	}
 }
 
-func BenchmarkReferenceFile(b *testing.B) {
-	bench(b, func(r runner, b *testing.B) {
-		bytes, err := ioutil.ReadFile("benchmark.toml")
-		if err != nil {
-			b.Fatal(err)
-		}
-		b.SetBytes(int64(len(bytes)))
-		b.ReportAllocs()
-		b.ResetTimer()
-		for i := 0; i < b.N; i++ {
-			d := benchmarkDoc{}
-			err := r.unmarshal(bytes, &d)
-			if err != nil {
-				panic(err)
-			}
-		}
-	})
-}
-
-func TestReferenceFile(t *testing.T) {
+func TestUnmarshalReferenceFile(t *testing.T) {
 	bytes, err := ioutil.ReadFile("benchmark.toml")
 	require.NoError(t, err)
 	d := benchmarkDoc{}
 	err = toml.Unmarshal(bytes, &d)
 	require.NoError(t, err)
+
+	expected := benchmarkDoc{
+		Table: struct {
+			Key      string
+			Subtable struct{ Key string }
+			Inline   struct {
+				Name struct {
+					First string
+					Last  string
+				}
+				Point struct {
+					X int64
+					Y int64
+				}
+			}
+		}{
+			Key: "value",
+			Subtable: struct{ Key string }{
+				Key: "another value",
+			},
+			// note: x.y.z.w is purposefully missing
+			Inline: struct {
+				Name struct {
+					First string
+					Last  string
+				}
+				Point struct {
+					X int64
+					Y int64
+				}
+			}{
+				Name: struct {
+					First string
+					Last  string
+				}{
+					First: "Tom",
+					Last:  "Preston-Werner",
+				},
+				Point: struct {
+					X int64
+					Y int64
+				}{
+					X: 1,
+					Y: 2,
+				},
+			},
+		},
+		String: struct {
+			Basic     struct{ Basic string }
+			Multiline struct {
+				Key1      string
+				Key2      string
+				Key3      string
+				Continued struct {
+					Key1 string
+					Key2 string
+					Key3 string
+				}
+			}
+			Literal struct {
+				Winpath   string
+				Winpath2  string
+				Quoted    string
+				Regex     string
+				Multiline struct {
+					Regex2 string
+					Lines  string
+				}
+			}
+		}{
+			Basic: struct{ Basic string }{
+				Basic: "I'm a string. \"You can quote me\". Name\tJos\u00E9\nLocation\tSF.",
+			},
+			Multiline: struct {
+				Key1      string
+				Key2      string
+				Key3      string
+				Continued struct {
+					Key1 string
+					Key2 string
+					Key3 string
+				}
+			}{
+				Key1: "One\nTwo",
+				Key2: "One\nTwo",
+				Key3: "One\nTwo",
+
+				Continued: struct {
+					Key1 string
+					Key2 string
+					Key3 string
+				}{
+					Key1: `The quick brown fox jumps over the lazy dog.`,
+					Key2: `The quick brown fox jumps over the lazy dog.`,
+					Key3: `The quick brown fox jumps over the lazy dog.`,
+				},
+			},
+			Literal: struct {
+				Winpath   string
+				Winpath2  string
+				Quoted    string
+				Regex     string
+				Multiline struct {
+					Regex2 string
+					Lines  string
+				}
+			}{
+				Winpath:  `C:\Users\nodejs\templates`,
+				Winpath2: `\\ServerX\admin$\system32\`,
+				Quoted:   `Tom "Dubs" Preston-Werner`,
+				Regex:    `<\i\c*\s*>`,
+
+				Multiline: struct {
+					Regex2 string
+					Lines  string
+				}{
+					Regex2: `I [dw]on't need \d{2} apples`,
+					Lines: `The first newline is
+trimmed in raw strings.
+   All other whitespace
+   is preserved.
+`,
+				},
+			},
+		},
+		Integer: struct {
+			Key1        int64
+			Key2        int64
+			Key3        int64
+			Key4        int64
+			Underscores struct {
+				Key1 int64
+				Key2 int64
+				Key3 int64
+			}
+		}{
+			Key1: 99,
+			Key2: 42,
+			Key3: 0,
+			Key4: -17,
+
+			Underscores: struct {
+				Key1 int64
+				Key2 int64
+				Key3 int64
+			}{
+				Key1: 1000,
+				Key2: 5349221,
+				Key3: 12345,
+			},
+		},
+		Float: struct {
+			Fractional struct {
+				Key1 float64
+				Key2 float64
+				Key3 float64
+			}
+			Exponent struct {
+				Key1 float64
+				Key2 float64
+				Key3 float64
+			}
+			Both        struct{ Key float64 }
+			Underscores struct {
+				Key1 float64
+				Key2 float64
+			}
+		}{
+			Fractional: struct {
+				Key1 float64
+				Key2 float64
+				Key3 float64
+			}{
+				Key1: 1.0,
+				Key2: 3.1415,
+				Key3: -0.01,
+			},
+			Exponent: struct {
+				Key1 float64
+				Key2 float64
+				Key3 float64
+			}{
+				Key1: 5e+22,
+				Key2: 1e6,
+				Key3: -2e-2,
+			},
+			Both: struct{ Key float64 }{
+				Key: 6.626e-34,
+			},
+			Underscores: struct {
+				Key1 float64
+				Key2 float64
+			}{
+				Key1: 9224617.445991228313,
+				Key2: 1e100,
+			},
+		},
+		Boolean: struct {
+			True  bool
+			False bool
+		}{
+			True:  true,
+			False: false,
+		},
+		Datetime: struct {
+			Key1 time.Time
+			Key2 time.Time
+			Key3 time.Time
+		}{
+			Key1: time.Date(1979, 5, 27, 7, 32, 0, 0, time.UTC),
+			Key2: time.Date(1979, 5, 27, 0, 32, 0, 0, time.FixedZone("", -7*3600)),
+			Key3: time.Date(1979, 5, 27, 0, 32, 0, 999999000, time.FixedZone("", -7*3600)),
+		},
+		Array: struct {
+			Key1 []int64
+			Key2 []string
+			Key3 [][]int64
+			Key4 []interface{}
+			Key5 []int64
+			Key6 []int64
+		}{
+			Key1: []int64{1, 2, 3},
+			Key2: []string{"red", "yellow", "green"},
+			Key3: [][]int64{{1, 2}, {3, 4, 5}},
+			Key4: []interface{}{
+				[]interface{}{int64(1), int64(2)},
+				[]interface{}{"a", "b", "c"},
+			},
+			Key5: []int64{1, 2, 3},
+			Key6: []int64{1, 2},
+		},
+		Products: []struct {
+			Name  string
+			Sku   int64
+			Color string
+		}{
+			{
+				Name: "Hammer",
+				Sku:  738594937,
+			},
+			{},
+			{
+				Name:  "Nail",
+				Sku:   284758393,
+				Color: "gray",
+			},
+		},
+		Fruit: []struct {
+			Name     string
+			Physical struct {
+				Color string
+				Shape string
+			}
+			Variety []struct{ Name string }
+		}{
+			{
+				Name: "apple",
+				Physical: struct {
+					Color string
+					Shape string
+				}{
+					Color: "red",
+					Shape: "round",
+				},
+				Variety: []struct{ Name string }{
+					{Name: "red delicious"},
+					{Name: "granny smith"},
+				},
+			},
+			{
+				Name: "banana",
+				Variety: []struct{ Name string }{
+					{Name: "plantain"},
+				},
+			},
+		},
+	}
+
+	require.Equal(t, expected, d)
 }
+
+var hugoFrontMatterbytes = []byte(`
+categories = ["Development", "VIM"]
+date = "2012-04-06"
+description = "spf13-vim is a cross platform distribution of vim plugins and resources for Vim."
+slug = "spf13-vim-3-0-release-and-new-website"
+tags = [".vimrc", "plugins", "spf13-vim", "vim"]
+title = "spf13-vim 3.0 release and new website"
+include_toc = true
+show_comments = false
+
+[[cascade]]
+  background = "yosemite.jpg"
+  [cascade._target]
+    kind = "page"
+    lang = "en"
+    path = "/blog/**"
+
+[[cascade]]
+  background = "goldenbridge.jpg"
+  [cascade._target]
+    kind = "section"
+`)

benchmark/go.mod

@@ -1,14 +0,0 @@
-module github.com/pelletier/go-toml/v2/benchmark
-
-go 1.16
-
-replace github.com/pelletier/go-toml/v2 => ../
-
-replace github.com/pelletier/go-toml-v1 => github.com/pelletier/go-toml v1.8.1
-
-require (
-	github.com/BurntSushi/toml v0.3.1
-	github.com/pelletier/go-toml-v1 v0.0.0-00010101000000-000000000000
-	github.com/pelletier/go-toml/v2 v2.0.0-00010101000000-000000000000
-	github.com/stretchr/testify v1.7.0
-)

benchmark/go.sum

@@ -1,16 +0,0 @@
-github.com/BurntSushi/toml v0.3.1 h1:WXkYYl6Yr3qBf1K79EBnL4mak0OimBfB0XUf9Vl28OQ=
-github.com/BurntSushi/toml v0.3.1/go.mod h1:xHWCNGjB5oqiDr8zfno3MHue2Ht5sIBksp03qcyfWMU=
-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/pelletier/go-toml v1.8.1 h1:1Nf83orprkJyknT6h7zbuEGUEjcyVlCxSUGTENmNCRM=
-github.com/pelletier/go-toml v1.8.1/go.mod h1:T2/BmBdy8dvIRq1a/8aqjN41wvWlN4lrapLU/GW4pbc=
-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 v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
-github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-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 h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

ci.sh

@@ -0,0 +1,273 @@
+#!/usr/bin/env bash
+
+
+stderr() {
+    echo "$@" 1>&2
+}
+
+usage() {
+    b=$(basename "$0")
+    echo $b: ERROR: "$@" 1>&2
+
+    cat 1>&2 <<EOF
+
+DESCRIPTION
+
+    $(basename "$0") is the script to run continuous integration commands for
+    go-toml on unix.
+
+    Requires Go and Git to be available in the PATH. Expects to be ran from the
+    root of go-toml's Git repository.
+
+USAGE
+
+    $b COMMAND [OPTIONS...]
+
+COMMANDS
+
+benchmark [OPTIONS...] [BRANCH]
+
+    Run benchmarks.
+
+    ARGUMENTS
+
+        BRANCH Optional. Defines which Git branch to use when running
+               benchmarks.
+
+    OPTIONS
+
+        -d      Compare benchmarks of HEAD with BRANCH using benchstats. In
+                this form the BRANCH argument is required.
+
+        -a      Compare benchmarks of HEAD against go-toml v1 and
+                BurntSushi/toml.
+
+        -html   When used with -a, emits the output as HTML, ready to be
+                embedded in the README.
+
+coverage [OPTIONS...] [BRANCH]
+
+    Generates code coverage.
+
+    ARGUMENTS
+
+        BRANCH  Optional. Defines which Git branch to use when reporting
+                coverage. Defaults to HEAD.
+
+    OPTIONS
+
+        -d      Compare coverage of HEAD with the one of BRANCH. In this form,
+                the BRANCH argument is required. Exit code is non-zero when
+                coverage percentage decreased.
+EOF
+    exit 1
+}
+
+cover() {
+    branch="${1}"
+    dir="$(mktemp -d)"
+
+    stderr "Executing coverage for ${branch} at ${dir}"
+
+    if [ "${branch}" = "HEAD" ]; then
+	    cp -r . "${dir}/"
+    else
+	    git worktree add "$dir" "$branch"
+    fi
+
+    pushd "$dir"
+    go test -covermode=atomic -coverprofile=coverage.out ./...
+    go tool cover -func=coverage.out
+    popd
+
+    if [ "${branch}" != "HEAD" ]; then
+	    git worktree remove --force "$dir"
+    fi
+}
+
+coverage() {
+    case "$1" in
+	-d)
+	    shift
+	    target="${1?Need to provide a target branch argument}"
+
+	    output_dir="$(mktemp -d)"
+	    target_out="${output_dir}/target.txt"
+	    head_out="${output_dir}/head.txt"
+	    
+	    cover "${target}" > "${target_out}"
+	    cover "HEAD" > "${head_out}"
+
+	    cat "${target_out}"
+	    cat "${head_out}"
+
+	    echo ""
+
+	    target_pct="$(cat ${target_out} |sed -E 's/.*total.*\t([0-9.]+)%/\1/;t;d')"
+	    head_pct="$(cat ${head_out} |sed -E 's/.*total.*\t([0-9.]+)%/\1/;t;d')"
+	    echo "Results: ${target} ${target_pct}% HEAD ${head_pct}%"
+
+	    delta_pct=$(echo "$head_pct - $target_pct" | bc -l)
+	    echo "Delta: ${delta_pct}"
+
+	    if [[ $delta_pct = \-* ]]; then
+		echo "Regression!";
+		return 1
+	    fi
+	    return 0
+	    ;;
+    esac
+
+    cover "${1-HEAD}"
+}
+
+bench() {
+    branch="${1}"
+    out="${2}"
+    replace="${3}"
+    dir="$(mktemp -d)"
+
+    stderr "Executing benchmark for ${branch} at ${dir}"
+
+    if [ "${branch}" = "HEAD" ]; then
+    	cp -r . "${dir}/"
+    else
+	    git worktree add "$dir" "$branch"
+    fi
+
+    pushd "$dir"
+
+    if [ "${replace}" != "" ]; then
+        find ./benchmark/ -iname '*.go' -exec sed -i -E "s|github.com/pelletier/go-toml/v2|${replace}|g" {} \;
+        go get "${replace}"
+        # hack: remove canada.toml.gz because it is not supported by
+        # burntsushi, and replace is only used for benchmark -a
+        rm -f benchmark/testdata/canada.toml.gz
+    fi
+
+    go test -bench=. -count=10 ./... | tee "${out}"
+    popd
+
+    if [ "${branch}" != "HEAD" ]; then
+	    git worktree remove --force "$dir"
+    fi
+}
+
+fmktemp() {
+    if mktemp --version|grep GNU >/dev/null; then
+        mktemp --suffix=-$1;
+    else
+        mktemp -t $1;
+    fi
+}
+
+benchstathtml() {
+python3 - $1 <<'EOF'
+import sys
+
+lines = []
+stop = False
+
+with open(sys.argv[1]) as f:
+    for line in f.readlines():
+        line = line.strip()
+        if line == "":
+            stop = True
+        if not stop:
+            lines.append(line.split(','))
+
+results = []
+for line in reversed(lines[1:]):
+    v2 = float(line[1])
+    results.append([
+        line[0].replace("-32", ""),
+        "%.1fx" % (float(line[3])/v2),  # v1
+        "%.1fx" % (float(line[5])/v2),  # bs
+    ])
+# move geomean to the end
+results.append(results[0])
+del results[0]
+
+
+def printtable(data):
+    print("""
+<table>
+    <thead>
+        <tr><th>Benchmark</th><th>go-toml v1</th><th>BurntSushi/toml</th></tr>
+    </thead>
+    <tbody>""")
+
+    for r in data:
+        print("        <tr><td>{}</td><td>{}</td><td>{}</td></tr>".format(*r))
+
+    print("""     </tbody>
+</table>""")
+
+
+def match(x):
+    return "ReferenceFile" in x[0] or "HugoFrontMatter" in x[0]
+
+above = [x for x in results if match(x)]
+below = [x for x in results if not match(x)]
+
+printtable(above)
+print("<details><summary>See more</summary>")
+print("""<p>The table above has the results of the most common use-cases. The table below
+contains the results of all benchmarks, including unrealistic ones. It is
+provided for completeness.</p>""")
+printtable(below)
+print('<p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>')
+print("</details>")
+
+EOF
+}
+
+benchmark() {
+    case "$1" in
+    -d)
+        shift
+     	target="${1?Need to provide a target branch argument}"
+
+        old=`fmktemp ${target}`
+        bench "${target}" "${old}"
+
+        new=`fmktemp HEAD`
+        bench HEAD "${new}"
+
+        benchstat "${old}" "${new}"
+        return 0
+        ;;
+    -a)
+        shift
+
+        v2stats=`fmktemp go-toml-v2`
+        bench HEAD "${v2stats}" "github.com/pelletier/go-toml/v2"
+        v1stats=`fmktemp go-toml-v1`
+        bench HEAD "${v1stats}" "github.com/pelletier/go-toml"
+        bsstats=`fmktemp bs-toml`
+        bench HEAD "${bsstats}" "github.com/BurntSushi/toml"
+
+        cp "${v2stats}" go-toml-v2.txt
+        cp "${v1stats}" go-toml-v1.txt
+        cp "${bsstats}" bs-toml.txt
+
+        if [ "$1" = "-html" ]; then
+            tmpcsv=`fmktemp csv`
+            benchstat -csv -geomean 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
+        fi
+
+        rm -f go-toml-v2.txt go-toml-v1.txt bs-toml.txt
+        return $?
+    esac
+
+    bench "${1-HEAD}" `mktemp`
+}
+
+case "$1" in
+    coverage) shift; coverage $@;;
+    benchmark) shift; benchmark $@;;
+    *) usage "bad argument $1";;
+esac

decode.go

@@ -1,11 +1,9 @@
 package toml
 
 import (
-	"errors"
 	"fmt"
 	"math"
 	"strconv"
-	"strings"
 	"time"
 )
 
@@ -19,7 +17,7 @@ func parseInteger(b []byte) (int64, error) {
 		case 'o':
 			return parseIntOct(b)
 		default:
-			return 0, newDecodeError(b[1:2], "invalid base: '%c'", b[1])
+			panic(fmt.Errorf("invalid base '%c', should have been checked by scanIntOrFloat", b[1]))
 		}
 	}
 
@@ -37,52 +35,34 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 		return date, newDecodeError(b, "dates are expected to have the format YYYY-MM-DD")
 	}
 
-	var err error
+	date.Year = parseDecimalDigits(b[0:4])
 
-	date.Year, err = parseDecimalDigits(b[0:4])
-	if err != nil {
-		return date, err
-	}
-
-	v, err := parseDecimalDigits(b[5:7])
-	if err != nil {
-		return date, err
-	}
+	v := parseDecimalDigits(b[5:7])
 
 	date.Month = time.Month(v)
 
-	date.Day, err = parseDecimalDigits(b[8:10])
-	if err != nil {
-		return date, err
-	}
+	date.Day = parseDecimalDigits(b[8:10])
 
 	return date, nil
 }
 
-var errNotDigit = errors.New("not a digit")
-
-func parseDecimalDigits(b []byte) (int, error) {
+func parseDecimalDigits(b []byte) int {
 	v := 0
 
 	for _, c := range b {
-		if !isDigit(c) {
-			return 0, fmt.Errorf("%s: %w", b, errNotDigit)
-		}
-
 		v *= 10
 		v += int(c - '0')
 	}
 
-	return v, nil
+	return v
 }
 
-var errParseDateTimeMissingInfo = errors.New("date-time missing timezone information")
-
 func parseDateTime(b []byte) (time.Time, error) {
 	// offset-date-time = full-date time-delim full-time
 	// full-time      = partial-time time-offset
 	// time-offset    = "Z" / time-numoffset
 	// time-numoffset = ( "+" / "-" ) time-hour ":" time-minute
+
 	dt, b, err := parseLocalDateTime(b)
 	if err != nil {
 		return time.Time{}, err
@@ -91,7 +71,8 @@ func parseDateTime(b []byte) (time.Time, error) {
 	var zone *time.Location
 
 	if len(b) == 0 {
-		return time.Time{}, errParseDateTimeMissingInfo
+		// parser should have checked that when assigning the date time node
+		panic("date time should have a timezone")
 	}
 
 	if b[0] == 'Z' {
@@ -103,18 +84,15 @@ func parseDateTime(b []byte) (time.Time, error) {
 			return time.Time{}, newDecodeError(b, "invalid date-time timezone")
 		}
 		direction := 1
-		switch b[0] {
-		case '+':
-		case '-':
+		if b[0] == '-' {
 			direction = -1
-		default:
-			return time.Time{}, newDecodeError(b[0:1], "invalid timezone offset character")
 		}
 
 		hours := digitsToInt(b[1:3])
 		minutes := digitsToInt(b[4:6])
 		seconds := direction * (hours*3600 + minutes*60)
 		zone = time.FixedZone("", seconds)
+		b = b[dateTimeByteLen:]
 	}
 
 	if len(b) > 0 {
@@ -134,19 +112,12 @@ func parseDateTime(b []byte) (time.Time, error) {
 	return t, nil
 }
 
-var (
-	errParseLocalDateTimeWrongLength = errors.New(
-		"local datetimes are expected to have the format YYYY-MM-DDTHH:MM:SS[.NNNNNN]",
-	)
-	errParseLocalDateTimeWrongSeparator = errors.New("datetime separator is expected to be T or a space")
-)
-
 func parseLocalDateTime(b []byte) (LocalDateTime, []byte, error) {
 	var dt LocalDateTime
 
-	const localDateTimeByteLen = 11
-	if len(b) < localDateTimeByteLen {
-		return dt, nil, errParseLocalDateTimeWrongLength
+	const localDateTimeByteMinLen = 11
+	if len(b) < localDateTimeByteMinLen {
+		return dt, nil, newDecodeError(b, "local datetimes are expected to have the format YYYY-MM-DDTHH:MM:SS[.NNNNNNNNN]")
 	}
 
 	date, err := parseLocalDate(b[:10])
@@ -157,7 +128,7 @@ func parseLocalDateTime(b []byte) (LocalDateTime, []byte, error) {
 
 	sep := b[10]
 	if sep != 'T' && sep != ' ' {
-		return dt, nil, errParseLocalDateTimeWrongSeparator
+		return dt, nil, newDecodeError(b[10:11], "datetime separator is expected to be T or a space")
 	}
 
 	t, rest, err := parseLocalTime(b[11:])
@@ -169,213 +140,183 @@ func parseLocalDateTime(b []byte) (LocalDateTime, []byte, error) {
 	return dt, rest, nil
 }
 
-var errParseLocalTimeWrongLength = errors.New("times are expected to have the format HH:MM:SS[.NNNNNN]")
-
 // parseLocalTime is a bit different because it also returns the remaining
 // []byte that is didn't need. This is to allow parseDateTime to parse those
 // remaining bytes as a timezone.
 func parseLocalTime(b []byte) (LocalTime, []byte, error) {
-	var t LocalTime
+	var (
+		nspow = [10]int{0, 1e8, 1e7, 1e6, 1e5, 1e4, 1e3, 1e2, 1e1, 1e0}
+		t     LocalTime
+	)
 
 	const localTimeByteLen = 8
 	if len(b) < localTimeByteLen {
-		return t, nil, errParseLocalTimeWrongLength
-	}
-
-	var err error
-
-	t.Hour, err = parseDecimalDigits(b[0:2])
-	if err != nil {
-		return t, nil, err
+		return t, nil, newDecodeError(b, "times are expected to have the format HH:MM:SS[.NNNNNN]")
 	}
 
+	t.Hour = parseDecimalDigits(b[0:2])
 	if b[2] != ':' {
 		return t, nil, newDecodeError(b[2:3], "expecting colon between hours and minutes")
 	}
 
-	t.Minute, err = parseDecimalDigits(b[3:5])
-	if err != nil {
-		return t, nil, err
-	}
-
+	t.Minute = parseDecimalDigits(b[3:5])
 	if b[5] != ':' {
 		return t, nil, newDecodeError(b[5:6], "expecting colon between minutes and seconds")
 	}
 
-	t.Second, err = parseDecimalDigits(b[6:8])
-	if err != nil {
-		return t, nil, err
-	}
+	t.Second = parseDecimalDigits(b[6:8])
 
-	if len(b) >= 15 && b[8] == '.' {
-		t.Nanosecond, err = parseDecimalDigits(b[9:15])
-		if err != nil {
-			return t, nil, err
+	const minLengthWithFrac = 9
+	if len(b) >= minLengthWithFrac && b[minLengthWithFrac-1] == '.' {
+		frac := 0
+		digits := 0
+
+		for i, c := range b[minLengthWithFrac:] {
+			if !isDigit(c) {
+				if i == 0 {
+					return t, nil, newDecodeError(b[i:i+1], "need at least one digit after fraction point")
+				}
+
+				break
+			}
+
+			const maxFracPrecision = 9
+			if i >= maxFracPrecision {
+				return t, nil, newDecodeError(b[i:i+1], "maximum precision for date time is nanosecond")
+			}
+
+			frac *= 10
+			frac += int(c - '0')
+			digits++
 		}
 
-		return t, b[15:], nil
+		t.Nanosecond = frac * nspow[digits]
+
+		return t, b[9+digits:], nil
 	}
 
 	return t, b[8:], nil
 }
 
-var (
-	errParseFloatStartDot = errors.New("float cannot start with a dot")
-	errParseFloatEndDot   = errors.New("float cannot end with a dot")
-)
-
 //nolint:cyclop
 func parseFloat(b []byte) (float64, error) {
-	//nolint:godox
-	// TODO: inefficient
 	if len(b) == 4 && (b[0] == '+' || b[0] == '-') && b[1] == 'n' && b[2] == 'a' && b[3] == 'n' {
 		return math.NaN(), nil
 	}
 
-	tok := string(b)
-
-	err := numberContainsInvalidUnderscore(tok)
+	cleaned, err := checkAndRemoveUnderscores(b)
 	if err != nil {
 		return 0, err
 	}
 
-	cleanedVal := cleanupNumberToken(tok)
-	if cleanedVal[0] == '.' {
-		return 0, errParseFloatStartDot
+	if cleaned[0] == '.' {
+		return 0, newDecodeError(b, "float cannot start with a dot")
 	}
 
-	if cleanedVal[len(cleanedVal)-1] == '.' {
-		return 0, errParseFloatEndDot
+	if cleaned[len(cleaned)-1] == '.' {
+		return 0, newDecodeError(b, "float cannot end with a dot")
 	}
 
-	f, err := strconv.ParseFloat(cleanedVal, 64)
+	f, err := strconv.ParseFloat(string(cleaned), 64)
 	if err != nil {
-		return 0, fmt.Errorf("coudn't ParseFloat %w", err)
+		return 0, newDecodeError(b, "unable to parse float: %w", err)
 	}
 
 	return f, nil
 }
 
 func parseIntHex(b []byte) (int64, error) {
-	tok := string(b)
-	cleanedVal := cleanupNumberToken(tok)
-
-	err := hexNumberContainsInvalidUnderscore(cleanedVal)
+	cleaned, err := checkAndRemoveUnderscores(b[2:])
 	if err != nil {
 		return 0, err
 	}
 
-	i, err := strconv.ParseInt(cleanedVal[2:], 16, 64)
+	i, err := strconv.ParseInt(string(cleaned), 16, 64)
 	if err != nil {
-		return 0, fmt.Errorf("coudn't ParseIntHex %w", err)
+		return 0, newDecodeError(b, "couldn't parse hexadecimal number: %w", err)
 	}
 
 	return i, nil
 }
 
 func parseIntOct(b []byte) (int64, error) {
-	tok := string(b)
-	cleanedVal := cleanupNumberToken(tok)
-
-	err := numberContainsInvalidUnderscore(cleanedVal)
+	cleaned, err := checkAndRemoveUnderscores(b[2:])
 	if err != nil {
 		return 0, err
 	}
 
-	i, err := strconv.ParseInt(cleanedVal[2:], 8, 64)
+	i, err := strconv.ParseInt(string(cleaned), 8, 64)
 	if err != nil {
-		return 0, fmt.Errorf("coudn't ParseIntOct %w", err)
+		return 0, newDecodeError(b, "couldn't parse octal number: %w", err)
 	}
 
 	return i, nil
 }
 
 func parseIntBin(b []byte) (int64, error) {
-	tok := string(b)
-	cleanedVal := cleanupNumberToken(tok)
-
-	err := numberContainsInvalidUnderscore(cleanedVal)
+	cleaned, err := checkAndRemoveUnderscores(b[2:])
 	if err != nil {
 		return 0, err
 	}
 
-	i, err := strconv.ParseInt(cleanedVal[2:], 2, 64)
+	i, err := strconv.ParseInt(string(cleaned), 2, 64)
 	if err != nil {
-		return 0, fmt.Errorf("coudn't ParseIntBin %w", err)
+		return 0, newDecodeError(b, "couldn't parse binary number: %w", err)
 	}
 
 	return i, nil
 }
 
 func parseIntDec(b []byte) (int64, error) {
-	tok := string(b)
-	cleanedVal := cleanupNumberToken(tok)
-
-	err := numberContainsInvalidUnderscore(cleanedVal)
+	cleaned, err := checkAndRemoveUnderscores(b)
 	if err != nil {
 		return 0, err
 	}
 
-	i, err := strconv.ParseInt(cleanedVal, 10, 64)
+	i, err := strconv.ParseInt(string(cleaned), 10, 64)
 	if err != nil {
-		return 0, fmt.Errorf("coudn't parseIntDec %w", err)
+		return 0, newDecodeError(b, "couldn't parse decimal number: %w", err)
 	}
 
 	return i, nil
 }
 
-func numberContainsInvalidUnderscore(value string) error {
-	// For large numbers, you may use underscores between digits to enhance
-	// readability. Each underscore must be surrounded by at least one digit on
-	// each side.
-	hasBefore := false
-
-	for idx, r := range value {
-		if r == '_' {
-			if !hasBefore || idx+1 >= len(value) {
-				// can't end with an underscore
-				return errInvalidUnderscore
-			}
-		}
-		hasBefore = isDigitRune(r)
+func checkAndRemoveUnderscores(b []byte) ([]byte, error) {
+	if b[0] == '_' {
+		return nil, newDecodeError(b[0:1], "number cannot start with underscore")
 	}
 
-	return nil
-}
-
-func hexNumberContainsInvalidUnderscore(value string) error {
-	hasBefore := false
-
-	for idx, r := range value {
-		if r == '_' {
-			if !hasBefore || idx+1 >= len(value) {
-				// can't end with an underscore
-				return errInvalidUnderscoreHex
-			}
-		}
-		hasBefore = isHexDigit(r)
+	if b[len(b)-1] == '_' {
+		return nil, newDecodeError(b[len(b)-1:], "number cannot end with underscore")
 	}
 
-	return nil
+	// fast path
+	i := 0
+	for ; i < len(b); i++ {
+		if b[i] == '_' {
+			break
+		}
+	}
+	if i == len(b) {
+		return b, nil
+	}
+
+	before := false
+	cleaned := make([]byte, i, len(b))
+	copy(cleaned, b)
+
+	for i++; i < len(b); i++ {
+		c := b[i]
+		if c == '_' {
+			if !before {
+				return nil, newDecodeError(b[i-1:i+1], "number must have at least one digit between underscores")
+			}
+			before = false
+		} else {
+			before = true
+			cleaned = append(cleaned, c)
+		}
+	}
+
+	return cleaned, nil
 }
-
-func cleanupNumberToken(value string) string {
-	cleanedVal := strings.ReplaceAll(value, "_", "")
-
-	return cleanedVal
-}
-
-func isHexDigit(r rune) bool {
-	return isDigitRune(r) ||
-		(r >= 'a' && r <= 'f') ||
-		(r >= 'A' && r <= 'F')
-}
-
-func isDigitRune(r rune) bool {
-	return r >= '0' && r <= '9'
-}
-
-var (
-	errInvalidUnderscore    = errors.New("invalid use of _ in number")
-	errInvalidUnderscoreHex = errors.New("invalid use of _ in hex number")
-)

doc.go

@@ -0,0 +1,2 @@
+// Package toml is a library to read and write TOML documents.
+package toml

errors.go

@@ -5,7 +5,7 @@ import (
 	"strconv"
 	"strings"
 
-	"github.com/pelletier/go-toml/v2/internal/unsafe"
+	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
 // DecodeError represents an error encountered during the parsing or decoding
@@ -18,15 +18,49 @@ type DecodeError struct {
 	message string
 	line    int
 	column  int
+	key     Key
 
 	human string
 }
 
+// StrictMissingError occurs in a TOML document that does not have a
+// corresponding field in the target value. It contains all the missing fields
+// in Errors.
+//
+// Emitted by Decoder when SetStrict(true) was called.
+type StrictMissingError struct {
+	// One error per field that could not be found.
+	Errors []DecodeError
+}
+
+// Error returns the canonical string for this error.
+func (s *StrictMissingError) Error() string {
+	return "strict mode: fields in the document are missing in the target struct"
+}
+
+// String returns a human readable description of all errors.
+func (s *StrictMissingError) String() string {
+	var buf strings.Builder
+
+	for i, e := range s.Errors {
+		if i > 0 {
+			buf.WriteString("\n---\n")
+		}
+
+		buf.WriteString(e.String())
+	}
+
+	return buf.String()
+}
+
+type Key []string
+
 // internal version of DecodeError that is used as the base to create a
 // DecodeError with full context.
 type decodeError struct {
 	highlight []byte
 	message   string
+	key       Key // optional
 }
 
 func (de *decodeError) Error() string {
@@ -36,13 +70,13 @@ func (de *decodeError) Error() string {
 func newDecodeError(highlight []byte, format string, args ...interface{}) error {
 	return &decodeError{
 		highlight: highlight,
-		message:   fmt.Sprintf(format, args...),
+		message:   fmt.Errorf(format, args...).Error(),
 	}
 }
 
 // Error returns the error message contained in the DecodeError.
 func (e *DecodeError) Error() string {
-	return e.message
+	return "toml: " + e.message
 }
 
 // String returns the human-readable contextualized error. This string is multi-line.
@@ -56,7 +90,13 @@ func (e *DecodeError) Position() (row int, column int) {
 	return e.line, e.column
 }
 
-// decodeErrorFromHighlight creates a DecodeError referencing to a highlighted
+// Key that was being processed when the error occurred. The key is present only
+// if this DecodeError is part of a StrictMissingError.
+func (e *DecodeError) Key() Key {
+	return e.key
+}
+
+// decodeErrorFromHighlight creates a DecodeError referencing a highlighted
 // range of bytes from document.
 //
 // highlight needs to be a sub-slice of document, or this function panics.
@@ -64,14 +104,10 @@ func (e *DecodeError) Position() (row int, column int) {
 // The function copies all bytes used in DecodeError, so that document and
 // highlight can be freely deallocated.
 //nolint:funlen
-func wrapDecodeError(document []byte, de *decodeError) error {
-	if de == nil {
-		return nil
-	}
+func wrapDecodeError(document []byte, de *decodeError) *DecodeError {
+	offset := danger.SubsliceOffset(document, de.highlight)
 
-	offset := unsafe.SubsliceOffset(document, de.highlight)
-
-	errMessage := de.message
+	errMessage := de.Error()
 	errLine, errColumn := positionAtEnd(document[:offset])
 	before, after := linesOfContext(document, de.highlight, offset, 3)
 
@@ -137,6 +173,7 @@ func wrapDecodeError(document []byte, de *decodeError) error {
 		message: errMessage,
 		line:    errLine,
 		column:  errColumn,
+		key:     de.key,
 		human:   buf.String(),
 	}
 }

errors_test.go

@@ -3,6 +3,7 @@ package toml
 import (
 	"bytes"
 	"errors"
+	"fmt"
 	"strings"
 	"testing"
 
@@ -11,7 +12,6 @@ import (
 
 //nolint:funlen
 func TestDecodeError(t *testing.T) {
-	t.Parallel()
 
 	examples := []struct {
 		desc     string
@@ -153,7 +153,7 @@ line 5`,
 	for _, e := range examples {
 		e := e
 		t.Run(e.desc, func(t *testing.T) {
-			t.Parallel()
+
 			b := bytes.Buffer{}
 			b.Write([]byte(e.doc[0]))
 			start := b.Len()
@@ -179,3 +179,41 @@ line 5`,
 		})
 	}
 }
+
+func TestDecodeError_Accessors(t *testing.T) {
+
+	e := DecodeError{
+		message: "foo",
+		line:    1,
+		column:  2,
+		key:     []string{"one", "two"},
+		human:   "bar",
+	}
+	assert.Equal(t, "toml: foo", e.Error())
+	r, c := e.Position()
+	assert.Equal(t, 1, r)
+	assert.Equal(t, 2, c)
+	assert.Equal(t, Key{"one", "two"}, e.Key())
+	assert.Equal(t, "bar", e.String())
+}
+
+func ExampleDecodeError() {
+	doc := `name = 123__456`
+
+	s := map[string]interface{}{}
+	err := Unmarshal([]byte(doc), &s)
+
+	fmt.Println(err)
+
+	//nolint:errorlint
+	de := err.(*DecodeError)
+	fmt.Println(de.String())
+
+	row, col := de.Position()
+	fmt.Println("error occurred at row", row, "column", col)
+	// Output:
+	// toml: number must have at least one digit between underscores
+	// 1| name = 123__456
+	//  |           ~~ number must have at least one digit between underscores
+	// error occurred at row 1 column 11
+}

fast_test.go

@@ -0,0 +1,100 @@
+package toml_test
+
+import (
+	"testing"
+
+	"github.com/pelletier/go-toml/v2"
+	"github.com/stretchr/testify/require"
+)
+
+func TestFastSimple(t *testing.T) {
+	m := map[string]int64{}
+	err := toml.Unmarshal([]byte(`a = 42`), &m)
+	require.NoError(t, err)
+	require.Equal(t, map[string]int64{"a": 42}, m)
+}
+
+func TestFastSimpleString(t *testing.T) {
+	m := map[string]string{}
+	err := toml.Unmarshal([]byte(`a = "hello"`), &m)
+	require.NoError(t, err)
+	require.Equal(t, map[string]string{"a": "hello"}, m)
+}
+
+func TestFastSimpleInterface(t *testing.T) {
+	m := map[string]interface{}{}
+	err := toml.Unmarshal([]byte(`
+	a = "hello"
+	b = 42`), &m)
+	require.NoError(t, err)
+	require.Equal(t, map[string]interface{}{
+		"a": "hello",
+		"b": int64(42),
+	}, m)
+}
+
+func TestFastMultipartKeyInterface(t *testing.T) {
+	m := map[string]interface{}{}
+	err := toml.Unmarshal([]byte(`
+	a.interim = "test"
+	a.b.c = "hello"
+	b = 42`), &m)
+	require.NoError(t, err)
+	require.Equal(t, map[string]interface{}{
+		"a": map[string]interface{}{
+			"interim": "test",
+			"b": map[string]interface{}{
+				"c": "hello",
+			},
+		},
+		"b": int64(42),
+	}, m)
+}
+
+func TestFastExistingMap(t *testing.T) {
+	m := map[string]interface{}{
+		"ints": map[string]int{},
+	}
+	err := toml.Unmarshal([]byte(`
+	ints.one = 1
+	ints.two = 2
+	strings.yo = "hello"`), &m)
+	require.NoError(t, err)
+	require.Equal(t, map[string]interface{}{
+		"ints": map[string]interface{}{
+			"one": int64(1),
+			"two": int64(2),
+		},
+		"strings": map[string]interface{}{
+			"yo": "hello",
+		},
+	}, m)
+}
+
+func TestFastArrayTable(t *testing.T) {
+	b := []byte(`
+	[root]
+	[[root.nested]]
+	name = 'Bob'
+	[[root.nested]]
+	name = 'Alice'
+	`)
+
+	m := map[string]interface{}{}
+
+	err := toml.Unmarshal(b, &m)
+	require.NoError(t, err)
+
+	require.Equal(t, map[string]interface{}{
+		"root": map[string]interface{}{
+			"nested": []interface{}{
+				map[string]interface{}{
+					"name": "Bob",
+				},
+				map[string]interface{}{
+					"name": "Alice",
+				},
+			},
+		},
+	}, m)
+}

go.mod

@@ -2,4 +2,5 @@ module github.com/pelletier/go-toml/v2
 
 go 1.15
 
-require github.com/stretchr/testify v1.7.0
+// latest (v1.7.0) doesn't have the fix for time.Time
+require github.com/stretchr/testify v1.7.1-0.20210427113832-6241f9ab9942

go.sum

@@ -3,8 +3,8 @@ github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSs
 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 v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
-github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.7.1-0.20210427113832-6241f9ab9942 h1:t0lM6y/M5IiUZyvbBTcngso8SZEZICH7is9B6g/obVU=
+github.com/stretchr/testify v1.7.1-0.20210427113832-6241f9ab9942/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 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 h1:dUUwHk2QECo/6vqA44rthZ8ie2QXMNeKRTHCNY2nXvo=

internal/ast/ast.go

@@ -2,6 +2,9 @@ package ast
 
 import (
 	"fmt"
+	"unsafe"
+
+	"github.com/pelletier/go-toml/v2/internal/danger"
 )
 
 // Iterator starts uninitialized, you need to call Next() first.
@@ -14,7 +17,7 @@ import (
 // }
 type Iterator struct {
 	started bool
-	node    Node
+	node    *Node
 }
 
 // Next moves the iterator forward and returns true if points to a node, false
@@ -28,8 +31,14 @@ func (c *Iterator) Next() bool {
 	return c.node.Valid()
 }
 
+// IsLast returns true if the current node of the iterator is the last one.
+// Subsequent call to Next() will return false.
+func (c *Iterator) IsLast() bool {
+	return c.node.next == 0
+}
+
 // Node returns a copy of the node pointed at by the iterator.
-func (c *Iterator) Node() Node {
+func (c *Iterator) Node() *Node {
 	return c.node
 }
 
@@ -44,14 +53,13 @@ type Root struct {
 func (r *Root) Iterator() Iterator {
 	it := Iterator{}
 	if len(r.nodes) > 0 {
-		it.node = r.nodes[0]
+		it.node = &r.nodes[0]
 	}
 	return it
 }
 
-func (r *Root) at(idx int) Node {
-	// TODO: unsafe to point to the node directly
-	return r.nodes[idx]
+func (r *Root) at(idx Reference) *Node {
+	return &r.nodes[idx]
 }
 
 // Arrays have one child per element in the array.
@@ -63,42 +71,48 @@ func (r *Root) at(idx int) Node {
 // children []Node
 type Node struct {
 	Kind Kind
-	Data []byte // Raw bytes from the input
+	Raw  Range  // Raw bytes from the input.
+	Data []byte // Node value (could be either allocated or referencing the input).
 
-	// next idx (in the root array). 0 if last of the collection.
-	next int
-	// child idx (in the root array). 0 if no child.
-	child int
-	// pointer to the root array
-	root *Root
+	// References to other nodes, as offsets in the backing array from this
+	// node. References can go backward, so those can be negative.
+	next  int // 0 if last element
+	child int // 0 if no child
+}
+
+type Range struct {
+	Offset uint32
+	Length uint32
 }
 
 // Next returns a copy of the next node, or an invalid Node if there is no
 // next node.
-func (n Node) Next() Node {
-	if n.next <= 0 {
-		return noNode
+func (n *Node) Next() *Node {
+	if n.next == 0 {
+		return nil
 	}
-	return n.root.at(n.next)
+	ptr := unsafe.Pointer(n)
+	size := unsafe.Sizeof(Node{})
+	return (*Node)(danger.Stride(ptr, size, n.next))
 }
 
 // Child returns a copy of the first child node of this node. Other children
 // can be accessed calling Next on the first child.
 // Returns an invalid Node if there is none.
-func (n Node) Child() Node {
-	if n.child <= 0 {
-		return noNode
+func (n *Node) Child() *Node {
+	if n.child == 0 {
+		return nil
 	}
-	return n.root.at(n.child)
+	ptr := unsafe.Pointer(n)
+	size := unsafe.Sizeof(Node{})
+	return (*Node)(danger.Stride(ptr, size, n.child))
 }
 
 // Valid returns true if the node's kind is set (not to Invalid).
-func (n Node) Valid() bool {
-	return n.Kind != Invalid
+func (n *Node) Valid() bool {
+	return n != nil
 }
 
-var noNode = Node{}
-
 // Key returns the child nodes making the Key on a supported node. Panics
 // otherwise.
 // They are guaranteed to be all be of the Kind Key. A simple key would return
@@ -121,13 +135,13 @@ func (n *Node) Key() Iterator {
 // Value returns a pointer to the value node of a KeyValue.
 // Guaranteed to be non-nil.
 // Panics if not called on a KeyValue node, or if the Children are malformed.
-func (n Node) Value() Node {
-	assertKind(KeyValue, n)
+func (n *Node) Value() *Node {
+	assertKind(KeyValue, *n)
 	return n.Child()
 }
 
 // Children returns an iterator over a node's children.
-func (n Node) Children() Iterator {
+func (n *Node) Children() Iterator {
 	return Iterator{node: n.Child()}
 }
 

internal/ast/builder.go

@@ -1,12 +1,11 @@
 package ast
 
-type Reference struct {
-	idx int
-	set bool
-}
+type Reference int
+
+const InvalidReference Reference = -1
 
 func (r Reference) Valid() bool {
-	return r.set
+	return r != InvalidReference
 }
 
 type Builder struct {
@@ -18,8 +17,8 @@ func (b *Builder) Tree() *Root {
 	return &b.tree
 }
 
-func (b *Builder) NodeAt(ref Reference) Node {
-	return b.tree.at(ref.idx)
+func (b *Builder) NodeAt(ref Reference) *Node {
+	return b.tree.at(ref)
 }
 
 func (b *Builder) Reset() {
@@ -28,33 +27,25 @@ func (b *Builder) Reset() {
 }
 
 func (b *Builder) Push(n Node) Reference {
-	n.root = &b.tree
 	b.lastIdx = len(b.tree.nodes)
 	b.tree.nodes = append(b.tree.nodes, n)
-	return Reference{
-		idx: b.lastIdx,
-		set: true,
-	}
+	return Reference(b.lastIdx)
 }
 
 func (b *Builder) PushAndChain(n Node) Reference {
-	n.root = &b.tree
 	newIdx := len(b.tree.nodes)
 	b.tree.nodes = append(b.tree.nodes, n)
 	if b.lastIdx >= 0 {
-		b.tree.nodes[b.lastIdx].next = newIdx
+		b.tree.nodes[b.lastIdx].next = newIdx - b.lastIdx
 	}
 	b.lastIdx = newIdx
-	return Reference{
-		idx: b.lastIdx,
-		set: true,
-	}
+	return Reference(b.lastIdx)
 }
 
 func (b *Builder) AttachChild(parent Reference, child Reference) {
-	b.tree.nodes[parent.idx].child = child.idx
+	b.tree.nodes[parent].child = int(child) - int(parent)
 }
 
 func (b *Builder) Chain(from Reference, to Reference) {
-	b.tree.nodes[from.idx].next = to.idx
+	b.tree.nodes[from].next = int(to) - int(from)
 }

internal/danger/danger.go

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

internal/danger/danger_test.go

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

internal/imported_tests/marshal_imported_test.go

@@ -4,6 +4,7 @@ package imported_tests
 // defaults of v2.
 
 import (
+	"fmt"
 	"testing"
 	"time"
 
@@ -164,3 +165,34 @@ stringlist = []
 
 	require.Equal(t, string(expected), string(result))
 }
+
+type textMarshaler struct {
+	FirstName string
+	LastName  string
+}
+
+func (m textMarshaler) MarshalText() ([]byte, error) {
+	fullName := fmt.Sprintf("%s %s", m.FirstName, m.LastName)
+	return []byte(fullName), nil
+}
+
+func TestTextMarshaler(t *testing.T) {
+	type wrap struct {
+		TM textMarshaler
+	}
+
+	m := textMarshaler{FirstName: "Sally", LastName: "Fields"}
+
+	t.Run("at root", func(t *testing.T) {
+		_, err := toml.Marshal(m)
+		// in v2 we do not allow TextMarshaler at root
+		require.Error(t, err)
+	})
+
+	t.Run("leaf", func(t *testing.T) {
+		res, err := toml.Marshal(wrap{m})
+		require.NoError(t, err)
+
+		require.Equal(t, "TM = 'Sally Fields'\n", string(res))
+	})
+}

internal/imported_tests/unmarshal_imported_test.go

@@ -7,6 +7,7 @@ package imported_tests
 // marked as skipped until we figure out if that's something we want in v2.
 
 import (
+	"bytes"
 	"errors"
 	"fmt"
 	"reflect"
@@ -222,11 +223,13 @@ type testSubDoc struct {
 	unexported int    `toml:"shouldntBeHere"`
 }
 
-var biteMe = "Bite me"
-var float1 float32 = 12.3
-var float2 float32 = 45.6
-var float3 float32 = 78.9
-var subdoc = testSubDoc{"Second", 0}
+var (
+	biteMe         = "Bite me"
+	float1 float32 = 12.3
+	float2 float32 = 45.6
+	float3 float32 = 78.9
+	subdoc         = testSubDoc{"Second", 0}
+)
 
 var docData = testDoc{
 	Title:       "TOML Marshal Testing",
@@ -381,7 +384,7 @@ var intErrTomls = []string{
 }
 
 func TestErrUnmarshal(t *testing.T) {
-	var errTomls = []string{
+	errTomls := []string{
 		"bool = truly\ndate = 1979-05-27T07:32:00Z\nfloat = 123.4\nint = 5000\nstring = \"Bite me\"",
 		"bool = true\ndate = 1979-05-27T07:3200Z\nfloat = 123.4\nint = 5000\nstring = \"Bite me\"",
 		"bool = true\ndate = 1979-05-27T07:32:00Z\nfloat = 123a4\nint = 5000\nstring = \"Bite me\"",
@@ -467,7 +470,7 @@ func TestEmptyUnmarshalOmit(t *testing.T) {
 		Map        map[string]string       `toml:"map,omitempty"`
 	}
 
-	var emptyTestData2 = emptyMarshalTestStruct2{
+	emptyTestData2 := emptyMarshalTestStruct2{
 		Title:      "Placeholder",
 		Bool:       false,
 		Int:        0,
@@ -495,21 +498,23 @@ type pointerMarshalTestStruct struct {
 	DblPtr    *[]*[]*string
 }
 
-var pointerStr = "Hello"
-var pointerList = []string{"Hello back"}
-var pointerListPtr = []*string{&pointerStr}
-var pointerMap = map[string]string{"response": "Goodbye"}
-var pointerMapPtr = map[string]*string{"alternate": &pointerStr}
-var pointerTestData = pointerMarshalTestStruct{
-	Str:       &pointerStr,
-	List:      &pointerList,
-	ListPtr:   &pointerListPtr,
-	Map:       &pointerMap,
-	MapPtr:    &pointerMapPtr,
-	EmptyStr:  nil,
-	EmptyList: nil,
-	EmptyMap:  nil,
-}
+var (
+	pointerStr      = "Hello"
+	pointerList     = []string{"Hello back"}
+	pointerListPtr  = []*string{&pointerStr}
+	pointerMap      = map[string]string{"response": "Goodbye"}
+	pointerMapPtr   = map[string]*string{"alternate": &pointerStr}
+	pointerTestData = pointerMarshalTestStruct{
+		Str:       &pointerStr,
+		List:      &pointerList,
+		ListPtr:   &pointerListPtr,
+		Map:       &pointerMap,
+		MapPtr:    &pointerMapPtr,
+		EmptyStr:  nil,
+		EmptyList: nil,
+		EmptyMap:  nil,
+	}
+)
 
 var pointerTestToml = []byte(`List = ["Hello back"]
 ListPtr = ["Hello"]
@@ -537,15 +542,17 @@ func TestUnmarshalTypeMismatch(t *testing.T) {
 
 type nestedMarshalTestStruct struct {
 	String [][]string
-	//Struct [][]basicMarshalTestSubStruct
+	// Struct [][]basicMarshalTestSubStruct
 	StringPtr *[]*[]*string
 	// StructPtr *[]*[]*basicMarshalTestSubStruct
 }
 
-var str1 = "Three"
-var str2 = "Four"
-var strPtr = []*string{&str1, &str2}
-var strPtr2 = []*[]*string{&strPtr}
+var (
+	str1    = "Three"
+	str2    = "Four"
+	strPtr  = []*string{&str1, &str2}
+	strPtr2 = []*[]*string{&strPtr}
+)
 
 var nestedTestData = nestedMarshalTestStruct{
 	String:    [][]string{{"Five", "Six"}, {"One", "Two"}},
@@ -596,6 +603,7 @@ var nestedCustomMarshalerData = customMarshalerParent{
 var nestedCustomMarshalerToml = []byte(`friends = ["Sally Fields"]
 me = "Maiku Suteda"
 `)
+
 var nestedCustomMarshalerTomlForUnmarshal = []byte(`[friends]
 FirstName = "Sally"
 LastName = "Fields"`)
@@ -611,22 +619,12 @@ func (x *IntOrString) MarshalTOML() ([]byte, error) {
 	return []byte(s), nil
 }
 
-type textMarshaler struct {
-	FirstName string
-	LastName  string
-}
-
-func (m textMarshaler) MarshalText() ([]byte, error) {
-	fullName := fmt.Sprintf("%s %s", m.FirstName, m.LastName)
-	return []byte(fullName), nil
-}
-
 func TestUnmarshalTextMarshaler(t *testing.T) {
-	var nested = struct {
+	nested := struct {
 		Friends textMarshaler `toml:"friends"`
 	}{}
 
-	var expected = struct {
+	expected := struct {
 		Friends textMarshaler `toml:"friends"`
 	}{
 		Friends: textMarshaler{FirstName: "Sally", LastName: "Fields"},
@@ -1369,7 +1367,6 @@ func TestUnmarshalPreservesUnexportedFields(t *testing.T) {
 	t.Run("unexported field should not be set from toml", func(t *testing.T) {
 		var actual unexportedFieldPreservationTest
 		err := toml.Unmarshal([]byte(doc), &actual)
-
 		if err != nil {
 			t.Fatal("did not expect an error")
 		}
@@ -1403,7 +1400,6 @@ func TestUnmarshalPreservesUnexportedFields(t *testing.T) {
 			Nested3:    &unexportedFieldPreservationTestNested{"baz", "bax"},
 		}
 		err := toml.Unmarshal([]byte(doc), &actual)
-
 		if err != nil {
 			t.Fatal("did not expect an error")
 		}
@@ -1429,211 +1425,206 @@ func TestUnmarshalPreservesUnexportedFields(t *testing.T) {
 	})
 }
 
-//
-//func TestUnmarshalLocalDate(t *testing.T) {
-//	t.Run("ToLocalDate", func(t *testing.T) {
-//		type dateStruct struct {
-//			Date toml.LocalDate
-//		}
-//
-//		doc := `date = 1979-05-27`
-//
-//		var obj dateStruct
-//
-//		err := toml.Unmarshal([]byte(doc), &obj)
-//
-//		if err != nil {
-//			t.Fatal(err)
-//		}
-//
-//		if obj.Date.Year != 1979 {
-//			t.Errorf("expected year 1979, got %d", obj.Date.Year)
-//		}
-//		if obj.Date.Month != 5 {
-//			t.Errorf("expected month 5, got %d", obj.Date.Month)
-//		}
-//		if obj.Date.Day != 27 {
-//			t.Errorf("expected day 27, got %d", obj.Date.Day)
-//		}
-//	})
-//
-//	t.Run("ToLocalDate", func(t *testing.T) {
-//		type dateStruct struct {
-//			Date time.Time
-//		}
-//
-//		doc := `date = 1979-05-27`
-//
-//		var obj dateStruct
-//
-//		err := toml.Unmarshal([]byte(doc), &obj)
-//
-//		if err != nil {
-//			t.Fatal(err)
-//		}
-//
-//		if obj.Date.Year() != 1979 {
-//			t.Errorf("expected year 1979, got %d", obj.Date.Year())
-//		}
-//		if obj.Date.Month() != 5 {
-//			t.Errorf("expected month 5, got %d", obj.Date.Month())
-//		}
-//		if obj.Date.Day() != 27 {
-//			t.Errorf("expected day 27, got %d", obj.Date.Day())
-//		}
-//	})
-//}
-//
-//func TestUnmarshalLocalDateTime(t *testing.T) {
-//	examples := []struct {
-//		name string
-//		in   string
-//		out  toml.LocalDateTime
-//	}{
-//		{
-//			name: "normal",
-//			in:   "1979-05-27T07:32:00",
-//			out: toml.LocalDateTime{
-//				Date: toml.LocalDate{
-//					Year:  1979,
-//					Month: 5,
-//					Day:   27,
-//				},
-//				Time: toml.LocalTime{
-//					Hour:       7,
-//					Minute:     32,
-//					Second:     0,
-//					Nanosecond: 0,
-//				},
-//			}},
-//		{
-//			name: "with nanoseconds",
-//			in:   "1979-05-27T00:32:00.999999",
-//			out: toml.LocalDateTime{
-//				Date: toml.LocalDate{
-//					Year:  1979,
-//					Month: 5,
-//					Day:   27,
-//				},
-//				Time: toml.LocalTime{
-//					Hour:       0,
-//					Minute:     32,
-//					Second:     0,
-//					Nanosecond: 999999000,
-//				},
-//			},
-//		},
-//	}
-//
-//	for i, example := range examples {
-//		doc := fmt.Sprintf(`date = %s`, example.in)
-//
-//		t.Run(fmt.Sprintf("ToLocalDateTime_%d_%s", i, example.name), func(t *testing.T) {
-//			type dateStruct struct {
-//				Date toml.LocalDateTime
-//			}
-//
-//			var obj dateStruct
-//
-//			err := toml.Unmarshal([]byte(doc), &obj)
-//
-//			if err != nil {
-//				t.Fatal(err)
-//			}
-//
-//			if obj.Date != example.out {
-//				t.Errorf("expected '%s', got '%s'", example.out, obj.Date)
-//			}
-//		})
-//
-//		t.Run(fmt.Sprintf("ToTime_%d_%s", i, example.name), func(t *testing.T) {
-//			type dateStruct struct {
-//				Date time.Time
-//			}
-//
-//			var obj dateStruct
-//
-//			err := toml.Unmarshal([]byte(doc), &obj)
-//
-//			if err != nil {
-//				t.Fatal(err)
-//			}
-//
-//			if obj.Date.Year() != example.out.Date.Year {
-//				t.Errorf("expected year %d, got %d", example.out.Date.Year, obj.Date.Year())
-//			}
-//			if obj.Date.Month() != example.out.Date.Month {
-//				t.Errorf("expected month %d, got %d", example.out.Date.Month, obj.Date.Month())
-//			}
-//			if obj.Date.Day() != example.out.Date.Day {
-//				t.Errorf("expected day %d, got %d", example.out.Date.Day, obj.Date.Day())
-//			}
-//			if obj.Date.Hour() != example.out.Time.Hour {
-//				t.Errorf("expected hour %d, got %d", example.out.Time.Hour, obj.Date.Hour())
-//			}
-//			if obj.Date.Minute() != example.out.Time.Minute {
-//				t.Errorf("expected minute %d, got %d", example.out.Time.Minute, obj.Date.Minute())
-//			}
-//			if obj.Date.Second() != example.out.Time.Second {
-//				t.Errorf("expected second %d, got %d", example.out.Time.Second, obj.Date.Second())
-//			}
-//			if obj.Date.Nanosecond() != example.out.Time.Nanosecond {
-//				t.Errorf("expected nanoseconds %d, got %d", example.out.Time.Nanosecond, obj.Date.Nanosecond())
-//			}
-//		})
-//	}
-//}
-//
-//func TestUnmarshalLocalTime(t *testing.T) {
-//	examples := []struct {
-//		name string
-//		in   string
-//		out  toml.LocalTime
-//	}{
-//		{
-//			name: "normal",
-//			in:   "07:32:00",
-//			out: toml.LocalTime{
-//				Hour:       7,
-//				Minute:     32,
-//				Second:     0,
-//				Nanosecond: 0,
-//			},
-//		},
-//		{
-//			name: "with nanoseconds",
-//			in:   "00:32:00.999999",
-//			out: toml.LocalTime{
-//				Hour:       0,
-//				Minute:     32,
-//				Second:     0,
-//				Nanosecond: 999999000,
-//			},
-//		},
-//	}
-//
-//	for i, example := range examples {
-//		doc := fmt.Sprintf(`Time = %s`, example.in)
-//
-//		t.Run(fmt.Sprintf("ToLocalTime_%d_%s", i, example.name), func(t *testing.T) {
-//			type dateStruct struct {
-//				Time toml.LocalTime
-//			}
-//
-//			var obj dateStruct
-//
-//			err := toml.Unmarshal([]byte(doc), &obj)
-//
-//			if err != nil {
-//				t.Fatal(err)
-//			}
-//
-//			if obj.Time != example.out {
-//				t.Errorf("expected '%s', got '%s'", example.out, obj.Time)
-//			}
-//		})
-//	}
-//}
+func TestUnmarshalLocalDate(t *testing.T) {
+	t.Run("ToLocalDate", func(t *testing.T) {
+		type dateStruct struct {
+			Date toml.LocalDate
+		}
+
+		doc := `date = 1979-05-27`
+
+		var obj dateStruct
+
+		err := toml.Unmarshal([]byte(doc), &obj)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if obj.Date.Year != 1979 {
+			t.Errorf("expected year 1979, got %d", obj.Date.Year)
+		}
+		if obj.Date.Month != 5 {
+			t.Errorf("expected month 5, got %d", obj.Date.Month)
+		}
+		if obj.Date.Day != 27 {
+			t.Errorf("expected day 27, got %d", obj.Date.Day)
+		}
+	})
+
+	t.Run("ToLocalDate", func(t *testing.T) {
+		type dateStruct struct {
+			Date time.Time
+		}
+
+		doc := `date = 1979-05-27`
+
+		var obj dateStruct
+
+		err := toml.Unmarshal([]byte(doc), &obj)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if obj.Date.Year() != 1979 {
+			t.Errorf("expected year 1979, got %d", obj.Date.Year())
+		}
+		if obj.Date.Month() != 5 {
+			t.Errorf("expected month 5, got %d", obj.Date.Month())
+		}
+		if obj.Date.Day() != 27 {
+			t.Errorf("expected day 27, got %d", obj.Date.Day())
+		}
+	})
+}
+
+func TestUnmarshalLocalDateTime(t *testing.T) {
+	examples := []struct {
+		name string
+		in   string
+		out  toml.LocalDateTime
+	}{
+		{
+			name: "normal",
+			in:   "1979-05-27T07:32:00",
+			out: toml.LocalDateTime{
+				Date: toml.LocalDate{
+					Year:  1979,
+					Month: 5,
+					Day:   27,
+				},
+				Time: toml.LocalTime{
+					Hour:       7,
+					Minute:     32,
+					Second:     0,
+					Nanosecond: 0,
+				},
+			},
+		},
+		{
+			name: "with nanoseconds",
+			in:   "1979-05-27T00:32:00.999999",
+			out: toml.LocalDateTime{
+				Date: toml.LocalDate{
+					Year:  1979,
+					Month: 5,
+					Day:   27,
+				},
+				Time: toml.LocalTime{
+					Hour:       0,
+					Minute:     32,
+					Second:     0,
+					Nanosecond: 999999000,
+				},
+			},
+		},
+	}
+
+	for i, example := range examples {
+		doc := fmt.Sprintf(`date = %s`, example.in)
+
+		t.Run(fmt.Sprintf("ToLocalDateTime_%d_%s", i, example.name), func(t *testing.T) {
+			type dateStruct struct {
+				Date toml.LocalDateTime
+			}
+
+			var obj dateStruct
+
+			err := toml.Unmarshal([]byte(doc), &obj)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if obj.Date != example.out {
+				t.Errorf("expected '%s', got '%s'", example.out, obj.Date)
+			}
+		})
+
+		t.Run(fmt.Sprintf("ToTime_%d_%s", i, example.name), func(t *testing.T) {
+			type dateStruct struct {
+				Date time.Time
+			}
+
+			var obj dateStruct
+
+			err := toml.Unmarshal([]byte(doc), &obj)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if obj.Date.Year() != example.out.Date.Year {
+				t.Errorf("expected year %d, got %d", example.out.Date.Year, obj.Date.Year())
+			}
+			if obj.Date.Month() != example.out.Date.Month {
+				t.Errorf("expected month %d, got %d", example.out.Date.Month, obj.Date.Month())
+			}
+			if obj.Date.Day() != example.out.Date.Day {
+				t.Errorf("expected day %d, got %d", example.out.Date.Day, obj.Date.Day())
+			}
+			if obj.Date.Hour() != example.out.Time.Hour {
+				t.Errorf("expected hour %d, got %d", example.out.Time.Hour, obj.Date.Hour())
+			}
+			if obj.Date.Minute() != example.out.Time.Minute {
+				t.Errorf("expected minute %d, got %d", example.out.Time.Minute, obj.Date.Minute())
+			}
+			if obj.Date.Second() != example.out.Time.Second {
+				t.Errorf("expected second %d, got %d", example.out.Time.Second, obj.Date.Second())
+			}
+			if obj.Date.Nanosecond() != example.out.Time.Nanosecond {
+				t.Errorf("expected nanoseconds %d, got %d", example.out.Time.Nanosecond, obj.Date.Nanosecond())
+			}
+		})
+	}
+}
+
+func TestUnmarshalLocalTime(t *testing.T) {
+	examples := []struct {
+		name string
+		in   string
+		out  toml.LocalTime
+	}{
+		{
+			name: "normal",
+			in:   "07:32:00",
+			out: toml.LocalTime{
+				Hour:       7,
+				Minute:     32,
+				Second:     0,
+				Nanosecond: 0,
+			},
+		},
+		{
+			name: "with nanoseconds",
+			in:   "00:32:00.999999",
+			out: toml.LocalTime{
+				Hour:       0,
+				Minute:     32,
+				Second:     0,
+				Nanosecond: 999999000,
+			},
+		},
+	}
+
+	for i, example := range examples {
+		doc := fmt.Sprintf(`Time = %s`, example.in)
+
+		t.Run(fmt.Sprintf("ToLocalTime_%d_%s", i, example.name), func(t *testing.T) {
+			type dateStruct struct {
+				Time toml.LocalTime
+			}
+
+			var obj dateStruct
+
+			err := toml.Unmarshal([]byte(doc), &obj)
+			if err != nil {
+				t.Fatal(err)
+			}
+
+			if obj.Time != example.out {
+				t.Errorf("expected '%s', got '%s'", example.out, obj.Time)
+			}
+		})
+	}
+}
 
 // test case for issue #339
 func TestUnmarshalSameInnerField(t *testing.T) {
@@ -1955,66 +1946,80 @@ String2="2"`
 	assert.Error(t, err)
 }
 
+func decoder(doc string) *toml.Decoder {
+	return toml.NewDecoder(bytes.NewReader([]byte(doc)))
+}
+
+func strictDecoder(doc string) *toml.Decoder {
+	d := decoder(doc)
+	d.SetStrict(true)
+	return d
+}
+
 func TestDecoderStrict(t *testing.T) {
-	t.Skip()
-	//	input := `
-	//[decoded]
-	//  key = ""
-	//
-	//[undecoded]
-	//  key = ""
-	//
-	//  [undecoded.inner]
-	//	key = ""
-	//
-	//  [[undecoded.array]]
-	//	key = ""
-	//
-	//  [[undecoded.array]]
-	//	key = ""
-	//
-	//`
-	//	var doc struct {
-	//		Decoded struct {
-	//			Key string
-	//		}
-	//	}
-	//
-	//	expected := `undecoded keys: ["undecoded.array.0.key" "undecoded.array.1.key" "undecoded.inner.key" "undecoded.key"]`
-	//
-	//	err := NewDecoder(bytes.NewReader([]byte(input))).Strict(true).Decode(&doc)
-	//	if err == nil {
-	//		t.Error("expected error, got none")
-	//	} else if err.Error() != expected {
-	//		t.Errorf("expect err: %s, got: %s", expected, err.Error())
-	//	}
-	//
-	//	if err := NewDecoder(bytes.NewReader([]byte(input))).Decode(&doc); err != nil {
-	//		t.Errorf("unexpected err: %s", err)
-	//	}
-	//
-	//	var m map[string]interface{}
-	//	if err := NewDecoder(bytes.NewReader([]byte(input))).Decode(&m); err != nil {
-	//		t.Errorf("unexpected err: %s", err)
-	//	}
+	input := `
+	[decoded]
+	 key = ""
+	
+	[undecoded]
+	 key = ""
+	
+	 [undecoded.inner]
+		key = ""
+	
+	 [[undecoded.array]]
+		key = ""
+	
+	 [[undecoded.array]]
+		key = ""
+	
+	`
+	var doc struct {
+		Decoded struct {
+			Key string
+		}
+	}
+
+	err := strictDecoder(input).Decode(&doc)
+	require.Error(t, err)
+	require.IsType(t, &toml.StrictMissingError{}, err)
+	se := err.(*toml.StrictMissingError)
+
+	keys := []toml.Key{}
+
+	for _, e := range se.Errors {
+		keys = append(keys, e.Key())
+	}
+
+	expectedKeys := []toml.Key{
+		{"undecoded"},
+		{"undecoded", "inner"},
+		{"undecoded", "array"},
+		{"undecoded", "array"},
+	}
+
+	require.Equal(t, expectedKeys, keys)
+
+	err = decoder(input).Decode(&doc)
+	require.NoError(t, err)
+
+	var m map[string]interface{}
+	err = decoder(input).Decode(&m)
 }
 
 func TestDecoderStrictValid(t *testing.T) {
-	t.Skip()
-	//	input := `
-	//[decoded]
-	//  key = ""
-	//`
-	//	var doc struct {
-	//		Decoded struct {
-	//			Key string
-	//		}
-	//	}
-	//
-	//	err := NewDecoder(bytes.NewReader([]byte(input))).Strict(true).Decode(&doc)
-	//	if err != nil {
-	//		t.Fatal("unexpected error:", err)
-	//	}
+	input := `
+	[decoded]
+	 key = ""
+	`
+	var doc struct {
+		Decoded struct {
+			Key string
+		}
+	}
+
+	err := strictDecoder(input).Decode(&doc)
+	require.NoError(t, err)
 }
 
 type docUnmarshalTOML struct {
@@ -2279,8 +2284,7 @@ func (d *durationString) UnmarshalTOML(v interface{}) error {
 	return nil
 }
 
-type config437Error struct {
-}
+type config437Error struct{}
 
 func (e *config437Error) UnmarshalTOML(v interface{}) error {
 	return errors.New("expected")

internal/tracker/key.go

@@ -0,0 +1,50 @@
+package tracker
+
+import (
+	"github.com/pelletier/go-toml/v2/internal/ast"
+)
+
+// KeyTracker is a tracker that keeps track of the current Key as the AST is
+// walked.
+type KeyTracker struct {
+	k []string
+}
+
+// UpdateTable sets the state of the tracker with the AST table node.
+func (t *KeyTracker) UpdateTable(node *ast.Node) {
+	t.reset()
+	t.Push(node)
+}
+
+// UpdateArrayTable sets the state of the tracker with the AST array table node.
+func (t *KeyTracker) UpdateArrayTable(node *ast.Node) {
+	t.reset()
+	t.Push(node)
+}
+
+// Push the given key on the stack.
+func (t *KeyTracker) Push(node *ast.Node) {
+	it := node.Key()
+	for it.Next() {
+		t.k = append(t.k, string(it.Node().Data))
+	}
+}
+
+// Pop key from stack.
+func (t *KeyTracker) Pop(node *ast.Node) {
+	it := node.Key()
+	for it.Next() {
+		t.k = t.k[:len(t.k)-1]
+	}
+}
+
+// Key returns the current key
+func (t *KeyTracker) Key() []string {
+	k := make([]string, len(t.k))
+	copy(k, t.k)
+	return k
+}
+
+func (t *KeyTracker) reset() {
+	t.k = t.k[:0]
+}

internal/tracker/seen.go

@@ -0,0 +1,257 @@
+package tracker
+
+import (
+	"bytes"
+	"fmt"
+
+	"github.com/pelletier/go-toml/v2/internal/ast"
+)
+
+type keyKind uint8
+
+const (
+	invalidKind keyKind = iota
+	valueKind
+	tableKind
+	arrayTableKind
+)
+
+func (k keyKind) String() string {
+	switch k {
+	case invalidKind:
+		return "invalid"
+	case valueKind:
+		return "value"
+	case tableKind:
+		return "table"
+	case arrayTableKind:
+		return "array table"
+	}
+	panic("missing keyKind string mapping")
+}
+
+// SeenTracker tracks which keys have been seen with which TOML type to flag
+// duplicates and mismatches according to the spec.
+//
+// Each node in the visited tree is represented by an entry. Each entry has an
+// identifier, which is provided by a counter. Entries are stored in the array
+// entries. As new nodes are discovered (referenced for the first time in the
+// TOML document), entries are created and appended to the array. An entry
+// points to its parent using its id.
+//
+// To find whether a given key (sequence of []byte) has already been visited,
+// the entries are linearly searched, looking for one with the right name and
+// parent id.
+//
+// Given that all keys appear in the document after their parent, it is
+// guaranteed that all descendants of a node are stored after the node, this
+// speeds up the search process.
+//
+// When encountering [[array tables]], the descendants of that node are removed
+// to allow that branch of the tree to be "rediscovered". To maintain the
+// invariant above, the deletion process needs to keep the order of entries.
+// This results in more copies in that case.
+type SeenTracker struct {
+	entries    []entry
+	currentIdx int
+	nextID     int
+}
+
+type entry struct {
+	id       int
+	parent   int
+	name     []byte
+	kind     keyKind
+	explicit bool
+}
+
+// Remove all descendent of node at position idx.
+func (s *SeenTracker) clear(idx int) {
+	p := s.entries[idx].id
+	rest := clear(p, s.entries[idx+1:])
+	s.entries = s.entries[:idx+1+len(rest)]
+}
+
+func clear(parentID int, entries []entry) []entry {
+	for i := 0; i < len(entries); {
+		if entries[i].parent == parentID {
+			id := entries[i].id
+			copy(entries[i:], entries[i+1:])
+			entries = entries[:len(entries)-1]
+			rest := clear(id, entries[i:])
+			entries = entries[:i+len(rest)]
+		} else {
+			i++
+		}
+	}
+	return entries
+}
+
+func (s *SeenTracker) create(parentIdx int, name []byte, kind keyKind, explicit bool) int {
+	parentID := s.id(parentIdx)
+
+	idx := len(s.entries)
+	s.entries = append(s.entries, entry{
+		id:       s.nextID,
+		parent:   parentID,
+		name:     name,
+		kind:     kind,
+		explicit: explicit,
+	})
+	s.nextID++
+	return idx
+}
+
+// CheckExpression takes a top-level node and checks that it does not contain keys
+// that have been seen in previous calls, and validates that types are consistent.
+func (s *SeenTracker) CheckExpression(node *ast.Node) error {
+	if s.entries == nil {
+		// s.entries = make([]entry, 0, 8)
+		// Skip ID = 0 to remove the confusion between nodes whose parent has
+		// id 0 and root nodes (parent id is 0 because it's the zero value).
+		s.nextID = 1
+		// Start unscoped, so idx is negative.
+		s.currentIdx = -1
+	}
+	switch node.Kind {
+	case ast.KeyValue:
+		return s.checkKeyValue(node)
+	case ast.Table:
+		return s.checkTable(node)
+	case ast.ArrayTable:
+		return s.checkArrayTable(node)
+	default:
+		panic(fmt.Errorf("this should not be a top level node type: %s", node.Kind))
+	}
+}
+
+func (s *SeenTracker) checkTable(node *ast.Node) error {
+	it := node.Key()
+
+	parentIdx := -1
+
+	// This code is duplicated in checkArrayTable. This is because factoring
+	// it in a function requires to copy the iterator, or allocate it to the
+	// heap, which is not cheap.
+	for it.Next() {
+		if it.IsLast() {
+			break
+		}
+
+		k := it.Node().Data
+
+		idx := s.find(parentIdx, k)
+
+		if idx < 0 {
+			idx = s.create(parentIdx, k, tableKind, false)
+		}
+		parentIdx = idx
+	}
+
+	k := it.Node().Data
+	idx := s.find(parentIdx, k)
+
+	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)
+		}
+		if s.entries[idx].explicit {
+			return fmt.Errorf("toml: table %s already exists", string(k))
+		}
+		s.entries[idx].explicit = true
+	} else {
+		idx = s.create(parentIdx, k, tableKind, true)
+	}
+
+	s.currentIdx = idx
+
+	return nil
+}
+
+func (s *SeenTracker) checkArrayTable(node *ast.Node) error {
+	it := node.Key()
+
+	parentIdx := -1
+
+	for it.Next() {
+		if it.IsLast() {
+			break
+		}
+
+		k := it.Node().Data
+
+		idx := s.find(parentIdx, k)
+
+		if idx < 0 {
+			idx = s.create(parentIdx, k, tableKind, false)
+		}
+		parentIdx = idx
+	}
+
+	k := it.Node().Data
+	idx := s.find(parentIdx, k)
+
+	if idx >= 0 {
+		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))
+		}
+		s.clear(idx)
+	} else {
+		idx = s.create(parentIdx, k, arrayTableKind, true)
+	}
+
+	s.currentIdx = idx
+
+	return nil
+}
+
+func (s *SeenTracker) checkKeyValue(node *ast.Node) error {
+	it := node.Key()
+
+	parentIdx := s.currentIdx
+
+	for it.Next() {
+		k := it.Node().Data
+
+		idx := s.find(parentIdx, k)
+
+		if idx >= 0 {
+			if s.entries[idx].kind != tableKind {
+				return fmt.Errorf("toml: expected %s to be a table, not a %s", string(k), s.entries[idx].kind)
+			}
+		} else {
+			idx = s.create(parentIdx, k, tableKind, false)
+		}
+		parentIdx = idx
+	}
+
+	kind := valueKind
+
+	if node.Value().Kind == ast.InlineTable {
+		kind = tableKind
+	}
+	s.entries[parentIdx].kind = kind
+
+	return nil
+}
+
+func (s *SeenTracker) id(idx int) int {
+	if idx >= 0 {
+		return s.entries[idx].id
+	}
+	return 0
+}
+
+func (s *SeenTracker) find(parentIdx int, k []byte) int {
+	parentID := s.id(parentIdx)
+
+	for i := parentIdx + 1; i < len(s.entries); i++ {
+		if s.entries[i].parent == parentID && bytes.Equal(s.entries[i].name, k) {
+			return i
+		}
+	}
+
+	return -1
+}

internal/tracker/tracker.go

@@ -1,200 +1 @@
 package tracker
-
-import (
-	"fmt"
-
-	"github.com/pelletier/go-toml/v2/internal/ast"
-)
-
-type keyKind uint8
-
-const (
-	invalidKind keyKind = iota
-	valueKind
-	tableKind
-	arrayTableKind
-)
-
-func (k keyKind) String() string {
-	switch k {
-	case invalidKind:
-		return "invalid"
-	case valueKind:
-		return "value"
-	case tableKind:
-		return "table"
-	case arrayTableKind:
-		return "array table"
-	}
-	panic("missing keyKind string mapping")
-}
-
-// Tracks which keys have been seen with which TOML type to flag duplicates
-// and mismatches according to the spec.
-type Seen struct {
-	root    *info
-	current *info
-}
-
-type info struct {
-	parent   *info
-	kind     keyKind
-	children map[string]*info
-	explicit bool
-}
-
-func (i *info) Clear() {
-	i.children = nil
-}
-
-func (i *info) Has(k string) (*info, bool) {
-	c, ok := i.children[k]
-	return c, ok
-}
-
-func (i *info) SetKind(kind keyKind) {
-	i.kind = kind
-}
-
-func (i *info) CreateTable(k string, explicit bool) *info {
-	return i.createChild(k, tableKind, explicit)
-}
-
-func (i *info) CreateArrayTable(k string, explicit bool) *info {
-	return i.createChild(k, arrayTableKind, explicit)
-}
-
-func (i *info) createChild(k string, kind keyKind, explicit bool) *info {
-	if i.children == nil {
-		i.children = make(map[string]*info, 1)
-	}
-
-	x := &info{
-		parent:   i,
-		kind:     kind,
-		explicit: explicit,
-	}
-	i.children[k] = x
-	return x
-}
-
-// CheckExpression takes a top-level node and checks that it does not contain keys
-// that have been seen in previous calls, and validates that types are consistent.
-func (s *Seen) CheckExpression(node ast.Node) error {
-	if s.root == nil {
-		s.root = &info{
-			kind: tableKind,
-		}
-		s.current = s.root
-	}
-	switch node.Kind {
-	case ast.KeyValue:
-		return s.checkKeyValue(s.current, node)
-	case ast.Table:
-		return s.checkTable(node)
-	case ast.ArrayTable:
-		return s.checkArrayTable(node)
-	default:
-		panic(fmt.Errorf("this should not be a top level node type: %s", node.Kind))
-	}
-
-}
-func (s *Seen) checkTable(node ast.Node) error {
-	s.current = s.root
-
-	it := node.Key()
-	// handle the first parts of the key, excluding the last one
-	for it.Next() {
-		if !it.Node().Next().Valid() {
-			break
-		}
-
-		k := string(it.Node().Data)
-		child, found := s.current.Has(k)
-		if !found {
-			child = s.current.CreateTable(k, false)
-		}
-		s.current = child
-	}
-
-	// handle the last part of the key
-	k := string(it.Node().Data)
-
-	i, found := s.current.Has(k)
-	if found {
-		if i.kind != tableKind {
-			return fmt.Errorf("key %s should be a table", k)
-		}
-		if i.explicit {
-			return fmt.Errorf("table %s already exists", k)
-		}
-		i.explicit = true
-		s.current = i
-	} else {
-		s.current = s.current.CreateTable(k, true)
-	}
-
-	return nil
-}
-
-func (s *Seen) checkArrayTable(node ast.Node) error {
-	s.current = s.root
-
-	it := node.Key()
-
-	// handle the first parts of the key, excluding the last one
-	for it.Next() {
-		if !it.Node().Next().Valid() {
-			break
-		}
-
-		k := string(it.Node().Data)
-		child, found := s.current.Has(k)
-		if !found {
-			child = s.current.CreateTable(k, false)
-		}
-		s.current = child
-	}
-
-	// handle the last part of the key
-	k := string(it.Node().Data)
-
-	info, found := s.current.Has(k)
-	if found {
-		if info.kind != arrayTableKind {
-			return fmt.Errorf("key %s already exists but is not an array table", k)
-		}
-		info.Clear()
-	} else {
-		info = s.current.CreateArrayTable(k, true)
-	}
-
-	s.current = info
-	return nil
-}
-
-func (s *Seen) checkKeyValue(context *info, node ast.Node) error {
-	it := node.Key()
-
-	// handle the first parts of the key, excluding the last one
-	for it.Next() {
-		k := string(it.Node().Data)
-		child, found := context.Has(k)
-		if found {
-			if child.kind != tableKind {
-				return fmt.Errorf("expected %s to be a table, not a %s", k, child.kind)
-			}
-		} else {
-			child = context.CreateTable(k, false)
-		}
-		context = child
-	}
-
-	if node.Value().Kind == ast.InlineTable {
-		context.SetKind(tableKind)
-	} else {
-		context.SetKind(valueKind)
-	}
-
-	return nil
-}

internal/unsafe/unsafe.go

@@ -1,35 +0,0 @@
-package unsafe
-
-import (
-	"fmt"
-	"reflect"
-	"unsafe"
-)
-
-const maxInt = uintptr(int(^uint(0) >> 1))
-
-func SubsliceOffset(data []byte, subslice []byte) int {
-	datap := (*reflect.SliceHeader)(unsafe.Pointer(&data))
-	hlp := (*reflect.SliceHeader)(unsafe.Pointer(&subslice))
-
-	if hlp.Data < datap.Data {
-		panic(fmt.Errorf("subslice address (%d) is before data address (%d)", hlp.Data, datap.Data))
-	}
-	offset := hlp.Data - datap.Data
-
-	if offset > maxInt {
-		panic(fmt.Errorf("slice offset larger than int (%d)", offset))
-	}
-
-	intoffset := int(offset)
-
-	if intoffset > datap.Len {
-		panic(fmt.Errorf("slice offset (%d) is farther than data length (%d)", intoffset, datap.Len))
-	}
-
-	if intoffset+hlp.Len > datap.Len {
-		panic(fmt.Errorf("slice ends (%d+%d) is farther than data length (%d)", intoffset, hlp.Len, datap.Len))
-	}
-
-	return intoffset
-}

internal/unsafe/unsafe_test.go

@@ -1,79 +0,0 @@
-package unsafe_test
-
-import (
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	"github.com/pelletier/go-toml/v2/internal/unsafe"
-)
-
-func TestUnsafeSubsliceOffsetValid(t *testing.T) {
-	examples := []struct {
-		desc   string
-		test   func() ([]byte, []byte)
-		offset int
-	}{
-		{
-			desc: "simple",
-			test: func() ([]byte, []byte) {
-				data := []byte("hello")
-				return data, data[1:]
-			},
-			offset: 1,
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			d, s := e.test()
-			offset := unsafe.SubsliceOffset(d, s)
-			assert.Equal(t, e.offset, offset)
-		})
-	}
-}
-
-func TestUnsafeSubsliceOffsetInvalid(t *testing.T) {
-	examples := []struct {
-		desc string
-		test func() ([]byte, []byte)
-	}{
-		{
-			desc: "unrelated arrays",
-			test: func() ([]byte, []byte) {
-				return []byte("one"), []byte("two")
-			},
-		},
-		{
-			desc: "slice starts before data",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[5:], full[1:]
-			},
-		},
-		{
-			desc: "slice starts after data",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[:3], full[5:]
-			},
-		},
-		{
-			desc: "slice ends after data",
-			test: func() ([]byte, []byte) {
-				full := []byte("hello world")
-				return full[:5], full[3:8]
-			},
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			d, s := e.test()
-			require.Panics(t, func() {
-				unsafe.SubsliceOffset(d, s)
-			})
-		})
-	}
-}

localtime.go

@@ -23,6 +23,7 @@
 //
 // Because they lack location information, these types do not represent unique
 // moments or intervals of time. Use time.Time for that purpose.
+
 package toml
 
 import (
@@ -44,6 +45,7 @@ type LocalDate struct {
 func LocalDateOf(t time.Time) LocalDate {
 	var d LocalDate
 	d.Year, d.Month, d.Day = t.Date()
+
 	return d
 }
 
@@ -53,6 +55,7 @@ func ParseLocalDate(s string) (LocalDate, error) {
 	if err != nil {
 		return LocalDate{}, err
 	}
+
 	return LocalDateOf(t), nil
 }
 
@@ -92,23 +95,28 @@ func (d LocalDate) DaysSince(s LocalDate) (days int) {
 	// We convert to Unix time so we do not have to worry about leap seconds:
 	// Unix time increases by exactly 86400 seconds per day.
 	deltaUnix := d.In(time.UTC).Unix() - s.In(time.UTC).Unix()
-	return int(deltaUnix / 86400)
+
+	const secondsInADay = 86400
+
+	return int(deltaUnix / secondsInADay)
 }
 
-// Before reports whether d1 occurs before d2.
-func (d1 LocalDate) Before(d2 LocalDate) bool {
-	if d1.Year != d2.Year {
-		return d1.Year < d2.Year
+// Before reports whether d1 occurs before future date.
+func (d LocalDate) Before(future LocalDate) bool {
+	if d.Year != future.Year {
+		return d.Year < future.Year
 	}
-	if d1.Month != d2.Month {
-		return d1.Month < d2.Month
+
+	if d.Month != future.Month {
+		return d.Month < future.Month
 	}
-	return d1.Day < d2.Day
+
+	return d.Day < future.Day
 }
 
-// After reports whether d1 occurs after d2.
-func (d1 LocalDate) After(d2 LocalDate) bool {
-	return d2.Before(d1)
+// After reports whether d1 occurs after past date.
+func (d LocalDate) After(past LocalDate) bool {
+	return past.Before(d)
 }
 
 // MarshalText implements the encoding.TextMarshaler interface.
@@ -122,6 +130,7 @@ func (d LocalDate) MarshalText() ([]byte, error) {
 func (d *LocalDate) UnmarshalText(data []byte) error {
 	var err error
 	*d, err = ParseLocalDate(string(data))
+
 	return err
 }
 
@@ -145,6 +154,7 @@ func LocalTimeOf(t time.Time) LocalTime {
 	var tm LocalTime
 	tm.Hour, tm.Minute, tm.Second = t.Clock()
 	tm.Nanosecond = t.Nanosecond()
+
 	return tm
 }
 
@@ -158,6 +168,7 @@ func ParseLocalTime(s string) (LocalTime, error) {
 	if err != nil {
 		return LocalTime{}, err
 	}
+
 	return LocalTimeOf(t), nil
 }
 
@@ -169,6 +180,7 @@ func (t LocalTime) String() string {
 	if t.Nanosecond == 0 {
 		return s
 	}
+
 	return s + fmt.Sprintf(".%09d", t.Nanosecond)
 }
 
@@ -176,6 +188,7 @@ func (t LocalTime) String() string {
 func (t LocalTime) IsValid() bool {
 	// Construct a non-zero time.
 	tm := time.Date(2, 2, 2, t.Hour, t.Minute, t.Second, t.Nanosecond, time.UTC)
+
 	return LocalTimeOf(tm) == t
 }
 
@@ -190,6 +203,7 @@ func (t LocalTime) MarshalText() ([]byte, error) {
 func (t *LocalTime) UnmarshalText(data []byte) error {
 	var err error
 	*t, err = ParseLocalTime(string(data))
+
 	return err
 }
 
@@ -226,6 +240,7 @@ func ParseLocalDateTime(s string) (LocalDateTime, error) {
 			return LocalDateTime{}, err
 		}
 	}
+
 	return LocalDateTimeOf(t), nil
 }
 
@@ -253,17 +268,20 @@ func (dt LocalDateTime) IsValid() bool {
 //
 // In panics if loc is nil.
 func (dt LocalDateTime) In(loc *time.Location) time.Time {
-	return time.Date(dt.Date.Year, dt.Date.Month, dt.Date.Day, dt.Time.Hour, dt.Time.Minute, dt.Time.Second, dt.Time.Nanosecond, loc)
+	return time.Date(
+		dt.Date.Year, dt.Date.Month, dt.Date.Day,
+		dt.Time.Hour, dt.Time.Minute, dt.Time.Second, dt.Time.Nanosecond, loc,
+	)
 }
 
-// Before reports whether dt1 occurs before dt2.
-func (dt1 LocalDateTime) Before(dt2 LocalDateTime) bool {
-	return dt1.In(time.UTC).Before(dt2.In(time.UTC))
+// Before reports whether dt occurs before future.
+func (dt LocalDateTime) Before(future LocalDateTime) bool {
+	return dt.In(time.UTC).Before(future.In(time.UTC))
 }
 
-// After reports whether dt1 occurs after dt2.
-func (dt1 LocalDateTime) After(dt2 LocalDateTime) bool {
-	return dt2.Before(dt1)
+// After reports whether dt occurs after past.
+func (dt LocalDateTime) After(past LocalDateTime) bool {
+	return past.Before(dt)
 }
 
 // MarshalText implements the encoding.TextMarshaler interface.
@@ -273,9 +291,10 @@ func (dt LocalDateTime) MarshalText() ([]byte, error) {
 }
 
 // UnmarshalText implements the encoding.TextUnmarshaler interface.
-// The datetime is expected to be a string in a format accepted by ParseLocalDateTime
+// The datetime is expected to be a string in a format accepted by ParseLocalDateTime.
 func (dt *LocalDateTime) UnmarshalText(data []byte) error {
 	var err error
 	*dt, err = ParseLocalDateTime(string(data))
+
 	return err
 }

localtime_test.go

@@ -26,6 +26,7 @@ func cmpEqual(x, y interface{}) bool {
 }
 
 func TestDates(t *testing.T) {
+
 	for _, test := range []struct {
 		date     LocalDate
 		loc      *time.Location
@@ -54,6 +55,7 @@ func TestDates(t *testing.T) {
 		if got := test.date.String(); got != test.wantStr {
 			t.Errorf("%#v.String() = %q, want %q", test.date, got, test.wantStr)
 		}
+
 		if got := test.date.In(test.loc); !got.Equal(test.wantTime) {
 			t.Errorf("%#v.In(%v) = %v, want %v", test.date, test.loc, got, test.wantTime)
 		}
@@ -61,6 +63,7 @@ func TestDates(t *testing.T) {
 }
 
 func TestDateIsValid(t *testing.T) {
+
 	for _, test := range []struct {
 		date LocalDate
 		want bool
@@ -86,6 +89,9 @@ func TestDateIsValid(t *testing.T) {
 }
 
 func TestParseDate(t *testing.T) {
+
+	var emptyDate LocalDate
+
 	for _, test := range []struct {
 		str  string
 		want LocalDate // if empty, expect an error
@@ -93,21 +99,23 @@ func TestParseDate(t *testing.T) {
 		{"2016-01-02", LocalDate{2016, 1, 2}},
 		{"2016-12-31", LocalDate{2016, 12, 31}},
 		{"0003-02-04", LocalDate{3, 2, 4}},
-		{"999-01-26", LocalDate{}},
-		{"", LocalDate{}},
-		{"2016-01-02x", LocalDate{}},
+		{"999-01-26", emptyDate},
+		{"", emptyDate},
+		{"2016-01-02x", emptyDate},
 	} {
 		got, err := ParseLocalDate(test.str)
 		if got != test.want {
 			t.Errorf("ParseLocalDate(%q) = %+v, want %+v", test.str, got, test.want)
 		}
-		if err != nil && test.want != (LocalDate{}) {
+
+		if err != nil && test.want != (emptyDate) {
 			t.Errorf("Unexpected error %v from ParseLocalDate(%q)", err, test.str)
 		}
 	}
 }
 
 func TestDateArithmetic(t *testing.T) {
+
 	for _, test := range []struct {
 		desc  string
 		start LocalDate
@@ -160,6 +168,7 @@ func TestDateArithmetic(t *testing.T) {
 		if got := test.start.AddDays(test.days); got != test.end {
 			t.Errorf("[%s] %#v.AddDays(%v) = %#v, want %#v", test.desc, test.start, test.days, got, test.end)
 		}
+
 		if got := test.end.DaysSince(test.start); got != test.days {
 			t.Errorf("[%s] %#v.Sub(%#v) = %v, want %v", test.desc, test.end, test.start, got, test.days)
 		}
@@ -167,6 +176,7 @@ func TestDateArithmetic(t *testing.T) {
 }
 
 func TestDateBefore(t *testing.T) {
+
 	for _, test := range []struct {
 		d1, d2 LocalDate
 		want   bool
@@ -183,6 +193,7 @@ func TestDateBefore(t *testing.T) {
 }
 
 func TestDateAfter(t *testing.T) {
+
 	for _, test := range []struct {
 		d1, d2 LocalDate
 		want   bool
@@ -198,6 +209,7 @@ func TestDateAfter(t *testing.T) {
 }
 
 func TestTimeToString(t *testing.T) {
+
 	for _, test := range []struct {
 		str       string
 		time      LocalTime
@@ -212,11 +224,14 @@ func TestTimeToString(t *testing.T) {
 		gotTime, err := ParseLocalTime(test.str)
 		if err != nil {
 			t.Errorf("ParseLocalTime(%q): got error: %v", test.str, err)
+
 			continue
 		}
+
 		if gotTime != test.time {
 			t.Errorf("ParseLocalTime(%q) = %+v, want %+v", test.str, gotTime, test.time)
 		}
+
 		if test.roundTrip {
 			gotStr := test.time.String()
 			if gotStr != test.str {
@@ -227,6 +242,7 @@ func TestTimeToString(t *testing.T) {
 }
 
 func TestTimeOf(t *testing.T) {
+
 	for _, test := range []struct {
 		time time.Time
 		want LocalTime
@@ -241,6 +257,7 @@ func TestTimeOf(t *testing.T) {
 }
 
 func TestTimeIsValid(t *testing.T) {
+
 	for _, test := range []struct {
 		time LocalTime
 		want bool
@@ -265,23 +282,27 @@ func TestTimeIsValid(t *testing.T) {
 }
 
 func TestDateTimeToString(t *testing.T) {
+
 	for _, test := range []struct {
 		str       string
 		dateTime  LocalDateTime
 		roundTrip bool // ParseLocalDateTime(str).String() == str?
 	}{
-		{"2016-03-22T13:26:33", LocalDateTime{LocalDate{2016, 03, 22}, LocalTime{13, 26, 33, 0}}, true},
-		{"2016-03-22T13:26:33.000000600", LocalDateTime{LocalDate{2016, 03, 22}, LocalTime{13, 26, 33, 600}}, true},
-		{"2016-03-22t13:26:33", LocalDateTime{LocalDate{2016, 03, 22}, LocalTime{13, 26, 33, 0}}, false},
+		{"2016-03-22T13:26:33", LocalDateTime{LocalDate{2016, 3, 22}, LocalTime{13, 26, 33, 0}}, true},
+		{"2016-03-22T13:26:33.000000600", LocalDateTime{LocalDate{2016, 3, 22}, LocalTime{13, 26, 33, 600}}, true},
+		{"2016-03-22t13:26:33", LocalDateTime{LocalDate{2016, 3, 22}, LocalTime{13, 26, 33, 0}}, false},
 	} {
 		gotDateTime, err := ParseLocalDateTime(test.str)
 		if err != nil {
 			t.Errorf("ParseLocalDateTime(%q): got error: %v", test.str, err)
+
 			continue
 		}
+
 		if gotDateTime != test.dateTime {
 			t.Errorf("ParseLocalDateTime(%q) = %+v, want %+v", test.str, gotDateTime, test.dateTime)
 		}
+
 		if test.roundTrip {
 			gotStr := test.dateTime.String()
 			if gotStr != test.str {
@@ -292,6 +313,7 @@ func TestDateTimeToString(t *testing.T) {
 }
 
 func TestParseDateTimeErrors(t *testing.T) {
+
 	for _, str := range []string{
 		"",
 		"2016-03-22",           // just a date
@@ -306,14 +328,19 @@ func TestParseDateTimeErrors(t *testing.T) {
 }
 
 func TestDateTimeOf(t *testing.T) {
+
 	for _, test := range []struct {
 		time time.Time
 		want LocalDateTime
 	}{
-		{time.Date(2014, 8, 20, 15, 8, 43, 1, time.Local),
-			LocalDateTime{LocalDate{2014, 8, 20}, LocalTime{15, 8, 43, 1}}},
-		{time.Date(1, 1, 1, 0, 0, 0, 0, time.UTC),
-			LocalDateTime{LocalDate{1, 1, 1}, LocalTime{0, 0, 0, 0}}},
+		{
+			time.Date(2014, 8, 20, 15, 8, 43, 1, time.Local),
+			LocalDateTime{LocalDate{2014, 8, 20}, LocalTime{15, 8, 43, 1}},
+		},
+		{
+			time.Date(1, 1, 1, 0, 0, 0, 0, time.UTC),
+			LocalDateTime{LocalDate{1, 1, 1}, LocalTime{0, 0, 0, 0}},
+		},
 	} {
 		if got := LocalDateTimeOf(test.time); got != test.want {
 			t.Errorf("LocalDateTimeOf(%v) = %+v, want %+v", test.time, got, test.want)
@@ -322,6 +349,7 @@ func TestDateTimeOf(t *testing.T) {
 }
 
 func TestDateTimeIsValid(t *testing.T) {
+
 	// No need to be exhaustive here; it's just LocalDate.IsValid && LocalTime.IsValid.
 	for _, test := range []struct {
 		dt   LocalDateTime
@@ -339,19 +367,22 @@ func TestDateTimeIsValid(t *testing.T) {
 }
 
 func TestDateTimeIn(t *testing.T) {
+
 	dt := LocalDateTime{LocalDate{2016, 1, 2}, LocalTime{3, 4, 5, 6}}
-	got := dt.In(time.UTC)
+
 	want := time.Date(2016, 1, 2, 3, 4, 5, 6, time.UTC)
-	if !got.Equal(want) {
+	if got := dt.In(time.UTC); !got.Equal(want) {
 		t.Errorf("got %v, want %v", got, want)
 	}
 }
 
 func TestDateTimeBefore(t *testing.T) {
+
 	d1 := LocalDate{2016, 12, 31}
 	d2 := LocalDate{2017, 1, 1}
 	t1 := LocalTime{5, 6, 7, 8}
 	t2 := LocalTime{5, 6, 7, 9}
+
 	for _, test := range []struct {
 		dt1, dt2 LocalDateTime
 		want     bool
@@ -368,10 +399,12 @@ func TestDateTimeBefore(t *testing.T) {
 }
 
 func TestDateTimeAfter(t *testing.T) {
+
 	d1 := LocalDate{2016, 12, 31}
 	d2 := LocalDate{2017, 1, 1}
 	t1 := LocalTime{5, 6, 7, 8}
 	t2 := LocalTime{5, 6, 7, 9}
+
 	for _, test := range []struct {
 		dt1, dt2 LocalDateTime
 		want     bool
@@ -388,6 +421,7 @@ func TestDateTimeAfter(t *testing.T) {
 }
 
 func TestMarshalJSON(t *testing.T) {
+
 	for _, test := range []struct {
 		value interface{}
 		want  string
@@ -400,6 +434,7 @@ func TestMarshalJSON(t *testing.T) {
 		if err != nil {
 			t.Fatal(err)
 		}
+
 		if got := string(bgot); got != test.want {
 			t.Errorf("%#v: got %s, want %s", test.value, got, test.want)
 		}
@@ -407,9 +442,13 @@ func TestMarshalJSON(t *testing.T) {
 }
 
 func TestUnmarshalJSON(t *testing.T) {
-	var d LocalDate
-	var tm LocalTime
-	var dt LocalDateTime
+
+	var (
+		d  LocalDate
+		tm LocalTime
+		dt LocalDateTime
+	)
+
 	for _, test := range []struct {
 		data string
 		ptr  interface{}
@@ -423,12 +462,14 @@ func TestUnmarshalJSON(t *testing.T) {
 		if err := json.Unmarshal([]byte(test.data), test.ptr); err != nil {
 			t.Fatalf("%s: %v", test.data, err)
 		}
+
 		if !cmpEqual(test.ptr, test.want) {
 			t.Errorf("%s: got %#v, want %#v", test.data, test.ptr, test.want)
 		}
 	}
 
-	for _, bad := range []string{"", `""`, `"bad"`, `"1987-04-15x"`,
+	for _, bad := range []string{
+		"", `""`, `"bad"`, `"1987-04-15x"`,
 		`19870415`,     // a JSON number
 		`11987-04-15x`, // not a JSON string
 
@@ -436,9 +477,11 @@ func TestUnmarshalJSON(t *testing.T) {
 		if json.Unmarshal([]byte(bad), &d) == nil {
 			t.Errorf("%q, LocalDate: got nil, want error", bad)
 		}
+
 		if json.Unmarshal([]byte(bad), &tm) == nil {
 			t.Errorf("%q, LocalTime: got nil, want error", bad)
 		}
+
 		if json.Unmarshal([]byte(bad), &dt) == nil {
 			t.Errorf("%q, LocalDateTime: got nil, want error", bad)
 		}

marshaler.go

@@ -2,7 +2,7 @@ package toml
 
 import (
 	"bytes"
-	"errors"
+	"encoding"
 	"fmt"
 	"io"
 	"reflect"
@@ -18,16 +18,134 @@ import (
 func Marshal(v interface{}) ([]byte, error) {
 	var buf bytes.Buffer
 	enc := NewEncoder(&buf)
+
 	err := enc.Encode(v)
 	if err != nil {
 		return nil, err
 	}
+
 	return buf.Bytes(), nil
 }
 
 // Encoder writes a TOML document to an output stream.
 type Encoder struct {
+	// output
 	w io.Writer
+
+	// global settings
+	tablesInline    bool
+	arraysMultiline bool
+	indentSymbol    string
+	indentTables    bool
+}
+
+// NewEncoder returns a new Encoder that writes to w.
+func NewEncoder(w io.Writer) *Encoder {
+	return &Encoder{
+		w:            w,
+		indentSymbol: "  ",
+	}
+}
+
+// SetTablesInline forces the encoder to emit all tables inline.
+//
+// This behavior can be controlled on an individual struct field basis with the
+// inline tag:
+//
+//   MyField `inline:"true"`
+func (enc *Encoder) SetTablesInline(inline bool) {
+	enc.tablesInline = inline
+}
+
+// SetArraysMultiline forces the encoder to emit all arrays with one element per
+// line.
+//
+// This behavior can be controlled on an individual struct field basis with the multiline tag:
+//
+//   MyField `multiline:"true"`
+func (enc *Encoder) SetArraysMultiline(multiline bool) {
+	enc.arraysMultiline = multiline
+}
+
+// SetIndentSymbol defines the string that should be used for indentation. The
+// provided string is repeated for each indentation level. Defaults to two
+// spaces.
+func (enc *Encoder) SetIndentSymbol(s string) {
+	enc.indentSymbol = s
+}
+
+// SetIndentTables forces the encoder to intent tables and array tables.
+func (enc *Encoder) SetIndentTables(indent bool) {
+	enc.indentTables = indent
+}
+
+// Encode writes a TOML representation of v to the stream.
+//
+// If v cannot be represented to TOML it returns an error.
+//
+// Encoding rules
+//
+// A top level slice containing only maps or structs is encoded as [[table
+// array]].
+//
+// All slices not matching rule 1 are encoded as [array]. As a result, any map
+// or struct they contain is encoded as an {inline table}.
+//
+// Nil interfaces and nil pointers are not supported.
+//
+// Keys in key-values always have one part.
+//
+// Intermediate tables are always printed.
+//
+// By default, strings are encoded as literal string, unless they contain either
+// a newline character or a single quote. In that case they are emitted as quoted
+// strings.
+//
+// When encoding structs, fields are encoded in order of definition, with their
+// exact name.
+//
+// Struct tags
+//
+// The following struct tags are available to tweak encoding on a per-field
+// basis:
+//
+//   toml:"foo"
+//     Changes the name of the key to use for the field to foo.
+//
+//   multiline:"true"
+//     When the field contains a string, it will be emitted as a quoted
+//     multi-line TOML string.
+//
+//   inline:"true"
+//     When the field would normally be encoded as a table, it is instead
+//     encoded as an inline table.
+func (enc *Encoder) Encode(v interface{}) error {
+	var (
+		b   []byte
+		ctx encoderCtx
+	)
+
+	ctx.inline = enc.tablesInline
+
+	if v == nil {
+		return fmt.Errorf("toml: cannot encode a nil interface")
+	}
+
+	b, err := enc.encode(b, ctx, reflect.ValueOf(v))
+	if err != nil {
+		return err
+	}
+
+	_, err = enc.w.Write(b)
+	if err != nil {
+		return fmt.Errorf("toml: cannot write: %w", err)
+	}
+
+	return nil
+}
+
+type valueOptions struct {
+	multiline bool
 }
 
 type encoderCtx struct {
@@ -46,11 +164,14 @@ type encoderCtx struct {
 	// Set to true to skip the first table header in an array table.
 	skipTableHeader bool
 
-	options valueOptions
-}
+	// Should the next table be encoded as inline
+	inline bool
 
-type valueOptions struct {
-	multiline bool
+	// Indentation level
+	indent int
+
+	// Options coming from struct tags
+	options valueOptions
 }
 
 func (ctx *encoderCtx) shiftKey() {
@@ -70,62 +191,36 @@ func (ctx *encoderCtx) clearKey() {
 	ctx.hasKey = false
 }
 
-// NewEncoder returns a new Encoder that writes to w.
-func NewEncoder(w io.Writer) *Encoder {
-	return &Encoder{
-		w: w,
-	}
-}
-
-// Encode writes a TOML representation of v to the stream.
-//
-// If v cannot be represented to TOML it returns an error.
-//
-// Encoding rules:
-//
-// 1. A top level slice containing only maps or structs is encoded as [[table
-// array]].
-//
-// 2. All slices not matching rule 1 are encoded as [array]. As a result, any
-// map or struct they contain is encoded as an {inline table}.
-//
-// 3. Nil interfaces and nil pointers are not supported.
-//
-// 4. Keys in key-values always have one part.
-//
-// 5. Intermediate tables are always printed.
-//
-// By default, strings are encoded as literal string, unless they contain either
-// a newline character or a single quote. In that case they are emited as quoted
-// strings.
-//
-// When encoding structs, fields are encoded in order of definition, with their
-// exact name. The following struct tags are available:
-//
-//   `toml:"foo"`: changes the name of the key to use for the field to foo.
-//
-//   `multiline:"true"`: when the field contains a string, it will be emitted as
-//   a quoted multi-line TOML string.
-func (enc *Encoder) Encode(v interface{}) error {
-	var b []byte
-	var ctx encoderCtx
-	b, err := enc.encode(b, ctx, reflect.ValueOf(v))
-	if err != nil {
-		return err
-	}
-	_, err = enc.w.Write(b)
-	return err
+func (ctx *encoderCtx) isRoot() bool {
+	return len(ctx.parentKey) == 0 && !ctx.hasKey
 }
 
+//nolint:cyclop,funlen
 func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
-	switch i := v.Interface().(type) {
-	case time.Time: // TODO: add TextMarshaler
-		b = i.AppendFormat(b, time.RFC3339)
+	if !v.IsZero() {
+		i, ok := v.Interface().(time.Time)
+		if ok {
+			return i.AppendFormat(b, time.RFC3339), nil
+		}
+	}
+
+	if v.Type().Implements(textMarshalerType) {
+		if ctx.isRoot() {
+			return nil, fmt.Errorf("toml: type %s implementing the TextMarshaler interface cannot be a root element", v.Type())
+		}
+
+		text, err := v.Interface().(encoding.TextMarshaler).MarshalText()
+		if err != nil {
+			return nil, err
+		}
+
+		b = enc.encodeString(b, string(text), ctx.options)
+
 		return b, nil
 	}
 
-	// containers
 	switch v.Kind() {
+	// containers
 	case reflect.Map:
 		return enc.encodeMap(b, ctx, v)
 	case reflect.Struct:
@@ -134,21 +229,20 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 		return enc.encodeSlice(b, ctx, v)
 	case reflect.Interface:
 		if v.IsNil() {
-			return nil, errNilInterface
+			return nil, fmt.Errorf("toml: encoding a nil interface is not supported")
 		}
+
 		return enc.encode(b, ctx, v.Elem())
 	case reflect.Ptr:
 		if v.IsNil() {
 			return enc.encode(b, ctx, reflect.Zero(v.Type().Elem()))
 		}
+
 		return enc.encode(b, ctx, v.Elem())
-	}
 
 	// values
-	var err error
-	switch v.Kind() {
 	case reflect.String:
-		b, err = enc.encodeString(b, v.String(), ctx.options)
+		b = enc.encodeString(b, v.String(), ctx.options)
 	case reflect.Float32:
 		b = strconv.AppendFloat(b, v.Float(), 'f', -1, 32)
 	case reflect.Float64:
@@ -164,10 +258,7 @@ func (enc *Encoder) encode(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, e
 	case reflect.Int64, reflect.Int32, reflect.Int16, reflect.Int8, reflect.Int:
 		b = strconv.AppendInt(b, v.Int(), 10)
 	default:
-		err = fmt.Errorf("unsupported encode value kind: %s", v.Kind())
-	}
-	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("toml: cannot encode value of type %s", v.Kind())
 	}
 
 	return b, nil
@@ -188,10 +279,7 @@ func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v r
 	if !ctx.hasKey {
 		panic("caller of encodeKv should have set the key in the context")
 	}
-
-	if isNil(v) {
-		return b, nil
-	}
+	b = enc.indent(ctx.indent, b)
 
 	b, err = enc.encodeKey(b, ctx.key)
 	if err != nil {
@@ -217,30 +305,31 @@ func (enc *Encoder) encodeKv(b []byte, ctx encoderCtx, options valueOptions, v r
 
 const literalQuote = '\''
 
-func (enc *Encoder) encodeString(b []byte, v string, options valueOptions) ([]byte, error) {
+func (enc *Encoder) encodeString(b []byte, v string, options valueOptions) []byte {
 	if needsQuoting(v) {
-		b = enc.encodeQuotedString(options.multiline, b, v)
-	} else {
-		b = enc.encodeLiteralString(b, v)
+		return enc.encodeQuotedString(options.multiline, b, v)
 	}
-	return b, nil
+
+	return enc.encodeLiteralString(b, v)
 }
 
 func needsQuoting(v string) bool {
 	return strings.ContainsAny(v, "'\b\f\n\r\t")
 }
 
-// caller should have checked that the string does not contain new lines or '
+// caller should have checked that the string does not contain new lines or ' .
 func (enc *Encoder) encodeLiteralString(b []byte, v string) []byte {
 	b = append(b, literalQuote)
 	b = append(b, v...)
 	b = append(b, literalQuote)
+
 	return b
 }
 
+//nolint:cyclop
 func (enc *Encoder) encodeQuotedString(multiline bool, b []byte, v string) []byte {
-	const hextable = "0123456789ABCDEF"
 	stringQuote := `"`
+
 	if multiline {
 		stringQuote = `"""`
 	}
@@ -250,6 +339,16 @@ func (enc *Encoder) encodeQuotedString(multiline bool, b []byte, v string) []byt
 		b = append(b, '\n')
 	}
 
+	const (
+		hextable = "0123456789ABCDEF"
+		// U+0000 to U+0008, U+000A to U+001F, U+007F
+		nul = 0x0
+		bs  = 0x8
+		lf  = 0xa
+		us  = 0x1f
+		del = 0x7f
+	)
+
 	for _, r := range []byte(v) {
 		switch r {
 		case '\\':
@@ -272,7 +371,7 @@ func (enc *Encoder) encodeQuotedString(multiline bool, b []byte, v string) []byt
 			b = append(b, `\t`...)
 		default:
 			switch {
-			case r >= 0x0 && r <= 0x8, r >= 0xA && r <= 0x1F, r == 0x7F:
+			case r >= nul && r <= bs, r >= lf && r <= us, r == del:
 				b = append(b, `\u00`...)
 				b = append(b, hextable[r>>4])
 				b = append(b, hextable[r&0x0f])
@@ -280,33 +379,37 @@ func (enc *Encoder) encodeQuotedString(multiline bool, b []byte, v string) []byt
 				b = append(b, r)
 			}
 		}
-		// U+0000 to U+0008, U+000A to U+001F, U+007F
 	}
 
 	b = append(b, stringQuote...)
+
 	return b
 }
 
-// called should have checked that the string is in A-Z / a-z / 0-9 / - / _
+// called should have checked that the string is in A-Z / a-z / 0-9 / - / _ .
 func (enc *Encoder) encodeUnquotedKey(b []byte, v string) []byte {
 	return append(b, v...)
 }
 
-func (enc *Encoder) encodeTableHeader(b []byte, key []string) ([]byte, error) {
-	if len(key) == 0 {
+func (enc *Encoder) encodeTableHeader(ctx encoderCtx, b []byte) ([]byte, error) {
+	if len(ctx.parentKey) == 0 {
 		return b, nil
 	}
 
+	b = enc.indent(ctx.indent, b)
+
 	b = append(b, '[')
 
 	var err error
-	b, err = enc.encodeKey(b, key[0])
+
+	b, err = enc.encodeKey(b, ctx.parentKey[0])
 	if err != nil {
 		return nil, err
 	}
 
-	for _, k := range key[1:] {
+	for _, k := range ctx.parentKey[1:] {
 		b = append(b, '.')
+
 		b, err = enc.encodeKey(b, k)
 		if err != nil {
 			return nil, err
@@ -318,6 +421,7 @@ func (enc *Encoder) encodeTableHeader(b []byte, key []string) ([]byte, error) {
 	return b, nil
 }
 
+//nolint:cyclop
 func (enc *Encoder) encodeKey(b []byte, k string) ([]byte, error) {
 	needsQuotation := false
 	cannotUseLiteral := false
@@ -326,32 +430,37 @@ func (enc *Encoder) encodeKey(b []byte, k string) ([]byte, error) {
 		if (c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '-' || c == '_' {
 			continue
 		}
+
 		if c == '\n' {
-			return nil, fmt.Errorf("TOML does not support multiline keys")
+			return nil, fmt.Errorf("toml: new line characters in keys are not supported")
 		}
+
 		if c == literalQuote {
 			cannotUseLiteral = true
 		}
+
 		needsQuotation = true
 	}
 
-	if cannotUseLiteral {
-		b = enc.encodeQuotedString(false, b, k)
-	} else if needsQuotation {
-		b = enc.encodeLiteralString(b, k)
-	} else {
-		b = enc.encodeUnquotedKey(b, k)
+	switch {
+	case cannotUseLiteral:
+		return enc.encodeQuotedString(false, b, k), nil
+	case needsQuotation:
+		return enc.encodeLiteralString(b, k), nil
+	default:
+		return enc.encodeUnquotedKey(b, k), nil
 	}
-
-	return b, nil
 }
 
 func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
 	if v.Type().Key().Kind() != reflect.String {
-		return nil, fmt.Errorf("type '%s' not supported as map key", v.Type().Key().Kind())
+		return nil, fmt.Errorf("toml: type %s is not supported as a map key", v.Type().Key().Kind())
 	}
 
-	t := table{}
+	var (
+		t                 table
+		emptyValueOptions valueOptions
+	)
 
 	iter := v.MapRange()
 	for iter.Next() {
@@ -362,15 +471,10 @@ func (enc *Encoder) encodeMap(b []byte, ctx encoderCtx, v reflect.Value) ([]byte
 			continue
 		}
 
-		table, err := willConvertToTableOrArrayTable(v)
-		if err != nil {
-			return nil, err
-		}
-
-		if table {
-			t.pushTable(k, v, valueOptions{})
+		if willConvertToTableOrArrayTable(ctx, v) {
+			t.pushTable(k, v, emptyValueOptions)
 		} else {
-			t.pushKV(k, v, valueOptions{})
+			t.pushKV(k, v, emptyValueOptions)
 		}
 	}
 
@@ -405,13 +509,10 @@ func (t *table) pushTable(k string, v reflect.Value, options valueOptions) {
 	t.tables = append(t.tables, entry{Key: k, Value: v, Options: options})
 }
 
-func (t *table) hasKVs() bool {
-	return len(t.kvs) > 0
-}
-
 func (enc *Encoder) encodeStruct(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
-	t := table{}
+	var t table
 
+	//nolint:godox
 	// TODO: cache this?
 	typ := v.Type()
 	for i := 0; i < typ.NumField(); i++ {
@@ -438,167 +539,167 @@ func (enc *Encoder) encodeStruct(b []byte, ctx encoderCtx, v reflect.Value) ([]b
 			continue
 		}
 
-		willConvert, err := willConvertToTableOrArrayTable(f)
-		if err != nil {
-			return nil, err
+		options := valueOptions{
+			multiline: fieldBoolTag(fieldType, "multiline"),
 		}
 
-		options := valueOptions{}
+		inline := fieldBoolTag(fieldType, "inline")
 
-		ml, ok := fieldType.Tag.Lookup("multiline")
-		if ok {
-			options.multiline = ml == "true"
-		}
-
-		if willConvert {
-			t.pushTable(k, f, options)
-		} else {
+		if inline || !willConvertToTableOrArrayTable(ctx, f) {
 			t.pushKV(k, f, options)
+		} else {
+			t.pushTable(k, f, options)
 		}
 	}
 
 	return enc.encodeTable(b, ctx, t)
 }
 
+func fieldBoolTag(field reflect.StructField, tag string) bool {
+	x, ok := field.Tag.Lookup(tag)
+
+	return ok && x == "true"
+}
+
+//nolint:cyclop
 func (enc *Encoder) encodeTable(b []byte, ctx encoderCtx, t table) ([]byte, error) {
 	var err error
 
 	ctx.shiftKey()
 
-	if ctx.insideKv {
-		b = append(b, '{')
-
-		first := true
-		for _, kv := range t.kvs {
-			if first {
-				first = false
-			} else {
-				b = append(b, `, `...)
-			}
-			ctx.setKey(kv.Key)
-			b, err = enc.encodeKv(b, ctx, kv.Options, kv.Value)
-			if err != nil {
-				return nil, err
-			}
-		}
-
-		for _, table := range t.tables {
-			if first {
-				first = false
-			} else {
-				b = append(b, `, `...)
-			}
-			ctx.setKey(table.Key)
-			b, err = enc.encode(b, ctx, table.Value)
-			if err != nil {
-				return nil, err
-			}
-			b = append(b, '\n')
-		}
-
-		b = append(b, "}\n"...)
-		return b, nil
+	if ctx.insideKv || (ctx.inline && !ctx.isRoot()) {
+		return enc.encodeTableInline(b, ctx, t)
 	}
 
 	if !ctx.skipTableHeader {
-		b, err = enc.encodeTableHeader(b, ctx.parentKey)
+		b, err = enc.encodeTableHeader(ctx, b)
 		if err != nil {
 			return nil, err
 		}
+
+		if enc.indentTables && len(ctx.parentKey) > 0 {
+			ctx.indent++
+		}
 	}
 	ctx.skipTableHeader = false
 
 	for _, kv := range t.kvs {
 		ctx.setKey(kv.Key)
+
 		b, err = enc.encodeKv(b, ctx, kv.Options, kv.Value)
 		if err != nil {
 			return nil, err
 		}
+
 		b = append(b, '\n')
 	}
 
 	for _, table := range t.tables {
 		ctx.setKey(table.Key)
+
+		ctx.options = table.Options
+
 		b, err = enc.encode(b, ctx, table.Value)
 		if err != nil {
 			return nil, err
 		}
+
 		b = append(b, '\n')
 	}
 
 	return b, nil
 }
 
-var errNilInterface = errors.New("nil interface not supported")
-var errNilPointer = errors.New("nil pointer not supported")
+func (enc *Encoder) encodeTableInline(b []byte, ctx encoderCtx, t table) ([]byte, error) {
+	var err error
 
-func willConvertToTable(v reflect.Value) (bool, error) {
-	switch v.Interface().(type) {
-	case time.Time: // TODO: add TextMarshaler
-		return false, nil
+	b = append(b, '{')
+
+	first := true
+	for _, kv := range t.kvs {
+		if first {
+			first = false
+		} else {
+			b = append(b, `, `...)
+		}
+
+		ctx.setKey(kv.Key)
+
+		b, err = enc.encodeKv(b, ctx, kv.Options, kv.Value)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	if len(t.tables) > 0 {
+		panic("inline table cannot contain nested tables, online key-values")
+	}
+
+	b = append(b, "}"...)
+
+	return b, nil
+}
+
+func willConvertToTable(ctx encoderCtx, v reflect.Value) bool {
+	if !v.IsValid() {
+		return false
+	}
+	if v.Type() == timeType || v.Type().Implements(textMarshalerType) {
+		return false
 	}
 
 	t := v.Type()
 	switch t.Kind() {
 	case reflect.Map, reflect.Struct:
-		return true, nil
+		return !ctx.inline
 	case reflect.Interface:
-		if v.IsNil() {
-			return false, errNilInterface
-		}
-		return willConvertToTable(v.Elem())
+		return willConvertToTable(ctx, v.Elem())
 	case reflect.Ptr:
 		if v.IsNil() {
-			return false, nil
+			return false
 		}
-		return willConvertToTable(v.Elem())
+
+		return willConvertToTable(ctx, v.Elem())
 	default:
-		return false, nil
+		return false
 	}
 }
 
-func willConvertToTableOrArrayTable(v reflect.Value) (bool, error) {
+func willConvertToTableOrArrayTable(ctx encoderCtx, v reflect.Value) bool {
 	t := v.Type()
 
 	if t.Kind() == reflect.Interface {
-		if v.IsNil() {
-			return false, errNilInterface
-		}
-		return willConvertToTableOrArrayTable(v.Elem())
+		return willConvertToTableOrArrayTable(ctx, v.Elem())
 	}
 
 	if t.Kind() == reflect.Slice {
 		if v.Len() == 0 {
 			// An empty slice should be a kv = [].
-			return false, nil
+			return false
 		}
+
 		for i := 0; i < v.Len(); i++ {
-			t, err := willConvertToTable(v.Index(i))
-			if err != nil {
-				return false, err
-			}
+			t := willConvertToTable(ctx, v.Index(i))
+
 			if !t {
-				return false, nil
+				return false
 			}
 		}
-		return true, nil
+
+		return true
 	}
 
-	return willConvertToTable(v)
+	return willConvertToTable(ctx, v)
 }
 
 func (enc *Encoder) encodeSlice(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
 	if v.Len() == 0 {
 		b = append(b, "[]"...)
+
 		return b, nil
 	}
 
-	allTables, err := willConvertToTableOrArrayTable(v)
-	if err != nil {
-		return nil, err
-	}
-
-	if allTables {
+	if willConvertToTableOrArrayTable(ctx, v) {
 		return enc.encodeSliceAsArrayTable(b, ctx, v)
 	}
 
@@ -608,54 +709,89 @@ func (enc *Encoder) encodeSlice(b []byte, ctx encoderCtx, v reflect.Value) ([]by
 // caller should have checked that v is a slice that only contains values that
 // encode into tables.
 func (enc *Encoder) encodeSliceAsArrayTable(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
-	if v.Len() == 0 {
-		return b, nil
-	}
-
 	ctx.shiftKey()
 
 	var err error
 	scratch := make([]byte, 0, 64)
 	scratch = append(scratch, "[["...)
+
 	for i, k := range ctx.parentKey {
 		if i > 0 {
 			scratch = append(scratch, '.')
 		}
+
 		scratch, err = enc.encodeKey(scratch, k)
 		if err != nil {
 			return nil, err
 		}
 	}
+
 	scratch = append(scratch, "]]\n"...)
 	ctx.skipTableHeader = true
 
 	for i := 0; i < v.Len(); i++ {
 		b = append(b, scratch...)
+
 		b, err = enc.encode(b, ctx, v.Index(i))
 		if err != nil {
 			return nil, err
 		}
 	}
+
 	return b, nil
 }
 
 func (enc *Encoder) encodeSliceAsArray(b []byte, ctx encoderCtx, v reflect.Value) ([]byte, error) {
+	multiline := ctx.options.multiline || enc.arraysMultiline
+	separator := ", "
+
 	b = append(b, '[')
 
+	subCtx := ctx
+	subCtx.options = valueOptions{}
+
+	if multiline {
+		separator = ",\n"
+
+		b = append(b, '\n')
+
+		subCtx.indent++
+	}
+
 	var err error
 	first := true
-	for i := 0; i < v.Len(); i++ {
-		if !first {
-			b = append(b, ", "...)
-		}
-		first = false
 
-		b, err = enc.encode(b, ctx, v.Index(i))
+	for i := 0; i < v.Len(); i++ {
+		if first {
+			first = false
+		} else {
+			b = append(b, separator...)
+		}
+
+		if multiline {
+			b = enc.indent(subCtx.indent, b)
+		}
+
+		b, err = enc.encode(b, subCtx, v.Index(i))
 		if err != nil {
 			return nil, err
 		}
 	}
 
+	if multiline {
+		b = append(b, '\n')
+		b = enc.indent(ctx.indent, b)
+	}
+
 	b = append(b, ']')
+
 	return b, nil
 }
+
+func (enc *Encoder) indent(level int, b []byte) []byte {
+	for i := 0; i < level; i++ {
+		b = append(b, enc.indentSymbol...)
+	}
+
+	return b
+}

marshaler_test.go

@@ -3,6 +3,7 @@ package toml_test
 import (
 	"bytes"
 	"encoding/json"
+	"fmt"
 	"strings"
 	"testing"
 
@@ -11,7 +12,14 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+//nolint:funlen
 func TestMarshal(t *testing.T) {
+	someInt := 42
+
+	type structInline struct {
+		A interface{} `inline:"true"`
+	}
+
 	examples := []struct {
 		desc     string
 		v        interface{}
@@ -65,8 +73,6 @@ hello = 'world'`,
 a = 'test'`,
 		},
 		{
-			// TODO: this test is flaky because output changes depending on
-			//   the map iteration order.
 			desc: "map in map in map and string with values",
 			v: map[string]interface{}{
 				"this": map[string]interface{}{
@@ -89,6 +95,16 @@ a = 'test'`,
 			},
 			expected: `array = ['one', 'two', 'three']`,
 		},
+		{
+			desc:     "empty string array",
+			v:        map[string][]string{},
+			expected: ``,
+		},
+		{
+			desc:     "map",
+			v:        map[string][]string{},
+			expected: ``,
+		},
 		{
 			desc: "nested string arrays",
 			v: map[string][][]string{
@@ -104,7 +120,7 @@ a = 'test'`,
 			expected: `array = ['a string', ['one', 'two'], 'last']`,
 		},
 		{
-			desc: "slice of maps",
+			desc: "array of maps",
 			v: map[string][]map[string]string{
 				"top": {
 					{"map1.1": "v1.1"},
@@ -157,7 +173,7 @@ K2 = 'v2'
 `,
 		},
 		{
-			desc: "structs in slice with interfaces",
+			desc: "structs in array with interfaces",
 			v: map[string]interface{}{
 				"root": map[string]interface{}{
 					"nested": []interface{}{
@@ -234,17 +250,349 @@ name = 'Alice'
 hello
 world"""`,
 		},
+		{
+			desc: "inline field",
+			v: struct {
+				A map[string]string `inline:"true"`
+				B map[string]string
+			}{
+				A: map[string]string{
+					"isinline": "yes",
+				},
+				B: map[string]string{
+					"isinline": "no",
+				},
+			},
+			expected: `
+A = {isinline = 'yes'}
+[B]
+isinline = 'no'
+`,
+		},
+		{
+			desc: "mutiline array int",
+			v: struct {
+				A []int `multiline:"true"`
+				B []int
+			}{
+				A: []int{1, 2, 3, 4},
+				B: []int{1, 2, 3, 4},
+			},
+			expected: `
+A = [
+  1,
+  2,
+  3,
+  4
+]
+B = [1, 2, 3, 4]
+`,
+		},
+		{
+			desc: "mutiline array in array",
+			v: struct {
+				A [][]int `multiline:"true"`
+			}{
+				A: [][]int{{1, 2}, {3, 4}},
+			},
+			expected: `
+A = [
+  [1, 2],
+  [3, 4]
+]
+`,
+		},
+		{
+			desc: "nil interface not supported at root",
+			v:    nil,
+			err:  true,
+		},
+		{
+			desc: "nil interface not supported in slice",
+			v: map[string]interface{}{
+				"a": []interface{}{"a", nil, 2},
+			},
+			err: true,
+		},
+		{
+			desc: "nil pointer in slice uses zero value",
+			v: struct {
+				A []*int
+			}{
+				A: []*int{nil},
+			},
+			expected: `A = [0]`,
+		},
+		{
+			desc: "nil pointer in slice uses zero value",
+			v: struct {
+				A []*int
+			}{
+				A: []*int{nil},
+			},
+			expected: `A = [0]`,
+		},
+		{
+			desc: "pointer in slice",
+			v: struct {
+				A []*int
+			}{
+				A: []*int{&someInt},
+			},
+			expected: `A = [42]`,
+		},
+		{
+			desc: "inline table in inline table",
+			v: structInline{
+				A: structInline{
+					A: structInline{
+						A: "hello",
+					},
+				},
+			},
+			expected: `A = {A = {A = 'hello'}}`,
+		},
+		{
+			desc: "empty slice in map",
+			v: map[string][]string{
+				"a": {},
+			},
+			expected: `a = []`,
+		},
+		{
+			desc: "map in slice",
+			v: map[string][]map[string]string{
+				"a": {{"hello": "world"}},
+			},
+			expected: `
+[[a]]
+hello = 'world'`,
+		},
+		{
+			desc: "newline in map in slice",
+			v: map[string][]map[string]string{
+				"a\n": {{"hello": "world"}},
+			},
+			err: true,
+		},
+		{
+			desc: "newline in map in slice",
+			v: map[string][]map[string]*customTextMarshaler{
+				"a": {{"hello": &customTextMarshaler{1}}},
+			},
+			err: true,
+		},
+		{
+			desc: "empty slice of empty struct",
+			v: struct {
+				A []struct{}
+			}{
+				A: []struct{}{},
+			},
+			expected: `A = []`,
+		},
+		{
+			desc: "nil field is ignored",
+			v: struct {
+				A interface{}
+			}{
+				A: nil,
+			},
+			expected: ``,
+		},
+		{
+			desc: "private fields are ignored",
+			v: struct {
+				Public  string
+				private string
+			}{
+				Public:  "shown",
+				private: "hidden",
+			},
+			expected: `Public = 'shown'`,
+		},
+		{
+			desc: "fields tagged - are ignored",
+			v: struct {
+				Public  string `toml:"-"`
+				private string
+			}{
+				Public: "hidden",
+			},
+			expected: ``,
+		},
+		{
+			desc: "nil value in map is ignored",
+			v: map[string]interface{}{
+				"A": nil,
+			},
+			expected: ``,
+		},
+		{
+			desc: "new line in table key",
+			v: map[string]interface{}{
+				"hello\nworld": 42,
+			},
+			err: true,
+		},
+		{
+			desc: "new line in parent of nested table key",
+			v: map[string]interface{}{
+				"hello\nworld": map[string]interface{}{
+					"inner": 42,
+				},
+			},
+			err: true,
+		},
+		{
+			desc: "new line in nested table key",
+			v: map[string]interface{}{
+				"parent": map[string]interface{}{
+					"in\ner": map[string]interface{}{
+						"foo": 42,
+					},
+				},
+			},
+			err: true,
+		},
+		{
+			desc: "invalid map key",
+			v:    map[int]interface{}{},
+			err:  true,
+		},
+		{
+			desc: "unhandled type",
+			v: struct {
+				A chan int
+			}{
+				A: make(chan int),
+			},
+			err: true,
+		},
+		{
+			desc: "numbers",
+			v: struct {
+				A float32
+				B uint64
+				C uint32
+				D uint16
+				E uint8
+				F uint
+				G int64
+				H int32
+				I int16
+				J int8
+				K int
+			}{
+				A: 1.1,
+				B: 42,
+				C: 42,
+				D: 42,
+				E: 42,
+				F: 42,
+				G: 42,
+				H: 42,
+				I: 42,
+				J: 42,
+				K: 42,
+			},
+			expected: `
+A = 1.1
+B = 42
+C = 42
+D = 42
+E = 42
+F = 42
+G = 42
+H = 42
+I = 42
+J = 42
+K = 42`,
+		},
 	}
 
 	for _, e := range examples {
+		e := e
 		t.Run(e.desc, func(t *testing.T) {
 			b, err := toml.Marshal(e.v)
 			if e.err {
 				require.Error(t, err)
-			} else {
-				require.NoError(t, err)
-				equalStringsIgnoreNewlines(t, e.expected, string(b))
+
+				return
 			}
+
+			require.NoError(t, err)
+			equalStringsIgnoreNewlines(t, e.expected, string(b))
+
+			// make sure the output is always valid TOML
+			defaultMap := map[string]interface{}{}
+			err = toml.Unmarshal(b, &defaultMap)
+			require.NoError(t, err)
+
+			testWithAllFlags(t, func(t *testing.T, flags int) {
+				t.Helper()
+
+				var buf bytes.Buffer
+				enc := toml.NewEncoder(&buf)
+				setFlags(enc, flags)
+
+				err := enc.Encode(e.v)
+				require.NoError(t, err)
+
+				inlineMap := map[string]interface{}{}
+				err = toml.Unmarshal(buf.Bytes(), &inlineMap)
+				require.NoError(t, err)
+
+				require.Equal(t, defaultMap, inlineMap)
+			})
+		})
+	}
+}
+
+type flagsSetters []struct {
+	name string
+	f    func(enc *toml.Encoder, flag bool)
+}
+
+var allFlags = flagsSetters{
+	{"arrays-multiline", (*toml.Encoder).SetArraysMultiline},
+	{"tables-inline", (*toml.Encoder).SetTablesInline},
+	{"indent-tables", (*toml.Encoder).SetIndentTables},
+}
+
+func setFlags(enc *toml.Encoder, flags int) {
+	for i := 0; i < len(allFlags); i++ {
+		enabled := flags&1 > 0
+		allFlags[i].f(enc, enabled)
+	}
+}
+
+func testWithAllFlags(t *testing.T, testfn func(t *testing.T, flags int)) {
+	t.Helper()
+	testWithFlags(t, 0, allFlags, testfn)
+}
+
+func testWithFlags(t *testing.T, flags int, setters flagsSetters, testfn func(t *testing.T, flags int)) {
+	t.Helper()
+
+	if len(setters) == 0 {
+		testfn(t, flags)
+
+		return
+	}
+
+	s := setters[0]
+
+	for _, enabled := range []bool{false, true} {
+		name := fmt.Sprintf("%s=%t", s.name, enabled)
+		newFlags := flags << 1
+
+		if enabled {
+			newFlags++
+		}
+
+		t.Run(name, func(t *testing.T) {
+			testWithFlags(t, newFlags, setters[1:], testfn)
 		})
 	}
 }
@@ -255,6 +603,137 @@ func equalStringsIgnoreNewlines(t *testing.T, expected string, actual string) {
 	assert.Equal(t, strings.Trim(expected, cutset), strings.Trim(actual, cutset))
 }
 
+//nolint:funlen
+func TestMarshalIndentTables(t *testing.T) {
+	examples := []struct {
+		desc     string
+		v        interface{}
+		expected string
+	}{
+		{
+			desc: "one kv",
+			v: map[string]interface{}{
+				"foo": "bar",
+			},
+			expected: `foo = 'bar'`,
+		},
+		{
+			desc: "one level table",
+			v: map[string]map[string]string{
+				"foo": {
+					"one": "value1",
+					"two": "value2",
+				},
+			},
+			expected: `
+[foo]
+  one = 'value1'
+  two = 'value2'
+`,
+		},
+		{
+			desc: "two levels table",
+			v: map[string]interface{}{
+				"root": "value0",
+				"level1": map[string]interface{}{
+					"one": "value1",
+					"level2": map[string]interface{}{
+						"two": "value2",
+					},
+				},
+			},
+			expected: `
+root = 'value0'
+[level1]
+  one = 'value1'
+  [level1.level2]
+    two = 'value2'
+`,
+		},
+	}
+
+	for _, e := range examples {
+		e := e
+		t.Run(e.desc, func(t *testing.T) {
+			var buf strings.Builder
+			enc := toml.NewEncoder(&buf)
+			enc.SetIndentTables(true)
+			err := enc.Encode(e.v)
+			require.NoError(t, err)
+			equalStringsIgnoreNewlines(t, e.expected, buf.String())
+		})
+	}
+}
+
+type customTextMarshaler struct {
+	value int64
+}
+
+func (c *customTextMarshaler) MarshalText() ([]byte, error) {
+	if c.value == 1 {
+		return nil, fmt.Errorf("cannot represent 1 because this is a silly test")
+	}
+	return []byte(fmt.Sprintf("::%d", c.value)), nil
+}
+
+func TestMarshalTextMarshaler_NoRoot(t *testing.T) {
+	c := customTextMarshaler{}
+	_, err := toml.Marshal(&c)
+	require.Error(t, err)
+}
+
+func TestMarshalTextMarshaler_Error(t *testing.T) {
+	m := map[string]interface{}{"a": &customTextMarshaler{value: 1}}
+	_, err := toml.Marshal(m)
+	require.Error(t, err)
+}
+
+func TestMarshalTextMarshaler_ErrorInline(t *testing.T) {
+	type s struct {
+		A map[string]interface{} `inline:"true"`
+	}
+
+	d := s{
+		A: map[string]interface{}{"a": &customTextMarshaler{value: 1}},
+	}
+
+	_, err := toml.Marshal(d)
+	require.Error(t, err)
+}
+
+func TestMarshalTextMarshaler(t *testing.T) {
+	m := map[string]interface{}{"a": &customTextMarshaler{value: 2}}
+	r, err := toml.Marshal(m)
+	require.NoError(t, err)
+	equalStringsIgnoreNewlines(t, "a = '::2'", string(r))
+}
+
+type brokenWriter struct{}
+
+func (b *brokenWriter) Write([]byte) (int, error) {
+	return 0, fmt.Errorf("dead")
+}
+
+func TestEncodeToBrokenWriter(t *testing.T) {
+	w := brokenWriter{}
+	enc := toml.NewEncoder(&w)
+	err := enc.Encode(map[string]string{"hello": "world"})
+	require.Error(t, err)
+}
+
+func TestEncoderSetIndentSymbol(t *testing.T) {
+	var w strings.Builder
+	enc := toml.NewEncoder(&w)
+	enc.SetIndentTables(true)
+	enc.SetIndentSymbol(">>>")
+	err := enc.Encode(map[string]map[string]string{"parent": {"hello": "world"}})
+	require.NoError(t, err)
+	expected := `
+[parent]
+>>>hello = 'world'`
+	equalStringsIgnoreNewlines(t, expected, w.String())
+}
+
 func TestIssue436(t *testing.T) {
 	data := []byte(`{"a": [ { "b": { "c": "d" } } ]}`)
 
@@ -273,3 +752,57 @@ c = 'd'
 `
 	equalStringsIgnoreNewlines(t, expected, buf.String())
 }
+
+func TestIssue424(t *testing.T) {
+	type Message1 struct {
+		Text string
+	}
+
+	type Message2 struct {
+		Text string `multiline:"true"`
+	}
+
+	msg1 := Message1{"Hello\\World"}
+	msg2 := Message2{"Hello\\World"}
+
+	toml1, err := toml.Marshal(msg1)
+	require.NoError(t, err)
+
+	toml2, err := toml.Marshal(msg2)
+	require.NoError(t, err)
+
+	msg1parsed := Message1{}
+	err = toml.Unmarshal(toml1, &msg1parsed)
+	require.NoError(t, err)
+	require.Equal(t, msg1, msg1parsed)
+
+	msg2parsed := Message2{}
+	err = toml.Unmarshal(toml2, &msg2parsed)
+	require.NoError(t, err)
+	require.Equal(t, msg2, msg2parsed)
+}
+
+func ExampleMarshal() {
+	type MyConfig struct {
+		Version int
+		Name    string
+		Tags    []string
+	}
+
+	cfg := MyConfig{
+		Version: 2,
+		Name:    "go-toml",
+		Tags:    []string{"go", "toml"},
+	}
+
+	b, err := toml.Marshal(cfg)
+	if err != nil {
+		panic(err)
+	}
+	fmt.Println(string(b))
+
+	// Output:
+	// Version = 2
+	// Name = 'go-toml'
+	// Tags = ['go', 'toml']
+}

parser_test.go

@@ -7,6 +7,7 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+//nolint:funlen
 func TestParser_AST_Numbers(t *testing.T) {
 	examples := []struct {
 		desc  string
@@ -132,6 +133,7 @@ func TestParser_AST_Numbers(t *testing.T) {
 	}
 
 	for _, e := range examples {
+		e := e
 		t.Run(e.desc, func(t *testing.T) {
 			p := parser{}
 			p.Reset([]byte(`A = ` + e.input))
@@ -155,19 +157,16 @@ func TestParser_AST_Numbers(t *testing.T) {
 	}
 }
 
-type astRoot []astNode
-type astNode struct {
-	Kind     ast.Kind
-	Data     []byte
-	Children []astNode
-}
+type (
+	astNode struct {
+		Kind     ast.Kind
+		Data     []byte
+		Children []astNode
+	}
+)
 
-func compareAST(t *testing.T, expected astRoot, actual *ast.Root) {
-	it := actual.Iterator()
-	compareIterator(t, expected, it)
-}
-
-func compareNode(t *testing.T, e astNode, n ast.Node) {
+func compareNode(t *testing.T, e astNode, n *ast.Node) {
+	t.Helper()
 	require.Equal(t, e.Kind, n.Kind)
 	require.Equal(t, e.Data, n.Data)
 
@@ -175,6 +174,7 @@ func compareNode(t *testing.T, e astNode, n ast.Node) {
 }
 
 func compareIterator(t *testing.T, expected []astNode, actual ast.Iterator) {
+	t.Helper()
 	idx := 0
 
 	for actual.Next() {
@@ -195,54 +195,7 @@ func compareIterator(t *testing.T, expected []astNode, actual ast.Iterator) {
 	}
 }
 
-func (r astRoot) toOrig() *ast.Root {
-	builder := &ast.Builder{}
-
-	var last ast.Reference
-
-	for i, n := range r {
-		ref := builder.Push(ast.Node{
-			Kind: n.Kind,
-			Data: n.Data,
-		})
-
-		if i > 0 {
-			builder.Chain(last, ref)
-		}
-		last = ref
-
-		if len(n.Children) > 0 {
-			c := childrenToOrig(builder, n.Children)
-			builder.AttachChild(ref, c)
-		}
-	}
-
-	return builder.Tree()
-}
-
-func childrenToOrig(b *ast.Builder, nodes []astNode) ast.Reference {
-	var first ast.Reference
-	var last ast.Reference
-	for i, n := range nodes {
-		ref := b.Push(ast.Node{
-			Kind: n.Kind,
-			Data: n.Data,
-		})
-		if i == 0 {
-			first = ref
-		} else {
-			b.Chain(last, ref)
-		}
-		last = ref
-
-		if len(n.Children) > 0 {
-			c := childrenToOrig(b, n.Children)
-			b.AttachChild(ref, c)
-		}
-	}
-	return first
-}
-
+//nolint:funlen
 func TestParser_AST(t *testing.T) {
 	examples := []struct {
 		desc  string
@@ -380,6 +333,7 @@ func TestParser_AST(t *testing.T) {
 	}
 
 	for _, e := range examples {
+		e := e
 		t.Run(e.desc, func(t *testing.T) {
 			p := parser{}
 			p.Reset([]byte(e.input))

scanner.go

@@ -1,36 +1,44 @@
 package toml
 
-import "fmt"
+func scanFollows(b []byte, pattern string) bool {
+	n := len(pattern)
 
-func scanFollows(pattern []byte) func(b []byte) bool {
-	return func(b []byte) bool {
-		if len(b) < len(pattern) {
-			return false
-		}
-		for i, c := range pattern {
-			if b[i] != c {
-				return false
-			}
-		}
-		return true
-	}
+	return len(b) >= n && string(b[:n]) == pattern
 }
 
-var scanFollowsMultilineBasicStringDelimiter = scanFollows([]byte{'"', '"', '"'})
-var scanFollowsMultilineLiteralStringDelimiter = scanFollows([]byte{'\'', '\'', '\''})
-var scanFollowsTrue = scanFollows([]byte{'t', 'r', 'u', 'e'})
-var scanFollowsFalse = scanFollows([]byte{'f', 'a', 'l', 's', 'e'})
-var scanFollowsInf = scanFollows([]byte{'i', 'n', 'f'})
-var scanFollowsNan = scanFollows([]byte{'n', 'a', 'n'})
+func scanFollowsMultilineBasicStringDelimiter(b []byte) bool {
+	return scanFollows(b, `"""`)
+}
 
-func scanUnquotedKey(b []byte) ([]byte, []byte, error) {
-	//unquoted-key = 1*( ALPHA / DIGIT / %x2D / %x5F ) ; A-Z / a-z / 0-9 / - / _
+func scanFollowsMultilineLiteralStringDelimiter(b []byte) bool {
+	return scanFollows(b, `'''`)
+}
+
+func scanFollowsTrue(b []byte) bool {
+	return scanFollows(b, `true`)
+}
+
+func scanFollowsFalse(b []byte) bool {
+	return scanFollows(b, `false`)
+}
+
+func scanFollowsInf(b []byte) bool {
+	return scanFollows(b, `inf`)
+}
+
+func scanFollowsNan(b []byte) bool {
+	return scanFollows(b, `nan`)
+}
+
+func scanUnquotedKey(b []byte) ([]byte, []byte) {
+	// unquoted-key = 1*( ALPHA / DIGIT / %x2D / %x5F ) ; A-Z / a-z / 0-9 / - / _
 	for i := 0; i < len(b); i++ {
 		if !isUnquotedKeyChar(b[i]) {
-			return b[:i], b[i:], nil
+			return b[:i], b[i:]
 		}
 	}
-	return b, b[len(b):], nil
+
+	return b, b[len(b):]
 }
 
 func isUnquotedKeyChar(r byte) bool {
@@ -38,9 +46,9 @@ func isUnquotedKeyChar(r byte) bool {
 }
 
 func scanLiteralString(b []byte) ([]byte, []byte, error) {
-	//literal-string = apostrophe *literal-char apostrophe
-	//apostrophe = %x27 ; ' apostrophe
-	//literal-char = %x09 / %x20-26 / %x28-7E / non-ascii
+	// literal-string = apostrophe *literal-char apostrophe
+	// apostrophe = %x27 ; ' apostrophe
+	// literal-char = %x09 / %x20-26 / %x28-7E / non-ascii
 	for i := 1; i < len(b); i++ {
 		switch b[i] {
 		case '\'':
@@ -49,24 +57,22 @@ func scanLiteralString(b []byte) ([]byte, []byte, error) {
 			return nil, nil, newDecodeError(b[i:i+1], "literal strings cannot have new lines")
 		}
 	}
+
 	return nil, nil, newDecodeError(b[len(b):], "unterminated literal string")
 }
 
 func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
-	//ml-literal-string = ml-literal-string-delim [ newline ] ml-literal-body
-	//ml-literal-string-delim
-	//ml-literal-string-delim = 3apostrophe
-	//ml-literal-body = *mll-content *( mll-quotes 1*mll-content ) [ mll-quotes ]
+	// ml-literal-string = ml-literal-string-delim [ newline ] ml-literal-body
+	// ml-literal-string-delim
+	// ml-literal-string-delim = 3apostrophe
+	// ml-literal-body = *mll-content *( mll-quotes 1*mll-content ) [ mll-quotes ]
 	//
-	//mll-content = mll-char / newline
-	//mll-char = %x09 / %x20-26 / %x28-7E / non-ascii
-	//mll-quotes = 1*2apostrophe
+	// mll-content = mll-char / newline
+	// mll-char = %x09 / %x20-26 / %x28-7E / non-ascii
+	// mll-quotes = 1*2apostrophe
 	for i := 3; i < len(b); i++ {
-		switch b[i] {
-		case '\'':
-			if scanFollowsMultilineLiteralStringDelimiter(b[i:]) {
-				return b[:i+3], b[i+3:], nil
-			}
+		if b[i] == '\'' && scanFollowsMultilineLiteralStringDelimiter(b[i:]) {
+			return b[:i+3], b[i+3:], nil
 		}
 	}
 
@@ -74,13 +80,16 @@ func scanMultilineLiteralString(b []byte) ([]byte, []byte, error) {
 }
 
 func scanWindowsNewline(b []byte) ([]byte, []byte, error) {
-	if len(b) < 2 {
-		return nil, nil, fmt.Errorf(`windows new line missing \n`)
+	const lenCRLF = 2
+	if len(b) < lenCRLF {
+		return nil, nil, newDecodeError(b, "windows new line expected")
 	}
+
 	if b[1] != '\n' {
-		return nil, nil, fmt.Errorf(`windows new line should be \r\n`)
+		return nil, nil, newDecodeError(b, `windows new line should be \r\n`)
 	}
-	return b[:2], b[2:], nil
+
+	return b[:lenCRLF], b[lenCRLF:], nil
 }
 
 func scanWhitespace(b []byte) ([]byte, []byte) {
@@ -92,34 +101,32 @@ func scanWhitespace(b []byte) ([]byte, []byte) {
 			return b[:i], b[i:]
 		}
 	}
+
 	return b, b[len(b):]
 }
 
-func scanComment(b []byte) ([]byte, []byte, error) {
-	//;; Comment
+//nolint:unparam
+func scanComment(b []byte) ([]byte, []byte) {
+	// comment-start-symbol = %x23 ; #
+	// non-ascii = %x80-D7FF / %xE000-10FFFF
+	// non-eol = %x09 / %x20-7F / non-ascii
 	//
-	//comment-start-symbol = %x23 ; #
-	//non-ascii = %x80-D7FF / %xE000-10FFFF
-	//non-eol = %x09 / %x20-7F / non-ascii
-	//
-	//comment = comment-start-symbol *non-eol
-
+	// comment = comment-start-symbol *non-eol
 	for i := 1; i < len(b); i++ {
-		switch b[i] {
-		case '\n':
-			return b[:i], b[i:], nil
+		if b[i] == '\n' {
+			return b[:i], b[i:]
 		}
 	}
-	return b, nil, nil
+
+	return b, nil
 }
 
-// TODO perform validation on the string?
 func scanBasicString(b []byte) ([]byte, []byte, error) {
-	//basic-string = quotation-mark *basic-char quotation-mark
-	//quotation-mark = %x22            ; "
-	//basic-char = basic-unescaped / escaped
-	//basic-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
-	//escaped = escape escape-seq-char
+	// basic-string = quotation-mark *basic-char quotation-mark
+	// quotation-mark = %x22            ; "
+	// basic-char = basic-unescaped / escaped
+	// basic-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
+	// escaped = escape escape-seq-char
 	for i := 1; i < len(b); i++ {
 		switch b[i] {
 		case '"':
@@ -134,22 +141,20 @@ func scanBasicString(b []byte) ([]byte, []byte, error) {
 		}
 	}
 
-	return nil, nil, fmt.Errorf(`basic string not terminated by "`)
+	return nil, nil, newDecodeError(b[len(b):], `basic string not terminated by "`)
 }
 
-// TODO perform validation on the string?
 func scanMultilineBasicString(b []byte) ([]byte, []byte, error) {
-	//ml-basic-string = ml-basic-string-delim [ newline ] ml-basic-body
-	//ml-basic-string-delim
-	//ml-basic-string-delim = 3quotation-mark
-	//ml-basic-body = *mlb-content *( mlb-quotes 1*mlb-content ) [ mlb-quotes ]
+	// ml-basic-string = ml-basic-string-delim [ newline ] ml-basic-body
+	// ml-basic-string-delim
+	// ml-basic-string-delim = 3quotation-mark
+	// ml-basic-body = *mlb-content *( mlb-quotes 1*mlb-content ) [ mlb-quotes ]
 	//
-	//mlb-content = mlb-char / newline / mlb-escaped-nl
-	//mlb-char = mlb-unescaped / escaped
-	//mlb-quotes = 1*2quotation-mark
-	//mlb-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
-	//mlb-escaped-nl = escape ws newline *( wschar / newline )
-
+	// mlb-content = mlb-char / newline / mlb-escaped-nl
+	// mlb-char = mlb-unescaped / escaped
+	// mlb-quotes = 1*2quotation-mark
+	// mlb-unescaped = wschar / %x21 / %x23-5B / %x5D-7E / non-ascii
+	// mlb-escaped-nl = escape ws newline *( wschar / newline )
 	for i := 3; i < len(b); i++ {
 		switch b[i] {
 		case '"':

strict.go

@@ -0,0 +1,107 @@
+package toml
+
+import (
+	"github.com/pelletier/go-toml/v2/internal/ast"
+	"github.com/pelletier/go-toml/v2/internal/danger"
+	"github.com/pelletier/go-toml/v2/internal/tracker"
+)
+
+type strict struct {
+	Enabled bool
+
+	// Tracks the current key being processed.
+	key tracker.KeyTracker
+
+	missing []decodeError
+}
+
+func (s *strict) EnterTable(node *ast.Node) {
+	if !s.Enabled {
+		return
+	}
+
+	s.key.UpdateTable(node)
+}
+
+func (s *strict) EnterArrayTable(node *ast.Node) {
+	if !s.Enabled {
+		return
+	}
+
+	s.key.UpdateArrayTable(node)
+}
+
+func (s *strict) EnterKeyValue(node *ast.Node) {
+	if !s.Enabled {
+		return
+	}
+
+	s.key.Push(node)
+}
+
+func (s *strict) ExitKeyValue(node *ast.Node) {
+	if !s.Enabled {
+		return
+	}
+
+	s.key.Pop(node)
+}
+
+func (s *strict) MissingTable(node *ast.Node) {
+	if !s.Enabled {
+		return
+	}
+
+	s.missing = append(s.missing, decodeError{
+		highlight: keyLocation(node),
+		message:   "missing table",
+		key:       s.key.Key(),
+	})
+}
+
+func (s *strict) MissingField(node *ast.Node) {
+	if !s.Enabled {
+		return
+	}
+
+	s.missing = append(s.missing, decodeError{
+		highlight: keyLocation(node),
+		message:   "missing field",
+		key:       s.key.Key(),
+	})
+}
+
+func (s *strict) Error(doc []byte) error {
+	if !s.Enabled || len(s.missing) == 0 {
+		return nil
+	}
+
+	err := &StrictMissingError{
+		Errors: make([]DecodeError, 0, len(s.missing)),
+	}
+
+	for _, derr := range s.missing {
+		derr := derr
+		err.Errors = append(err.Errors, *wrapDecodeError(doc, &derr))
+	}
+
+	return err
+}
+
+func keyLocation(node *ast.Node) []byte {
+	k := node.Key()
+
+	hasOne := k.Next()
+	if !hasOne {
+		panic("should not be called with empty key")
+	}
+
+	start := k.Node().Data
+	end := k.Node().Data
+
+	for k.Next() {
+		end = k.Node().Data
+	}
+
+	return danger.BytesRange(start, end)
+}

targets.go

@@ -1,554 +0,0 @@
-package toml
-
-import (
-	"fmt"
-	"math"
-	"reflect"
-	"strings"
-	"sync"
-)
-
-type target interface {
-	// Dereferences the target.
-	get() reflect.Value
-
-	// Store a string at the target.
-	setString(v string) error
-
-	// Store a boolean at the target
-	setBool(v bool) error
-
-	// Store an int64 at the target
-	setInt64(v int64) error
-
-	// Store a float64 at the target
-	setFloat64(v float64) error
-
-	// Stores any  value at the target
-	set(v reflect.Value) error
-}
-
-// valueTarget just contains a reflect.Value that can be set.
-// It is used for struct fields.
-type valueTarget reflect.Value
-
-func (t valueTarget) get() reflect.Value {
-	return reflect.Value(t)
-}
-
-func (t valueTarget) set(v reflect.Value) error {
-	reflect.Value(t).Set(v)
-	return nil
-}
-
-func (t valueTarget) setString(v string) error {
-	t.get().SetString(v)
-	return nil
-}
-
-func (t valueTarget) setBool(v bool) error {
-	t.get().SetBool(v)
-	return nil
-}
-
-func (t valueTarget) setInt64(v int64) error {
-	t.get().SetInt(v)
-	return nil
-}
-
-func (t valueTarget) setFloat64(v float64) error {
-	t.get().SetFloat(v)
-	return nil
-}
-
-// interfaceTarget wraps an other target to dereference on get.
-type interfaceTarget struct {
-	x target
-}
-
-func (t interfaceTarget) get() reflect.Value {
-	return t.x.get().Elem()
-}
-
-func (t interfaceTarget) set(v reflect.Value) error {
-	return t.x.set(v)
-}
-
-func (t interfaceTarget) setString(v string) error {
-	return t.x.setString(v)
-}
-
-func (t interfaceTarget) setBool(v bool) error {
-	return t.x.setBool(v)
-}
-
-func (t interfaceTarget) setInt64(v int64) error {
-	return t.x.setInt64(v)
-}
-
-func (t interfaceTarget) setFloat64(v float64) error {
-	return t.x.setFloat64(v)
-}
-
-// mapTarget targets a specific key of a map.
-type mapTarget struct {
-	v reflect.Value
-	k reflect.Value
-}
-
-func (t mapTarget) get() reflect.Value {
-	return t.v.MapIndex(t.k)
-}
-
-func (t mapTarget) set(v reflect.Value) error {
-	t.v.SetMapIndex(t.k, v)
-	return nil
-}
-
-func (t mapTarget) setString(v string) error {
-	return t.set(reflect.ValueOf(v))
-}
-
-func (t mapTarget) setBool(v bool) error {
-	return t.set(reflect.ValueOf(v))
-}
-
-func (t mapTarget) setInt64(v int64) error {
-	return t.set(reflect.ValueOf(v))
-}
-
-func (t mapTarget) setFloat64(v float64) error {
-	return t.set(reflect.ValueOf(v))
-}
-
-// makes sure that the value pointed at by t is indexable (Slice, Array), or
-// dereferences to an indexable (Ptr, Interface).
-func ensureValueIndexable(t target) error {
-	f := t.get()
-
-	switch f.Type().Kind() {
-	case reflect.Slice:
-		if f.IsNil() {
-			return t.set(reflect.MakeSlice(f.Type(), 0, 0))
-		}
-	case reflect.Interface:
-		if f.IsNil() || f.Elem().Type() != sliceInterfaceType {
-			return t.set(reflect.MakeSlice(sliceInterfaceType, 0, 0))
-		}
-		if f.Elem().Type().Kind() != reflect.Slice {
-			return fmt.Errorf("interface is pointing to a %s, not a slice", f.Kind())
-		}
-	case reflect.Ptr:
-		if f.IsNil() {
-			ptr := reflect.New(f.Type().Elem())
-			err := t.set(ptr)
-			if err != nil {
-				return err
-			}
-			f = t.get()
-		}
-		return ensureValueIndexable(valueTarget(f.Elem()))
-	case reflect.Array:
-		// arrays are always initialized.
-	default:
-		return fmt.Errorf("cannot initialize a slice in %s", f.Kind())
-	}
-	return nil
-}
-
-var sliceInterfaceType = reflect.TypeOf([]interface{}{})
-var mapStringInterfaceType = reflect.TypeOf(map[string]interface{}{})
-
-func ensureMapIfInterface(x target) {
-	v := x.get()
-	if v.Kind() == reflect.Interface && v.IsNil() {
-		newElement := reflect.MakeMap(mapStringInterfaceType)
-		x.set(newElement)
-	}
-}
-
-func setString(t target, v string) error {
-	f := t.get()
-
-	switch f.Kind() {
-	case reflect.String:
-		return t.setString(v)
-	case reflect.Interface:
-		return t.set(reflect.ValueOf(v))
-	default:
-		return fmt.Errorf("cannot assign string to a %s", f.Kind())
-	}
-}
-
-func setBool(t target, v bool) error {
-	f := t.get()
-
-	switch f.Kind() {
-	case reflect.Bool:
-		return t.setBool(v)
-	case reflect.Interface:
-		return t.set(reflect.ValueOf(v))
-	default:
-		return fmt.Errorf("cannot assign bool to a %s", f.String())
-	}
-}
-
-const maxInt = int64(^uint(0) >> 1)
-const minInt = -maxInt - 1
-
-func setInt64(t target, v int64) error {
-	f := t.get()
-
-	switch f.Kind() {
-	case reflect.Int64:
-		return t.setInt64(v)
-	case reflect.Int32:
-		if v < math.MinInt32 || v > math.MaxInt32 {
-			return fmt.Errorf("integer %d does not fit in an int32", v)
-		}
-		return t.set(reflect.ValueOf(int32(v)))
-	case reflect.Int16:
-		if v < math.MinInt16 || v > math.MaxInt16 {
-			return fmt.Errorf("integer %d does not fit in an int16", v)
-		}
-		return t.set(reflect.ValueOf(int16(v)))
-	case reflect.Int8:
-		if v < math.MinInt8 || v > math.MaxInt8 {
-			return fmt.Errorf("integer %d does not fit in an int8", v)
-		}
-		return t.set(reflect.ValueOf(int8(v)))
-	case reflect.Int:
-		if v < minInt || v > maxInt {
-			return fmt.Errorf("integer %d does not fit in an int", v)
-		}
-		return t.set(reflect.ValueOf(int(v)))
-
-	case reflect.Uint64:
-		if v < 0 {
-			return fmt.Errorf("negative integer %d cannot be stored in an uint64", v)
-		}
-		return t.set(reflect.ValueOf(uint64(v)))
-	case reflect.Uint32:
-		if v < 0 {
-			return fmt.Errorf("negative integer %d cannot be stored in an uint32", v)
-		}
-		if v > math.MaxUint32 {
-			return fmt.Errorf("integer %d cannot be stored in an uint32", v)
-		}
-		return t.set(reflect.ValueOf(uint32(v)))
-	case reflect.Uint16:
-		if v < 0 {
-			return fmt.Errorf("negative integer %d cannot be stored in an uint16", v)
-		}
-		if v > math.MaxUint16 {
-			return fmt.Errorf("integer %d cannot be stored in an uint16", v)
-		}
-		return t.set(reflect.ValueOf(uint16(v)))
-	case reflect.Uint8:
-		if v < 0 {
-			return fmt.Errorf("negative integer %d cannot be stored in an uint8", v)
-		}
-		if v > math.MaxUint8 {
-			return fmt.Errorf("integer %d cannot be stored in an uint8", v)
-		}
-		return t.set(reflect.ValueOf(uint8(v)))
-	case reflect.Uint:
-		if v < 0 {
-			return fmt.Errorf("negative integer %d cannot be stored in an uint", v)
-		}
-		return t.set(reflect.ValueOf(uint(v)))
-	case reflect.Interface:
-		return t.set(reflect.ValueOf(v))
-	default:
-		return fmt.Errorf("cannot assign int64 to a %s", f.String())
-	}
-}
-
-func setFloat64(t target, v float64) error {
-	f := t.get()
-
-	switch f.Kind() {
-	case reflect.Float64:
-		return t.setFloat64(v)
-	case reflect.Float32:
-		if v > math.MaxFloat32 {
-			return fmt.Errorf("float %f cannot be stored in a float32", v)
-		}
-		return t.set(reflect.ValueOf(float32(v)))
-	case reflect.Interface:
-		return t.set(reflect.ValueOf(v))
-	default:
-		return fmt.Errorf("cannot assign float64 to a %s", f.String())
-	}
-}
-
-// Returns the element at idx of the value pointed at by target, or an error if
-// t does not point to an indexable.
-// If the target points to an Array and idx is out of bounds, it returns
-// (nil, nil) as this is not a fatal error (the unmarshaler will skip).
-func elementAt(t target, idx int) (target, error) {
-	f := t.get()
-
-	switch f.Kind() {
-	case reflect.Slice:
-		// TODO: use the idx function argument and avoid alloc if possible.
-		idx := f.Len()
-		err := t.set(reflect.Append(f, reflect.New(f.Type().Elem()).Elem()))
-		if err != nil {
-			return nil, err
-		}
-		return valueTarget(t.get().Index(idx)), nil
-	case reflect.Array:
-		if idx >= f.Len() {
-			return nil, nil
-		}
-		return valueTarget(f.Index(idx)), nil
-	case reflect.Interface:
-		if f.IsNil() {
-			panic("interface should have been initialized")
-		}
-		ifaceElem := f.Elem()
-		if ifaceElem.Kind() != reflect.Slice {
-			return nil, fmt.Errorf("cannot elementAt on a %s", f.Kind())
-		}
-		idx := ifaceElem.Len()
-		newElem := reflect.New(ifaceElem.Type().Elem()).Elem()
-		newSlice := reflect.Append(ifaceElem, newElem)
-		err := t.set(newSlice)
-		if err != nil {
-			return nil, err
-		}
-		return valueTarget(t.get().Elem().Index(idx)), nil
-	case reflect.Ptr:
-		return elementAt(valueTarget(f.Elem()), idx)
-	default:
-		return nil, fmt.Errorf("cannot elementAt on a %s", f.Kind())
-	}
-}
-
-func (d *decoder) scopeTableTarget(append bool, t target, name string) (target, bool, error) {
-	x := t.get()
-
-	switch x.Kind() {
-	// Kinds that need to recurse
-
-	case reflect.Interface:
-		t, err := scopeInterface(append, t)
-		if err != nil {
-			return t, false, err
-		}
-		return d.scopeTableTarget(append, t, name)
-	case reflect.Ptr:
-		t, err := scopePtr(t)
-		if err != nil {
-			return t, false, err
-		}
-		return d.scopeTableTarget(append, t, name)
-	case reflect.Slice:
-		t, err := scopeSlice(append, t)
-		if err != nil {
-			return t, false, err
-		}
-		append = false
-		return d.scopeTableTarget(append, t, name)
-	case reflect.Array:
-		t, err := d.scopeArray(append, t)
-		if err != nil {
-			return t, false, err
-		}
-		append = false
-		return d.scopeTableTarget(append, t, name)
-
-	// Terminal kinds
-
-	case reflect.Struct:
-		return scopeStruct(x, name)
-	case reflect.Map:
-		if x.IsNil() {
-			t.set(reflect.MakeMap(x.Type()))
-			x = t.get()
-		}
-
-		return scopeMap(x, name)
-	default:
-		panic(fmt.Errorf("can't scope on a %s", x.Kind()))
-	}
-}
-
-func scopeInterface(append bool, t target) (target, error) {
-	err := initInterface(append, t)
-	if err != nil {
-		return t, err
-	}
-	return interfaceTarget{t}, nil
-}
-
-func scopePtr(t target) (target, error) {
-	err := initPtr(t)
-	if err != nil {
-		return t, err
-	}
-	return valueTarget(t.get().Elem()), nil
-}
-
-func initPtr(t target) error {
-	x := t.get()
-	if !x.IsNil() {
-		return nil
-	}
-	return t.set(reflect.New(x.Type().Elem()))
-}
-
-// initInterface makes sure that the interface pointed at by the target is not
-// nil.
-// Returns the target to the initialized value of the target.
-func initInterface(append bool, t target) error {
-	x := t.get()
-
-	if x.Kind() != reflect.Interface {
-		panic("this should only be called on interfaces")
-	}
-
-	if !x.IsNil() && (x.Elem().Type() == sliceInterfaceType || x.Elem().Type() == mapStringInterfaceType) {
-		return nil
-	}
-
-	var newElement reflect.Value
-	if append {
-		newElement = reflect.MakeSlice(sliceInterfaceType, 0, 0)
-	} else {
-		newElement = reflect.MakeMap(mapStringInterfaceType)
-	}
-	err := t.set(newElement)
-	if err != nil {
-		return err
-	}
-
-	return nil
-}
-
-func scopeSlice(append bool, t target) (target, error) {
-	v := t.get()
-
-	if append {
-		newElem := reflect.New(v.Type().Elem())
-		newSlice := reflect.Append(v, newElem.Elem())
-		err := t.set(newSlice)
-		if err != nil {
-			return t, err
-		}
-		v = t.get()
-	}
-	return valueTarget(v.Index(v.Len() - 1)), nil
-}
-
-func (d *decoder) scopeArray(append bool, t target) (target, error) {
-	v := t.get()
-
-	idx := d.arrayIndex(append, v)
-
-	if idx >= v.Len() {
-		return nil, fmt.Errorf("not enough space in the array")
-	}
-
-	return valueTarget(v.Index(idx)), nil
-}
-
-func scopeMap(v reflect.Value, name string) (target, bool, error) {
-	k := reflect.ValueOf(name)
-
-	keyType := v.Type().Key()
-	if !k.Type().AssignableTo(keyType) {
-		if !k.Type().ConvertibleTo(keyType) {
-			return nil, false, fmt.Errorf("cannot convert string into map key type %s", keyType)
-		}
-		k = k.Convert(keyType)
-	}
-
-	if !v.MapIndex(k).IsValid() {
-		newElem := reflect.New(v.Type().Elem())
-		v.SetMapIndex(k, newElem.Elem())
-	}
-
-	return mapTarget{
-		v: v,
-		k: k,
-	}, true, nil
-}
-
-type fieldPathsMap = map[string][]int
-
-type fieldPathsCache struct {
-	m map[reflect.Type]fieldPathsMap
-	l sync.RWMutex
-}
-
-func (c *fieldPathsCache) get(t reflect.Type) (fieldPathsMap, bool) {
-	c.l.RLock()
-	paths, ok := c.m[t]
-	c.l.RUnlock()
-	return paths, ok
-}
-
-func (c *fieldPathsCache) set(t reflect.Type, m fieldPathsMap) {
-	c.l.Lock()
-	c.m[t] = m
-	c.l.Unlock()
-}
-
-var globalFieldPathsCache = fieldPathsCache{
-	m: map[reflect.Type]fieldPathsMap{},
-	l: sync.RWMutex{},
-}
-
-func scopeStruct(v reflect.Value, name string) (target, bool, error) {
-	// TODO: cache this, and reduce allocations
-
-	fieldPaths, ok := globalFieldPathsCache.get(v.Type())
-	if !ok {
-		fieldPaths = map[string][]int{}
-
-		path := make([]int, 0, 16)
-		var walk func(reflect.Value)
-		walk = func(v reflect.Value) {
-			t := v.Type()
-			for i := 0; i < t.NumField(); i++ {
-				l := len(path)
-				path = append(path, i)
-				f := t.Field(i)
-				if f.PkgPath != "" {
-					// only consider exported fields
-				} else if f.Anonymous {
-					walk(v.Field(i))
-				} else {
-					fieldName, ok := f.Tag.Lookup("toml")
-					if !ok {
-						fieldName = f.Name
-					}
-
-					pathCopy := make([]int, len(path))
-					copy(pathCopy, path)
-
-					fieldPaths[fieldName] = pathCopy
-					// extra copy for the case-insensitive match
-					fieldPaths[strings.ToLower(fieldName)] = pathCopy
-				}
-				path = path[:l]
-			}
-		}
-
-		walk(v)
-
-		globalFieldPathsCache.set(v.Type(), fieldPaths)
-	}
-
-	path, ok := fieldPaths[name]
-	if !ok {
-		path, ok = fieldPaths[strings.ToLower(name)]
-	}
-	if !ok {
-		return nil, false, nil
-	}
-
-	return valueTarget(v.FieldByIndex(path)), true, nil
-}

targets_test.go

@@ -1,184 +0,0 @@
-package toml
-
-import (
-	"reflect"
-	"testing"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-)
-
-func TestStructTarget_Ensure(t *testing.T) {
-	examples := []struct {
-		desc  string
-		input reflect.Value
-		name  string
-		test  func(v reflect.Value, err error)
-	}{
-		{
-			desc:  "handle a nil slice of string",
-			input: reflect.ValueOf(&struct{ A []string }{}).Elem(),
-			name:  "A",
-			test: func(v reflect.Value, err error) {
-				assert.NoError(t, err)
-				assert.False(t, v.IsNil())
-			},
-		},
-		{
-			desc:  "handle an existing slice of string",
-			input: reflect.ValueOf(&struct{ A []string }{A: []string{"foo"}}).Elem(),
-			name:  "A",
-			test: func(v reflect.Value, err error) {
-				assert.NoError(t, err)
-				require.False(t, v.IsNil())
-				s := v.Interface().([]string)
-				assert.Equal(t, []string{"foo"}, s)
-			},
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			d := decoder{}
-			target, _, err := d.scopeTableTarget(false, valueTarget(e.input), e.name)
-			require.NoError(t, err)
-			err = ensureValueIndexable(target)
-			v := target.get()
-			e.test(v, err)
-		})
-	}
-}
-
-func TestStructTarget_SetString(t *testing.T) {
-	str := "value"
-
-	examples := []struct {
-		desc  string
-		input reflect.Value
-		name  string
-		test  func(v reflect.Value, err error)
-	}{
-		{
-			desc:  "sets a string",
-			input: reflect.ValueOf(&struct{ A string }{}).Elem(),
-			name:  "A",
-			test: func(v reflect.Value, err error) {
-				assert.NoError(t, err)
-				assert.Equal(t, str, v.String())
-			},
-		},
-		{
-			desc:  "fails on a float",
-			input: reflect.ValueOf(&struct{ A float64 }{}).Elem(),
-			name:  "A",
-			test: func(v reflect.Value, err error) {
-				assert.Error(t, err)
-			},
-		},
-		{
-			desc:  "fails on a slice",
-			input: reflect.ValueOf(&struct{ A []string }{}).Elem(),
-			name:  "A",
-			test: func(v reflect.Value, err error) {
-				assert.Error(t, err)
-			},
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			d := decoder{}
-			target, _, err := d.scopeTableTarget(false, valueTarget(e.input), e.name)
-			require.NoError(t, err)
-			err = setString(target, str)
-			v := target.get()
-			e.test(v, err)
-		})
-	}
-}
-
-func TestPushNew(t *testing.T) {
-	t.Run("slice of strings", func(t *testing.T) {
-		type Doc struct {
-			A []string
-		}
-		d := Doc{}
-
-		dec := decoder{}
-		x, _, err := dec.scopeTableTarget(false, valueTarget(reflect.ValueOf(&d).Elem()), "A")
-		require.NoError(t, err)
-
-		n, err := elementAt(x, 0)
-		require.NoError(t, err)
-		require.NoError(t, n.setString("hello"))
-		require.Equal(t, []string{"hello"}, d.A)
-
-		n, err = elementAt(x, 1)
-		require.NoError(t, err)
-		require.NoError(t, n.setString("world"))
-		require.Equal(t, []string{"hello", "world"}, d.A)
-	})
-
-	t.Run("slice of interfaces", func(t *testing.T) {
-		type Doc struct {
-			A []interface{}
-		}
-		d := Doc{}
-
-		dec := decoder{}
-		x, _, err := dec.scopeTableTarget(false, valueTarget(reflect.ValueOf(&d).Elem()), "A")
-		require.NoError(t, err)
-
-		n, err := elementAt(x, 0)
-		require.NoError(t, err)
-		require.NoError(t, setString(n, "hello"))
-		require.Equal(t, []interface{}{"hello"}, d.A)
-
-		n, err = elementAt(x, 1)
-		require.NoError(t, err)
-		require.NoError(t, setString(n, "world"))
-		require.Equal(t, []interface{}{"hello", "world"}, d.A)
-	})
-}
-
-func TestScope_Struct(t *testing.T) {
-	examples := []struct {
-		desc  string
-		input reflect.Value
-		name  string
-		err   bool
-		found bool
-		idx   []int
-	}{
-		{
-			desc:  "simple field",
-			input: reflect.ValueOf(&struct{ A string }{}).Elem(),
-			name:  "A",
-			idx:   []int{0},
-			found: true,
-		},
-		{
-			desc:  "fails not-exported field",
-			input: reflect.ValueOf(&struct{ a string }{}).Elem(),
-			name:  "a",
-			err:   false,
-			found: false,
-		},
-	}
-
-	for _, e := range examples {
-		t.Run(e.desc, func(t *testing.T) {
-			dec := decoder{}
-			x, found, err := dec.scopeTableTarget(false, valueTarget(e.input), e.name)
-			assert.Equal(t, e.found, found)
-			if e.err {
-				assert.Error(t, err)
-			}
-			if found {
-				x2, ok := x.(valueTarget)
-				require.True(t, ok)
-				x2.get()
-			}
-		})
-	}
-}

toml.abnf

@@ -59,6 +59,7 @@ val = string / boolean / array / inline-table / date-time / float / integer
 ;; String
 
 string = ml-basic-string / basic-string / ml-literal-string / literal-string
+
 ;; Basic String
 
 basic-string = quotation-mark *basic-char quotation-mark

toml_testgen_support_test.go

@@ -30,6 +30,7 @@ func testgenValid(t *testing.T, input string, jsonRef string) {
 	t.Logf("Input TOML:\n%s", input)
 
 	doc := map[string]interface{}{}
+
 	err := toml.Unmarshal([]byte(input), &doc)
 	if err != nil {
 		t.Fatalf("failed parsing toml: %s", err)
@@ -49,25 +50,23 @@ func testgenValid(t *testing.T, input string, jsonRef string) {
 	require.Equal(t, refDoc, doc2)
 }
 
-type testGenDescNode struct {
-	Type  string
-	Value interface{}
-}
-
 func testgenBuildRefDoc(jsonRef string) map[string]interface{} {
 	descTree := map[string]interface{}{}
+
 	err := json.Unmarshal([]byte(jsonRef), &descTree)
 	if err != nil {
-		panic(fmt.Errorf("reference doc should be valid JSON: %s", err))
+		panic(fmt.Sprintf("reference doc should be valid JSON: %s", err))
 	}
 
 	doc := testGenTranslateDesc(descTree)
 	if doc == nil {
 		return map[string]interface{}{}
 	}
+
 	return doc.(map[string]interface{})
 }
 
+//nolint:funlen,gocognit,cyclop
 func testGenTranslateDesc(input interface{}) interface{} {
 	a, ok := input.([]interface{})
 	if ok {
@@ -75,48 +74,61 @@ func testGenTranslateDesc(input interface{}) interface{} {
 		for i, v := range a {
 			xs[i] = testGenTranslateDesc(v)
 		}
+
 		return xs
 	}
 
-	d := input.(map[string]interface{})
+	d, ok := input.(map[string]interface{})
+	if !ok {
+		panic(fmt.Sprintf("input should be valid map[string]: %v", input))
+	}
 
-	var dtype string
-	var dvalue interface{}
+	var (
+		dtype  string
+		dvalue interface{}
+	)
 
+	//nolint:nestif
 	if len(d) == 2 {
 		dtypeiface, ok := d["type"]
 		if ok {
 			dvalue, ok = d["value"]
 			if ok {
 				dtype = dtypeiface.(string)
+
 				switch dtype {
 				case "string":
 					return dvalue.(string)
 				case "float":
 					v, err := strconv.ParseFloat(dvalue.(string), 64)
 					if err != nil {
-						panic(fmt.Errorf("invalid float '%s': %s", dvalue, err))
+						panic(fmt.Sprintf("invalid float '%s': %s", dvalue, err))
 					}
+
 					return v
 				case "integer":
 					v, err := strconv.ParseInt(dvalue.(string), 10, 64)
 					if err != nil {
-						panic(fmt.Errorf("invalid int '%s': %s", dvalue, err))
+						panic(fmt.Sprintf("invalid int '%s': %s", dvalue, err))
 					}
+
 					return v
 				case "bool":
 					return dvalue.(string) == "true"
 				case "datetime":
 					dt, err := time.Parse("2006-01-02T15:04:05Z", dvalue.(string))
 					if err != nil {
-						panic(fmt.Errorf("invalid datetime '%s': %s", dvalue, err))
+						panic(fmt.Sprintf("invalid datetime '%s': %s", dvalue, err))
 					}
+
 					return dt
 				case "array":
 					if dvalue == nil {
 						return nil
 					}
+
 					a := dvalue.([]interface{})
+
 					xs := make([]interface{}, len(a))
 
 					for i, v := range a {
@@ -125,7 +137,8 @@ func testGenTranslateDesc(input interface{}) interface{} {
 
 					return xs
 				}
-				panic(fmt.Errorf("unknown type: %s", dtype))
+
+				panic(fmt.Sprintf("unknown type: %s", dtype))
 			}
 		}
 	}
@@ -134,5 +147,6 @@ func testGenTranslateDesc(input interface{}) interface{} {
 	for k, v := range d {
 		dest[k] = testGenTranslateDesc(v)
 	}
+
 	return dest
 }

toml_testgen_test.go

@@ -6,26 +6,31 @@ import (
 )
 
 func TestInvalidDatetimeMalformedNoLeads(t *testing.T) {
+
 	input := `no-leads = 1987-7-05T17:45:00Z`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidDatetimeMalformedNoSecs(t *testing.T) {
+
 	input := `no-secs = 1987-07-05T17:45Z`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidDatetimeMalformedNoT(t *testing.T) {
+
 	input := `no-t = 1987-07-0517:45:00Z`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidDatetimeMalformedWithMilli(t *testing.T) {
+
 	input := `with-milli = 1987-07-5T17:45:00.12Z`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidDuplicateKeyTable(t *testing.T) {
+
 	input := `[fruit]
 type = "apple"
 
@@ -35,71 +40,84 @@ apple = "yes"`
 }
 
 func TestInvalidDuplicateKeys(t *testing.T) {
+
 	input := `dupe = false
 dupe = true`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidDuplicateTables(t *testing.T) {
+
 	input := `[a]
 [a]`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidEmptyImplicitTable(t *testing.T) {
+
 	input := `[naughty..naughty]`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidEmptyTable(t *testing.T) {
+
 	input := `[]`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidFloatNoLeadingZero(t *testing.T) {
+
 	input := `answer = .12345
 neganswer = -.12345`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidFloatNoTrailingDigits(t *testing.T) {
+
 	input := `answer = 1.
 neganswer = -1.`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeyEmpty(t *testing.T) {
+
 	input := ` = 1`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeyHash(t *testing.T) {
+
 	input := `a# = 1`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeyNewline(t *testing.T) {
+
 	input := `a
 = 1`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeyOpenBracket(t *testing.T) {
+
 	input := `[abc = 1`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeySingleOpenBracket(t *testing.T) {
+
 	input := `[`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeySpace(t *testing.T) {
+
 	input := `a b = 1`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidKeyStartBracket(t *testing.T) {
+
 	input := `[a]
 [xyz = 5
 [b]`
@@ -107,31 +125,37 @@ func TestInvalidKeyStartBracket(t *testing.T) {
 }
 
 func TestInvalidKeyTwoEquals(t *testing.T) {
+
 	input := `key= = 1`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidStringBadByteEscape(t *testing.T) {
+
 	input := `naughty = "\xAg"`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidStringBadEscape(t *testing.T) {
+
 	input := `invalid-escape = "This string has a bad \a escape character."`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidStringByteEscapes(t *testing.T) {
+
 	input := `answer = "\x33"`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidStringNoClose(t *testing.T) {
+
 	input := `no-ending-quote = "One time, at band camp`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableArrayImplicit(t *testing.T) {
+
 	input := "# This test is a bit tricky. It should fail because the first use of\n" +
 		"# `[[albums.songs]]` without first declaring `albums` implies that `albums`\n" +
 		"# must be a table. The alternative would be quite weird. Namely, it wouldn't\n" +
@@ -150,46 +174,54 @@ func TestInvalidTableArrayImplicit(t *testing.T) {
 }
 
 func TestInvalidTableArrayMalformedBracket(t *testing.T) {
+
 	input := `[[albums]
 name = "Born to Run"`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableArrayMalformedEmpty(t *testing.T) {
+
 	input := `[[]]
 name = "Born to Run"`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableEmpty(t *testing.T) {
+
 	input := `[]`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableNestedBracketsClose(t *testing.T) {
+
 	input := `[a]b]
 zyx = 42`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableNestedBracketsOpen(t *testing.T) {
+
 	input := `[a[b]
 zyx = 42`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableWhitespace(t *testing.T) {
+
 	input := `[invalid key]`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTableWithPound(t *testing.T) {
+
 	input := `[key#group]
 answer = 42`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTextAfterArrayEntries(t *testing.T) {
+
 	input := `array = [
   "Is there life after an array separator?", No
   "Entry"
@@ -198,21 +230,25 @@ func TestInvalidTextAfterArrayEntries(t *testing.T) {
 }
 
 func TestInvalidTextAfterInteger(t *testing.T) {
+
 	input := `answer = 42 the ultimate answer?`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTextAfterString(t *testing.T) {
+
 	input := `string = "Is there life after strings?" No.`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTextAfterTable(t *testing.T) {
+
 	input := `[error] this shouldn't be here`
 	testgenInvalid(t, input)
 }
 
 func TestInvalidTextBeforeArraySeparator(t *testing.T) {
+
 	input := `array = [
   "Is there life before an array separator?" No,
   "Entry"
@@ -221,6 +257,7 @@ func TestInvalidTextBeforeArraySeparator(t *testing.T) {
 }
 
 func TestInvalidTextInArray(t *testing.T) {
+
 	input := `array = [
   "Entry 1",
   I don't belong,
@@ -230,6 +267,7 @@ func TestInvalidTextInArray(t *testing.T) {
 }
 
 func TestValidArrayEmpty(t *testing.T) {
+
 	input := `thevoid = [[[[[]]]]]`
 	jsonRef := `{
     "thevoid": { "type": "array", "value": [
@@ -246,6 +284,7 @@ func TestValidArrayEmpty(t *testing.T) {
 }
 
 func TestValidArrayNospaces(t *testing.T) {
+
 	input := `ints = [1,2,3]`
 	jsonRef := `{
     "ints": {
@@ -261,6 +300,7 @@ func TestValidArrayNospaces(t *testing.T) {
 }
 
 func TestValidArraysHetergeneous(t *testing.T) {
+
 	input := `mixed = [[1, 2], ["a", "b"], [1.1, 2.1]]`
 	jsonRef := `{
     "mixed": {
@@ -285,6 +325,7 @@ func TestValidArraysHetergeneous(t *testing.T) {
 }
 
 func TestValidArraysNested(t *testing.T) {
+
 	input := `nest = [["a"], ["b"]]`
 	jsonRef := `{
     "nest": {
@@ -303,6 +344,7 @@ func TestValidArraysNested(t *testing.T) {
 }
 
 func TestValidArrays(t *testing.T) {
+
 	input := `ints = [1, 2, 3]
 floats = [1.1, 2.1, 3.1]
 strings = ["a", "b", "c"]
@@ -349,6 +391,7 @@ dates = [
 }
 
 func TestValidBool(t *testing.T) {
+
 	input := `t = true
 f = false`
 	jsonRef := `{
@@ -359,6 +402,7 @@ f = false`
 }
 
 func TestValidCommentsEverywhere(t *testing.T) {
+
 	input := `# Top comment.
   # Top comment.
 # Top comment.
@@ -368,7 +412,7 @@ func TestValidCommentsEverywhere(t *testing.T) {
 [group] # Comment
 answer = 42 # Comment
 # no-extraneous-keys-please = 999
-# Inbetween comment.
+# In between comment.
 more = [ # Comment
   # What about multiple # comments?
   # Can you handle it?
@@ -399,6 +443,7 @@ more = [ # Comment
 }
 
 func TestValidDatetime(t *testing.T) {
+
 	input := `bestdayever = 1987-07-05T17:45:00Z`
 	jsonRef := `{
     "bestdayever": {"type": "datetime", "value": "1987-07-05T17:45:00Z"}
@@ -407,12 +452,14 @@ func TestValidDatetime(t *testing.T) {
 }
 
 func TestValidEmpty(t *testing.T) {
+
 	input := ``
 	jsonRef := `{}`
 	testgenValid(t, input, jsonRef)
 }
 
 func TestValidExample(t *testing.T) {
+
 	input := `best-day-ever = 1987-07-05T17:45:00Z
 
 [numtheory]
@@ -436,6 +483,7 @@ perfection = [6, 28, 496]`
 }
 
 func TestValidFloat(t *testing.T) {
+
 	input := `pi = 3.14
 negpi = -3.14`
 	jsonRef := `{
@@ -446,6 +494,7 @@ negpi = -3.14`
 }
 
 func TestValidImplicitAndExplicitAfter(t *testing.T) {
+
 	input := `[a.b.c]
 answer = 42
 
@@ -465,6 +514,7 @@ better = 43`
 }
 
 func TestValidImplicitAndExplicitBefore(t *testing.T) {
+
 	input := `[a]
 better = 43
 
@@ -484,6 +534,7 @@ answer = 42`
 }
 
 func TestValidImplicitGroups(t *testing.T) {
+
 	input := `[a.b.c]
 answer = 42`
 	jsonRef := `{
@@ -499,6 +550,7 @@ answer = 42`
 }
 
 func TestValidInteger(t *testing.T) {
+
 	input := `answer = 42
 neganswer = -42`
 	jsonRef := `{
@@ -509,6 +561,7 @@ neganswer = -42`
 }
 
 func TestValidKeyEqualsNospace(t *testing.T) {
+
 	input := `answer=42`
 	jsonRef := `{
     "answer": {"type": "integer", "value": "42"}
@@ -517,6 +570,7 @@ func TestValidKeyEqualsNospace(t *testing.T) {
 }
 
 func TestValidKeySpace(t *testing.T) {
+
 	input := `"a b" = 1`
 	jsonRef := `{
     "a b": {"type": "integer", "value": "1"}
@@ -525,6 +579,7 @@ func TestValidKeySpace(t *testing.T) {
 }
 
 func TestValidKeySpecialChars(t *testing.T) {
+
 	input := "\"~!@$^&*()_+-`1234567890[]|/?><.,;:'\" = 1\n"
 	jsonRef := "{\n" +
 		"    \"~!@$^&*()_+-`1234567890[]|/?><.,;:'\": {\n" +
@@ -535,6 +590,7 @@ func TestValidKeySpecialChars(t *testing.T) {
 }
 
 func TestValidLongFloat(t *testing.T) {
+
 	input := `longpi = 3.141592653589793
 neglongpi = -3.141592653589793`
 	jsonRef := `{
@@ -545,6 +601,7 @@ neglongpi = -3.141592653589793`
 }
 
 func TestValidLongInteger(t *testing.T) {
+
 	input := `answer = 9223372036854775807
 neganswer = -9223372036854775808`
 	jsonRef := `{
@@ -555,6 +612,7 @@ neganswer = -9223372036854775808`
 }
 
 func TestValidMultilineString(t *testing.T) {
+
 	input := `multiline_empty_one = """"""
 multiline_empty_two = """
 """
@@ -612,6 +670,7 @@ equivalent_three = """\
 }
 
 func TestValidRawMultilineString(t *testing.T) {
+
 	input := `oneline = '''This string has a ' quote character.'''
 firstnl = '''
 This string has a ' quote character.'''
@@ -639,6 +698,7 @@ in it.'''`
 }
 
 func TestValidRawString(t *testing.T) {
+
 	input := `backspace = 'This string has a \b backspace character.'
 tab = 'This string has a \t tab character.'
 newline = 'This string has a \n new line character.'
@@ -680,6 +740,7 @@ backslash = 'This string has a \\ backslash character.'`
 }
 
 func TestValidStringEmpty(t *testing.T) {
+
 	input := `answer = ""`
 	jsonRef := `{
     "answer": {
@@ -691,6 +752,7 @@ func TestValidStringEmpty(t *testing.T) {
 }
 
 func TestValidStringEscapes(t *testing.T) {
+
 	input := `backspace = "This string has a \b backspace character."
 tab = "This string has a \t tab character."
 newline = "This string has a \n new line character."
@@ -752,6 +814,7 @@ notunicode4 = "This string does not have a unicode \\\u0075 escape."`
 }
 
 func TestValidStringSimple(t *testing.T) {
+
 	input := `answer = "You are not drinking enough whisky."`
 	jsonRef := `{
     "answer": {
@@ -763,6 +826,7 @@ func TestValidStringSimple(t *testing.T) {
 }
 
 func TestValidStringWithPound(t *testing.T) {
+
 	input := `pound = "We see no # comments here."
 poundcomment = "But there are # some comments here." # Did I # mess you up?`
 	jsonRef := `{
@@ -776,6 +840,7 @@ poundcomment = "But there are # some comments here." # Did I # mess you up?`
 }
 
 func TestValidTableArrayImplicit(t *testing.T) {
+
 	input := `[[albums.songs]]
 name = "Glory Days"`
 	jsonRef := `{
@@ -789,6 +854,7 @@ name = "Glory Days"`
 }
 
 func TestValidTableArrayMany(t *testing.T) {
+
 	input := `[[people]]
 first_name = "Bruce"
 last_name = "Springsteen"
@@ -820,6 +886,7 @@ last_name = "Seger"`
 }
 
 func TestValidTableArrayNest(t *testing.T) {
+
 	input := `[[albums]]
 name = "Born to Run"
 
@@ -831,7 +898,7 @@ name = "Born to Run"
 
 [[albums]]
 name = "Born in the USA"
-  
+
   [[albums.songs]]
   name = "Glory Days"
 
@@ -859,6 +926,7 @@ name = "Born in the USA"
 }
 
 func TestValidTableArrayOne(t *testing.T) {
+
 	input := `[[people]]
 first_name = "Bruce"
 last_name = "Springsteen"`
@@ -874,6 +942,7 @@ last_name = "Springsteen"`
 }
 
 func TestValidTableEmpty(t *testing.T) {
+
 	input := `[a]`
 	jsonRef := `{
     "a": {}
@@ -882,6 +951,7 @@ func TestValidTableEmpty(t *testing.T) {
 }
 
 func TestValidTableSubEmpty(t *testing.T) {
+
 	input := `[a]
 [a.b]`
 	jsonRef := `{
@@ -891,6 +961,7 @@ func TestValidTableSubEmpty(t *testing.T) {
 }
 
 func TestValidTableWhitespace(t *testing.T) {
+
 	input := `["valid key"]`
 	jsonRef := `{
     "valid key": {}
@@ -899,6 +970,7 @@ func TestValidTableWhitespace(t *testing.T) {
 }
 
 func TestValidTableWithPound(t *testing.T) {
+
 	input := `["key#group"]
 answer = 42`
 	jsonRef := `{
@@ -910,6 +982,7 @@ answer = 42`
 }
 
 func TestValidUnicodeEscape(t *testing.T) {
+
 	input := `answer4 = "\u03B4"
 answer8 = "\U000003B4"`
 	jsonRef := `{
@@ -920,6 +993,7 @@ answer8 = "\U000003B4"`
 }
 
 func TestValidUnicodeLiteral(t *testing.T) {
+
 	input := `answer = "δ"`
 	jsonRef := `{
     "answer": {"type": "string", "value": "δ"}

types.go

@@ -0,0 +1,13 @@
+package toml
+
+import (
+	"encoding"
+	"reflect"
+	"time"
+)
+
+var timeType = reflect.TypeOf(time.Time{})
+var textMarshalerType = reflect.TypeOf(new(encoding.TextMarshaler)).Elem()
+var textUnmarshalerType = reflect.TypeOf(new(encoding.TextUnmarshaler)).Elem()
+var mapStringInterfaceType = reflect.TypeOf(map[string]interface{}{})
+var sliceInterfaceType = reflect.TypeOf([]interface{}{})