553 lines
16 KiB
Markdown
553 lines
16 KiB
Markdown
# go-toml v2
|
|
|
|
Go library for the [TOML](https://toml.io/en/) format.
|
|
|
|
This library supports [TOML v1.0.0](https://toml.io/en/v1.0.0).
|
|
|
|
[🐞 Bug Reports](https://github.com/pelletier/go-toml/issues)
|
|
|
|
[💬 Anything else](https://github.com/pelletier/go-toml/discussions)
|
|
|
|
## Documentation
|
|
|
|
Full API, examples, and implementation notes are available in the Go
|
|
documentation.
|
|
|
|
[](https://pkg.go.dev/github.com/pelletier/go-toml/v2)
|
|
|
|
## Import
|
|
|
|
```go
|
|
import "github.com/pelletier/go-toml/v2"
|
|
```
|
|
|
|
See [Modules](#Modules).
|
|
|
|
## 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 present 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.DisallowUnknownFields
|
|
|
|
### Contextualized errors
|
|
|
|
When most decoding errors occur, go-toml returns [`DecodeError`][decode-err]),
|
|
which contains a human readable contextualized version of the error. For
|
|
example:
|
|
|
|
```
|
|
2| key1 = "value1"
|
|
3| key2 = "missing2"
|
|
| ~~~~ missing field
|
|
4| key3 = "missing3"
|
|
5| key4 = "value4"
|
|
```
|
|
|
|
[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-2</td><td>1.9x</td><td>1.9x</td></tr>
|
|
<tr><td>Marshal/ReferenceFile/map-2</td><td>1.7x</td><td>1.8x</td></tr>
|
|
<tr><td>Marshal/ReferenceFile/struct-2</td><td>2.2x</td><td>2.5x</td></tr>
|
|
<tr><td>Unmarshal/HugoFrontMatter-2</td><td>2.9x</td><td>2.9x</td></tr>
|
|
<tr><td>Unmarshal/ReferenceFile/map-2</td><td>2.6x</td><td>2.9x</td></tr>
|
|
<tr><td>Unmarshal/ReferenceFile/struct-2</td><td>4.4x</td><td>5.3x</td></tr>
|
|
</tbody>
|
|
</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-2</td><td>1.8x</td><td>2.9x</td></tr>
|
|
<tr><td>Marshal/SimpleDocument/struct-2</td><td>2.7x</td><td>4.2x</td></tr>
|
|
<tr><td>Unmarshal/SimpleDocument/map-2</td><td>4.5x</td><td>3.1x</td></tr>
|
|
<tr><td>Unmarshal/SimpleDocument/struct-2</td><td>6.2x</td><td>3.9x</td></tr>
|
|
<tr><td>UnmarshalDataset/example-2</td><td>3.1x</td><td>3.5x</td></tr>
|
|
<tr><td>UnmarshalDataset/code-2</td><td>2.3x</td><td>3.1x</td></tr>
|
|
<tr><td>UnmarshalDataset/twitter-2</td><td>2.5x</td><td>2.6x</td></tr>
|
|
<tr><td>UnmarshalDataset/citm_catalog-2</td><td>2.1x</td><td>2.2x</td></tr>
|
|
<tr><td>UnmarshalDataset/canada-2</td><td>1.6x</td><td>1.3x</td></tr>
|
|
<tr><td>UnmarshalDataset/config-2</td><td>4.3x</td><td>3.2x</td></tr>
|
|
<tr><td>[Geo mean]</td><td>2.7x</td><td>2.8x</td></tr>
|
|
</tbody>
|
|
</table>
|
|
<p>This table can be generated with <code>./ci.sh benchmark -a -html</code>.</p>
|
|
</details>
|
|
|
|
## Modules
|
|
|
|
go-toml uses Go's standard modules system.
|
|
|
|
Installation instructions:
|
|
|
|
- Go ≥ 1.16: Nothing to do. Use the import in your code. The `go` command deals
|
|
with it automatically.
|
|
- Go ≥ 1.13: `GO111MODULE=on go get github.com/pelletier/go-toml/v2`.
|
|
|
|
In case of trouble: [Go Modules FAQ][mod-faq].
|
|
|
|
[mod-faq]: https://github.com/golang/go/wiki/Modules#why-does-installing-a-tool-via-go-get-fail-with-error-cannot-find-main-module
|
|
|
|
## Tools
|
|
|
|
Go-toml provides three handy command line tools:
|
|
|
|
* `tomljson`: Reads a TOML file and outputs its JSON representation.
|
|
|
|
```
|
|
$ go install github.com/pelletier/go-toml/v2/cmd/tomljson@latest
|
|
$ tomljson --help
|
|
```
|
|
|
|
* `jsontoml`: Reads a JSON file and outputs a TOML representation.
|
|
|
|
```
|
|
$ go install github.com/pelletier/go-toml/v2/cmd/jsontoml@latest
|
|
$ jsontoml --help
|
|
```
|
|
|
|
* `tomll`: Lints and reformats a TOML file.
|
|
|
|
```
|
|
$ go install github.com/pelletier/go-toml/v2/cmd/tomll@latest
|
|
$ tomll --help
|
|
```
|
|
|
|
### Docker image
|
|
|
|
Those tools are also available as a [Docker image][docker]. For example, to use
|
|
`tomljson`:
|
|
|
|
```
|
|
docker run -i ghcr.io/pelletier/go-toml:v2 tomljson < example.toml
|
|
```
|
|
|
|
Multiple versions are availble on [ghcr.io][docker].
|
|
|
|
[docker]: https://github.com/pelletier/go-toml/pkgs/container/go-toml
|
|
|
|
## 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
|
|
|
|
#### `toml.Tree` replacement
|
|
|
|
This structure was the initial attempt at providing a document model for
|
|
go-toml. It allows manipulating the structure of any document, encoding and
|
|
decoding from their TOML representation. While a more robust feature was
|
|
initially planned in go-toml v2, this has been ultimately [removed from
|
|
scope][nodoc] of this library, with no plan to add it back at the moment. The
|
|
closest equivalent at the moment would be to unmarshal into an `interface{}` and
|
|
use type assertions and/or reflection to manipulate the arbitrary
|
|
structure. However this would fall short of providing all of the TOML features
|
|
such as adding comments and be specific about whitespace.
|
|
|
|
|
|
#### `toml.Position` are not retrievable anymore
|
|
|
|
The API for retrieving the position (line, column) of a specific TOML element do
|
|
not exist anymore. This was done to minimize the amount of concepts introduced
|
|
by the library (query path), and avoid the performance hit related to storing
|
|
positions in the absence of a document model, for a feature that seemed to have
|
|
little use. Errors however have gained more detailed position
|
|
information. Position retrieval seems better fitted for a document model, which
|
|
has been [removed from the scope][nodoc] of go-toml v2 at the moment.
|
|
|
|
### 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, or generate
|
|
struct types using `reflect.StructOf`.
|
|
|
|
#### 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. As a
|
|
result of this change, `Encoder.QuoteMapKeys` has been removed, as it is not
|
|
useful anymore.
|
|
|
|
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
|
|
|
|
#### `Encoder.CompactComments` has been removed
|
|
|
|
Emitting compact comments is now the default behavior of go-toml. This option
|
|
is not necessary anymore.
|
|
|
|
#### Struct tags have been merged
|
|
|
|
V1 used to provide multiple struct tags: `comment`, `commented`, `multiline`,
|
|
`toml`, and `omitempty`. To behave more like the standard library, v2 has merged
|
|
`toml`, `multiline`, and `omitempty`. For example:
|
|
|
|
```go
|
|
type doc struct {
|
|
// v1
|
|
F string `toml:"field" multiline:"true" omitempty:"true"`
|
|
// v2
|
|
F string `toml:"field,multiline,omitempty"`
|
|
}
|
|
```
|
|
|
|
Has a result, the `Encoder.SetTag*` methods have been removed, as there is just
|
|
one tag now.
|
|
|
|
|
|
#### `commented` tag has been removed
|
|
|
|
There is no replacement for the `commented` tag. This feature would be better
|
|
suited in a proper document model for go-toml v2, which has been [cut from
|
|
scope][nodoc] at the moment.
|
|
|
|
#### `Encoder.ArraysWithOneElementPerLine` has been renamed
|
|
|
|
The new name is `Encoder.SetArraysMultiline`. The behavior should be the same.
|
|
|
|
#### `Encoder.Indentation` has been renamed
|
|
|
|
The new name is `Encoder.SetIndentSymbol`. The behavior should be the same.
|
|
|
|
|
|
#### Embedded structs behave like stdlib
|
|
|
|
V1 defaults to merging embedded struct fields into the embedding struct. This
|
|
behavior was unexpected because it does not follow the standard library. To
|
|
avoid breaking backward compatibility, the `Encoder.PromoteAnonymous` method was
|
|
added to make the encoder behave correctly. Given backward compatibility is not
|
|
a problem anymore, v2 does the right thing by default: it follows the behavior
|
|
of `encoding/json`. `Encoder.PromoteAnonymous` has been removed.
|
|
|
|
[nodoc]: https://github.com/pelletier/go-toml/discussions/506#discussioncomment-1526038
|
|
|
|
### `query`
|
|
|
|
go-toml v1 provided the [`go-toml/query`][query] package. It allowed to run
|
|
JSONPath-style queries on TOML files. This feature is not available in v2. For a
|
|
replacement, check out [dasel][dasel].
|
|
|
|
This package has been removed because it was essentially not supported anymore
|
|
(last commit May 2020), increased the complexity of the code base, and more
|
|
complete solutions exist out there.
|
|
|
|
[query]: https://github.com/pelletier/go-toml/tree/f99d6bbca119636aeafcf351ee52b3d202782627/query
|
|
[dasel]: https://github.com/TomWright/dasel
|
|
|
|
## Versioning
|
|
|
|
Go-toml follows [Semantic Versioning](http://semver.org/). The supported version
|
|
of [TOML](https://github.com/toml-lang/toml) is indicated at the beginning of
|
|
this document. The last two major versions of Go are supported
|
|
(see [Go Release Policy](https://golang.org/doc/devel/release.html#policy)).
|
|
|
|
## License
|
|
|
|
The MIT License (MIT). Read [LICENSE](LICENSE).
|