151 lines
3.4 KiB
Markdown
151 lines
3.4 KiB
Markdown
# YAML support for the Go language
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Introduction
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------------
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The yaml package enables Go programs to comfortably encode and decode YAML
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values. It was developed within [Canonical](https://www.canonical.com) as
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part of the [juju](https://juju.ubuntu.com) project, and is based on a
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pure Go port of the well-known [libyaml](http://pyyaml.org/wiki/LibYAML)
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C library to parse and generate YAML data quickly and reliably.
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Compatibility
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-------------
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The yaml package supports most of YAML 1.2, but preserves some behavior
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from 1.1 for backwards compatibility.
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Specifically, as of v3 of the yaml package:
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- YAML 1.1 bools (_yes/no, on/off_) are supported as long as they are being
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decoded into a typed bool value. Otherwise they behave as a string. Booleans
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in YAML 1.2 are _true/false_ only.
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- Octals encode and decode as _0777_ per YAML 1.1, rather than _0o777_
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as specified in YAML 1.2, because most parsers still use the old format.
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Octals in the _0o777_ format are supported though, so new files work.
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- Does not support base-60 floats. These are gone from YAML 1.2, and were
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actually never supported by this package as it's clearly a poor choice.
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and offers backwards
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compatibility with YAML 1.1 in some cases.
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1.2, including support for
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anchors, tags, map merging, etc. Multi-document unmarshalling is not yet
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implemented, and base-60 floats from YAML 1.1 are purposefully not
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supported since they're a poor design and are gone in YAML 1.2.
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Installation and usage
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----------------------
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The import path for the package is *gopkg.in/yaml.v3*.
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To install it, run:
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go get gopkg.in/yaml.v3
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API documentation
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-----------------
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If opened in a browser, the import path itself leads to the API documentation:
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- [https://gopkg.in/yaml.v3](https://gopkg.in/yaml.v3)
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API stability
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-------------
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The package API for yaml v3 will remain stable as described in [gopkg.in](https://gopkg.in).
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License
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-------
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The yaml package is licensed under the MIT and Apache License 2.0 licenses.
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Please see the LICENSE file for details.
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Example
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-------
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```Go
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package main
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import (
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"fmt"
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"log"
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"gopkg.in/yaml.v3"
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)
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var data = `
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a: Easy!
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b:
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c: 2
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d: [3, 4]
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`
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// Note: struct fields must be public in order for unmarshal to
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// correctly populate the data.
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type T struct {
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A string
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B struct {
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RenamedC int `yaml:"c"`
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D []int `yaml:",flow"`
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}
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}
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func main() {
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t := T{}
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err := yaml.Unmarshal([]byte(data), &t)
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if err != nil {
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log.Fatalf("error: %v", err)
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}
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fmt.Printf("--- t:\n%v\n\n", t)
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d, err := yaml.Marshal(&t)
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if err != nil {
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log.Fatalf("error: %v", err)
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}
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fmt.Printf("--- t dump:\n%s\n\n", string(d))
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m := make(map[interface{}]interface{})
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err = yaml.Unmarshal([]byte(data), &m)
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if err != nil {
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log.Fatalf("error: %v", err)
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}
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fmt.Printf("--- m:\n%v\n\n", m)
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d, err = yaml.Marshal(&m)
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if err != nil {
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log.Fatalf("error: %v", err)
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}
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fmt.Printf("--- m dump:\n%s\n\n", string(d))
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}
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```
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This example will generate the following output:
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```
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--- t:
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{Easy! {2 [3 4]}}
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--- t dump:
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a: Easy!
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b:
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c: 2
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d: [3, 4]
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--- m:
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map[a:Easy! b:map[c:2 d:[3 4]]]
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--- m dump:
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a: Easy!
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b:
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c: 2
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d:
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- 3
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- 4
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```
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