How to parse YAML with dynamic key in Golang

Question

I am trying to parse a YAML file with Go. The problem is that the keys in the YAML file might not always be the same. This is to do API versioning so the user can define the

Answer 1

First, you are trying to parse the root as an Environment, but its actual type is map[string]Environment. Second, you are going to need a custom Unmarshaler if you want to keep that type structure. Something like this:

package main

import (
    "fmt"

    "gopkg.in/yaml.v2"
)

var data = `
---
development:
  skip-header-validation: true
  V1:
    current: "1.0.0"
    mime_types:
      - application/vnd.company.jk.identity+json;
      - application/vnd.company.jk.user+json;
      - application/vnd.company.jk.role+json;
      - application/vnd.company.jk.scope+json;
      - application/vnd.company.jk.test+json;
    skip-mime-type-validation: true
    skip-version-validation: true
  V2:
    current: "2.0.0"
    mime_types:
      - application/vnd.company.jk.identity+json;
      - application/vnd.company.jk.user+json;
      - application/vnd.company.jk.role+json;
      - application/vnd.company.jk.scope+json;
      - application/vnd.company.jk.test+json;

`

type MajorVersion struct {
    Current                string   `yaml:"current"`
    MimeTypes              []string `yaml:"mime_types"`
    SkipVersionValidation  bool     `yaml:"skip-version-validation"`
    SkipMimeTypeValidation bool     `yaml:"skip-mime-type-validation"`
}

type Environment struct {
    SkipHeaderValidation bool
    Versions             map[string]MajorVersion
}

func (e *Environment) UnmarshalYAML(unmarshal func(interface{}) error) error {
    var params struct {
        SkipHeaderValidation bool `yaml:"skip-header-validation"`
    }
    if err := unmarshal(&params); err != nil {
        return err
    }
    var versions map[string]MajorVersion
    if err := unmarshal(&versions); err != nil {
        // Here we expect an error because a boolean cannot be converted to a
        // a MajorVersion
        if _, ok := err.(*yaml.TypeError); !ok {
            return err
        }
    }
    e.SkipHeaderValidation = params.SkipHeaderValidation
    e.Versions = versions
    return nil
}

func main() {
    var e map[string]Environment
    if err := yaml.Unmarshal([]byte(data), &e); err != nil {
        fmt.Println(err.Error())
    }
    fmt.Printf("%#v\n", e)
}

Output (after using makeup):

map[string]main.Environment{
    "development": {
        SkipHeaderValidation: true,
        Versions:             {
            "V2": {
                Current:                "2.0.0",
                MimeTypes:              {"application/vnd.company.jk.identity+json;", "application/vnd.company.jk.user+json;", "application/vnd.company.jk.role+json;", "application/vnd.company.jk.scope+json;", "application/vnd.company.jk.test+json;"},
                SkipVersionValidation:  false,
                SkipMimeTypeValidation: false,
            },
            "V1": {
                Current:                "1.0.0",
                MimeTypes:              {"application/vnd.company.jk.identity+json;", "application/vnd.company.jk.user+json;", "application/vnd.company.jk.role+json;", "application/vnd.company.jk.scope+json;", "application/vnd.company.jk.test+json;"},
                SkipVersionValidation:  true,
                SkipMimeTypeValidation: true,
            },
        },
    },
}