Unmarshal yaml map dict key to struct property - go

Question

I really searched a while here, but didn't found an adequate answer:
I am trying to unmarshall yaml dict keys onto a property of a struct rather than the key of a map.
Given this yaml
commands:
php:
service: php
bin: /bin/php
node:
service: node
bin: /bin/node
I am able to unmarshall this into a struct like this:
type Config struct {
Commands map[string]struct {
Service string
Bin string
}
}
But how am I able to unmarshall it into a struct like this:
type Config struct {
Commands []struct {
Name string // <-- this should be key from the yaml (i.e. php or node)
Service string
Bin string
}
}
Thx in advance for the help

Answer 1

You can write a custom unmarshaler, like this (on Go playground):
package main
import (
"fmt"
"gopkg.in/yaml.v3"
)
var input []byte = []byte(`
commands:
php:
service: php
bin: /bin/php
node:
service: node
bin: /bin/node
`)
type Command struct {
Service string
Bin string
}
type NamedCommand struct {
Command
Name string
}
type NamedCommands []NamedCommand
type Config struct {
Commands NamedCommands
}
func (p *NamedCommands) UnmarshalYAML(value *yaml.Node) error {
if value.Kind != yaml.MappingNode {
return fmt.Errorf("`commands` must contain YAML mapping, has %v", value.Kind)
}
*p = make([]NamedCommand, len(value.Content)/2)
for i := 0; i < len(value.Content); i += 2 {
var res = &(*p)[i/2]
if err := value.Content[i].Decode(&res.Name); err != nil {
return err
}
if err := value.Content[i+1].Decode(&res.Command); err != nil {
return err
}
}
return nil
}
func main() {
var f Config
var err error
if err = yaml.Unmarshal(input, &f); err != nil {
panic(err)
}
for _, cmd := range f.Commands {
fmt.Printf("%+v\n", cmd)
}
}
I have split the command data into Command and NamedCommand to make the code simpler, since you can just call Decode giving the embedded Command struct for the values. If everything was in the same struct, you'd need to manually map keys to struct fields.