使用地图将YAML编组为结构

Question

I'm attempting to unmarshal a YAML file into a struct containing two maps (using go-yaml).

YAML-file:

'Include':
    - 'string1'
    - 'string2'

'Exclude':
    - 'string3'
    - 'string4'

The struct:

type Paths struct {
    Include map[string]struct{}
    Exclude map[string]struct{}
}

A simplified version (i.e. removed error handling etc.) of the function attempting to unmarshal:

import "gopkg.in/yaml.v2"

func getYamlPaths(filename string) (Paths, error) {
    loadedPaths := Paths{
        Include: make(map[string]struct{}),
        Exclude: make(map[string]struct{}),
    }

    filenameabs, _ := filepath.Abs(filename)
    yamlFile, err := ioutil.ReadFile(filenameabs)

    err = yaml.Unmarshal(yamlFile, &loadedPaths)
    return loadedPaths, nil
}

Data is being read from the file, but the unmarshal-function is not putting anything into the struct, and is returning no errors.

I suspect that the unmarshal-function cannot turn the YAML collections into map[string]struct{}, but as mentioned it is producing no errors, and I've looked around for similar issues and can't seem to find any.

Any clues or insight would be much appreciated!

Answer 1

Through debugging I found multiple problems. First, yaml doesn't seem to care about the fields names. You have to annotate the fields with a

`yaml:"NAME"`

Second, in the YAML file, Include and Exclude both contain only a list of strings, not something similar to a map. So your struct becomes:

type Paths struct {
    Include []string `yaml:"Include"`
    Exclude []string `yaml:"Exclude"`
}

And it works. Full code:

package main

import (
    "fmt"
    "gopkg.in/yaml.v2"
)

var str string = `
'Include':
    - 'string1'
    - 'string2'

'Exclude':
    - 'string3'
    - 'string4'
`

type Paths struct {
    Include []string `yaml:"Include"`
    Exclude []string `yaml:"Exclude"`
}

func main() {
    paths := Paths{}

    err := yaml.Unmarshal([]byte(str), &paths)

    fmt.Printf("%v
", err)
    fmt.Printf("%+v
", paths)
}