Unmarshal methods does not work with embedded structures

[toby3d]

Expected behavior (what you expected to happen):

(syndication.Config) {
	Target: (syndication.Target) {
		UID: (string) "https://mstdn.io/@toby3d",
		Name: (string) "toby3d@mstdn.io",
		Service: (*syndication.Details) {
			Name: (string) "Mastodon",
			URL: (string) "https://mstdn.io/"
		},
		User: (*syndication.Details) {
			Name: (string) "toby3d@mstdn.io",
			URL: (string) "https://mstdn.io/@toby3d"
		}
	},
	Client: (syndication.Client) {
		ID: (string) (len=43) "hackme",
		Secret: (string) (len=43) "hackmetwice"
	}
}

Actual behavior (what actually happened):

(syndication.Config) {
	Target: (syndication.Target) {
		UID: (string) "",
		Name: (string) "",
		Service: (*syndication.Details) (nil),
		User: (*syndication.Details) (nil)
	},
	Client: (syndication.Client) {
		ID: (string) (len=43) "hackme",
		Secret: (string) (len=43) "hackmetwice"
	}
}

Repl.it link: https://repl.it/@toby3d/viper#main_test.go

Code reproducing the issue:

package debug_test

import (
	"io/ioutil"
	"os"
	"testing"

	"github.com/spf13/viper"
	"github.com/stretchr/testify/assert"
)

type (
	Syndication struct {
		Target Target `yaml:",inline"` // NOTE(toby3d): why nil?
		Client Client `yaml:"client"`
	}

	Client struct {
		ID     string `yaml:"id"`
		Secret string `yaml:"secret"`
	}

	Target struct {
		UID     string   `yaml:"uid" json:"uid"`
		Name    string   `yaml:"name" json:"name"`
		Service *Details `yaml:"service,omitempty" json:"service,omitempty"`
		User    *Details `yaml:"user,omitempty" json:"user,omitempty"`
	}

	Details struct {
		Name  string `yaml:"name" json:"name"`
		URL   string `yaml:"url,omitempty" json:"url,omitempty"`
		Photo string `yaml:"photo,omitempty" json:"photo,omitempty"`
	}
)

const raw = `---
baseURL: https://toby3d.test/
silos:
  - uid: https://mstdn.io/@toby3d
    name: toby3d@mstdn.io
    user:
      name: "toby3d@mstdn.io"
      url: "https://mstdn.io/@toby3d"
    service:
      name: Mastodon
      url: https://mstdn.io/
    client:
      id: hackme
      secret: hackmetwice
`

func TestRead(t *testing.T) {
	assert := assert.New(t)

	f, err := ioutil.TempFile(os.TempDir(), "config.*.yaml")
	if !assert.NoError(err) {
		t.FailNow()
	}
	defer f.Close()
	f.WriteString(raw)

	v := viper.New()
	v.AddConfigPath(os.TempDir())
	v.SetConfigFile(f.Name())
	if !assert.NoError(v.ReadInConfig()) {
		t.FailNow()
	}

	silos := make([]Syndication, 0)
	if !assert.NoError(v.UnmarshalKey("silos", &silos)) {
		t.FailNow()
	}

	assert.Contains(silos, Syndication{
		Target: Target{
			UID:  "https://mstdn.io/@toby3d",
			Name: "toby3d@mstdn.io",
			Service: &Details{
				Name: "Mastodon",
				URL:  "https://mstdn.io/",
			},
			User: &Details{
				Name: "toby3d@mstdn.io",
				URL:  "https://mstdn.io/@toby3d",
			},
		},
		Client: Client{
			ID:     "hackme",
			Secret: "hackmetwice",
		},
	})
}

Environment:

• Viper version: v1.7.1
• Config source: file
• File format: YAML

[github-actions]

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[toby3d]

To decode the keys into an embedded structure, I used the yaml:",inline" tag from the documentation package for YAML that Viper uses: https://pkg.go.dev/gopkg.in/yaml.v2#example-Unmarshal-Embedded

[sagikazarmark]

Unfortunately, that doesn't work with mapstructure (the library used under the hood). You need to use mapstructure tag with ,squash.

[sagikazarmark]

Although this is explicitly mentioned in the documentation, I added a troubleshooting section to the readme: https://github.com/spf13/viper#unmarshaling-doesnt-work