UnmarshalKey / Sub only uses read config, neglects environment variables

[manuelstein]

Description:
A structured configuration is read using ReadConfig or ReadInConfig. Subsection keys are bound to environment variables. Viper correctly updates its config, i.e. key access Get / AllSettings works correctly. But when trying to use Unmarshal, only the config file seems to be used.

Code:

package main

import (
	"bytes"
	"fmt"
	"os"

	"github.com/spf13/viper"
)

func main() {
	v := viper.New()

	type Foo struct {
		Bar string `mapstructure:"bar"`
	}
	foo := Foo{
		Bar: "A",
	}
	var yamlExample = []byte(`
foo:
  bar: "B"
`)
	// Read config
	fmt.Println("Reading config")
	v.SetConfigType("yaml")
	v.ReadConfig(bytes.NewBuffer(yamlExample))
	fmt.Printf("%#v\n\n", v.AllSettings())

	// BindEnv
	fmt.Println("Setting env")
	os.Setenv("FOO_BAR", "C")
	v.BindEnv("foo.bar", "FOO_BAR")
	fmt.Printf("%#v\n\n", v.AllSettings())

	fmt.Println("Unmarshal")
	if err := v.Sub("foo").Unmarshal(&foo); err != nil {
		panic(err)
	}
	fmt.Printf("%#v\n\n", foo)
}

Output:

Reading config
map[string]interface {}{"foo":map[string]interface {}{"bar":"B"}}

Setting env
map[string]interface {}{"foo":map[string]interface {}{"bar":"C"}}

Unmarshal
main.Foo{Bar:"B"}

Expected Output:

...
Unmarshal
main.Foo{Bar:"C"}

[github-actions]

👋 Thanks for reporting!

A maintainer will take a look at your issue shortly. 👀

In the meantime: We are working on Viper v2 and we would love to hear your thoughts about what you like or don't like about Viper, so we can improve or fix those issues.

⏰ If you have a couple minutes, please take some time and share your thoughts: https://forms.gle/R6faU74qPRPAzchZ9

📣 If you've already given us your feedback, you can still help by spreading the news,
either by sharing the above link or telling people about this on Twitter:

https://twitter.com/sagikazarmark/status/1306904078967074816

Thank you! ❤️

[KalleDK]

Ran into the same issue

[KalleDK]

The error seems to come from the Get() method. If I do the same but change Sub to Get, I also "miss" the env values. But only in "nested" values. Get only works if you give the full path, but then it works correctly!

[KalleDK]

Example expanded with Get also

code

package main

import (
	"bytes"
	"fmt"
	"os"

	"github.com/spf13/viper"
)

func main() {
	v := viper.New()

	type Bar struct {
		Val string `mapstructure:"val"`
	}
	type Foo struct {
		Bar Bar `mapstructure:"bar"`
	}
	foo := Foo{
		Bar: Bar{
			Val: "A",
		},
	}
	var yamlExample = []byte(`
foo:
  bar:
    val: "B"
`)
	// Read config
	fmt.Println("Reading config")
	v.SetConfigType("yaml")
	v.ReadConfig(bytes.NewBuffer(yamlExample))
	fmt.Printf("%#v\n\n", v.AllSettings())

	// BindEnv
	fmt.Println("Setting env")
	os.Setenv("FOO_BAR_VAL", "C")
	v.BindEnv("foo.bar.val", "FOO_BAR_VAL")
	fmt.Printf("%#v\n\n", v.AllSettings())

	fmt.Println("Get")
	val := v.Get("foo")
	if val == nil {
		panic("missing key")
	}
	fmt.Printf("%#v\n\n", val)

	fmt.Println("Unmarshal")
	if err := v.Sub("foo").Unmarshal(&foo); err != nil {
		panic(err)
	}
	fmt.Printf("%#v\n\n", foo)
}

Output:

Reading config
map[string]interface {}{"foo":map[string]interface {}{"bar":map[string]interface {}{"val":"B"}}}

Setting env
map[string]interface {}{"foo":map[string]interface {}{"bar":map[string]interface {}{"val":"C"}}}

Get
map[string]interface {}{"bar":map[string]interface {}{"val":"B"}}

Unmarshal
main.Foo{Bar:main.Bar{Val:"B"}}

Expected:

Reading config
map[string]interface {}{"foo":map[string]interface {}{"bar":map[string]interface {}{"val":"B"}}}

Setting env
map[string]interface {}{"foo":map[string]interface {}{"bar":map[string]interface {}{"val":"C"}}}

Get
map[string]interface {}{"bar":map[string]interface {}{"val":"C"}}

Unmarshal
main.Foo{Bar:main.Bar{Val:"C"}}

[KalleDK]

Simple workaround until fixed (mileage may vary)

func Sub(v *viper.Viper, name string) *viper.Viper {
	r := viper.New()
	for _, key := range v.AllKeys() {
		if strings.Index(key, name+".") == 0 {
			r.Set(key[len(name)+1:], v.Get(key))
		}
	}
	return r
}

[pcting]

i encountered this bug today. for me it was a bit difficult to track down was i am currently merging multiple yaml files together; i thought the issue was in that part of the code.

[dizys]

Same here. Unmarshal isn't picking up on the environment variables.