Unmarshal using ENV without binding

[forward32]

Hi all,

Having this code:

type RpcConfig struct {
	ServerAddr string `mapstructure:"ADDR"`
}

func main() {
	v := viper.New()
	v.SetEnvKeyReplacer(strings.NewReplacer(".", "_"))
	v.AutomaticEnv()

	//v.BindEnv("ADDR")

	c := &RpcConfig{}
	if err := v.Unmarshal(c); err != nil {
		panic(err)
	}

	log.Printf("conf=%+v", c)
}

and running in this way:

ADDR="test" go run main.go

I got config with empty ServerAddr. If I remove comment from binding line it works but why viper couldn't get it from mapstructure tag itself?

Please let me know if I doing something wrong.

[cachance7]

I was able to work around this limitation by first marshaling my structs to a format viper could read and then using that data as a config. Note the yaml tags in the struct definitions below.

package app

import (
	"bytes"
	"github.com/spf13/viper"
	yaml "gopkg.in/yaml.v2"
)

type APIConfig struct {
	RootURL string `yaml:"rootUrl" mapstructure:"rootUrl"`
}

type HostPortConfig struct {
	Host string `yaml:"host" mapstructure:"host"`
	Port int    `yaml:"port" mapstructure:"port"`
}

type AppConfig struct {
	MyApi     *APIConfig      `yaml:"myapi" mapstructure:"myapi"`
	SrvAddr   *HostPortConfig `yaml:"srvaddr" mapstructure:"srvaddr"`
}

var Config *AppConfig

func init() {
	Config = new(AppConfig)
	Config.New()  // Initializes with some default values (definition not shown)

	// Marshal the struct into a format viper can read
	bs, err := yaml.Marshal(Config)
	if err != nil {
		panic("unable to marshal config to YAML")
	}

        // No bindings here!
	viper.AutomaticEnv()

        // Hydrate viper with fields
	viper.SetConfigType("yaml")
	viper.ReadConfig(bytes.NewBuffer(bs))

        // Now this call will take into account the env as well
	viper.Unmarshal(Config)
}

[forward32]

I guess viper was created to be independent from format, in your case it is .yaml. So you can't use .toml for example without changing of code.

But thanks for comment anyway.

[sagikazarmark]

Please see and follow the issue above. ☝️