AutomaticEnv does not seem to pull ENV anymore. Broken since 1.19.0, working in 1.18.0

[bludot]

Preflight Checklist

• I have searched the issue tracker for an issue that matches the one I want to file, without success.
• I am not looking for support or already pursued the available support channels without success.
• I have checked the troubleshooting guide for my problem, without success.

Viper Version

1.19.0

Go Version

1.21

Config Source

Environment variables, Files

Format

INI

Repl.it link

https://replit.com/@jamestrotter4/Go

Code reproducing the issue

package main

import (
	"errors"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"reflect"
	"runtime"
	"strings"

	"github.com/go-playground/validator"
	"github.com/spf13/viper"
)

// config struct

type Config struct {
	Name   string `mapstructure:"name" validate:"required"`
	Nested Nested `mapstructure:"nested"`
}

type Nested struct {
	Val string `mapstructure:"value" validate:"required"`
}

func main() {
	var config Config
	// set env for test
	os.Setenv("NAME", "test")
	os.Setenv("NESTED_VALUE", "test")

	// get the path of the current file
	_, b, _, _ := runtime.Caller(0)
	basepath := filepath.Dir(b)
	err := GetConfig(&config, basepath)
	log.Println(err)

}

func GetConfig(config *Config, cwd string) error {
	if reflect.ValueOf(config).Kind() != reflect.Ptr {
		return errors.New("config must be a pointer")
	}

	//config should be in the same folder that config.go is called from
	viper.AddConfigPath(cwd)
	viper.SetConfigName("config")
	viper.SetConfigType("ini")
	viper.SetEnvKeyReplacer(strings.NewReplacer(`.`, `_`))
	viper.AutomaticEnv()

	// Will not load the config file in development, staging, and production environment. Instead will use configmap

	if err := viper.ReadInConfig(); err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); ok {
			log.Println(err)
			log.Println("error loading server env config file (expected)")
		}
	}

	err := viper.Unmarshal(config)
	if err != nil {
		return errors.New("unable to decode into struct")
	}

	// should log values
	log.Println("name: ", config.Name)
	log.Println("nested field: ", config.Nested.Val)

	validate := validator.New()
	if err := validate.Struct(config); err != nil {
		fmt.Print(fmt.Sprintf("%v", err))
		return errors.New("missing required attributes")
	}

	return nil
}

Expected Behavior

Expected to not throw error on validation and for name and nested.val to have a value in logs.

Actual Behavior

config in the end does not have any value, env seems to not be read.

Steps To Reproduce

1. use version 1.19.0 of viper
2. use above code (or similar, with AutomaticEnv)
3. Expect to see no values added

Additional Information

Provided code works with viper version 1.18.0. Ideally I would not want to add BindEnv for every field I want to use. I've tried prefixing the env and other things like that thinking maybe it was missing something. In the end I was not able to get it working.

2024/07/31 12:18:16 Config File "config" Not Found in "[/home/runner/Go]"
2024/07/31 12:18:16 error loading server env config file (expected)

these logs are expected when there is no file. I expect to then get from ENV

Actual

2024/07/31 12:18:16 name:  
2024/07/31 12:18:16 nested field:  
Key: 'Config.Name' Error:Field validation for 'Name' failed on the 'required' tag
Key: 'Config.Nested.Val' Error:Field validation for 'Val' failed on the 'required' tag2024/07/31 12:18:16 missing required attributes

Expected:

2024/07/31 12:18:16 Config File "config" Not Found in "[/home/runner/Go]"
2024/07/31 12:18:16 error loading server env config file (expected)
2024/07/31 12:18:16 name:  test
2024/07/31 12:18:16 nested field:  test

[github-actions]

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[tandem97]

Same problem. Downgrade to 1.18 solves this problem.

[vyas-git]

Same issue in 1.19 unable to map env to struct.

I checked in changelog after v1.18.2 we need to use viper_bind_struct in tags .

try go run --tags=viper_bind_struct main.go . It works !!

[parnic]

Confirmed, same thing happening here. Starting with version 1.18.2 and continuing into 1.19.0, the only way an environment variable override gets applied in my case is if a config file exists with the target key in it. If there's no config file, or it doesn't have the key I'm trying to override via env, its value isn't being pulled from the env var.

type AlertConfig struct {
	NotificationType string `mapstructure:"NOTIFICATION_TYPE"`
	NotificationURL  string `mapstructure:"NOTIFICATION_URL"`
}

func loadConfig(path string) (config AlertConfig, err error) {
	viper.AddConfigPath(path)
	viper.SetConfigName("alerts")
	viper.SetConfigType("env")

	viper.AutomaticEnv()

	err = viper.ReadInConfig()
	if err != nil {
		if _, ok := err.(viper.ConfigFileNotFoundError); !ok {
			return
		}
	}

	err = viper.Unmarshal(&config)
	return
}

version <1.18.2: whether an alerts.env exists or not, the final value of config.NotificationType is whatever is in the env var.
version >= 1.18.2: env var override only works if alerts.env exists containing a NOTIFICATION_TYPE=something entry.

[florianrusch]

I found a workaround to avoid the config file:

// The following is required to introduce the paths to viper. Else viper
// would not be able to fetch these configurations from environment
// variables as it does not know the key to search for. Only configs which
// don't have any default value (`viper.SetDefault`) needs to be mentioned
// here.
var configsWithoutDefaultValues = []byte(`
nested:
  var:
name:
`)
viper.SetConfigType("yaml")
viper.ReadConfig(bytes.NewBuffer(configsWithoutDefaultValues))

[florianrusch]

Or another solution would be to set the default e.g. to an empty string:

viper.SetDefault("nested.var", "")

[kt1755]

I workaround this issue by parsing empty json object config to viper, to init viper key as follow

var cfg Config

viper.SetConfigType("json")

b, err := json.Marshal(cfg)
if err != nil {
    return cfg, err
}

reader := bytes.NewReader(b)
err = viper.ReadConfig(reader)
if err != nil {
    return cfg, err
}
...