e.VIper.ReadInConfig run as part of Unmarshal clears merged in fields

[jkosecki]

Hi,

due to e.Viper.ReadInConfig() that is invoked as part of Enviper#Unmarshal any additional fields added via Viper#MergeConfigMap method are cleared. That prevents usage like that:

        e := enviper.New(viper.New())
	if err := e.ReadInConfig(); err != nil {
		panic(err.Error())
	}
	if err := e.MergeConfigMap(defaults.AllSettings()); err != nil {
		panic(err.Error())
	}
	if err := e.Unmarshal(&cfg); err != nil {
		panic(err.Error())
	}

Is there a reason why Unmarshal makes a call to ReadInConfig? Afaik, viper itself expects users to call ReadInConfig explicitly before Unmarshal is used

[iamolegga]

This was in original solution. I actually don't remember why is this required. You could fork this repo, drop that line and run tests and see if it will work for you