Feature request: custom type unmarshalling about fig HOT 4 CLOSED

type StringUnmarshaler interface {
	UnmarshalString(s string) error
}

func (l *ListenerType) UnmarshalString(s string) error {
	switch strings.ToLower(s) {
	case "unix":
		*l = ListenerUnix
	...
	}
	return nil
}

func StringToStringUnmarshalerHook() mapstructure.DecodeHookFunc {
	return func(f reflect.Type, t reflect.Type, data interface{}) (interface{}, error) {
		if f.Kind() != reflect.String {
			return data, nil
		}

		if reflect.PointerTo(t).Implements(reflect.TypeOf((*StringUnmarshaler)(nil)).Elem()) {
			val := reflect.New(t).Interface()

			if unmarshaler, ok := val.(StringUnmarshaler); ok {
				err := unmarshaler.UnmarshalString(data.(string))
				if err != nil {
					return nil, err
				}

				return reflect.ValueOf(val).Elem().Interface(), nil
			}
		}

		return data, nil
	}
}

// during map structure decoder init
dec, err := mapstructure.NewDecoder(&mapstructure.DecoderConfig{
	Result: &cfg,
	DecodeHook: mapstructure.ComposeDecodeHookFunc(
		StringToStringUnmarshalerHook(),
	),
})