feat: support map kind env (#244)

env.go

@@ -365,8 +365,11 @@ func set(field reflect.Value, sf reflect.StructField, value string, funcMap map[
 		return nil
 	}
 
-	if field.Kind() == reflect.Slice {
+	switch field.Kind() {
+	case reflect.Slice:
 		return handleSlice(field, value, sf, funcMap)
+	case reflect.Map:
+		return handleMap(field, value, sf, funcMap)
 	}
 
 	return newNoParserError(sf)
@@ -413,6 +416,54 @@ func handleSlice(field reflect.Value, value string, sf reflect.StructField, func
 	return nil
 }
 
+func handleMap(field reflect.Value, value string, sf reflect.StructField, funcMap map[reflect.Type]ParserFunc) error {
+	keyType := sf.Type.Key()
+	keyParserFunc, ok := funcMap[keyType]
+	if !ok {
+		keyParserFunc, ok = defaultBuiltInParsers[keyType.Kind()]
+		if !ok {
+			return newNoParserError(sf)
+		}
+	}
+
+	elemType := sf.Type.Elem()
+	elemParserFunc, ok := funcMap[elemType]
+	if !ok {
+		elemParserFunc, ok = defaultBuiltInParsers[elemType.Kind()]
+		if !ok {
+			return newNoParserError(sf)
+		}
+	}
+
+	separator := sf.Tag.Get("envSeparator")
+	if separator == "" {
+		separator = ","
+	}
+
+	result := reflect.MakeMap(sf.Type)
+	for _, part := range strings.Split(value, separator) {
+		pairs := strings.Split(part, ":")
+		if len(pairs) != 2 {
+			return fmt.Errorf("map pair: want 2 got %d", len(pairs))
+		}
+
+		key, err := keyParserFunc(pairs[0])
+		if err != nil {
+			return newParseError(sf, err)
+		}
+
+		elem, err := elemParserFunc(pairs[1])
+		if err != nil {
+			return newParseError(sf, err)
+		}
+
+		result.SetMapIndex(reflect.ValueOf(key).Convert(keyType), reflect.ValueOf(elem).Convert(elemType))
+	}
+
+	field.Set(result)
+	return nil
+}
+
 func asTextUnmarshaler(field reflect.Value) encoding.TextUnmarshaler {
 	if reflect.Ptr == field.Kind() {
 		if field.IsNil() {

env_test.go

@@ -401,6 +401,39 @@ func TestParsesEnv(t *testing.T) {
 	isEqual(t, cfg.unexported, "")
 }
 
+func TestParsesEnv_Map(t *testing.T) {
+	type config struct {
+		MapStringString map[string]string `env:"MAP_STRING_STRING" envSeparator:","`
+		MapStringInt64  map[string]int64  `env:"MAP_STRING_INT64"`
+		MapStringBool   map[string]bool   `env:"MAP_STRING_BOOL" envSeparator:";"`
+	}
+
+	mss := map[string]string{
+		"k1": "v1",
+		"k2": "v2",
+	}
+	setEnv(t, "MAP_STRING_STRING", "k1:v1,k2:v2")
+
+	msi := map[string]int64{
+		"k1": 1,
+		"k2": 2,
+	}
+	setEnv(t, "MAP_STRING_INT64", "k1:1,k2:2")
+
+	msb := map[string]bool{
+		"k1": true,
+		"k2": false,
+	}
+	setEnv(t, "MAP_STRING_BOOL", "k1:true;k2:false")
+
+	var cfg config
+	isNoErr(t, Parse(&cfg))
+
+	isEqual(t, mss, cfg.MapStringString)
+	isEqual(t, msi, cfg.MapStringInt64)
+	isEqual(t, msb, cfg.MapStringBool)
+}
+
 func TestSetEnvAndTagOptsChain(t *testing.T) {
 	type config struct {
 		Key1 string `mytag:"KEY1,required"`