Add GetFieldNameByTagValueDeep

reflections.go

@@ -104,6 +104,15 @@ func GetFieldTag(obj interface{}, fieldName, tagKey string) (string, error) {
 // The `obj` parameter must be a `struct`, or a `pointer` to one. If the `obj` parameter doesn't have a field tagged
 // with the `tagKey`, and the matching `tagValue`, this function returns an error.
 func GetFieldNameByTagValue(obj interface{}, tagKey, tagValue string) (string, error) {
+	return getFieldNameByTagValue(obj, tagKey, tagValue, false)
+}
+
+// GetFieldNameByTagValueDeep considers embedded fields too while scanning for a matching a matching `{tagKey}:"{tagValue}"` tag
+func GetFieldNameByTagValueDeep(obj interface{}, tagKey, tagValue string) (string, error) {
+	return getFieldNameByTagValue(obj, tagKey, tagValue, true)
+}
+
+func getFieldNameByTagValue(obj interface{}, tagKey, tagValue string, deep bool) (string, error) {
 	if !isSupportedType(obj, []reflect.Kind{reflect.Struct, reflect.Ptr}) {
 		return "", fmt.Errorf("cannot use GetFieldByTag on a non-struct interface: %w", ErrUnsupportedType)
 	}
@@ -114,8 +123,21 @@ func GetFieldNameByTagValue(obj interface{}, tagKey, tagValue string) (string, e
 
 	for i := range fieldsCount {
 		structField := objType.Field(i)
-		if structField.Tag.Get(tagKey) == tagValue {
-			return structField.Name, nil
+		if isExportableField(structField) {
+			if !deep || !structField.Anonymous {
+				if structField.Tag.Get(tagKey) == tagValue {
+					return structField.Name, nil
+				}
+				continue
+			}
+
+			fieldValue := objValue.Field(i)
+			m, err := getFieldNameByTagValue(fieldValue.Interface(), tagKey, tagValue, deep)
+			if err != nil {
+				return "", fmt.Errorf("cannot get items in %s: %w", structField.Name, err)
+			} else if m != "" {
+				return m, nil
+			}
 		}
 	}
 

reflections_test.go

@@ -553,6 +553,45 @@ func TestGetFieldNameByTagValue_on_non_existing_tag(t *testing.T) {
 	require.Error(t, errTagKeyValue)
 }
 
+func TestGetFieldNameByTagValueDeep(t *testing.T) {
+	t.Parallel()
+
+	type child struct {
+		TestStruct
+	}
+	dummyStruct := child{}
+
+	tagJSON := "dummytag"
+	field, err := GetFieldNameByTagValueDeep(dummyStruct, "test", tagJSON)
+
+	require.NoError(t, err)
+	assert.Equal(t, "Dummy", field)
+}
+
+func TestGetFieldNameByTagValueDeep_on_non_existing_tag(t *testing.T) {
+	t.Parallel()
+
+	type child struct {
+		TestStruct
+	}
+	dummyStruct := child{}
+
+	// non existing tag value with an existing tag key
+	tagJSON := "tag"
+	_, errTagValue := GetFieldNameByTagValueDeep(dummyStruct, "test", tagJSON)
+	require.Error(t, errTagValue)
+
+	// non existing tag key with an existing tag value
+	tagJSON = "dummytag"
+	_, errTagKey := GetFieldNameByTagValueDeep(dummyStruct, "json", tagJSON)
+	require.Error(t, errTagKey)
+
+	// non existing tag key and value
+	tagJSON = "tag"
+	_, errTagKeyValue := GetFieldNameByTagValueDeep(dummyStruct, "json", tagJSON)
+	require.Error(t, errTagKeyValue)
+}
+
 //nolint:unused
 func TestTags_deep(t *testing.T) {
 	t.Parallel()