respect tag name for structs in a slice

aconfig_test.go

@@ -1536,10 +1536,11 @@ func TestFileConfigFlagDelim(t *testing.T) {
 
 func TestSliceOfStructsWithSliceOfPrimitives(t *testing.T) {
 	type TestService struct {
-		Name     string
-		Strings  []string
-		Integers []int
-		Booleans []bool
+		Name           string
+		Strings        []string
+		Integers       []int
+		Booleans       []bool
+		AnotherStrings []string `json:"another_strings"`
 	}
 
 	type TestConfig struct {
@@ -1558,10 +1559,11 @@ func TestSliceOfStructsWithSliceOfPrimitives(t *testing.T) {
 	want := TestConfig{
 		Services: []TestService{
 			{
-				Name:     "service1",
-				Strings:  []string{"string1", "string2"},
-				Integers: []int{1, 2},
-				Booleans: []bool{true, false},
+				Name:           "service1",
+				Strings:        []string{"string1", "string2"},
+				Integers:       []int{1, 2},
+				Booleans:       []bool{true, false},
+				AnotherStrings: []string{"another1", "another2"},
 			},
 		},
 	}

reflection.go

@@ -358,22 +358,42 @@ func (l *Loader) setMap(field *fieldData, value string) error {
 }
 
 func (l *Loader) m2s(m map[string]interface{}, structValue reflect.Value) error {
-	for name, value := range m {
-		name = strings.Title(name)
-		structFieldValue := structValue.FieldByName(name)
-		if !structFieldValue.IsValid() {
-			return fmt.Errorf("no such field %q in struct", name)
-		}
+	for _, dec := range l.config.FileDecoders {
+		for name, value := range m {
+			structFieldValue := structValue.FieldByName(name)
+			for i := 0; i < structValue.NumField(); i++ {
+				// first try to find field by name
+				tagName := structValue.Type().Field(i).Tag.Get(dec.Format())
+				// if tag is set - use it
+				if strings.EqualFold(tagName, name) {
+					name = structValue.Type().Field(i).Name
+					structFieldValue = structValue.FieldByName(name)
+					break
+				}
+				// if tag is not set - try to find field by name
+				if tagName == "" {
+					if strings.EqualFold(structValue.Type().Field(i).Name, name) {
+						name = structValue.Type().Field(i).Name
+						structFieldValue = structValue.FieldByName(name)
+						break
+					}
+				}
+			}
 
-		if !structFieldValue.CanSet() {
-			return fmt.Errorf("cannot set %q field value", name)
-		}
+			if !structFieldValue.IsValid() {
+				return fmt.Errorf("no such field %q in struct", name)
+			}
 
-		field, _ := structValue.Type().FieldByName(name)
+			if !structFieldValue.CanSet() {
+				return fmt.Errorf("cannot set %q field value", name)
+			}
 
-		fd := l.newFieldData(field, structFieldValue, nil)
-		if err := l.setFieldData(fd, value); err != nil {
-			return err
+			field, _ := structValue.Type().FieldByName(name)
+
+			fd := l.newFieldData(field, structFieldValue, nil)
+			if err := l.setFieldData(fd, value); err != nil {
+				return err
+			}
 		}
 	}
 	return nil

testdata/slice-struct-primitive-slice.json

@@ -4,7 +4,8 @@
       "name": "service1",
       "strings": ["string1", "string2"],
       "integers": [1, 2],
-      "booleans": [true, false]
+      "booleans": [true, false],
+      "another_strings": ["another1", "another2"]
     }
   ]
 }