Support struct with slice of primitives (#134)

aconfig_test.go

@@ -1414,6 +1414,40 @@ func TestFileConfigFlagDelim(t *testing.T) {
 	mustEqual(t, cfg, want)
 }
 
+func TestSliceOfStructsWithSliceOfPrimitives(t *testing.T) {
+	type TestService struct {
+		Name     string
+		Strings  []string
+		Integers []int
+		Booleans []bool
+	}
+
+	type TestConfig struct {
+		Services []TestService
+	}
+	var cfg TestConfig
+	loader := LoaderFor(&cfg, Config{
+		SkipDefaults: true,
+		SkipEnv:      true,
+		SkipFlags:    true,
+		Files:        []string{"testdata/slice-struct-primitive-slice.json"},
+	})
+
+	failIfErr(t, loader.Load())
+
+	want := TestConfig{
+		Services: []TestService{
+			{
+				Name:     "service1",
+				Strings:  []string{"string1", "string2"},
+				Integers: []int{1, 2},
+				Booleans: []bool{true, false},
+			},
+		},
+	}
+	mustEqual(t, cfg, want)
+}
+
 func failIfOk(t testing.TB, err error) {
 	t.Helper()
 	if err == nil {

reflection.go

@@ -201,7 +201,7 @@ func (l *Loader) setFieldData(field *fieldData, value interface{}) error {
 				vv := mii(val)
 
 				fd := l.newFieldData(reflect.StructField{}, slice.Index(i), nil)
-				if err := m2s(vv, fd.value); err != nil {
+				if err := l.m2s(vv, fd.value); err != nil {
 					return err
 				}
 			}
@@ -345,7 +345,7 @@ func (l *Loader) setMap(field *fieldData, value string) error {
 	return nil
 }
 
-func m2s(m map[string]interface{}, structValue reflect.Value) 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)
@@ -362,11 +362,20 @@ func m2s(m map[string]interface{}, structValue reflect.Value) error {
 			if structFieldValue.Kind() == reflect.Slice && val.Kind() == reflect.Slice {
 				vals := value.([]interface{})
 				slice := reflect.MakeSlice(structFieldValue.Type(), len(vals), len(vals))
-				for i := 0; i < len(vals); i++ {
-					a := mii(vals[i])
-					b := slice.Index(i)
-					if err := m2s(a, b); err != nil {
-						return err
+				if isPrimitive(structFieldValue.Type().Elem()) {
+					for i := 0; i < len(vals); i++ {
+						fd := l.newFieldData(reflect.StructField{}, slice.Index(i), nil)
+						if err := l.setFieldData(fd, vals[i]); err != nil {
+							return fmt.Errorf("incorrect slice item %q: %w", vals[i], err)
+						}
+					}
+				} else {
+					for i := 0; i < len(vals); i++ {
+						a := mii(vals[i])
+						b := slice.Index(i)
+						if err := l.m2s(a, b); err != nil {
+							return err
+						}
 					}
 				}
 				structFieldValue.Set(slice)
@@ -395,3 +404,7 @@ func mii(m interface{}) map[string]interface{} {
 		panic(fmt.Sprintf("%T %v", m, m))
 	}
 }
+
+func isPrimitive(v reflect.Type) bool {
+	return v.Kind() < reflect.Array || v.Kind() == reflect.String
+}

testdata/slice-struct-primitive-slice.json

@@ -0,0 +1,10 @@
+{
+  "services": [
+    {
+      "name": "service1",
+      "strings": ["string1", "string2"],
+      "integers": [1, 2],
+      "booleans": [true, false]
+    }
+  ]
+}