propertyIndexesWithTag can handle slice of struct

The function now can traverse into a field whose type is slice of
struct. When reading field values from the returned indexes, Soong will
check if the next field is a slice of struct or not. If so, it will
recurse into all the values in the slice.

Bug: 181018147
Test: m nothing
Change-Id: Ib8a7b7911a0be37a6dc03079adeb906497e60875

proptools/proptools.go

@@ -125,3 +125,7 @@ func isStructPtr(t reflect.Type) bool {
 func isSlice(t reflect.Type) bool {
 	return t.Kind() == reflect.Slice
 }
+
+func isSliceOfStruct(t reflect.Type) bool {
+	return isSlice(t) && isStruct(t.Elem())
+}

proptools/tag.go

@@ -56,8 +56,8 @@ func propertyIndexesWithTag(t reflect.Type, key, value string) [][]int {
 	for i := 0; i < t.NumField(); i++ {
 		field := t.Field(i)
 		ft := field.Type
-		if isStruct(ft) || isStructPtr(ft) {
+		if isStruct(ft) || isStructPtr(ft) || isSliceOfStruct(ft) {
-			if ft.Kind() == reflect.Ptr {
+			if ft.Kind() == reflect.Ptr || ft.Kind() == reflect.Slice {
 				ft = ft.Elem()
 			}
 			subIndexes := propertyIndexesWithTag(ft, key, value)

proptools/tag_test.go

@@ -155,6 +155,31 @@ func TestPropertyIndexesWithTag(t *testing.T) {
 			}{},
 			want: [][]int{{0, 0}},
 		},
+		{
+			name: "slice of struct",
+			ps: &struct {
+				Other int
+				Foo   []struct {
+					Other int
+					Bar   string `name:"value"`
+				}
+			}{},
+			want: [][]int{{1, 1}},
+		},
+		{
+			name: "slice^2 of struct",
+			ps: &struct {
+				Other int
+				Foo   []struct {
+					Other int
+					Bar   []struct {
+						Other int
+						Baz   string `name:"value"`
+					}
+				}
+			}{},
+			want: [][]int{{1, 1, 1}},
+		},
 		{
 			name: "nil",
 			ps: (*struct {