Data: add json marshal/unmarshal to data.Frames type (#638)

Author: kylebrandt

data/frame.go

@@ -75,6 +75,25 @@ func (f *Frame) MarshalJSON() ([]byte, error) {
 //swagger:model
 type Frames []*Frame
 
+func (frames *Frames) MarshalJSON() ([]byte, error) {
+	cfg := jsoniter.ConfigCompatibleWithStandardLibrary
+	stream := cfg.BorrowStream(nil)
+	defer cfg.ReturnStream(stream)
+
+	writeDataFrames(frames, stream)
+	if stream.Error != nil {
+		return nil, stream.Error
+	}
+
+	return append([]byte(nil), stream.Buffer()...), nil
+}
+
+// UnmarshalJSON allows unmarshalling Frame from JSON.
+func (frames *Frames) UnmarshalJSON(b []byte) error {
+	iter := jsoniter.ParseBytes(jsoniter.ConfigDefault, b)
+	return readDataFramesJSON(frames, iter)
+}
+
 // AppendRow adds a new row to the Frame by appending to each element of vals to
 // the corresponding Field in the data.
 // The Frame's Fields must be initialized or AppendRow will panic.

data/frame_json.go

@@ -247,6 +247,18 @@ func readDataFrameJSON(frame *Frame, iter *jsoniter.Iterator) error {
 	return iter.Error
 }
 
+func readDataFramesJSON(frames *Frames, iter *jsoniter.Iterator) error {
+	for iter.ReadArray() {
+		frame := &Frame{}
+		iter.ReadVal(frame)
+		if iter.Error != nil {
+			return iter.Error
+		}
+		*frames = append(*frames, frame)
+	}
+	return nil
+}
+
 func readFrameData(iter *jsoniter.Iterator, frame *Frame) error {
 	for l2Field := iter.ReadObject(); l2Field != ""; l2Field = iter.ReadObject() {
 		switch l2Field {
@@ -848,6 +860,17 @@ func writeDataFrameData(frame *Frame, stream *jsoniter.Stream) {
 	stream.WriteObjectEnd()
 }
 
+func writeDataFrames(frames *Frames, stream *jsoniter.Stream) {
+	if frames == nil {
+		return
+	}
+	stream.WriteArrayStart()
+	for _, frame := range *frames {
+		stream.WriteVal(frame)
+	}
+	stream.WriteArrayEnd()
+}
+
 // ArrowBufferToJSON writes a frame to JSON
 // NOTE: the format should be considered experimental until grafana 8 is released.
 func ArrowBufferToJSON(b []byte, include FrameInclude) ([]byte, error) {

data/frame_json_test.go

@@ -115,6 +115,21 @@ func TestFieldTypeToJSON(t *testing.T) {
 	require.JSONEq(t, string(orig), string(second))
 }
 
+func TestJSONFrames(t *testing.T) {
+	frames := data.Frames{goldenDF()}
+	b, err := json.Marshal(frames)
+	require.NoError(t, err)
+
+	var rFrames data.Frames
+
+	err = json.Unmarshal(b, &rFrames)
+	require.NoError(t, err)
+
+	if diff := cmp.Diff(frames, rFrames, data.FrameTestCompareOptions()...); diff != "" {
+		t.Errorf("Result mismatch (-want +got):\n%s", diff)
+	}
+}
+
 func BenchmarkFrameToJSON(b *testing.B) {
 	f := goldenDF()
 	b.ReportAllocs()