bugfix: add missing comma in vector/matrix array (#14047)

* bugfix: Add missing comma when encoding JSON results in web API

---------

Signed-off-by: Amir Vejahat <amir.vejahat.av@gmail.com>
Co-authored-by: Arthur Silva Sens <arthur.sens@coralogix.com>

web/api/v1/json_codec.go

@@ -241,8 +241,11 @@ func labelsIsEmpty(ptr unsafe.Pointer) bool {
 func unsafeMarshalVectorJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	v := *((*promql.Vector)(ptr))
 	stream.WriteArrayStart()
-	for _, s := range v {
+	for i, s := range v {
 		marshalSampleJSON(s, stream)
+		if i != len(v)-1 {
+			stream.WriteMore()
+		}
 	}
 	stream.WriteArrayEnd()
 }
@@ -251,8 +254,11 @@ func unsafeMarshalVectorJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 func unsafeMarshalMatrixJSON(ptr unsafe.Pointer, stream *jsoniter.Stream) {
 	m := *((*promql.Matrix)(ptr))
 	stream.WriteArrayStart()
-	for _, s := range m {
+	for i, s := range m {
 		marshalSeriesJSON(s, stream)
+		if i != len(m)-1 {
+			stream.WriteMore()
+		}
 	}
 	stream.WriteArrayEnd()
 }

web/api/v1/json_codec_test.go

@@ -29,6 +29,40 @@ func TestJsonCodec_Encode(t *testing.T) {
 		response interface{}
 		expected string
 	}{
+		{
+			response: &QueryData{
+				ResultType: parser.ValueTypeVector,
+				Result: promql.Vector{
+					promql.Sample{
+						Metric: labels.FromStrings("__name__", "foo"),
+						T:      1000,
+						F:      1,
+					},
+					promql.Sample{
+						Metric: labels.FromStrings("__name__", "bar"),
+						T:      2000,
+						F:      2,
+					},
+				},
+			},
+			expected: `{"status":"success","data":{"resultType":"vector","result":[{"metric":{"__name__":"foo"},"value":[1,"1"]},{"metric":{"__name__":"bar"},"value":[2,"2"]}]}}`,
+		},
+		{
+			response: &QueryData{
+				ResultType: parser.ValueTypeMatrix,
+				Result: promql.Matrix{
+					promql.Series{
+						Metric: labels.FromStrings("__name__", "foo"),
+						Floats: []promql.FPoint{{F: 1, T: 1000}},
+					},
+					promql.Series{
+						Metric: labels.FromStrings("__name__", "bar"),
+						Floats: []promql.FPoint{{F: 2, T: 2000}},
+					},
+				},
+			},
+			expected: `{"status":"success","data":{"resultType":"matrix","result":[{"metric":{"__name__":"foo"},"values":[[1,"1"]]},{"metric":{"__name__":"bar"},"values":[[2,"2"]]}]}}`,
+		},
 		{
 			response: &QueryData{
 				ResultType: parser.ValueTypeMatrix,