fix issue when one of the stream field is defined (#36)

* fix issue when one of the stream field is defined

* update CHANGELOG.md

CHANGELOG.md

@@ -2,6 +2,8 @@
 
 ## tip
 
+* BUGFIX: fix bug with displaying response when one of the stream field is defined and lines are not collected. See [this issue](https://github.com/VictoriaMetrics/victorialogs-datasource/issues/34).
+
 ## v0.2.2
 
 * BUGFIX: fix bug with displaying responses with a custom set of fields. See [this issue](https://github.com/VictoriaMetrics/victorialogs-datasource/issues/23).

pkg/plugin/response.go

@@ -92,6 +92,14 @@ func parseStreamResponse(reader io.Reader) backend.DataResponse {
 		}
 	}
 
+	// Grafana expects lineFields to be always non-empty.
+	if lineField.Len() == 0 {
+		for i := 0; i < labelsField.Len(); i++ {
+			label := labelsField.At(i)
+			lineField.Append(fmt.Sprintf("%s", label))
+		}
+	}
+
 	// Grafana expects time field to be always non-empty.
 	if timeFd.Len() == 0 {
 		now := time.Now()

pkg/plugin/response_test.go

@@ -198,6 +198,49 @@ func Test_parseStreamResponse(t *testing.T) {
 				frame.Meta = &data.FrameMeta{}
 				rsp.Frames = append(rsp.Frames, frame)
 
+				return rsp
+			},
+		},
+		{
+			name: "response when one stream field is defined and other is free fields",
+			response: `{"_time":"2024-06-26T13:00:00Z","logs":"1400"}
+{"_time":"2024-06-26T14:00:00Z","logs":"374"}`,
+			want: func() backend.DataResponse {
+				labelsField := data.NewFieldFromFieldType(data.FieldTypeJSON, 0)
+				labelsField.Name = gLabelsField
+
+				timeFd := data.NewFieldFromFieldType(data.FieldTypeTime, 0)
+				timeFd.Name = gTimeField
+
+				lineField := data.NewFieldFromFieldType(data.FieldTypeString, 0)
+				lineField.Name = gLineField
+
+				timeFd.Append(time.Date(2024, 06, 26, 13, 00, 00, 0, time.UTC))
+				timeFd.Append(time.Date(2024, 06, 26, 14, 00, 00, 0, time.UTC))
+
+				lineField.Append(`{"logs":"1400"}`)
+				lineField.Append(`{"logs":"374"}`)
+
+				labels := data.Labels{
+					"logs": "1400",
+				}
+
+				b, _ := labelsToJSON(labels)
+				labelsField.Append(b)
+
+				labels = data.Labels{
+					"logs": "374",
+				}
+
+				b, _ = labelsToJSON(labels)
+				labelsField.Append(b)
+
+				frame := data.NewFrame("", timeFd, lineField, labelsField)
+
+				rsp := backend.DataResponse{}
+				frame.Meta = &data.FrameMeta{}
+				rsp.Frames = append(rsp.Frames, frame)
+
 				return rsp
 			},
 		},