Alerting: Use correct time series name override from frame fields (#29693)

* cater for empty labels and new DisplayNameFromDS field

* simplify

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

* increase priority for ds display name

Co-authored-by: Arve Knudsen <arve.knudsen@gmail.com>

pkg/services/alerting/conditions/query.go

@@ -333,7 +333,9 @@ func FrameToSeriesSlice(frame *data.Frame) (tsdb.TimeSeriesSlice, error) {
 		switch {
 		case field.Config != nil && field.Config.DisplayName != "":
 			ts.Name = field.Config.DisplayName
-		case field.Labels != nil:
+		case field.Config != nil && field.Config.DisplayNameFromDS != "":
+			ts.Name = field.Config.DisplayNameFromDS
+		case len(field.Labels) > 0:
 			ts.Tags = field.Labels.Copy()
 			// Tags are appended to the name so they are eventually included in EvalMatch's Metric property
 			// for display in notifications.

pkg/services/alerting/conditions/query_test.go

@@ -306,6 +306,53 @@ func TestFrameToSeriesSlice(t *testing.T) {
 			},
 			Err: require.NoError,
 		},
+		{
+			name: "empty labels",
+			frame: data.NewFrame("",
+				data.NewField("Time", data.Labels{}, []time.Time{}),
+				data.NewField(`Values`, data.Labels{}, []float64{})),
+
+			seriesSlice: tsdb.TimeSeriesSlice{
+				&tsdb.TimeSeries{
+					Name:   "Values",
+					Points: tsdb.TimeSeriesPoints{},
+				},
+			},
+			Err: require.NoError,
+		},
+		{
+			name: "display name from data source",
+			frame: data.NewFrame("",
+				data.NewField("Time", data.Labels{}, []time.Time{}),
+				data.NewField(`Values`, data.Labels{}, []*int64{}).SetConfig(&data.FieldConfig{
+					DisplayNameFromDS: "sloth",
+				})),
+
+			seriesSlice: tsdb.TimeSeriesSlice{
+				&tsdb.TimeSeries{
+					Name:   "sloth",
+					Points: tsdb.TimeSeriesPoints{},
+				},
+			},
+			Err: require.NoError,
+		},
+		{
+			name: "prefer display name over data source display name",
+			frame: data.NewFrame("",
+				data.NewField("Time", data.Labels{}, []time.Time{}),
+				data.NewField(`Values`, data.Labels{}, []*int64{}).SetConfig(&data.FieldConfig{
+					DisplayName:       "sloth #1",
+					DisplayNameFromDS: "sloth #2",
+				})),
+
+			seriesSlice: tsdb.TimeSeriesSlice{
+				&tsdb.TimeSeries{
+					Name:   "sloth #1",
+					Points: tsdb.TimeSeriesPoints{},
+				},
+			},
+			Err: require.NoError,
+		},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {