Azure Monitor: Fix empty/errored responses for Logs variables (#59240)

pkg/tsdb/azuremonitor/loganalytics/azure-log-analytics-datasource.go

@@ -190,7 +190,10 @@ func (e *AzureLogAnalyticsDatasource) executeQuery(ctx context.Context, logger l
 	if err != nil {
 		return dataResponseErrorWithExecuted(err)
 	}
-	appendErrorNotice(frame, logResponse.Error)
+	frame = appendErrorNotice(frame, logResponse.Error)
+	if frame == nil {
+		return dataResponse
+	}
 
 	model, err := simplejson.NewJson(query.JSON)
 	if err != nil {
@@ -222,10 +225,15 @@ func (e *AzureLogAnalyticsDatasource) executeQuery(ctx context.Context, logger l
 	return dataResponse
 }
 
-func appendErrorNotice(frame *data.Frame, err *AzureLogAnalyticsAPIError) {
-	if err != nil {
-		frame.AppendNotices(apiErrorToNotice(err))
+func appendErrorNotice(frame *data.Frame, err *AzureLogAnalyticsAPIError) *data.Frame {
+	if err == nil {
+		return frame
 	}
+	if frame == nil {
+		frame = &data.Frame{}
+	}
+	frame.AppendNotices(apiErrorToNotice(err))
+	return frame
 }
 
 func (e *AzureLogAnalyticsDatasource) createRequest(ctx context.Context, logger log.Logger, url string) (*http.Request, error) {

pkg/tsdb/azuremonitor/loganalytics/azure-response-table-frame.go

@@ -45,12 +45,7 @@ func apiErrorToNotice(err *AzureLogAnalyticsAPIError) data.Notice {
 // ResponseTableToFrame converts an AzureResponseTable to a data.Frame.
 func ResponseTableToFrame(table *types.AzureResponseTable, refID string, executedQuery string) (*data.Frame, error) {
 	if len(table.Rows) == 0 {
-		return &data.Frame{
-			RefID: refID,
-			Meta: &data.FrameMeta{
-				ExecutedQueryString: executedQuery,
-			},
-		}, nil
+		return nil, nil
 	}
 
 	converterFrame, err := converterFrameForTable(table)

pkg/tsdb/azuremonitor/loganalytics/azure-response-table-frame_test.go

@@ -173,12 +173,7 @@ func TestLogTableToFrame(t *testing.T) {
 			name:     "empty data response",
 			testFile: "loganalytics/11-log-analytics-response-empty.json",
 			expectedFrame: func() *data.Frame {
-				return &data.Frame{
-					RefID: "A",
-					Meta: &data.FrameMeta{
-						ExecutedQueryString: "query",
-					},
-				}
+				return nil
 			},
 		},
 	}