Azure Monitor: Bug Fix for for template variables (#47478)

public/app/plugins/datasource/grafana-azure-monitor-datasource/variables.test.ts

@@ -471,6 +471,34 @@ describe('VariableSupport', () => {
         done();
       });
     });
+
+    it('should return None when there is no data', (done) => {
+      const variableSupport = new VariableSupport(
+        createMockDatasource({
+          azureLogAnalyticsDatasource: {
+            defaultSubscriptionId: 'defaultSubscriptionId',
+          },
+          getMetricNames: jest.fn().mockResolvedValueOnce([]),
+        })
+      );
+      const mockRequest = {
+        targets: [
+          {
+            refId: 'A',
+            queryType: AzureQueryType.GrafanaTemplateVariableFn,
+            grafanaTemplateVariableFn: {
+              kind: 'MetricNamesQuery',
+              rawQuery: 'metricNames(resourceGroup, metricDefinition, resourceName, metricNamespace)',
+            },
+          } as AzureMonitorQuery,
+        ],
+      } as DataQueryRequest<AzureMonitorQuery>;
+      const observables = variableSupport.query(mockRequest);
+      observables.subscribe((result: DataQueryResponseData) => {
+        expect(result.data.length).toBe(0);
+        done();
+      });
+    });
   });
 
   it('passes on the query to the main datasource for all non-grafana template variable fns', (done) => {

public/app/plugins/datasource/grafana-azure-monitor-datasource/variables.ts

@@ -32,7 +32,7 @@ export class VariableSupport extends CustomVariableSupport<DataSource, AzureMoni
         try {
           const templateVariablesResults = await this.callGrafanaTemplateVariableFn(queryObj.grafanaTemplateVariableFn);
           return {
-            data: templateVariablesResults ? [toDataFrame(templateVariablesResults)] : [],
+            data: templateVariablesResults?.length ? [toDataFrame(templateVariablesResults)] : [],
           };
         } catch (err) {
           return { data: [], error: { message: messageFromError(err) } };