Error Handling: support errors and data in a response (#20169)

public/app/plugins/datasource/testdata/datasource.ts

@@ -6,6 +6,7 @@ import {
   MetricFindValue,
   TableData,
   TimeSeries,
+  DataQueryError,
 } from '@grafana/data';
 import { Scenario, TestDataQuery } from './types';
 import { getBackendSrv } from 'app/core/services/backend_srv';
@@ -67,6 +68,7 @@ export class TestDataDataSource extends DataSourceApi<TestDataQuery> {
 
   processQueryResult(queries: any, res: any): DataQueryResponse {
     const data: TestData[] = [];
+    let error: DataQueryError | undefined = undefined;
 
     for (const query of queries) {
       const results = res.data.results[query.refId];
@@ -81,9 +83,15 @@ export class TestDataDataSource extends DataSourceApi<TestDataQuery> {
       for (const series of results.series || []) {
         data.push({ target: series.name, datapoints: series.points, refId: query.refId, tags: series.tags });
       }
+
+      if (results.error) {
+        error = {
+          message: results.error,
+        };
+      }
     }
 
-    return { data };
+    return { data, error };
   }
 
   annotationQuery(options: any) {