Templating: Fix error when response has data with empty array (#317)

src/DataSource.test.ts

@@ -0,0 +1,46 @@
+import { DataQueryResponse, DataSourceInstanceSettings, toDataFrame } from '@grafana/data';
+import { GitHubVariableQuery } from 'types';
+import { of } from 'rxjs';
+import { GithubDataSource } from 'DataSource';
+
+describe('DataSource', () => {
+  describe('metricFindQuery', () => {
+    it('should return empty array if data in response is empty array', async () => {
+      const ds = new GithubDataSource({} as DataSourceInstanceSettings);
+      const query = {} as GitHubVariableQuery;
+
+      jest.spyOn(ds, 'query').mockReturnValue(of({ data: [] }));
+      const res = await ds.metricFindQuery(query, {});
+      expect(res).toEqual([]);
+    });
+
+    it('should return empty array if no data in response', async () => {
+      const ds = new GithubDataSource({} as DataSourceInstanceSettings);
+      const query = {} as GitHubVariableQuery;
+
+      jest.spyOn(ds, 'query').mockReturnValue(of({} as DataQueryResponse));
+      const res = await ds.metricFindQuery(query, {});
+      expect(res).toEqual([]);
+    });
+
+    it('should return array with values if response has data', async () => {
+      const ds = new GithubDataSource({} as DataSourceInstanceSettings);
+      const query = { key: 'test', field: 'test' } as GitHubVariableQuery;
+
+      jest.spyOn(ds, 'query').mockReturnValue(
+        of({
+          data: [
+            toDataFrame({
+              fields: [{ name: 'test', values: ['value1', 'value2'] }],
+            }),
+          ],
+        } as DataQueryResponse)
+      );
+      const res = await ds.metricFindQuery(query, {});
+      expect(res).toEqual([
+        { value: 'value1', text: 'value1' },
+        { value: 'value2', text: 'value2' },
+      ]);
+    });
+  });
+});

src/DataSource.ts

@@ -113,8 +113,8 @@ export class GithubDataSource extends DataSourceWithBackend<GitHubQuery, GithubD
       rangeRaw: options.rangeRaw,
     } as DataQueryRequest;
     try {
-      let res = await this.query(request).toPromise();
-      if (!res || !res.data || res.data.length < 0) {
+      const res = await this.query(request).toPromise();
+      if (!res || !res.data || res.data.length <= 0) {
         return [];
       }
       const view = new DataFrameView(res.data[0] as DataFrame);