annotations: allows template variables to be used in tag filter

When filtering built in annotations by tag, interpolates the tag with
template variables. Fixes #9587

public/app/plugins/datasource/grafana/datasource.ts

@@ -3,7 +3,7 @@ import _ from 'lodash';
 class GrafanaDatasource {
 
   /** @ngInject */
-  constructor(private backendSrv, private $q) {}
+  constructor(private backendSrv, private $q, private templateSrv) {}
 
   query(options) {
     return this.backendSrv
@@ -58,6 +58,11 @@ class GrafanaDatasource {
       if (!_.isArray(options.annotation.tags) || options.annotation.tags.length === 0) {
         return this.$q.when([]);
       }
+      const tags = [];
+      for (let t of params.tags) {
+        tags.push(this.templateSrv.replace(t));
+      }
+      params.tags = tags;
     }
 
     return this.backendSrv.get('/api/annotations', params);

public/app/plugins/datasource/grafana/specs/datasource.jest.ts

@@ -0,0 +1,65 @@
+import {GrafanaDatasource} from "../datasource";
+import q from 'q';
+import moment from 'moment';
+
+describe('grafana data source', () => {
+  describe('when executing an annotations query', () => {
+    let calledBackendSrvParams;
+    const backendSrvStub = {
+      get: (url, options) => {
+        calledBackendSrvParams = options;
+        return q.resolve([]);
+      }
+    };
+
+    const templateSrvStub = {
+      replace: val => val.replace('$var', 'replaced')
+    };
+
+    const ds = new GrafanaDatasource(backendSrvStub, q, templateSrvStub);
+
+    describe('with tags that have template variables', () => {
+      const options = setupAnnotationQueryOptions(
+        {tags: ['tag1:$var']}
+      );
+
+      beforeEach(() => {
+        return ds.annotationQuery(options);
+      });
+
+      it('should interpolate template variables in tags in query options', () => {
+        expect(calledBackendSrvParams.tags[0]).toBe('tag1:replaced');
+      });
+    });
+
+    describe('with type dashboard', () => {
+      const options = setupAnnotationQueryOptions(
+        {
+          type: 'dashboard',
+          tags: ['tag1']
+        },
+        {id: 1}
+      );
+
+      beforeEach(() => {
+        return ds.annotationQuery(options);
+      });
+
+      it('should remove tags from query options', () => {
+        expect(calledBackendSrvParams.tags).toBe(undefined);
+      });
+    });
+  });
+});
+
+function setupAnnotationQueryOptions(annotation, dashboard?) {
+  return {
+    annotation: annotation,
+    dashboard: dashboard,
+    range: {
+      from: moment(1432288354),
+      to: moment(1432288401)
+    },
+    rangeRaw: {from: "now-24h", to: "now"}
+  };
+}