Fix: Elasticsearch fix template variables in the alias field (#16629)

Fixes #16040

Fix so that a template variable in the alias field is not interpolated on blur and only the value sent in the query is interpolated. Does a deep clone of the options.targets to avoid changing the original alias field.

public/app/plugins/datasource/elasticsearch/datasource.ts

 import angular from 'angular';
 import _ from 'lodash';
 import moment from 'moment';
-import { ElasticQueryBuilder } from './query_builder';
-import { IndexPattern } from './index_pattern';
 import { ElasticResponse } from './elastic_response';
+import { IndexPattern } from './index_pattern';
+import { ElasticQueryBuilder } from './query_builder';
 
 export class ElasticDatasource {
   basicAuth: string;
@@ -242,14 +242,13 @@ export class ElasticDatasource {
 
   query(options) {
     let payload = '';
-    let target;
+    const targets = _.cloneDeep(options.targets);
     const sentTargets = [];
 
     // add global adhoc filters to timeFilter
     const adhocFilters = this.templateSrv.getAdhocFilters(this.name);
 
-    for (let i = 0; i < options.targets.length; i++) {
-      target = options.targets[i];
+    for (const target of targets) {
       if (target.hide) {
         continue;
       }

public/app/plugins/datasource/elasticsearch/specs/datasource.test.ts

+import angular from 'angular';
+import * as dateMath from 'app/core/utils/datemath';
 import _ from 'lodash';
 import moment from 'moment';
-import angular from 'angular';
 import { ElasticDatasource } from '../datasource';
 
-import * as dateMath from 'app/core/utils/datemath';
-
 describe('ElasticDatasource', function(this: any) {
   const backendSrv = {
     datasourceRequest: jest.fn(),
@@ -73,9 +72,9 @@ describe('ElasticDatasource', function(this: any) {
   });
 
   describe('When issuing metric query with interval pattern', () => {
-    let requestOptions, parts, header, query;
+    let requestOptions, parts, header, query, result;
 
-    beforeEach(() => {
+    beforeEach(async () => {
       createDatasource({
         url: 'http://es.com',
         index: '[asd-]YYYY.MM.DD',
@@ -84,7 +83,24 @@ describe('ElasticDatasource', function(this: any) {
 
       ctx.backendSrv.datasourceRequest = jest.fn(options => {
         requestOptions = options;
-        return Promise.resolve({ data: { responses: [] } });
+        return Promise.resolve({
+          data: {
+            responses: [
+              {
+                aggregations: {
+                  '1': {
+                    buckets: [
+                      {
+                        doc_count: 10,
+                        key: 1000,
+                      },
+                    ],
+                  },
+                },
+              },
+            ],
+          },
+        });
       });
 
       query = {
@@ -95,14 +111,14 @@ describe('ElasticDatasource', function(this: any) {
         targets: [
           {
             alias: '$varAlias',
-            bucketAggs: [],
-            metrics: [{ type: 'raw_document' }],
+            bucketAggs: [{ type: 'date_histogram', field: '@timestamp', id: '1' }],
+            metrics: [{ type: 'count', id: '1' }],
             query: 'escape\\:test',
           },
         ],
       };
 
-      ctx.ds.query(query);
+      result = await ctx.ds.query(query);
 
       parts = requestOptions.data.split('\n');
       header = angular.fromJson(parts[0]);
@@ -112,8 +128,12 @@ describe('ElasticDatasource', function(this: any) {
       expect(header.index).toEqual(['asd-2015.05.30', 'asd-2015.05.31', 'asd-2015.06.01']);
     });
 
-    it('should resolve the alias variable', () => {
-      expect(query.targets[0].alias).toEqual('resolvedVariable');
+    it('should not resolve the variable in the original alias field in the query', () => {
+      expect(query.targets[0].alias).toEqual('$varAlias');
+    });
+
+    it('should resolve the alias variable for the alias/target in the result', () => {
+      expect(result.data[0].target).toEqual('resolvedVariable');
     });
 
     it('should json escape lucene query', () => {