Use lodash's differenceBy instead of filterByKey

Replace old custom utility function with standard lodash utility

app/assets/javascripts/reports/codequality_report/store/utils/filter_by_key.js

-/**
- * Compares two arrays by the given key and returns the difference
- *
- * @param {Array} firstArray
- * @param {Array} secondArray
- * @param {String} key
- * @returns {Array}
- */
-const filterByKey = (firstArray = [], secondArray = [], key = '') =>
-  firstArray.filter(item => !secondArray.find(el => el[key] === item[key]));
-
-export default filterByKey;

app/assets/javascripts/reports/codequality_report/workers/codequality_comparison_worker.js

-import filterByKey from '../store/utils/filter_by_key';
+import { differenceBy } from 'lodash';
 
 const KEY_TO_FILTER_BY = 'fingerprint';
 
@@ -19,8 +19,8 @@ self.addEventListener('message', e => {
 
   // eslint-disable-next-line no-restricted-globals
   self.postMessage({
-    newIssues: filterByKey(headIssues, baseIssues, KEY_TO_FILTER_BY),
-    resolvedIssues: filterByKey(baseIssues, headIssues, KEY_TO_FILTER_BY),
+    newIssues: differenceBy(headIssues, baseIssues, KEY_TO_FILTER_BY),
+    resolvedIssues: differenceBy(baseIssues, headIssues, KEY_TO_FILTER_BY),
   });
 
   // eslint-disable-next-line no-restricted-globals

spec/frontend/reports/codequality_report/store/utils/codequality_comparison_spec.js

@@ -2,7 +2,6 @@ import {
   parseCodeclimateMetrics,
   doCodeClimateComparison,
 } from '~/reports/codequality_report/store/utils/codequality_comparison';
-import mockFilterByKey from '~/reports/codequality_report/store/utils/filter_by_key';
 import { baseIssues, mockParsedHeadIssues, mockParsedBaseIssues } from '../../mock_data';
 
 jest.mock('~/reports/codequality_report/workers/codequality_comparison_worker', () => {
@@ -15,10 +14,15 @@ jest.mock('~/reports/codequality_report/workers/codequality_comparison_worker',
       postMessage: data => {
         if (!data.headIssues) return mockPostMessageCallback({ data: {} });
         if (!data.baseIssues) throw new Error();
+        const key = 'fingerprint';
         return mockPostMessageCallback({
           data: {
-            newIssues: mockFilterByKey(data.headIssues, data.baseIssues, 'fingerprint'),
-            resolvedIssues: mockFilterByKey(data.baseIssues, data.headIssues, 'fingerprint'),
+            newIssues: data.headIssues.filter(
+              item => !data.baseIssues.find(el => el[key] === item[key]),
+            ),
+            resolvedIssues: data.baseIssues.filter(
+              item => !data.headIssues.find(el => el[key] === item[key]),
+            ),
           },
         });
       },

spec/frontend/reports/codequality_report/store/utils/filter_by_key_spec.js

-import filterByKey from '~/reports/codequality_report/store/utils/filter_by_key';
-import { mockParsedHeadIssues, mockParsedBaseIssues, issueDiff } from '../../mock_data';
-
-describe('filterByKey', () => {
-  it('should return a diff of the arrays based on the given key', () => {
-    const result = filterByKey(mockParsedHeadIssues, mockParsedBaseIssues, 'fingerprint');
-
-    expect(result).toEqual(issueDiff);
-  });
-});