Prevent this from happening again

If worker doesn't receive headIssues and baseIssues,
send back an empty object

If store doesn't receive newIssues and resolvedIssues,
reject the code quality comparison promise and
display the "Failed to load code quality" error

ee/app/assets/javascripts/vue_merge_request_widget/stores/mr_widget_store.js

@@ -96,9 +96,11 @@ export default class MergeRequestStore extends CEMergeRequestStore {
 
   static doCodeClimateComparison(headIssues, baseIssues) {
     // Do these comparisons in worker threads to avoid blocking the main thread
-    return new Promise(resolve => {
+    return new Promise((resolve, reject) => {
       const worker = new CodeQualityComparisonWorker();
-      worker.addEventListener('message', ({ data }) => resolve(data));
+      worker.addEventListener('message', ({ data }) =>
+        data.newIssues && data.resolvedIssues ? resolve(data) : reject(data),
+      );
       worker.postMessage({
         headIssues,
         baseIssues,

ee/app/assets/javascripts/vue_merge_request_widget/workers/code_quality_comparison_worker.js

@@ -7,15 +7,22 @@ self.addEventListener('message', e => {
   const { data } = e;
 
   if (data === undefined) {
-    return;
+    return null;
+  }
+
+  const { headIssues, baseIssues } = data;
+
+  if (!headIssues || !baseIssues) {
+    // eslint-disable-next-line no-restricted-globals
+    return self.postMessage({});
   }
 
   // eslint-disable-next-line no-restricted-globals
   self.postMessage({
-    newIssues: filterByKey(data.parsedHeadIssues, data.parsedBaseIssues, keyToFilterBy),
-    resolvedIssues: filterByKey(data.parsedBaseIssues, data.parsedHeadIssues, keyToFilterBy),
+    newIssues: filterByKey(headIssues, baseIssues, keyToFilterBy),
+    resolvedIssues: filterByKey(baseIssues, headIssues, keyToFilterBy),
   });
 
   // eslint-disable-next-line no-restricted-globals
-  self.close();
+  return self.close();
 });

ee/changelogs/unreleased/mfluharty-code-quality-worker-variable-mismatch.yml

+---
+title: Fix variable mismatch in code quality widget
+merge_request: 14829
+author:
+type: fixed