Handle errors in successful notes reply

app/assets/javascripts/notes/stores/actions.js

@@ -268,11 +268,20 @@ export const saveNote = ({ commit, dispatch }, noteData) => {
     const { errors } = res;
     const commandsChanges = res.commands_changes;
 
-    if (hasQuickActions && errors && Object.keys(errors).length) {
+    if (errors && Object.keys(errors).length) {
+      /*
+       The following reply means that quick actions have been successfully applied:
+
+       {"commands_changes":{},"valid":false,"errors":{"commands_only":["Commands applied"]}}
+       */
+      if (hasQuickActions) {
         eTagPoll.makeRequest();
 
         $('.js-gfm-input').trigger('clear-commands-cache.atwho');
         Flash(__('Commands applied'), 'notice', noteData.flashContainer);
+      } else {
+        throw new Error(__('Failed to save comment!'));
+      }
     }
 
     if (commandsChanges) {

changelogs/unreleased/winh-notes-error-handling.yml

+---
+title: Handle errors in successful notes reply
+merge_request: 28082
+author:
+type: fixed

locale/gitlab.pot

@@ -4196,6 +4196,9 @@ msgstr ""
 msgid "Failed to remove user key."
 msgstr ""
 
+msgid "Failed to save comment!"
+msgstr ""
+
 msgid "Failed to save merge conflicts resolutions. Please try again!"
 msgstr ""