Fix `@` autocomplete selecting the loading icon

Fix this to prevent getting `@undefined` when pressing
`Enter` after pressing `@`

app/assets/javascripts/gfm_auto_complete.js

@@ -313,10 +313,6 @@ class GfmAutoComplete {
           return data;
         },
         sorter(query, items) {
-          if (!query) {
-            return items;
-          }
-
           // Disable auto-selecting the loading icon
           this.setting.highlightFirst = this.setting.alwaysHighlightFirst;
           if (GfmAutoComplete.isLoading(items)) {
@@ -324,6 +320,10 @@ class GfmAutoComplete {
             return items;
           }
 
+          if (!query) {
+            return items;
+          }
+
           const lowercaseQuery = query.toLowerCase();
           const members = items.slice();
           const { nameOrUsernameStartsWith, nameOrUsernameIncludes } = GfmAutoComplete.Members;

changelogs/unreleased/cngo-fix-autocomplete-selecting-loading.yml

+---
+title: Fix `@` autocomplete selecting the loading icon
+merge_request: 54925
+author:
+type: fixed

spec/features/issues/gfm_autocomplete_spec.rb

@@ -214,6 +214,13 @@ RSpec.describe 'GFM autocomplete', :js do
       expect(find_field('Description').value).to have_content "@#{user.username}"
     end
 
+    it 'does not show `@undefined` when pressing `@` then Enter' do
+      fill_in 'Description', with: "@\n"
+
+      expect(find_field('Description').value).to have_content "@"
+      expect(find_field('Description').value).not_to have_content "@undefined"
+    end
+
     it 'selects the first item for non-assignee dropdowns if a query is entered' do
       page.within '.timeline-content-form' do
         find('#note-body').native.send_keys(':1')