Fixed issue with autocomplete search not working with enter key

Closes #20165

app/assets/javascripts/gl_dropdown.js.coffee

@@ -218,12 +218,15 @@ class GitLabDropdown
             if @dropdown.find('.dropdown-toggle-page').length
               selector = ".dropdown-page-one #{selector}"
 
-            $(selector, @dropdown)
-              .first()
-              .find('a')
-              .addClass('is-focused')
+            if not $(@el).is('input')
+              $(selector, @dropdown)
+                .first()
+                .find('a')
+                .addClass('is-focused')
 
-            currentIndex = 0
+              currentIndex = 0
+            else
+              currentIndex = -1
 
 
     # Event listeners
@@ -559,10 +562,11 @@ class GitLabDropdown
     # simulate a click on the first link
     $el = $(selector, @dropdown)
 
-    if $el.length
+    if $el.length and currentIndex > -1
       e.preventDefault()
       e.stopImmediatePropagation()
       $el.first().trigger('click')
+      $el.first().get(0).click?()
 
   addArrowKeyEvent: ->
     ARROW_KEY_CODES = [38, 40]

app/assets/javascripts/search_autocomplete.js.coffee

@@ -63,6 +63,7 @@ class @SearchAutocomplete
         data: @getData.bind(@)
         selectable: true
         clicked: @onClick.bind(@)
+        id: (data) -> _.escape(data.text)
 
   getData: (term, callback) ->
     _this = @

spec/features/search_spec.rb

@@ -51,6 +51,16 @@ describe "Search", feature: true  do
   end
 
   describe 'Right header search field', feature: true do
+    it 'allows enter key to search', js: true do
+      visit namespace_project_path(project.namespace, project)
+      fill_in 'search', with: 'gitlab'
+      find('#search').native.send_keys(:enter)
+
+      page.within '.title' do
+        expect(page).to have_content 'Search'
+      end
+    end
+
     describe 'Search in project page' do
       before do
         visit namespace_project_path(project.namespace, project)