Add label autocomplete for groups

config/routes/group.rb

@@ -90,6 +90,7 @@ constraints(::Constraints::GroupUrlConstrainer.new) do
     resources :autocomplete_sources, only: [] do
       collection do
         get 'members'
+        get 'labels'
         get 'epics'
       end
     end

ee/app/controllers/groups/autocomplete_sources_controller.rb

@@ -5,6 +5,10 @@ class Groups::AutocompleteSourcesController < Groups::ApplicationController
     render json: ::Groups::ParticipantsService.new(@group, current_user).execute(target)
   end
 
+  def labels
+    render json: @autocomplete_service.labels(target)
+  end
+
   def epics
     render json: @autocomplete_service.epics
   end

ee/app/helpers/ee/application_helper.rb

@@ -67,6 +67,7 @@ module EE
 
       {
         members: members_group_autocomplete_sources_path(object, type: noteable_type, type_id: params[:id]),
+        labels: labels_group_autocomplete_sources_path(object),
         epics: epics_group_autocomplete_sources_path(object)
       }
     end

ee/app/services/groups/autocomplete_service.rb

 module Groups
   class AutocompleteService < BaseService
+    def labels(target = nil)
+      labels = LabelsFinder.new(
+        current_user,
+        group_id: group.id,
+        include_ancestor_groups: true,
+        only_group_labels: true
+      ).execute.select([:color, :title])
+
+      return labels unless target&.respond_to?(:labels)
+
+      issuable_label_titles = target.labels.pluck(:title)
+
+      if issuable_label_titles
+        labels = labels.as_json(only: [:title, :color])
+
+        issuable_label_titles.each do |issuable_label_title|
+          found_label = labels.find { |label| label['title'] == issuable_label_title }
+          found_label[:set] = true if found_label
+        end
+      end
+
+      labels
+    end
+
     def epics
       EpicsFinder.new(current_user, group_id: group.id).execute
     end

ee/spec/helpers/application_helper_spec.rb

@@ -6,7 +6,7 @@ describe ApplicationHelper do
     let(:noteable_type) { Epic }
     it 'returns paths for autocomplete_sources_controller' do
       sources = helper.autocomplete_data_sources(object, noteable_type)
-      expect(sources.keys).to match_array([:members])
+      expect(sources.keys).to match_array([:members, :labels, :epics])
       sources.keys.each do |key|
         expect(sources[key]).not_to be_nil
       end