add users search results to group scoped search

app/services/search/group_service.rb

@@ -11,6 +11,12 @@ module Search
       @group = group
     end
 
+    def execute
+      Gitlab::GroupSearchResults.new(
+        current_user, projects, group, params[:search], default_project_filter: default_project_filter
+      )
+    end
+
     def projects
       return Project.none unless group
       return @projects if defined? @projects

lib/gitlab/group_search_results.rb

+# frozen_string_literal: true
+
+module Gitlab
+  class GroupSearchResults < SearchResults
+    def initialize(current_user, limit_projects, group, query, default_project_filter: false, per_page: 20)
+      super(current_user, limit_projects, query, default_project_filter: default_project_filter, per_page: per_page)
+
+      @group = group
+    end
+
+    # rubocop:disable CodeReuse/ActiveRecord
+    def users
+      super.where(id: @group.users_with_descendants)
+    end
+    # rubocop:enable CodeReuse/ActiveRecord
+  end
+end

spec/features/search/user_searches_for_users_spec.rb

@@ -50,4 +50,34 @@ describe 'User searches for users' do
       expect(page).not_to have_content('@gob_2018')
     end
   end
+
+  context 'when on the group page' do
+    it 'finds the user belonging to the group' do
+      group = create(:group)
+
+      user1 = create(:user, username: 'gob_bluth', name: 'Gob Bluth')
+      create(:group_member, :developer, user: user1, group: group)
+
+      user2 = create(:user, username: 'michael_bluth', name: 'Michael Bluth')
+      create(:group_member, :developer, user: user2, group: group)
+
+      create(:user, username: 'gob_2018', name: 'George Oscar Bluth')
+
+      sign_in(user1)
+
+      visit group_path(group)
+
+      fill_in 'search', with: 'gob'
+      click_button 'Go'
+
+      expect(page).to have_content('Gob Bluth')
+      expect(page).to have_content('@gob_bluth')
+
+      expect(page).not_to have_content('Michael Bluth')
+      expect(page).not_to have_content('@michael_bluth')
+
+      expect(page).not_to have_content('George Oscar Bluth')
+      expect(page).not_to have_content('@gob_2018')
+    end
+  end
 end

spec/lib/gitlab/group_search_results_spec.rb

+require 'spec_helper'
+
+describe Gitlab::GroupSearchResults do
+  let(:user) { create(:user) }
+
+  describe 'user search' do
+    let(:group) { create(:group) }
+
+    it 'returns the users belonging to the group matching the search query' do
+      user1 = create(:user, username: 'gob_bluth')
+      create(:group_member, :developer, user: user1, group: group)
+
+      user2 = create(:user, username: 'michael_bluth')
+      create(:group_member, :developer, user: user2, group: group)
+
+      create(:user, username: 'gob_2018')
+
+      expect(described_class.new(user, anything, group, 'gob').objects('users')).to eq [user1]
+    end
+
+    it 'returns the user belonging to the subgroup matching the search query', :nested_groups do
+      user1 = create(:user, username: 'gob_bluth')
+      subgroup = create(:group, parent: group)
+      create(:group_member, :developer, user: user1, group: subgroup)
+
+      create(:user, username: 'gob_2018')
+
+      expect(described_class.new(user, anything, group, 'gob').objects('users')).to eq [user1]
+    end
+  end
+end