move `find_users` method into finder and add `load_group` method

app/controllers/autocomplete_controller.rb

@@ -3,10 +3,10 @@ class AutocompleteController < ApplicationController
 
   skip_before_action :authenticate_user!, only: [:users, :award_emojis]
   before_action :load_project, only: [:users]
-  before_action :find_users, only: [:users]
+  before_action :load_group, only: [:users]
 
   def users
-    @users = AutocompleteUsersFinder.new(params: params, current_user: current_user, users: @users).execute
+    @users = AutocompleteUsersFinder.new(params: params, current_user: current_user, project: @project, group: @group).execute
 
     render json: @users, only: [:name, :username, :id], methods: [:avatar_url]
   end
@@ -39,26 +39,14 @@ class AutocompleteController < ApplicationController
 
   private
 
-  def find_users
-    @users =
-      if @project
-        user_ids = @project.team.users.pluck(:id)
-
-        if params[:author_id].present?
-          user_ids << params[:author_id]
-        end
-
-        User.where(id: user_ids)
-      elsif params[:group_id].present?
+  def load_group
+    @group ||= begin
+      if @project.blank? && params[:group_id].present?
         group = Group.find(params[:group_id])
         return render_404 unless can?(current_user, :read_group, group)
-
-        group.users
-      elsif current_user
-        User.all
-      else
-        User.none
+        group
       end
+    end
   end
 
   def load_project

app/finders/autocomplete_users_finder.rb

 class AutocompleteUsersFinder
-  attr_reader :current_user, :users, :search, :skip_users, :page,
-              :per_page, :author_id, :params
+  attr_reader :current_user, :project, :group, :search, :skip_users,
+              :page, :per_page, :author_id, :params
 
-  def initialize(params:, current_user:, users: nil)
+  def initialize(params:, current_user:, project:, group:)
     @current_user = current_user
-    @users = users
+    @project = project
+    @group = group
     @search = params[:search]
     @skip_users = params[:skip_users]
     @page = params[:page]
@@ -14,7 +15,7 @@ class AutocompleteUsersFinder
   end
 
   def execute
-    items = users || User.none
+    items = find_users
     items = items.active
     items = items.reorder(:name)
     items = items.search(search) if search.present?
@@ -39,4 +40,21 @@ class AutocompleteUsersFinder
 
     items
   end
+
+  private
+
+  def find_users
+    return users_from_project if project
+    return group.users if group
+    return User.all if current_user
+
+    User.none
+  end
+
+  def users_from_project
+    user_ids = project.team.users.pluck(:id)
+    user_ids << author_id if author_id.present?
+
+    User.where(id: user_ids)
+  end
 end

spec/finders/autocomplete_users_finder_spec.rb

@@ -9,15 +9,39 @@ describe AutocompleteUsersFinder do
     let(:current_user) { create(:user) }
     let(:params) { {} }
 
-    let(:users) { User.all }
-    subject { described_class.new(params: params, current_user: current_user, users: users).execute.to_a }
+    let(:project) { nil }
+    let(:group) { nil }
 
-    context 'when users param not passed or nil' do
-      let(:users) { nil }
+    subject { described_class.new(params: params, current_user: current_user, project: project, group: group).execute.to_a }
+
+    context 'when current_user not passed or nil' do
+      let(:current_user) { nil }
 
       it { is_expected.to match_array([]) }
     end
 
+    context 'when project passed' do
+      let(:project) { create(:project) }
+
+      it { is_expected.to match_array([project.owner]) }
+
+      context 'when author_id passed' do
+        let(:params) { { author_id: user2.id } }
+
+        it { is_expected.to match_array([project.owner, user2]) }
+      end
+    end
+
+    context 'when group passed and project not passed' do
+      let(:group) { create(:group, :public) }
+
+      before do
+        group.add_users([user1], GroupMember::DEVELOPER)
+      end
+
+      it { is_expected.to match_array([user1]) }
+    end
+
     it { is_expected.to match_array([user1, external_user, omniauth_user, current_user]) }
 
     context 'when filtered by search' do