Use association search in issuable create service

app/services/issuable_base_service.rb

@@ -57,10 +57,11 @@ class IssuableBaseService < BaseService
   end
 
   def filter_milestone
-    return unless params[:milestone_id]
+    milestone_id = params[:milestone_id]
+    return unless milestone_id
 
-    if params[:milestone_id] == IssuableFinder::NONE ||
-        Milestone.find(params[:milestone_id]).try(:project) != project
+    if milestone_id == IssuableFinder::NONE ||
+        project.milestones.find_by(id: milestone_id).nil?
       params[:milestone_id] = ''
     end
   end
@@ -68,9 +69,8 @@ class IssuableBaseService < BaseService
   def filter_labels
     return if params[:label_ids].to_a.empty?
 
-    params[:label_ids].select! do |label_id|
-      Label.find(label_id).try(:project) == project
-    end
+    params[:label_ids] =
+      project.labels.where(id: params[:label_ids]).pluck(:id)
   end
 
   def update(issuable)

spec/services/issues/create_service_spec.rb

@@ -4,13 +4,13 @@ describe Issues::CreateService, services: true do
   let(:project) { create(:empty_project) }
   let(:user) { create(:user) }
 
-  describe :execute do
-    let(:issue) { Issues::CreateService.new(project, user, opts).execute }
+  describe '#execute' do
+    let(:issue) { described_class.new(project, user, opts).execute }
 
-    context 'valid params' do
+    context 'when params are valid' do
       let(:assignee) { create(:user) }
       let(:milestone) { create(:milestone, project: project) }
-      let(:labels) { create_list(:label, 4, project: project) }
+      let(:labels) { create_pair(:label, project: project) }
 
       before do
         project.team << [user, :master]
@@ -45,7 +45,7 @@ describe Issues::CreateService, services: true do
         expect(Todo.where(attributes).count).to eq 1
       end
 
-      context 'label that belongs to different project' do
+      context 'when label belongs to different project' do
         let(:label) { create(:label) }
 
         let(:opts) do
@@ -59,7 +59,7 @@ describe Issues::CreateService, services: true do
         end
       end
 
-      context 'milestone that belongs to different project' do
+      context 'when milestone belongs to different project' do
         let(:milestone) { create(:milestone) }
 
         let(:opts) do