Merge branch 'update_main_lang_if_unset' into 'master'

Only update main language if it is not already set

Related to gitlab-org/gitlab-ce#14937 (but does not fully fix) This is a temporary fix so performance isn't affected so much. 

cc @yorickpeterse @ayufan how does this look?

See merge request !3556

CHANGELOG

@@ -31,6 +31,7 @@ v 8.7.0 (unreleased)
   - API: Expose user location (Robert Schilling)
 
 v 8.6.5 (unreleased)
+  - Only update repository language if it is not set to improve performance
   - Check permissions when user attempts to import members from another project
 
 v 8.6.4

app/services/git_push_service.rb

@@ -55,15 +55,15 @@ class GitPushService < BaseService
   end
 
   def update_main_language
+    # Performance can be bad so for now only check main_language once
+    # See https://gitlab.com/gitlab-org/gitlab-ce/issues/14937
+    return if @project.main_language.present?
+
     return unless is_default_branch?
     return unless push_to_new_branch? || push_to_existing_branch?
 
     current_language = @project.repository.main_language
-
-    unless current_language == @project.main_language
-      return @project.update_attributes(main_language: current_language)
-    end
-
+    @project.update_attributes(main_language: current_language)
     true
   end
 

spec/services/git_push_service_spec.rb

@@ -164,21 +164,37 @@ describe GitPushService, services: true do
     end
 
     context "after push" do
-      before do
-        @service = execute_service(project, user, @oldrev, @newrev, ref)
+      def execute
+        execute_service(project, user, @oldrev, @newrev, ref)
       end
 
       context "to master" do
         let(:ref) { @ref }
 
-        it { expect(@service.update_main_language).to eq(true) }
-        it { expect(project.main_language).to eq("Ruby") }
+        context 'when main_language is nil' do
+          it 'obtains the language from the repository' do
+            expect(project.repository).to receive(:main_language)
+            execute
+          end
+
+          it 'sets the project main language' do
+            execute
+            expect(project.main_language).to eq("Ruby")
+          end
+        end
+
+        context 'when main_language is already set' do
+          it 'does not check the repository' do
+            execute # do an initial run to simulate lang being preset
+            expect(project.repository).not_to receive(:main_language)
+            execute
+          end
+        end
       end
 
       context "to other branch" do
         let(:ref) { 'refs/heads/feature/branch' }
 
-        it { expect(@service.update_main_language).to eq(nil) }
         it { expect(project.main_language).to eq(nil) }
       end
     end