Put deprecated serverless features behind feature flag

The flag is enabled by default, but can be switched off immediately to
hide the feature.

See https://gitlab.com/gitlab-org/gitlab/-/issues/352753

Changelog: changed

app/controllers/projects/serverless/functions_controller.rb

@@ -3,6 +3,7 @@
 module Projects
   module Serverless
     class FunctionsController < Projects::ApplicationController
+      before_action :ensure_feature_enabled!
       before_action :authorize_read_cluster!
 
       feature_category :not_owned
@@ -69,6 +70,10 @@ module Projects
       def serialize_function(function)
         Projects::Serverless::ServiceSerializer.new(current_user: @current_user, project: project).represent(function)
       end
+
+      def ensure_feature_enabled!
+        render_404 unless Feature.enabled?(:deprecated_serverless, project, default_enabled: :yaml, type: :ops)
+      end
     end
   end
 end

config/feature_flags/ops/deprecated_serverless.yml

+---
+name: deprecated_serverless
+introduced_by_url: 'https://gitlab.com/gitlab-org/gitlab/-/merge_requests/81493'
+rollout_issue_url: 'https://gitlab.com/gitlab-org/gitlab/-/issues/353901'
+milestone: '14.9'
+type: ops
+group: 'group::configure'
+default_enabled: true

lib/sidebars/projects/menus/infrastructure_menu.rb

@@ -64,7 +64,7 @@ module Sidebars
         end
 
         def serverless_menu_item
-          unless can?(context.current_user, :read_cluster, context.project)
+          unless Feature.enabled?(:deprecated_serverless, context.project, default_enabled: :yaml, type: :ops) && can?(context.current_user, :read_cluster, context.project)
             return ::Sidebars::NilMenuItem.new(item_id: :serverless)
           end
 

spec/controllers/projects/serverless/functions_controller_spec.rb

@@ -39,9 +39,24 @@ RSpec.describe Projects::Serverless::FunctionsController do
                        project_id: project.to_param)
   end
 
+  shared_examples_for 'behind :deprecated_serverless feature flag' do
+    before do
+      stub_feature_flags(deprecated_serverless: false)
+    end
+
+    it 'returns 404' do
+      action
+      expect(response).to have_gitlab_http_status(:not_found)
+    end
+  end
+
   describe 'GET #index' do
     let(:expected_json) { { 'knative_installed' => knative_state, 'functions' => functions } }
 
+    it_behaves_like 'behind :deprecated_serverless feature flag' do
+      let(:action) { get :index, params: params({ format: :json }) }
+    end
+
     context 'when cache is being read' do
       let(:knative_state) { 'checking' }
       let(:functions) { [] }
@@ -147,6 +162,10 @@ RSpec.describe Projects::Serverless::FunctionsController do
   end
 
   describe 'GET #show' do
+    it_behaves_like 'behind :deprecated_serverless feature flag' do
+      let(:action) { get :show, params: params({ format: :json, environment_id: "*", id: "foo" }) }
+    end
+
     context 'with function that does not exist' do
       it 'returns 404' do
         get :show, params: params({ format: :json, environment_id: "*", id: "foo" })
@@ -239,6 +258,10 @@ RSpec.describe Projects::Serverless::FunctionsController do
   end
 
   describe 'GET #metrics' do
+    it_behaves_like 'behind :deprecated_serverless feature flag' do
+      let(:action) { get :metrics, params: params({ format: :json, environment_id: "*", id: "foo" }) }
+    end
+
     context 'invalid data' do
       it 'has a bad function name' do
         get :metrics, params: params({ format: :json, environment_id: "*", id: "foo" })

spec/lib/sidebars/projects/menus/infrastructure_menu_spec.rb

@@ -92,6 +92,14 @@ RSpec.describe Sidebars::Projects::Menus::InfrastructureMenu do
       let(:item_id) { :serverless }
 
       it_behaves_like 'access rights checks'
+
+      context 'when feature :deprecated_serverless is disabled' do
+        before do
+          stub_feature_flags(deprecated_serverless: false)
+        end
+
+        it { is_expected.to be_nil }
+      end
     end
 
     describe 'Terraform' do