Sync code owner changes to approval rules

Update code owner rule when MR is updated.

app/services/merge_requests/create_service.rb

@@ -66,3 +66,5 @@ module MergeRequests
     end
   end
 end
+
+MergeRequests::CreateService.include(EE::MergeRequests::CreateService)

ee/app/models/approval_merge_request_rule.rb

@@ -3,6 +3,8 @@
 class ApprovalMergeRequestRule < ApplicationRecord
   include ApprovalRuleLike
 
+  DEFAULT_NAME_FOR_CODE_OWNER = 'Code Owner'
+
   scope :regular, -> { where(code_owner: false) }
   scope :code_owner, -> { where(code_owner: true) } # special code owner rules, updated internally when code changes
 

ee/app/models/ee/merge_request.rb

@@ -81,5 +81,14 @@ module EE
 
       compare_reports(::Ci::CompareLicenseManagementReportsService)
     end
+
+    def sync_code_owners_with_approvers
+      ActiveRecord::Base.transaction do
+        rule = approval_rules.code_owner.first
+        rule ||= approval_rules.code_owner.create!(name: ApprovalMergeRequestRule::DEFAULT_NAME_FOR_CODE_OWNER)
+
+        rule.users = code_owners
+      end
+    end
   end
 end

ee/app/services/ee/merge_requests/create_service.rb

+# frozen_string_literal: true
+
+module EE
+  module MergeRequests
+    module CreateService
+      extend ::Gitlab::Utils::Override
+
+      override :after_create
+      def after_create(issuable)
+        super
+
+        issuable.sync_code_owners_with_approvers
+      end
+    end
+  end
+end

ee/app/services/ee/merge_requests/refresh_service.rb

@@ -53,6 +53,8 @@ module EE
           new_code_owners = merge_request.code_owners - previous_code_owners
 
           create_approvers(merge_request, new_code_owners)
+
+          merge_request.sync_code_owners_with_approvers
         end
 
         results

ee/spec/models/merge_request_spec.rb

@@ -70,6 +70,41 @@ describe MergeRequest do
     end
   end
 
+  describe '#sync_code_owners_with_approvers' do
+    let(:owners) { [create(:user), create(:user)] }
+
+    before do
+      allow(subject).to receive(:code_owners).and_return(owners)
+    end
+
+    it 'sync code owner to the code owner rule' do
+      expect do
+        subject.sync_code_owners_with_approvers
+      end.to change { subject.approval_rules.count }.by(1)
+
+      expect(subject.approval_rules.code_owner.first.users).to contain_exactly(*owners)
+    end
+
+    context 'when code owner rule already exists' do
+      let!(:code_owner_rule) { subject.approval_rules.code_owner.create!(name: 'Code Owner') }
+
+      before do
+        code_owner_rule.users << create(:user)
+      end
+
+      it 'reuses existing rule' do
+        expect do
+          subject.sync_code_owners_with_approvers
+        end.not_to change { subject.approval_rules.count }
+
+        rule = subject.approval_rules.code_owner.first
+
+        expect(rule).to eq(code_owner_rule)
+        expect(rule.users).to contain_exactly(*owners)
+      end
+    end
+  end
+
   describe '#base_pipeline' do
     let!(:pipeline) { create(:ci_empty_pipeline, project: subject.project, sha: subject.diff_base_sha) }
 

ee/spec/services/ee/merge_requests/create_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe MergeRequests::CreateService do
+  include ProjectForksHelper
+
+  let(:project) { create(:project, :repository) }
+  let(:user) { create(:user) }
+  let(:service) { described_class.new(project, user, opts) }
+  let(:opts) do
+    {
+      title: 'Awesome merge_request',
+      description: 'please fix',
+      source_branch: 'feature',
+      target_branch: 'master',
+      force_remove_source_branch: '1'
+    }
+  end
+
+  before do
+    project.add_maintainer(user)
+    allow(service).to receive(:execute_hooks)
+  end
+
+  describe '#execute' do
+    context 'code owners' do
+      let!(:owners) { create_list(:user, 2) }
+
+      before do
+        allow(::Gitlab::CodeOwners).to receive(:for_merge_request).and_return(owners)
+      end
+
+      it 'syncs code owner to approval rule' do
+        merge_request = service.execute
+
+        rule = merge_request.approval_rules.code_owner.first
+
+        expect(rule.users).to contain_exactly(*owners)
+      end
+    end
+  end
+end

ee/spec/services/ee/merge_requests/refresh_service_spec.rb

@@ -102,6 +102,9 @@ describe MergeRequests::RefreshService do
 
             it 'does not create Approver' do
               expect { subject }.not_to change { Approver.count }
+
+              rule = merge_request.approval_rules.code_owner.first
+              expect(rule.users).to eq(new_owners)
             end
           end
         end
@@ -125,6 +128,9 @@ describe MergeRequests::RefreshService do
               expect(new_approver.user).to eq(owner)
               expect(new_approver.created_at).to be_present
               expect(new_approver.updated_at).to be_present
+
+              rule = merge_request.approval_rules.code_owner.first
+              expect(rule.users).to eq(new_owners)
             end
           end
         end