Enforce one escalation policy per project

ee/app/models/incident_management/escalation_policy.rb

@@ -7,6 +7,7 @@ module IncidentManagement
     belongs_to :project
     has_many :rules, class_name: 'EscalationRule', inverse_of: :policy, foreign_key: 'policy_id', index_errors: true
 
+    validates :project_id, uniqueness: { message: _('can only have one escalation policy') }
     validates :name, presence: true, uniqueness: { scope: [:project_id] }, length: { maximum: 72 }
     validates :description, length: { maximum: 160 }
     validates :rules, presence: true

ee/spec/finders/incident_management/escalation_policies_finder_spec.rb

@@ -6,7 +6,6 @@ RSpec.describe IncidentManagement::EscalationPoliciesFinder do
   let_it_be(:current_user) { create(:user) }
   let_it_be_with_refind(:project) { create(:project) }
   let_it_be(:escalation_policy) { create(:incident_management_escalation_policy, project: project) }
-  let_it_be(:escalation_policy_2) { create(:incident_management_escalation_policy, project: project) }
   let_it_be(:escalation_policy_from_another_project) { create(:incident_management_escalation_policy) }
 
   let(:params) { {} }
@@ -26,19 +25,13 @@ RSpec.describe IncidentManagement::EscalationPoliciesFinder do
         end
 
         it 'returns project escalation policies' do
-          is_expected.to contain_exactly(escalation_policy, escalation_policy_2)
+          is_expected.to contain_exactly(escalation_policy)
         end
 
         context 'when id given' do
           let(:params) { { id: escalation_policy.id } }
 
           it { is_expected.to contain_exactly(escalation_policy) }
-
-          context 'an array of ids given' do
-            let(:params) { { id: [escalation_policy.id, escalation_policy_2.id] } }
-
-            it { is_expected.to contain_exactly(escalation_policy, escalation_policy_2) }
-          end
         end
       end
 

ee/spec/models/incident_management/escalation_policy_spec.rb

@@ -17,6 +17,7 @@ RSpec.describe IncidentManagement::EscalationPolicy do
   describe 'validations' do
     it { is_expected.to validate_presence_of(:name) }
     it { is_expected.to validate_presence_of(:rules) }
+    it { is_expected.to validate_uniqueness_of(:project_id).with_message(/can only have one escalation policy/) }
     it { is_expected.to validate_uniqueness_of(:name).scoped_to(:project_id) }
     it { is_expected.to validate_length_of(:name).is_at_most(72) }
     it { is_expected.to validate_length_of(:description).is_at_most(160) }

ee/spec/requests/api/graphql/project/incident_management/escalation_policies_spec.rb

@@ -72,7 +72,6 @@ RSpec.describe 'getting Incident Management escalation policies' do
 
     context 'with escalation policies' do
       let_it_be(:policy) { create(:incident_management_escalation_policy, project: project) }
-      let_it_be(:second_policy) { create(:incident_management_escalation_policy, project: project) }
 
       let(:last_policy) { escalation_policies.last }
 
@@ -83,7 +82,6 @@ RSpec.describe 'getting Incident Management escalation policies' do
       it_behaves_like 'a working graphql query'
 
       it 'returns the correct properties of the escalation policy' do
-        expect(escalation_policies.size).to eq(2)
         expect(last_policy).to include(
           'id' => policy.to_global_id.to_s,
           'name' => policy.name,

ee/spec/services/incident_management/escalation_policies/create_service_spec.rb

@@ -78,6 +78,14 @@ RSpec.describe IncidentManagement::EscalationPolicies::CreateService do
 
         it_behaves_like 'error response', "Rules[0] oncall schedule can't be blank"
       end
+
+      context 'project has an existing escalation policy' do
+        before do
+          create(:incident_management_escalation_policy, project: project)
+        end
+
+        it_behaves_like 'error response', "Project can only have one escalation policy"
+      end
     end
 
     context 'valid params' do

locale/gitlab.pot

@@ -38033,6 +38033,9 @@ msgstr ""
 msgid "can only be changed by a group admin."
 msgstr ""
 
+msgid "can only have one escalation policy"
+msgstr ""
+
 msgid "can't be enabled because signed commits are required for this project"
 msgstr ""