Add IterationCadenceDestroy mutation

- Change issues/merge_requests sprint FK from delete cascade to nullify
- Add mutation to GQL API
- Add changelog entry for EE
- Add specs

changelogs/unreleased/322743-destroy-cadence-mutation.yml

+---
+title: Add support to destroy iteration cadences in GraphQL
+merge_request: 59060
+author:
+type: added

db/migrate/20210419224834_update_issues_iteration_foreign_key.rb

+# frozen_string_literal: true
+
+class UpdateIssuesIterationForeignKey < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:issues, column: :sprint_id)
+    end
+
+    add_concurrent_foreign_key(:issues, :sprints, column: :sprint_id, on_delete: :nullify)
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key_if_exists(:issues, column: :sprint_id)
+    end
+
+    add_concurrent_foreign_key(:issues, :sprints, column: :sprint_id, on_delete: :cascade)
+  end
+end

db/migrate/20210420221106_update_merge_requests_iteration_foreign_key.rb

+# frozen_string_literal: true
+
+class UpdateMergeRequestsIterationForeignKey < ActiveRecord::Migration[6.0]
+  include Gitlab::Database::MigrationHelpers
+
+  disable_ddl_transaction!
+
+  def up
+    with_lock_retries do
+      remove_foreign_key_if_exists(:merge_requests, column: :sprint_id)
+    end
+
+    add_concurrent_foreign_key(:merge_requests, :sprints, column: :sprint_id, on_delete: :nullify)
+  end
+
+  def down
+    with_lock_retries do
+      remove_foreign_key_if_exists(:merge_requests, column: :sprint_id)
+    end
+
+    add_concurrent_foreign_key(:merge_requests, :sprints, column: :sprint_id, on_delete: :cascade)
+  end
+end

db/schema_migrations/20210419224834

+145782c0cb0d24617e0e43c43f49a0f1d4033df3f303e4d4085e586c48e2408e
\ No newline at end of file

db/schema_migrations/20210420221106

+62842b9e9753b7880e980b0a16335e7d00bdce8b7b42d94b1ba26828724c01dd
\ No newline at end of file

db/structure.sql

@@ -24839,7 +24839,7 @@ ALTER TABLE ONLY ci_builds
     ADD CONSTRAINT fk_3a9eaa254d FOREIGN KEY (stage_id) REFERENCES ci_stages(id) ON DELETE CASCADE;
 
 ALTER TABLE ONLY issues
-    ADD CONSTRAINT fk_3b8c72ea56 FOREIGN KEY (sprint_id) REFERENCES sprints(id) ON DELETE CASCADE;
+    ADD CONSTRAINT fk_3b8c72ea56 FOREIGN KEY (sprint_id) REFERENCES sprints(id) ON DELETE SET NULL;
 
 ALTER TABLE ONLY epics
     ADD CONSTRAINT fk_3c1fd1cccc FOREIGN KEY (due_date_sourcing_milestone_id) REFERENCES milestones(id) ON DELETE SET NULL;
@@ -24983,7 +24983,7 @@ ALTER TABLE ONLY labels
     ADD CONSTRAINT fk_7de4989a69 FOREIGN KEY (project_id) REFERENCES projects(id) ON DELETE CASCADE;
 
 ALTER TABLE ONLY merge_requests
-    ADD CONSTRAINT fk_7e85395a64 FOREIGN KEY (sprint_id) REFERENCES sprints(id) ON DELETE CASCADE;
+    ADD CONSTRAINT fk_7e85395a64 FOREIGN KEY (sprint_id) REFERENCES sprints(id) ON DELETE SET NULL;
 
 ALTER TABLE ONLY merge_request_metrics
     ADD CONSTRAINT fk_7f28d925f3 FOREIGN KEY (merged_by_id) REFERENCES users(id) ON DELETE SET NULL;

doc/api/graphql/reference/index.md

@@ -2437,6 +2437,25 @@ Input type: `IterationCadenceCreateInput`
 | <a id="mutationiterationcadencecreateerrors"></a>`errors` | [`[String!]!`](#string) | Errors encountered during execution of the mutation. |
 | <a id="mutationiterationcadencecreateiterationcadence"></a>`iterationCadence` | [`IterationCadence`](#iterationcadence) | The created iteration cadence. |
 
+### `Mutation.iterationCadenceDestroy`
+
+Input type: `IterationCadenceDestroyInput`
+
+#### Arguments
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="mutationiterationcadencedestroyclientmutationid"></a>`clientMutationId` | [`String`](#string) | A unique identifier for the client performing the mutation. |
+| <a id="mutationiterationcadencedestroyid"></a>`id` | [`IterationsCadenceID!`](#iterationscadenceid) | Global ID of the iteration cadence. |
+
+#### Fields
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="mutationiterationcadencedestroyclientmutationid"></a>`clientMutationId` | [`String`](#string) | A unique identifier for the client performing the mutation. |
+| <a id="mutationiterationcadencedestroyerrors"></a>`errors` | [`[String!]!`](#string) | Errors encountered during execution of the mutation. |
+| <a id="mutationiterationcadencedestroygroup"></a>`group` | [`Group!`](#group) | Group the iteration cadence belongs to. |
+
 ### `Mutation.iterationCadenceUpdate`
 
 Input type: `IterationCadenceUpdateInput`

ee/app/graphql/ee/types/mutation_type.rb

@@ -27,6 +27,7 @@ module EE
         mount_mutation ::Mutations::Iterations::Update
         mount_mutation ::Mutations::Iterations::Cadences::Create
         mount_mutation ::Mutations::Iterations::Cadences::Update
+        mount_mutation ::Mutations::Iterations::Cadences::Destroy
         mount_mutation ::Mutations::RequirementsManagement::CreateRequirement
         mount_mutation ::Mutations::RequirementsManagement::ExportRequirements
         mount_mutation ::Mutations::RequirementsManagement::UpdateRequirement

ee/app/graphql/mutations/iterations/cadences/destroy.rb

+# frozen_string_literal: true
+
+module Mutations
+  module Iterations
+    module Cadences
+      class Destroy < BaseMutation
+        graphql_name 'IterationCadenceDestroy'
+
+        authorize :admin_iteration_cadence
+
+        argument :id, ::Types::GlobalIDType[::Iterations::Cadence], required: true,
+          description: copy_field_description(Types::Iterations::CadenceType, :id)
+
+        field :group, ::Types::GroupType, null: false, description: 'Group the iteration cadence belongs to.'
+
+        def resolve(id:)
+          iteration_cadence = authorized_find!(id: id)
+
+          response = ::Iterations::Cadences::DestroyService.new(iteration_cadence, current_user).execute
+
+          {
+            group: response.payload[:group],
+            errors: response.errors
+          }
+        end
+
+        private
+
+        def find_object(id:)
+          # TODO: Remove coercion when working on https://gitlab.com/gitlab-org/gitlab/-/issues/257883
+          id = ::Types::GlobalIDType[::Iterations::Cadence].coerce_isolated_input(id)
+          GitlabSchema.find_by_gid(id)
+        end
+      end
+    end
+  end
+end

ee/app/models/ee/board.rb

@@ -25,6 +25,7 @@ module EE
       has_many :labels, through: :board_labels
 
       scope :with_associations, -> { preload(:destroyable_lists, :labels, :assignee) }
+      scope :in_iterations, ->(iterations) { where(iteration: iterations) }
     end
 
     override :scoped?

ee/app/services/iterations/cadences/destroy_service.rb

+# frozen_string_literal: true
+
+module Iterations
+  module Cadences
+    class DestroyService
+      include Gitlab::Allowable
+
+      def initialize(iteration_cadence, user)
+        @iteration_cadence = iteration_cadence
+        @group = iteration_cadence.group
+        @current_user = user
+      end
+
+      def execute
+        response_payload = { group: @group }
+        return ::ServiceResponse.error(message: _('Operation not allowed'), payload: response_payload, http_status: 403) unless can_destroy_iteration_cadence?
+
+        if destroy_and_remove_references
+          ::ServiceResponse.success(payload: response_payload.merge(iteration_cadence: iteration_cadence))
+        else
+          ::ServiceResponse.error(message: iteration_cadence.errors.full_messages, payload: response_payload, http_status: 422)
+        end
+      end
+
+      private
+
+      attr_reader :iteration_cadence, :current_user, :group
+
+      def can_destroy_iteration_cadence?
+        group.iteration_cadences_feature_flag_enabled? &&
+          group.licensed_feature_available?(:iterations) &&
+          can?(current_user, :admin_iteration_cadence, iteration_cadence)
+      end
+
+      def destroy_and_remove_references
+        ApplicationRecord.transaction do
+          Board.in_iterations(iteration_cadence.iterations).update_all(iteration_id: nil) && iteration_cadence.destroy
+        end
+      end
+    end
+  end
+end

ee/spec/requests/api/graphql/mutations/iterations/cadences/destroy_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe 'Destroying an iteration cadence' do
+  include GraphqlHelpers
+
+  let_it_be(:current_user) { create(:user) }
+  let_it_be(:group) { create(:group) }
+  let_it_be(:iteration_cadence, refind: true) { create(:iterations_cadence, group: group) }
+
+  let(:params) do
+    { id: iteration_cadence.to_global_id.to_s }
+  end
+
+  let(:mutation) do
+    graphql_mutation(:iteration_cadence_destroy, params)
+  end
+
+  def mutation_response
+    graphql_mutation_response(:iteration_cadence_destroy)
+  end
+
+  context 'when the user does not have permission' do
+    before do
+      stub_licensed_features(iterations: true)
+    end
+
+    it_behaves_like 'a mutation that returns a top-level access error'
+  end
+
+  context 'when the user has permission' do
+    before do
+      group.add_developer(current_user)
+    end
+
+    context 'when iterations feature is disabled' do
+      before do
+        stub_licensed_features(iterations: false)
+      end
+
+      it_behaves_like 'a mutation that returns top-level errors', errors: [
+        'The resource that you are attempting to access does not exist or you don\'t have permission to ' \
+        'perform this action'
+      ]
+    end
+
+    context 'when iterations feature is enabled' do
+      before do
+        stub_licensed_features(iterations: true)
+      end
+
+      it 'destroys the iteration cadence', :aggregate_failures do
+        expect do
+          post_graphql_mutation(mutation, current_user: current_user)
+        end.to change(Iterations::Cadence, :count).by(-1)
+
+        expect(mutation_response).to include('group' => hash_including('id' => group.to_global_id.to_s))
+      end
+
+      context 'when iteration_cadences feature flag is disabled' do
+        before do
+          stub_feature_flags(iteration_cadences: false)
+        end
+
+        it_behaves_like 'a mutation that returns errors in the response', errors: ["Operation not allowed"]
+      end
+
+      context 'when required arguments are missing' do
+        let(:params) { {} }
+
+        it 'returns error about required argument' do
+          post_graphql_mutation(mutation, current_user: current_user)
+
+          expect_graphql_errors_to_include(/was provided invalid value for id \(Expected value to not be null\)/)
+        end
+      end
+    end
+  end
+end

ee/spec/services/iterations/cadences/destroy_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Iterations::Cadences::DestroyService do
+  subject(:results) { described_class.new(iteration_cadence, user).execute }
+
+  let_it_be(:group, refind: true) { create(:group) }
+  let_it_be(:project) { create(:project, :repository, group: group) }
+  let_it_be(:user) { create(:user) }
+  let_it_be(:iteration_cadence, refind: true) { create(:iterations_cadence, group: group, start_date: Date.today, duration_in_weeks: 1, iterations_in_advance: 2) }
+  let_it_be(:iteration) { create(:started_iteration, group: group, start_date: 2.days.ago, due_date: 5.days.from_now) }
+  let_it_be(:iteration_list, refind: true) { create(:iteration_list, iteration: iteration) }
+  let_it_be(:iteration_event, refind: true) { create(:resource_iteration_event, iteration: iteration) }
+  let_it_be(:board) { create(:board, iteration: iteration, group: group) }
+  let_it_be(:issue) { create(:issue, namespace: group, iteration: iteration) }
+  let_it_be(:merge_request) { create(:merge_request, source_project: project, iteration: iteration) }
+
+  RSpec.shared_examples 'cadence destroy fails with message' do |message:|
+    it { is_expected.to be_error }
+
+    it 'returns not allowed message' do
+      expect(results.message).to eq(message)
+    end
+  end
+
+  describe '#execute' do
+    context 'when iterations feature enabled' do
+      before do
+        stub_licensed_features(iterations: true)
+      end
+
+      context 'when user is authorized' do
+        before do
+          group.add_developer(user)
+        end
+
+        it { is_expected.to be_success }
+
+        it 'destroys the cadence and associated records' do
+          expect do
+            results
+            board.reload
+            issue.reload
+            merge_request.reload
+          end.to change(Iterations::Cadence, :count).by(-1).and(
+            change(List, :count).by(-1)
+          ).and(
+            change(ResourceIterationEvent, :count).by(-1)
+          ).and(
+            change(Iteration, :count).by(-1)
+          ).and(
+            change(board, :iteration_id).from(iteration.id).to(nil)
+          ).and(
+            change(issue, :iteration).from(iteration).to(nil)
+          ).and(
+            change(merge_request, :iteration).from(iteration).to(nil)
+          )
+        end
+
+        it 'returns the cadence as part of the response' do
+          expect(results.payload[:iteration_cadence]).to eq(iteration_cadence)
+        end
+      end
+
+      context 'when user is not authorized' do
+        it_behaves_like 'cadence destroy fails with message', message: 'Operation not allowed'
+      end
+    end
+
+    context 'when iterations feature disabled' do
+      before do
+        stub_licensed_features(iterations: false)
+      end
+
+      context 'when user is authorized' do
+        before do
+          group.add_developer(user)
+        end
+
+        it_behaves_like 'cadence destroy fails with message', message: 'Operation not allowed'
+      end
+
+      context 'when user is not authorized' do
+        it_behaves_like 'cadence destroy fails with message', message: 'Operation not allowed'
+      end
+    end
+
+    context 'when iteration cadences feature flag disabled' do
+      before do
+        stub_licensed_features(iterations: true)
+        stub_feature_flags(iteration_cadences: false)
+      end
+
+      context 'when user is authorized' do
+        before do
+          group.add_developer(user)
+        end
+
+        it_behaves_like 'cadence destroy fails with message', message: 'Operation not allowed'
+      end
+
+      context 'when user is not authorized' do
+        it_behaves_like 'cadence destroy fails with message', message: 'Operation not allowed'
+      end
+    end
+  end
+end