Merge branch 'add-add-to-merge-train-when-pipeline-succeeds-strategy' into 'master'

[New Auto Merge Strategy] Add To Merge Train When Pipeline Succeeds

See merge request gitlab-org/gitlab-ee!13767

ee/app/services/auto_merge/add_to_merge_train_when_pipeline_succeeds_service.rb

+# frozen_string_literal: true
+
+module AutoMerge
+  class AddToMergeTrainWhenPipelineSucceedsService < AutoMerge::BaseService
+    def execute(merge_request)
+      super do
+        SystemNoteService.add_to_merge_train_when_pipeline_succeeds(merge_request, project, current_user, merge_request.diff_head_commit)
+      end
+    end
+
+    def process(merge_request)
+      return unless merge_request.actual_head_pipeline&.success?
+
+      merge_train_service = AutoMerge::MergeTrainService.new(project, merge_request.merge_user)
+
+      ##
+      # We are currently abusing `#cancel` method to cancel the auto merge when
+      # a system failure happens. We should split the interfaces into two
+      # for explicitly telling that the cancel action is not triggered by the merge user directly.
+      # https://gitlab.com/gitlab-org/gitlab-ee/issues/12134
+      return cancel(merge_request) unless merge_train_service.available_for?(merge_request)
+
+      merge_train_service.execute(merge_request)
+    end
+
+    def cancel(merge_request)
+      super(merge_request) do
+        SystemNoteService.cancel_add_to_merge_train_when_pipeline_succeeds(merge_request, project, current_user)
+      end
+    end
+
+    def available_for?(merge_request)
+      merge_request.project.merge_trains_enabled? &&
+        !merge_request.for_fork? &&
+        merge_request.actual_head_pipeline&.active? &&
+        merge_request.mergeable_state?(skip_ci_check: true)
+    end
+  end
+end

ee/app/services/ee/auto_merge_service.rb

@@ -5,7 +5,8 @@ module EE
     extend ActiveSupport::Concern
 
     STRATEGY_MERGE_TRAIN = 'merge_train'.freeze
-    EE_STRATEGIES = [STRATEGY_MERGE_TRAIN].freeze
+    STRATEGY_ADD_TO_MERGE_TRAIN_WHEN_PIPELINE_SUCCEEDS = 'add_to_merge_train_when_pipeline_succeeds'.freeze
+    EE_STRATEGIES = [STRATEGY_MERGE_TRAIN, STRATEGY_ADD_TO_MERGE_TRAIN_WHEN_PIPELINE_SUCCEEDS].freeze
 
     class_methods do
       extend ::Gitlab::Utils::Override

ee/app/services/ee/system_note_service.rb

@@ -210,5 +210,19 @@ module EE
 
       create_note(NoteSummary.new(noteable, project, author, body, action: 'merge'))
     end
+
+    # Called when 'add to merge train when pipeline succeeds' is executed
+    def add_to_merge_train_when_pipeline_succeeds(noteable, project, author, last_commit)
+      body = "enabled automatic add to merge train when the pipeline for #{last_commit.to_reference(project)} succeeds"
+
+      create_note(NoteSummary.new(noteable, project, author, body, action: 'merge'))
+    end
+
+    # Called when 'add to merge train when pipeline succeeds' is canceled
+    def cancel_add_to_merge_train_when_pipeline_succeeds(noteable, project, author)
+      body = 'cancelled automatic add to merge train'
+
+      create_note(NoteSummary.new(noteable, project, author, body, action: 'merge'))
+    end
   end
 end

ee/changelogs/unreleased/add-add-to-merge-train-when-pipeline-succeeds-strategy.yml

+---
+title: "[New Auto Merge Strategy] Add To Merge Train When Pipeline Succeeds"
+merge_request: 13767
+author:
+type: added

ee/spec/factories/merge_requests.rb

@@ -24,6 +24,12 @@ FactoryBot.modify do
       end
     end
 
+    trait :add_to_merge_train_when_pipeline_succeeds do
+      auto_merge_enabled true
+      auto_merge_strategy AutoMergeService::STRATEGY_ADD_TO_MERGE_TRAIN_WHEN_PIPELINE_SUCCEEDS
+      merge_user { author }
+    end
+
     transient do
       approval_groups []
       approval_users []

ee/spec/services/auto_merge/add_to_merge_train_when_pipeline_succeeds_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe AutoMerge::AddToMergeTrainWhenPipelineSucceedsService do
+  set(:project) { create(:project, :repository) }
+  set(:user) { create(:user) }
+  let(:service) { described_class.new(project, user) }
+
+  let(:merge_request) do
+    create(:merge_request, :with_merge_request_pipeline,
+      source_project: project, source_branch: 'feature',
+      target_project: project, target_branch: 'master')
+  end
+
+  let(:pipeline) { merge_request.reload.all_pipelines.first }
+
+  before do
+    stub_licensed_features(merge_trains: true, merge_pipelines: true)
+    project.add_maintainer(user)
+    project.update!(merge_trains_enabled: true, merge_pipelines_enabled: true)
+    allow(AutoMergeProcessWorker).to receive(:perform_async) { }
+    merge_request.update_head_pipeline
+  end
+
+  describe '#execute' do
+    subject { service.execute(merge_request) }
+
+    it 'enables auto merge' do
+      expect(SystemNoteService)
+        .to receive(:add_to_merge_train_when_pipeline_succeeds)
+        .with(merge_request, project, user, merge_request.diff_head_commit)
+
+      subject
+
+      expect(merge_request).to be_auto_merge_enabled
+    end
+  end
+
+  describe '#process' do
+    subject { service.process(merge_request) }
+
+    context 'when the latest pipeline in the merge request has succeeded' do
+      before do
+        pipeline.succeed!
+      end
+
+      it 'executes MergeTrainService' do
+        expect_next_instance_of(AutoMerge::MergeTrainService) do |train_service|
+          expect(train_service).to receive(:execute).with(merge_request)
+        end
+
+        subject
+      end
+
+      context 'when merge train strategy is not available for the merge request' do
+        before do
+          train_service = double
+          allow(train_service).to receive(:available_for?) { false }
+          allow(AutoMerge::MergeTrainService).to receive(:new) { train_service }
+        end
+
+        it 'cancels auto merge' do
+          expect(service).to receive(:cancel).once
+
+          subject
+        end
+      end
+    end
+
+    context 'when the latest pipeline in the merge request is running' do
+      it 'does not initialize MergeTrainService' do
+        expect(AutoMerge::MergeTrainService).not_to receive(:new)
+
+        subject
+      end
+    end
+  end
+
+  describe '#cancel' do
+    subject { service.cancel(merge_request) }
+
+    let(:merge_request) { create(:merge_request, :add_to_merge_train_when_pipeline_succeeds, merge_user: user) }
+
+    it 'cancels auto merge' do
+      expect(SystemNoteService)
+        .to receive(:cancel_add_to_merge_train_when_pipeline_succeeds)
+        .with(merge_request, project, user)
+
+      subject
+
+      expect(merge_request).not_to be_auto_merge_enabled
+    end
+  end
+
+  describe '#available_for?' do
+    subject { service.available_for?(merge_request) }
+
+    it { is_expected.to eq(true) }
+
+    context 'when merge trains option is disabled' do
+      before do
+        expect(merge_request.project).to receive(:merge_trains_enabled?) { false }
+      end
+
+      it { is_expected.to eq(false) }
+    end
+
+    context 'when merge request is submitted from a forked project' do
+      before do
+        allow(merge_request).to receive(:for_fork?) { true }
+      end
+
+      it { is_expected.to eq(false) }
+    end
+
+    context 'when the latest pipeline in the merge request is not active' do
+      before do
+        pipeline.succeed!
+      end
+
+      it { is_expected.to eq(false) }
+    end
+
+    context 'when merge request is not mergeable' do
+      before do
+        merge_request.update!(title: merge_request.wip_title)
+      end
+
+      it { is_expected.to eq(false) }
+    end
+  end
+end

ee/spec/services/ee/auto_merge_service_spec.rb

@@ -7,7 +7,8 @@ describe AutoMergeService do
     subject { described_class.all_strategies }
 
     it 'includes all strategies' do
-      is_expected.to include(AutoMergeService::STRATEGY_MERGE_TRAIN)
+      is_expected.to include(AutoMergeService::STRATEGY_MERGE_TRAIN,
+                             AutoMergeService::STRATEGY_ADD_TO_MERGE_TRAIN_WHEN_PIPELINE_SUCCEEDS)
     end
   end
 end

ee/spec/services/system_note_service_spec.rb

@@ -370,4 +370,38 @@ describe SystemNoteService do
       end
     end
   end
+
+  describe '.add_to_merge_train_when_pipeline_succeeds' do
+    subject { described_class.add_to_merge_train_when_pipeline_succeeds(noteable, project, author, noteable.diff_head_commit) }
+
+    let(:pipeline) { build(:ci_pipeline_without_jobs) }
+
+    let(:noteable) do
+      create(:merge_request, source_project: project, target_project: project)
+    end
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'merge' }
+    end
+
+    it "posts the 'add to merge train when pipeline succeeds' system note" do
+      expect(subject.note).to match(%r{enabled automatic add to merge train when the pipeline for (\w+/\w+@)?\h{40} succeeds})
+    end
+  end
+
+  describe '.cancel_add_to_merge_train_when_pipeline_succeeds' do
+    subject { described_class.cancel_add_to_merge_train_when_pipeline_succeeds(noteable, project, author) }
+
+    let(:noteable) do
+      create(:merge_request, source_project: project, target_project: project)
+    end
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'merge' }
+    end
+
+    it "posts the 'add to merge train when pipeline succeeds' system note" do
+      expect(subject.note).to eq 'cancelled automatic add to merge train'
+    end
+  end
 end