Split AutoMergeService interfaces into two `cancel` and `abort`

Create explicit endpoint - abort.

app/services/auto_merge/base_service.rb

@@ -29,7 +29,7 @@ module AutoMerge
     end
 
     def cancel(merge_request)
-      if cancel_auto_merge(merge_request)
+      if clear_auto_merge_parameters(merge_request)
         yield if block_given?
 
         success
@@ -38,6 +38,16 @@ module AutoMerge
       end
     end
 
+    def abort(merge_request, reason)
+      if clear_auto_merge_parameters(merge_request)
+        yield if block_given?
+
+        success
+      else
+        error("Can't abort the automatic merge", 406)
+      end
+    end
+
     private
 
     def strategy
@@ -46,7 +56,7 @@ module AutoMerge
       end
     end
 
-    def cancel_auto_merge(merge_request)
+    def clear_auto_merge_parameters(merge_request)
       merge_request.auto_merge_enabled = false
       merge_request.merge_user = nil
 

app/services/auto_merge/merge_when_pipeline_succeeds_service.rb

@@ -19,7 +19,13 @@ module AutoMerge
 
     def cancel(merge_request)
       super do
-        SystemNoteService.cancel_merge_when_pipeline_succeeds(merge_request, @project, @current_user)
+        SystemNoteService.cancel_merge_when_pipeline_succeeds(merge_request, project, current_user)
+      end
+    end
+
+    def abort(merge_request, reason)
+      super do
+        SystemNoteService.abort_merge_when_pipeline_succeeds(merge_request, project, current_user, reason)
       end
     end
 

app/services/auto_merge_service.rb

@@ -42,6 +42,12 @@ class AutoMergeService < BaseService
     get_service_instance(merge_request.auto_merge_strategy).cancel(merge_request)
   end
 
+  def abort(merge_request, reason)
+    return error("Can't abort the automatic merge", 406) unless merge_request.auto_merge_enabled?
+
+    get_service_instance(merge_request.auto_merge_strategy).abort(merge_request, reason)
+  end
+
   def available_strategies(merge_request)
     self.class.all_strategies.select do |strategy|
       get_service_instance(strategy).available_for?(merge_request)

app/services/merge_requests/base_service.rb

@@ -68,8 +68,8 @@ module MergeRequests
         !merge_request.for_fork?
     end
 
-    def cancel_auto_merge(merge_request)
-      AutoMergeService.new(project, current_user).cancel(merge_request)
+    def abort_auto_merge(merge_request, reason)
+      AutoMergeService.new(project, current_user).abort(merge_request, reason)
     end
 
     # Returns all origin and fork merge requests from `@project` satisfying passed arguments.

app/services/merge_requests/close_service.rb

@@ -18,7 +18,7 @@ module MergeRequests
         invalidate_cache_counts(merge_request, users: merge_request.assignees)
         merge_request.update_project_counter_caches
         cleanup_environments(merge_request)
-        cancel_auto_merge(merge_request)
+        abort_auto_merge(merge_request, 'merge request was closed')
       end
 
       merge_request

app/services/merge_requests/refresh_service.rb

@@ -24,7 +24,7 @@ module MergeRequests
       reload_merge_requests
       outdate_suggestions
       refresh_pipelines_on_merge_requests
-      cancel_auto_merges
+      abort_auto_merges
       mark_pending_todos_done
       cache_merge_requests_closing_issues
 
@@ -142,9 +142,9 @@ module MergeRequests
       end
     end
 
-    def cancel_auto_merges
+    def abort_auto_merges
       merge_requests_for_source_branch.each do |merge_request|
-        cancel_auto_merge(merge_request)
+        abort_auto_merge(merge_request, 'source branch was updated')
       end
     end
 

app/services/merge_requests/update_service.rb

@@ -44,7 +44,7 @@ module MergeRequests
                                   merge_request.previous_changes['target_branch'].first,
                                   merge_request.target_branch)
 
-        cancel_auto_merge(merge_request)
+        abort_auto_merge(merge_request, 'target branch was changed')
       end
 
       if merge_request.assignees != old_assignees

app/services/system_note_service.rb

@@ -234,6 +234,16 @@ module SystemNoteService
     create_note(NoteSummary.new(noteable, project, author, body, action: 'merge'))
   end
 
+  # Called when 'merge when pipeline succeeds' is aborted
+  def abort_merge_when_pipeline_succeeds(noteable, project, author, reason)
+    body = "aborted the automatic merge because #{reason}"
+
+    ##
+    # TODO: Abort message should be sent by the system, not a particular user.
+    # See https://gitlab.com/gitlab-org/gitlab-ce/issues/63187.
+    create_note(NoteSummary.new(noteable, project, author, body, action: 'merge'))
+  end
+
   def handle_merge_request_wip(noteable, project, author)
     prefix = noteable.work_in_progress? ? "marked" : "unmarked"
 

spec/services/auto_merge/base_service_spec.rb

@@ -121,11 +121,7 @@ describe AutoMerge::BaseService do
     end
   end
 
-  describe '#cancel' do
-    subject { service.cancel(merge_request) }
-
-    let(:merge_request) { create(:merge_request, :merge_when_pipeline_succeeds) }
-
+  shared_examples_for 'Canceled or Dropped' do
     it 'removes properies from the merge request' do
       subject
 
@@ -173,6 +169,20 @@ describe AutoMerge::BaseService do
       it 'does not yield block' do
         expect { |b| service.execute(merge_request, &b) }.not_to yield_control
       end
+    end
+  end
+
+  describe '#cancel' do
+    subject { service.cancel(merge_request) }
+
+    let(:merge_request) { create(:merge_request, :merge_when_pipeline_succeeds) }
+
+    it_behaves_like 'Canceled or Dropped'
+
+    context 'when failed to save' do
+      before do
+        allow(merge_request).to receive(:save) { false }
+      end
 
       it 'returns error status' do
         expect(subject[:status]).to eq(:error)
@@ -180,4 +190,24 @@ describe AutoMerge::BaseService do
       end
     end
   end
+
+  describe '#abort' do
+    subject { service.abort(merge_request, reason) }
+
+    let(:merge_request) { create(:merge_request, :merge_when_pipeline_succeeds) }
+    let(:reason) { 'an error'}
+
+    it_behaves_like 'Canceled or Dropped'
+
+    context 'when failed to save' do
+      before do
+        allow(merge_request).to receive(:save) { false }
+      end
+
+      it 'returns error status' do
+        expect(subject[:status]).to eq(:error)
+        expect(subject[:message]).to eq("Can't abort the automatic merge")
+      end
+    end
+  end
 end

spec/services/auto_merge/merge_when_pipeline_succeeds_service_spec.rb

@@ -177,6 +177,17 @@ describe AutoMerge::MergeWhenPipelineSucceedsService do
     end
   end
 
+  describe "#abort" do
+    before do
+      service.abort(mr_merge_if_green_enabled, 'an error')
+    end
+
+    it 'posts a system note' do
+      note = mr_merge_if_green_enabled.notes.last
+      expect(note.note).to include 'aborted the automatic merge'
+    end
+  end
+
   describe 'pipeline integration' do
     context 'when there are multiple stages in the pipeline' do
       let(:ref) { mr_merge_if_green_enabled.source_branch }

spec/services/auto_merge_service_spec.rb

@@ -161,4 +161,29 @@ describe AutoMergeService do
       end
     end
   end
+
+  describe '#abort' do
+    subject { service.abort(merge_request, error) }
+
+    let(:merge_request) { create(:merge_request, :merge_when_pipeline_succeeds) }
+    let(:error) { 'an error' }
+
+    it 'delegates to a relevant service instance' do
+      expect_next_instance_of(AutoMerge::MergeWhenPipelineSucceedsService) do |service|
+        expect(service).to receive(:abort).with(merge_request, error)
+      end
+
+      subject
+    end
+
+    context 'when auto merge is not enabled' do
+      let(:merge_request) { create(:merge_request) }
+
+      it 'returns error' do
+        expect(subject[:message]).to eq("Can't abort the automatic merge")
+        expect(subject[:status]).to eq(:error)
+        expect(subject[:http_status]).to eq(406)
+      end
+    end
+  end
 end

spec/services/system_note_service_spec.rb

@@ -359,6 +359,22 @@ describe SystemNoteService do
     end
   end
 
+  describe '.abort_merge_when_pipeline_succeeds' do
+    let(:noteable) do
+      create(:merge_request, source_project: project, target_project: project)
+    end
+
+    subject { described_class.abort_merge_when_pipeline_succeeds(noteable, project, author, 'merge request was closed') }
+
+    it_behaves_like 'a system note' do
+      let(:action) { 'merge' }
+    end
+
+    it "posts the 'merge when pipeline succeeds' system note" do
+      expect(subject.note).to eq "aborted the automatic merge because merge request was closed"
+    end
+  end
+
   describe '.change_title' do
     let(:noteable) { create(:issue, project: project, title: 'Lorem ipsum') }