Add system note with link to diff comparison when MR discussion becomes outdated

2 files changed, 50 insertions, 1 deletions

diff --git a/spec/services/notes/diff_position_update_service_spec.rb b/spec/services/notes/diff_position_update_service_spec.rb
index d73ae51fbc3..380c296fd3a 100644
--- a/spec/services/notes/diff_position_update_service_spec.rb
+++ b/spec/services/notes/diff_position_update_service_spec.rb
@@ -2,6 +2,7 @@ require 'spec_helper'
 
 describe Notes::DiffPositionUpdateService, services: true do
   let(:project) { create(:project, :repository) }
+  let(:current_user) { project.owner }
   let(:create_commit) { project.commit("913c66a37b4a45b9769037c55c2d238bd0942d2e") }
   let(:modify_commit) { project.commit("874797c3a73b60d2187ed6e2fcabd289ff75171e") }
   let(:edit_commit) { project.commit("570e7b2abdd848b95f2f578043fc23bd6f6fd24d") }
@@ -25,7 +26,7 @@ describe Notes::DiffPositionUpdateService, services: true do
   subject do
     described_class.new(
       project,
-      nil,
+      current_user,
       old_diff_refs: old_diff_refs,
       new_diff_refs: new_diff_refs,
       paths: [path]
@@ -170,6 +171,23 @@ describe Notes::DiffPositionUpdateService, services: true do
         expect(note.original_position).to eq(old_position)
         expect(note.position).to eq(old_position)
       end
+
+      it 'sets the change position' do
+        subject.execute(note)
+
+        change_position = note.change_position
+        expect(change_position.start_sha).to eq(old_diff_refs.head_sha)
+        expect(change_position.head_sha).to eq(new_diff_refs.head_sha)
+        expect(change_position.old_line).to eq(9)
+        expect(change_position.new_line).to be_nil
+      end
+
+      it 'creates a system note' do
+        expect(SystemNoteService).to receive(:diff_discussion_outdated).with(
+          note.to_discussion, project, current_user, instance_of(Gitlab::Diff::Position))
+
+        subject.execute(note)
+      end
     end
   end
 end
diff --git a/spec/services/system_note_service_spec.rb b/spec/services/system_note_service_spec.rb
index 7a9cd7553b1..c737a1f82a3 100644
--- a/spec/services/system_note_service_spec.rb
+++ b/spec/services/system_note_service_spec.rb
@@ -1034,4 +1034,35 @@ describe SystemNoteService, services: true do
       expect(subject.note).to eq 'resolved all discussions'
     end
   end
+
+  describe '.diff_discussion_outdated' do
+    let(:discussion) { create(:diff_note_on_merge_request).to_discussion }
+    let(:merge_request) { discussion.noteable }
+    let(:project) { merge_request.source_project }
+    let(:change_position) { discussion.position }
+
+    def reloaded_merge_request
+      MergeRequest.find(merge_request.id)
+    end
+
+    subject { described_class.diff_discussion_outdated(discussion, project, author, change_position) }
+
+    it_behaves_like 'a system note' do
+      let(:expected_noteable) { discussion.first_note.noteable }
+      let(:action)              { 'outdated' }
+    end
+
+    it 'creates a new note in the discussion' do
+      # we need to completely rebuild the merge request object, or the `@discussions` on the merge request are not reloaded.
+      expect { subject }.to change { reloaded_merge_request.discussions.first.notes.size }.by(1)
+    end
+
+    it 'links to the diff in the system note' do
+      expect(subject.note).to include('version 1')
+
+      diff_id = merge_request.merge_request_diff.id
+      line_code = change_position.line_code(project.repository)
+      expect(subject.note).to include(diffs_namespace_project_merge_request_url(project.namespace, project, merge_request, diff_id: diff_id, anchor: line_code))
+    end
+  end
 end