Fix polling for transformed individual notes

Sets `updated_at` so that the transformed note is returned together with
the new reply

app/models/discussion.rb

@@ -17,8 +17,6 @@ class Discussion
             :for_commit?,
             :for_merge_request?,
 
-            :save,
-
             to: :first_note
 
   def project_id

app/models/individual_note_discussion.rb

@@ -17,8 +17,12 @@ class IndividualNoteDiscussion < Discussion
     noteable.supports_replying_to_individual_notes? && Feature.enabled?(:reply_to_individual_notes)
   end
 
-  def convert_to_discussion!
-    first_note.becomes!(Discussion.note_class).to_discussion
+  def convert_to_discussion!(save: false)
+    first_note.becomes!(Discussion.note_class).to_discussion.tap do
+      # Save needs to be called on first_note instead of the transformed note
+      # because of https://gitlab.com/gitlab-org/gitlab-ce/issues/57324
+      first_note.save if save
+    end
   end
 
   def reply_attributes

app/services/notes/create_service.rb

@@ -35,7 +35,7 @@ module Notes
 
       if !only_commands && note.save
         if note.part_of_discussion? && note.discussion.can_convert_to_discussion?
-          note.discussion.convert_to_discussion!.save(touch: false)
+          note.discussion.convert_to_discussion!(save: true)
         end
 
         todo_service.new_note(note, current_user)

spec/services/notes/create_service_spec.rb

@@ -311,7 +311,14 @@ describe Notes::CreateService do
         end
 
         it 'converts existing note to DiscussionNote' do
-          expect { subject }.to change { existing_note.reload.type }.from(nil).to('DiscussionNote')
+          expect do
+            existing_note
+
+            Timecop.freeze(Time.now + 1.minute) { subject }
+
+            existing_note.reload
+          end.to change { existing_note.type }.from(nil).to('DiscussionNote')
+             .and change { existing_note.updated_at }
         end
       end
     end