2 files changed, 26 insertions, 2 deletions
diff --git a/app/controllers/concerns/issuable_actions.rb b/app/controllers/concerns/issuable_actions.rb
index 337957c366d..a21e658fda1 100644
--- a/app/controllers/concerns/issuable_actions.rb
+++ b/app/controllers/concerns/issuable_actions.rb
@@ -77,6 +77,20 @@ module IssuableActions
     render json: { notice: "#{quantity} #{resource_name.pluralize(quantity)} updated" }
   end
 
+  def discussions
+    notes = issuable.notes
+      .inc_relations_for_view
+      .includes(:noteable)
+      .fresh
+
+    notes = prepare_notes_for_rendering(notes)
+    notes = notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
+
+    discussions = Discussion.build_collection(notes, issuable)
+
+    render json: DiscussionSerializer.new(project: project, noteable: issuable, current_user: current_user).represent(discussions, context: self)
+  end
+
   private
 
   def recaptcha_check_if_spammable(should_redirect = true, &block)
diff --git a/app/controllers/concerns/notes_actions.rb b/app/controllers/concerns/notes_actions.rb
index e82a5650935..03ed5b5310b 100644
--- a/app/controllers/concerns/notes_actions.rb
+++ b/app/controllers/concerns/notes_actions.rb
@@ -22,7 +22,7 @@ module NotesActions
     notes = notes.reject { |n| n.cross_reference_not_visible_for?(current_user) }
 
     notes_json[:notes] =
-      if noteable.discussions_rendered_on_frontend?
+      if use_note_serializer?
         note_serializer.represent(notes)
       else
         notes.map { |note| note_json(note) }
@@ -95,7 +95,7 @@ module NotesActions
     if note.persisted?
       attrs[:valid] = true
 
-      if noteable.discussions_rendered_on_frontend?
+      if use_note_serializer?
         attrs.merge!(note_serializer.represent(note))
       else
         attrs.merge!(
@@ -233,4 +233,14 @@ module NotesActions
       the_project
     end
   end
+
+  def use_note_serializer?
+    return false if params['html']
+
+    if noteable.is_a?(MergeRequest)
+      cookies[:vue_mr_discussions] == 'true'
+    else
+      noteable.discussions_rendered_on_frontend?
+    end
+  end
 end