Fix sharing localStorage with all MRs

Expose id field in the serializer in order
to store comments content in the localStorage
under the correct key

app/serializers/merge_request_noteable_entity.rb

 # frozen_string_literal: true
 
-class MergeRequestNoteableEntity < Grape::Entity
+class MergeRequestNoteableEntity < IssuableEntity
   include RequestAwareEntity
 
   # Currently this attr is exposed to be used in app/assets/javascripts/notes/stores/getters.js

changelogs/unreleased/id-autosave-for-new-mr.yml

+---
+title: Fix sharing localStorage with all MRs
+merge_request: 32699
+author:
+type: fixed

spec/features/merge_request/user_posts_notes_spec.rb

@@ -5,7 +5,8 @@ require 'spec_helper'
 describe 'Merge request > User posts notes', :js do
   include NoteInteractionHelpers
 
-  let(:project) { create(:project, :repository) }
+  set(:project) { create(:project, :repository) }
+
   let(:user) { project.creator }
   let(:merge_request) do
     create(:merge_request, source_project: project, target_project: project)
@@ -33,17 +34,21 @@ describe 'Merge request > User posts notes', :js do
     end
 
     describe 'with text' do
+      let(:text) { 'This is awesome' }
+
       before do
         page.within('.js-main-target-form') do
-          fill_in 'note[note]', with: 'This is awesome'
+          fill_in 'note[note]', with: text
         end
       end
 
-      it 'has enable submit button and preview button' do
+      it 'has enable submit button, preview button and saves content to local storage' do
         page.within('.js-main-target-form') do
           expect(page).not_to have_css('.js-comment-button[disabled]')
           expect(page).to have_css('.js-md-preview-button', visible: true)
         end
+
+        expect(page.evaluate_script("localStorage['autosave/Note/MergeRequest/#{merge_request.id}']")).to eq(text)
       end
     end
   end

spec/fixtures/api/schemas/entities/merge_request_noteable.json

 {
   "type": "object",
   "properties" : {
+    "id": { "type": "integer" },
+    "iid": { "type": "integer" },
+    "title": { "type": "string" },
+    "description": { "type": "string" },
     "merge_params": { "type": ["object", "null"] },
     "state": { "type": "string" },
     "source_branch": { "type": "string" },

spec/serializers/merge_request_serializer_spec.rb

 require 'spec_helper'
 
 describe MergeRequestSerializer do
-  let(:user) { create(:user) }
-  let(:resource) { create(:merge_request) }
+  set(:user) { create(:user) }
+  set(:resource) { create(:merge_request, description: "Description") }
+
   let(:json_entity) do
     described_class.new(current_user: user)
       .represent(resource, serializer: serializer)