Fix namespace problem with dynamic vuex import

Also add feature spec for testing discussion lock in
merge request pages.

app/assets/javascripts/sidebar/mount_sidebar.js

@@ -132,7 +132,9 @@ function mountLockComponent() {
       ({ store }) => store,
     );
   } else {
-    importStore = import(/* webpackChunkName: 'mrNotesStore' */ '~/mr_notes/stores');
+    importStore = import(/* webpackChunkName: 'mrNotesStore' */ '~/mr_notes/stores').then(
+      store => store.default,
+    );
   }
 
   importStore

spec/features/issuables/merge_request_discussion_lock_spec.rb

+# frozen_string_literal: true
+# TODO use shared examples to merge this spec with discussion_lock_spec.rb
+# https://gitlab.com/gitlab-org/gitlab/-/issues/255910
+
+require 'spec_helper'
+
+RSpec.describe 'Merge Request Discussion Lock', :js do
+  let(:user) { create(:user) }
+  let(:project) { create(:project, :public, :repository) }
+  let(:merge_request) { create(:merge_request, source_project: project, author: user) }
+
+  before do
+    sign_in(user)
+  end
+
+  context 'when a user is a team member' do
+    before do
+      project.add_developer(user)
+    end
+
+    context 'when the discussion is unlocked' do
+      it 'the user can lock the merge_request' do
+        visit project_merge_request_path(merge_request.project, merge_request)
+
+        expect(find('.issuable-sidebar')).to have_content('Unlocked')
+
+        page.within('.issuable-sidebar') do
+          find('.lock-edit').click
+          click_button('Lock')
+        end
+
+        expect(find('[data-testid="lock-status"]')).to have_content('Locked')
+      end
+    end
+
+    context 'when the discussion is locked' do
+      before do
+        merge_request.update_attribute(:discussion_locked, true)
+        visit project_merge_request_path(merge_request.project, merge_request)
+      end
+
+      it 'the user can unlock the merge_request' do
+        expect(find('.issuable-sidebar')).to have_content('Locked')
+
+        page.within('.issuable-sidebar') do
+          find('.lock-edit').click
+          click_button('Unlock')
+        end
+
+        expect(find('[data-testid="lock-status"]')).to have_content('Unlocked')
+      end
+    end
+  end
+
+  context 'when a user is not a team member' do
+    context 'when the discussion is unlocked' do
+      before do
+        visit project_merge_request_path(merge_request.project, merge_request)
+      end
+
+      it 'the user can not lock the merge_request' do
+        expect(find('.issuable-sidebar')).to have_content('Unlocked')
+        expect(find('.issuable-sidebar')).not_to have_selector('.lock-edit')
+      end
+    end
+
+    context 'when the discussion is locked' do
+      before do
+        merge_request.update_attribute(:discussion_locked, true)
+        visit project_merge_request_path(merge_request.project, merge_request)
+      end
+
+      it 'the user can not unlock the merge_request' do
+        expect(find('.issuable-sidebar')).to have_content('Locked')
+        expect(find('.issuable-sidebar')).not_to have_selector('.lock-edit')
+      end
+    end
+  end
+end