Resolve "Webpack Roadmap"

app/assets/javascripts/boards/components/board_sidebar.js

 /* eslint-disable comma-dangle, space-before-function-paren, no-new */
-/* global MilestoneSelect */
 
 import Vue from 'vue';
 import Flash from '../../flash';
@@ -12,6 +11,7 @@ import './sidebar/remove_issue';
 import IssuableContext from '../../issuable_context';
 import LabelsSelect from '../../labels_select';
 import subscriptions from '../../sidebar/components/subscriptions/subscriptions.vue';
+import MilestoneSelect from '../../milestone_select';
 
 const Store = gl.issueBoards.BoardsStore;
 

app/assets/javascripts/dispatcher.js

@@ -5,7 +5,7 @@ import IssuableIndex from './issuable_index';
 import Milestone from './milestone';
 import IssuableForm from './issuable_form';
 import LabelsSelect from './labels_select';
-/* global MilestoneSelect */
+import MilestoneSelect from './milestone_select';
 import NewBranchForm from './new_branch_form';
 import NotificationsForm from './notifications_form';
 import notificationsDropdown from './notifications_dropdown';

app/assets/javascripts/init_issuable_sidebar.js

 /* eslint-disable no-new */
-/* global MilestoneSelect */
+
+import MilestoneSelect from './milestone_select';
 import LabelsSelect from './labels_select';
 import IssuableContext from './issuable_context';
 import Sidebar from './right_sidebar';

app/assets/javascripts/init_legacy_filters.js

 /* eslint-disable no-new */
 import LabelsSelect from './labels_select';
-/* global MilestoneSelect */
 import subscriptionSelect from './subscription_select';
 import UsersSelect from './users_select';
 import issueStatusSelect from './issue_status_select';
+import MilestoneSelect from './milestone_select';
 
 export default () => {
   new UsersSelect();

app/assets/javascripts/issuable_bulk_update_sidebar.js

 /* eslint-disable class-methods-use-this, no-new */
-/* global MilestoneSelect */
 
 import IssuableBulkUpdateActions from './issuable_bulk_update_actions';
-import './milestone_select';
+import MilestoneSelect from './milestone_select';
 import issueStatusSelect from './issue_status_select';
 import subscriptionSelect from './subscription_select';
 import LabelsSelect from './labels_select';