Add loading state to initial load of assignees in dropdown

app/assets/javascripts/boards/components/board_assignee_dropdown.vue

@@ -6,6 +6,7 @@ import {
   GlAvatarLabeled,
   GlAvatarLink,
   GlSearchBoxByType,
+  GlLoadingIcon,
 } from '@gitlab/ui';
 import { __, n__ } from '~/locale';
 import IssuableAssignees from '~/sidebar/components/assignees/issuable_assignees.vue';
@@ -32,6 +33,7 @@ export default {
     GlAvatarLabeled,
     GlAvatarLink,
     GlSearchBoxByType,
+    GlLoadingIcon,
   },
   data() {
     return {
@@ -132,6 +134,8 @@ export default {
           <gl-search-box-by-type v-model.trim="search" />
         </template>
         <template #items>
+          <gl-loading-icon v-if="$apollo.queries.participants.loading" size="lg" />
+          <template v-else>
             <gl-dropdown-item
               :is-checked="selectedIsEmpty"
               data-testid="unassign"
@@ -172,6 +176,7 @@ export default {
               </gl-avatar-link>
             </gl-dropdown-item>
           </template>
+        </template>
       </multi-select-dropdown>
     </template>
   </board-editable-item>

changelogs/unreleased/ss-add-loading-to-assignees.yml

+---
+title: Add loading state to assignees dropdown
+merge_request: 47848
+author:
+type: added

ee/spec/frontend/boards/components/board_content_sidebar_spec.js

@@ -26,6 +26,15 @@ describe('ee/BoardContentSidebar', () => {
         'board-sidebar-due-date': '<div></div>',
         'board-sidebar-subscription': '<div></div>',
       },
+      mocks: {
+        $apollo: {
+          queries: {
+            participants: {
+              loading: false,
+            },
+          },
+        },
+      },
     });
   };
 
@@ -55,7 +64,7 @@ describe('ee/BoardContentSidebar', () => {
     expect(wrapper.find(IssuableTitle).text()).toContain('One');
   });
 
-  it('renders IssuableAssignees', () => {
+  it('renders BoardAssigneeDropdown', () => {
     expect(wrapper.find(BoardAssigneeDropdown).exists()).toBe(true);
   });
 

spec/frontend/boards/components/board_assignee_dropdown_spec.js

 import { mount, createLocalVue } from '@vue/test-utils';
-import { GlDropdownItem, GlAvatarLink, GlAvatarLabeled, GlSearchBoxByType } from '@gitlab/ui';
+import {
+  GlDropdownItem,
+  GlAvatarLink,
+  GlAvatarLabeled,
+  GlSearchBoxByType,
+  GlLoadingIcon,
+} from '@gitlab/ui';
 import createMockApollo from 'jest/helpers/mock_apollo_helper';
 import VueApollo from 'vue-apollo';
 import BoardAssigneeDropdown from '~/boards/components/board_assignee_dropdown.vue';
@@ -25,7 +31,7 @@ describe('BoardCardAssigneeDropdown', () => {
   const activeIssueName = 'test';
   const anotherIssueName = 'hello';
 
-  const createComponent = (search = '') => {
+  const createComponent = (search = '', loading = false) => {
     wrapper = mount(BoardAssigneeDropdown, {
       data() {
         return {
@@ -39,6 +45,15 @@ describe('BoardCardAssigneeDropdown', () => {
         canUpdate: true,
         rootPath: '',
       },
+      mocks: {
+        $apollo: {
+          queries: {
+            participants: {
+              loading,
+            },
+          },
+        },
+      },
     });
   };
 
@@ -82,6 +97,8 @@ describe('BoardCardAssigneeDropdown', () => {
     return wrapper.findAll(GlDropdownItem).wrappers.find(node => node.text().indexOf(text) === 0);
   };
 
+  const findLoadingIcon = () => wrapper.find(GlLoadingIcon);
+
   beforeEach(() => {
     store.state.activeId = '1';
     store.state.issues = {
@@ -243,6 +260,30 @@ describe('BoardCardAssigneeDropdown', () => {
     },
   );
 
+  describe('when participants is loading', () => {
+    beforeEach(() => {
+      createComponent('', true);
+    });
+
+    it('finds a loading icon in the dropdown', () => {
+      expect(findLoadingIcon().exists()).toBe(true);
+    });
+  });
+
+  describe('when participants is loading is false', () => {
+    beforeEach(() => {
+      createComponent();
+    });
+
+    it('does not find GlLoading icon in the dropdown', () => {
+      expect(findLoadingIcon().exists()).toBe(false);
+    });
+
+    it('finds at least 1 GlDropdownItem', () => {
+      expect(wrapper.findAll(GlDropdownItem).length).toBeGreaterThan(0);
+    });
+  });
+
   describe('Apollo', () => {
     beforeEach(() => {
       getIssueParticipantsSpy = jest.fn().mockResolvedValue({