Defer loading non-essential components

There are multiple components that are not essential for
WebIDE's loading, yet they are loaded and bootstrapped
together with the essential ones. This commit fixes that

app/assets/javascripts/ide/components/ide.vue

 <script>
 import { mapActions, mapGetters, mapState } from 'vuex';
-import { GlButton, GlLoadingIcon } from '@gitlab/ui';
 import { __ } from '~/locale';
 import {
   WEBIDE_MARK_APP_START,
@@ -14,15 +13,8 @@ import {
 import { performanceMarkAndMeasure } from '~/performance/utils';
 import { modalTypes } from '../constants';
 import eventHub from '../eventhub';
-import FindFile from '~/vue_shared/components/file_finder/index.vue';
-import NewModal from './new_dropdown/modal.vue';
 import IdeSidebar from './ide_side_bar.vue';
-import RepoTabs from './repo_tabs.vue';
-import IdeStatusBar from './ide_status_bar.vue';
 import RepoEditor from './repo_editor.vue';
-import RightPane from './panes/right.vue';
-import ErrorMessage from './error_message.vue';
-import CommitEditorHeader from './commit_sidebar/editor_header.vue';
 import glFeatureFlagsMixin from '~/vue_shared/mixins/gl_feature_flags_mixin';
 
 import { measurePerformance } from '../utils';
@@ -43,19 +35,24 @@ eventHub.$on(WEBIDE_MEASURE_FILE_AFTER_INTERACTION, () =>
 
 export default {
   components: {
-    NewModal,
     IdeSidebar,
-    RepoTabs,
-    IdeStatusBar,
     RepoEditor,
-    FindFile,
-    ErrorMessage,
-    CommitEditorHeader,
-    GlButton,
-    GlLoadingIcon,
-    RightPane,
+    'error-message': () => import('./error_message.vue'),
+    'gl-button': () => import('@gitlab/ui/src/components/base/button/button.vue'),
+    'gl-loading-icon': () => import('@gitlab/ui/src/components/base/loading_icon/loading_icon.vue'),
+    'commit-editor-header': () => import('./commit_sidebar/editor_header.vue'),
+    'repo-tabs': () => import('./repo_tabs.vue'),
+    'ide-status-bar': () => import('./ide_status_bar.vue'),
+    'find-file': () => import('~/vue_shared/components/file_finder/index.vue'),
+    'right-pane': () => import('./panes/right.vue'),
+    'new-modal': () => import('./new_dropdown/modal.vue'),
   },
   mixins: [glFeatureFlagsMixin()],
+  data() {
+    return {
+      loadDeferred: false,
+    };
+  },
   computed: {
     ...mapState([
       'openFiles',
@@ -107,6 +104,9 @@ export default {
     createNewFile() {
       this.$refs.newModal.open(modalTypes.blob);
     },
+    loadDeferredComponents() {
+      this.loadDeferred = true;
+    },
   },
 };
 </script>
@@ -118,6 +118,7 @@ export default {
   >
     <error-message v-if="errorMessage" :message="errorMessage" />
     <div class="ide-view flex-grow d-flex">
+      <template v-if="loadDeferred">
         <find-file
           v-show="fileFindVisible"
           :files="allBlobs"
@@ -126,11 +127,14 @@ export default {
           @toggle="toggleFileFinder"
           @click="openFile"
         />
-      <ide-sidebar />
+      </template>
+      <ide-sidebar @tree-ready="loadDeferredComponents" />
       <div class="multi-file-edit-pane">
         <template v-if="activeFile">
+          <template v-if="loadDeferred">
             <commit-editor-header v-if="isCommitModeActive" :active-file="activeFile" />
             <repo-tabs v-else :active-file="activeFile" :files="openFiles" :viewer="viewer" />
+          </template>
           <repo-editor :file="activeFile" class="multi-file-edit-pane-content" />
         </template>
         <template v-else>
@@ -177,9 +181,13 @@ export default {
           </div>
         </template>
       </div>
+      <template v-if="loadDeferred">
         <right-pane v-if="currentProjectId" />
+      </template>
     </div>
+    <template v-if="loadDeferred">
       <ide-status-bar />
       <new-modal ref="newModal" />
+    </template>
   </article>
 </template>

app/assets/javascripts/ide/components/ide_side_bar.vue

@@ -4,21 +4,19 @@ import { GlDeprecatedSkeletonLoading as GlSkeletonLoading } from '@gitlab/ui';
 import IdeTree from './ide_tree.vue';
 import ResizablePanel from './resizable_panel.vue';
 import ActivityBar from './activity_bar.vue';
-import RepoCommitSection from './repo_commit_section.vue';
 import CommitForm from './commit_sidebar/form.vue';
-import IdeReview from './ide_review.vue';
 import IdeProjectHeader from './ide_project_header.vue';
-import { SIDEBAR_INIT_WIDTH } from '../constants';
+import { SIDEBAR_INIT_WIDTH, leftSidebarViews } from '../constants';
 
 export default {
   components: {
     GlSkeletonLoading,
     ResizablePanel,
     ActivityBar,
-    RepoCommitSection,
     IdeTree,
+    [leftSidebarViews.review.name]: () => import('./ide_review.vue'),
+    [leftSidebarViews.commit.name]: () => import('./repo_commit_section.vue'),
     CommitForm,
-    IdeReview,
     IdeProjectHeader,
   },
   computed: {
@@ -49,7 +47,7 @@ export default {
         <div class="multi-file-commit-panel-inner" data-testid="ide-side-bar-inner">
           <div class="multi-file-commit-panel-inner-content">
             <keep-alive>
-              <component :is="currentActivityView" />
+              <component :is="currentActivityView" @tree-ready="$emit('tree-ready')" />
             </keep-alive>
           </div>
           <commit-form />

app/assets/javascripts/ide/components/ide_tree.vue

@@ -51,7 +51,7 @@ export default {
 </script>
 
 <template>
-  <ide-tree-list>
+  <ide-tree-list @tree-ready="$emit('tree-ready')">
     <template #header>
       {{ __('Edit') }}
       <div class="ide-tree-actions ml-auto d-flex" data-testid="ide-root-actions">

app/assets/javascripts/ide/components/ide_tree_list.vue

@@ -32,6 +32,13 @@ export default {
       return !this.currentTree || this.currentTree.loading;
     },
   },
+  watch: {
+    showLoading(newVal) {
+      if (!newVal) {
+        this.$emit('tree-ready');
+      }
+    },
+  },
   beforeCreate() {
     performanceMarkAndMeasure({ mark: WEBIDE_MARK_TREE_START });
   },

spec/frontend/ide/components/ide_side_bar_spec.js

 import { mount, createLocalVue } from '@vue/test-utils';
 import Vuex from 'vuex';
 import { GlSkeletonLoading } from '@gitlab/ui';
+import waitForPromises from 'helpers/wait_for_promises';
 import { createStore } from '~/ide/stores';
 import IdeSidebar from '~/ide/components/ide_side_bar.vue';
 import IdeTree from '~/ide/components/ide_tree.vue';
 import RepoCommitSection from '~/ide/components/repo_commit_section.vue';
+import IdeReview from '~/ide/components/ide_review.vue';
 import { leftSidebarViews } from '~/ide/constants';
 import { projectData } from '../mock_data';
 
@@ -15,11 +17,12 @@ describe('IdeSidebar', () => {
   let wrapper;
   let store;
 
-  function createComponent() {
+  function createComponent({ view = leftSidebarViews.edit.name } = {}) {
     store = createStore();
 
     store.state.currentProjectId = 'abcproject';
     store.state.projects.abcproject = projectData;
+    store.state.currentActivityView = view;
 
     return mount(IdeSidebar, {
       store,
@@ -48,22 +51,46 @@ describe('IdeSidebar', () => {
     expect(wrapper.findAll(GlSkeletonLoading)).toHaveLength(3);
   });
 
-  describe('activityBarComponent', () => {
-    it('renders tree component', () => {
+  describe('deferred rendering components', () => {
+    it('fetches components on demand', async () => {
       wrapper = createComponent();
 
       expect(wrapper.find(IdeTree).exists()).toBe(true);
-    });
+      expect(wrapper.find(IdeReview).exists()).toBe(false);
+      expect(wrapper.find(RepoCommitSection).exists()).toBe(false);
 
-    it('renders commit component', async () => {
-      wrapper = createComponent();
+      store.state.currentActivityView = leftSidebarViews.review.name;
+      await waitForPromises();
+      await wrapper.vm.$nextTick();
 
-      store.state.currentActivityView = leftSidebarViews.commit.name;
+      expect(wrapper.find(IdeTree).exists()).toBe(false);
+      expect(wrapper.find(IdeReview).exists()).toBe(true);
+      expect(wrapper.find(RepoCommitSection).exists()).toBe(false);
 
+      store.state.currentActivityView = leftSidebarViews.commit.name;
+      await waitForPromises();
       await wrapper.vm.$nextTick();
 
+      expect(wrapper.find(IdeTree).exists()).toBe(false);
+      expect(wrapper.find(IdeReview).exists()).toBe(false);
       expect(wrapper.find(RepoCommitSection).exists()).toBe(true);
     });
+    it.each`
+      view                            | tree     | review   | commit
+      ${leftSidebarViews.edit.name}   | ${true}  | ${false} | ${false}
+      ${leftSidebarViews.review.name} | ${false} | ${true}  | ${false}
+      ${leftSidebarViews.commit.name} | ${false} | ${false} | ${true}
+    `('renders correct panels for $view', async ({ view, tree, review, commit } = {}) => {
+      wrapper = createComponent({
+        view,
+      });
+      await waitForPromises();
+      await wrapper.vm.$nextTick();
+
+      expect(wrapper.find(IdeTree).exists()).toBe(tree);
+      expect(wrapper.find(IdeReview).exists()).toBe(review);
+      expect(wrapper.find(RepoCommitSection).exists()).toBe(commit);
+    });
   });
 
   it('keeps the current activity view components alive', async () => {
@@ -72,7 +99,7 @@ describe('IdeSidebar', () => {
     const ideTreeComponent = wrapper.find(IdeTree).element;
 
     store.state.currentActivityView = leftSidebarViews.commit.name;
-
+    await waitForPromises();
     await wrapper.vm.$nextTick();
 
     expect(wrapper.find(IdeTree).exists()).toBe(false);
@@ -80,6 +107,7 @@ describe('IdeSidebar', () => {
 
     store.state.currentActivityView = leftSidebarViews.edit.name;
 
+    await waitForPromises();
     await wrapper.vm.$nextTick();
 
     // reference to the elements remains the same, meaning the components were kept alive

spec/frontend/ide/components/ide_spec.js

 import Vue from 'vue';
 import { createComponentWithStore } from 'helpers/vue_mount_component_helper';
+import waitForPromises from 'helpers/wait_for_promises';
 import { createStore } from '~/ide/stores';
 import ide from '~/ide/components/ide.vue';
 import { file } from '../helpers';
@@ -63,18 +64,17 @@ describe('ide component, non-empty repo', () => {
     vm.$destroy();
   });
 
-  it('shows error message when set', done => {
+  it('shows error message when set', async () => {
     expect(vm.$el.querySelector('.gl-alert')).toBe(null);
 
     vm.$store.state.errorMessage = {
       text: 'error',
     };
 
-    vm.$nextTick(() => {
-      expect(vm.$el.querySelector('.gl-alert')).not.toBe(null);
+    await waitForPromises();
+    await vm.$nextTick();
 
-      done();
-    });
+    expect(vm.$el.querySelector('.gl-alert')).not.toBe(null);
   });
 
   describe('onBeforeUnload', () => {

spec/frontend_integration/ide/__snapshots__/ide_integration_spec.js.snap

@@ -8,12 +8,6 @@ exports[`WebIDE runs 1`] = `
     <div
       class="ide-view flex-grow d-flex"
     >
-      <div
-        class="file-finder-overlay"
-        style="display: none;"
-      >
-        (jest: contents hidden)
-      </div>
       <div
         class="gl-relative multi-file-commit-panel flex-column"
         style="width: 340px;"
@@ -109,28 +103,12 @@ exports[`WebIDE runs 1`] = `
                 <h4>
                   Make and review changes in the browser with the Web IDE
                 </h4>
-                <div
-                  class="gl-spinner-container"
-                >
-                  <span
-                    aria-label="Loading"
-                    class="align-text-bottom gl-spinner gl-spinner-dark gl-spinner-md"
-                  />
               </div>
             </div>
           </div>
         </div>
       </div>
     </div>
-    </div>
-    <footer
-      class="ide-status-bar"
-    >
-      <div
-        class="ide-status-list d-flex ml-auto"
-      >
-      </div>
-    </footer>
   </article>
 </div>
 `;