Add lazy option to UserAvatarImage

app/assets/javascripts/vue_shared/components/user_avatar/user_avatar_image.vue

@@ -7,6 +7,7 @@
   Sample configuration:
 
   <user-avatar-image
+    :lazy="true"
     :img-src="userAvatarSrc"
     :img-alt="tooltipText"
     :tooltip-text="tooltipText"
@@ -16,11 +17,17 @@
 */
 
 import defaultAvatarUrl from 'images/no_avatar.png';
+import { placeholderImage } from '../../../lazy_loader';
 import tooltip from '../../directives/tooltip';
 
 export default {
   name: 'UserAvatarImage',
   props: {
+    lazy: {
+      type: Boolean,
+      required: false,
+      default: false,
+    },
     imgSrc: {
       type: String,
       required: false,
@@ -56,18 +63,21 @@ export default {
     tooltip,
   },
   computed: {
+    // API response sends null when gravatar is disabled and
+    // we provide an empty string when we use it inside user avatar link.
+    // In both cases we should render the defaultAvatarUrl
+    sanitizedSource() {
+      return this.imgSrc === '' || this.imgSrc === null ? defaultAvatarUrl : this.imgSrc;
+    },
+    resultantSrcAttribute() {
+      return this.lazy ? placeholderImage : this.sanitizedSource;
+    },
     tooltipContainer() {
       return this.tooltipText ? 'body' : null;
     },
     avatarSizeClass() {
       return `s${this.size}`;
     },
-    // API response sends null when gravatar is disabled and
-    // we provide an empty string when we use it inside user avatar link.
-    // In both cases we should render the defaultAvatarUrl
-    imageSource() {
-      return this.imgSrc === '' || this.imgSrc === null ? defaultAvatarUrl : this.imgSrc;
-    },
   },
 };
 </script>
@@ -76,11 +86,16 @@ export default {
   <img
     v-tooltip
     class="avatar"
-    :class="[avatarSizeClass, cssClasses]"
-    :src="imageSource"
+    :class="{
+      lazy,
+      [avatarSizeClass]: true,
+      [cssClasses]: true
+    }"
+    :src="resultantSrcAttribute"
     :width="size"
     :height="size"
     :alt="imgAlt"
+    :data-src="sanitizedSource"
     :data-container="tooltipContainer"
     :data-placement="tooltipPlacement"
     :title="tooltipText"

changelogs/unreleased/add-lazy-option-to-user-avatar-image-component.yml

+---
+title: Add lazy option to UserAvatarImage
+merge_request: 14895
+author:
+type: changed

spec/javascripts/vue_shared/components/user_avatar/user_avatar_image_spec.js

 import Vue from 'vue';
-import UserAvatarImage from '~/vue_shared/components/user_avatar/user_avatar_image.vue';
+import { placeholderImage } from '~/lazy_loader';
+import userAvatarImage from '~/vue_shared/components/user_avatar/user_avatar_image.vue';
+import mountComponent from '../../../helpers/vue_mount_component_helper';
 
-const UserAvatarImageComponent = Vue.extend(UserAvatarImage);
+const DEFAULT_PROPS = {
+  size: 99,
+  imgSrc: 'myavatarurl.com',
+  imgAlt: 'mydisplayname',
+  cssClasses: 'myextraavatarclass',
+  tooltipText: 'tooltip text',
+  tooltipPlacement: 'bottom',
+};
 
 describe('User Avatar Image Component', function () {
+  let vm;
+  let UserAvatarImage;
+
+  beforeEach(() => {
+    UserAvatarImage = Vue.extend(userAvatarImage);
+  });
+
   describe('Initialization', function () {
     beforeEach(function () {
-      this.propsData = {
-        size: 99,
-        imgSrc: 'myavatarurl.com',
-        imgAlt: 'mydisplayname',
-        cssClasses: 'myextraavatarclass',
-        tooltipText: 'tooltip text',
-        tooltipPlacement: 'bottom',
-      };
-
-      this.userAvatarImage = new UserAvatarImageComponent({
-        propsData: this.propsData,
+      vm = mountComponent(UserAvatarImage, {
+        ...DEFAULT_PROPS,
       }).$mount();
     });
 
     it('should return a defined Vue component', function () {
-      expect(this.userAvatarImage).toBeDefined();
+      expect(vm).toBeDefined();
     });
 
     it('should have <img> as a child element', function () {
-      expect(this.userAvatarImage.$el.tagName).toBe('IMG');
+      expect(vm.$el.tagName).toBe('IMG');
+      expect(vm.$el.getAttribute('src')).toBe(DEFAULT_PROPS.imgSrc);
+      expect(vm.$el.getAttribute('data-src')).toBe(DEFAULT_PROPS.imgSrc);
+      expect(vm.$el.getAttribute('alt')).toBe(DEFAULT_PROPS.imgAlt);
     });
 
     it('should properly compute tooltipContainer', function () {
-      expect(this.userAvatarImage.tooltipContainer).toBe('body');
+      expect(vm.tooltipContainer).toBe('body');
     });
 
     it('should properly render tooltipContainer', function () {
-      expect(this.userAvatarImage.$el.getAttribute('data-container')).toBe('body');
+      expect(vm.$el.getAttribute('data-container')).toBe('body');
     });
 
     it('should properly compute avatarSizeClass', function () {
-      expect(this.userAvatarImage.avatarSizeClass).toBe('s99');
+      expect(vm.avatarSizeClass).toBe('s99');
     });
 
     it('should properly render img css', function () {
-      const classList = this.userAvatarImage.$el.classList;
+      const classList = vm.$el.classList;
       const containsAvatar = classList.contains('avatar');
       const containsSizeClass = classList.contains('s99');
-      const containsCustomClass = classList.contains('myextraavatarclass');
+      const containsCustomClass = classList.contains(DEFAULT_PROPS.cssClasses);
+      const lazyClass = classList.contains('lazy');
 
       expect(containsAvatar).toBe(true);
       expect(containsSizeClass).toBe(true);
       expect(containsCustomClass).toBe(true);
+      expect(lazyClass).toBe(false);
+    });
+  });
+
+  describe('Initialization when lazy', function () {
+    beforeEach(function () {
+      vm = mountComponent(UserAvatarImage, {
+        ...DEFAULT_PROPS,
+        lazy: true,
+      }).$mount();
+    });
+
+    it('should add lazy attributes', function () {
+      const classList = vm.$el.classList;
+      const lazyClass = classList.contains('lazy');
+
+      expect(lazyClass).toBe(true);
+      expect(vm.$el.getAttribute('src')).toBe(placeholderImage);
+      expect(vm.$el.getAttribute('data-src')).toBe(DEFAULT_PROPS.imgSrc);
     });
   });
 });