[r96943502] fix: provide a way to prevent default event to avoid jumping effect

Author: marinaaisa

src/components/ContentNode/LinkableHeading.vue

@@ -19,7 +19,7 @@
       :href="`#${anchor}`"
       class="header-anchor"
       aria-label="hidden"
-      @click="handleFocusAndScroll(anchor)"
+      @click="handleFocusAndScroll(anchor, { event: $event })"
     >#</a>
     <slot />
   </component>

src/mixins/scrollToElement.js

@@ -33,13 +33,25 @@ export default {
      * and that it is in view, even if the hash is in the url
      * @returns {Promise<Element>}
     */
-    async handleFocusAndScroll(hash) {
+    async handleFocusAndScroll(hash, preventDefault) {
       const element = document.getElementById(hash);
+      // if no element to focus or scroll, exit
       if (!element) return;
+      // create route hash
+      const routeHash = `#${hash}`;
+      // if preventDefault is true, prevent default to avoid jumping effect
+      if (preventDefault && preventDefault.event) {
+        preventDefault.event.preventDefault();
+        // update the hash since default behavior was prevented
+        // only if route hash is different that new
+        if (this.$route.hash !== routeHash) {
+          this.$router.push({ hash: routeHash });
+        }
+      }
       // Focus scrolls to the element
       element.focus();
       // but we need to compensate for the navigation height
-      await this.scrollToElement(`#${hash}`);
+      await this.scrollToElement(routeHash);
     },
   },
 };

tests/unit/mixins/scrollToElement.spec.js

@@ -11,32 +11,49 @@
 import { shallowMount } from '@vue/test-utils';
 import scrollToElement from 'docc-render/mixins/scrollToElement';
 import * as loading from 'docc-render/utils/loading';
+import { createEvent as createBaseEvent } from '../../../test-utils';
 
 const framesWait = jest.spyOn(loading, 'waitFrames');
 
 describe('scrollToElement', () => {
   const scrollOffset = { x: 0, y: 14 };
   const anchor = 'heres-why';
-
-  const wrapper = shallowMount({
-    name: 'MyComponent',
-    mixins: [scrollToElement],
-    render() {
-      return `<div id="${anchor}"/>`;
-    },
-  }, {
-    mocks: {
-      $router: {
-        resolve: ({ hash }) => ({ route: { hash } }),
-        options: {
-          scrollBehavior(to) {
-            return new Promise(resolve => (
-              resolve({ selector: to.hash, offset: scrollOffset })
-            ));
+  const pushMock = jest.fn();
+  const preventDefault = jest.fn();
+  let wrapper;
+
+  const event = createBaseEvent('click');
+  event.preventDefault = preventDefault;
+  document.dispatchEvent(event);
+
+  const createWrapper = (extraMocks) => {
+    wrapper = shallowMount({
+      name: 'MyComponent',
+      mixins: [scrollToElement],
+      render() {
+        return `<div id="${anchor}"/>`;
+      },
+    }, {
+      mocks: {
+        $router: {
+          resolve: ({ hash }) => ({ route: { hash } }),
+          push: ({ hash }) => pushMock(hash),
+          options: {
+            scrollBehavior(to) {
+              return new Promise(resolve => (
+                resolve({ selector: to.hash, offset: scrollOffset })
+              ));
+            },
           },
         },
+        ...extraMocks,
       },
-    },
+    });
+  };
+
+  beforeEach(() => {
+    createWrapper();
+    jest.clearAllMocks();
   });
 
   it('scrolls to the correct element when "scrollToElement" is called', async () => {
@@ -89,6 +106,48 @@ describe('scrollToElement', () => {
     getElementSpy.mockRestore();
   });
 
+  it('prevents default event, if preventDefault provides an event', async () => {
+    createWrapper({
+      $route: {
+        hash: '#foo',
+      },
+    });
+
+    const mockObject = { focus: jest.fn() };
+    jest.spyOn(document, 'getElementById').mockReturnValue(mockObject);
+
+    await wrapper.vm.handleFocusAndScroll('#blah', { event });
+    expect(preventDefault).toHaveBeenCalledTimes(1);
+  });
+
+  it('pushes hash on router, if preventDefault is true and hash is different than current one', async () => {
+    createWrapper({
+      $route: {
+        hash: '#foo',
+      },
+    });
+
+    const mockObject = { focus: jest.fn() };
+    jest.spyOn(document, 'getElementById').mockReturnValue(mockObject);
+
+    await wrapper.vm.handleFocusAndScroll('blah', { event });
+    expect(pushMock).toHaveBeenCalledTimes(1);
+  });
+
+  it('does not push hash on router, if preventDefault is true and hash is the same as current one', async () => {
+    createWrapper({
+      $route: {
+        hash: '#foo',
+      },
+    });
+
+    const mockObject = { focus: jest.fn() };
+    jest.spyOn(document, 'getElementById').mockReturnValue(mockObject);
+
+    await wrapper.vm.handleFocusAndScroll('foo', { event });
+    expect(pushMock).toHaveBeenCalledTimes(0);
+  });
+
   it('does not focus element and scroll if element is not in the document', async () => {
     wrapper.vm.scrollToElement = jest.fn();
     const hash = 'foo';