fix(button): redispatch click event with all original properties

Author: Mikhail Bashkirov

packages/button/src/LionButton.js

@@ -152,9 +152,14 @@ export class LionButton extends DelegateMixin(SlotMixin(LionLitElement)) {
     this.__teardownDelegation();
   }
 
-  __clickDelegationHandler(e) {
-    e.stopPropagation(); // prevent click on the fake element and cause click on the native button
-    this.$$slot('_button').click();
+  /**
+   * Prevent click on the fake element and cause click on the native button.
+   */
+  __clickDelegationHandler(oldEvent) {
+    oldEvent.stopPropagation();
+    // replacing `MouseEvent` with `oldEvent.constructor` breaks IE
+    const newEvent = new MouseEvent(oldEvent.type, oldEvent);
+    this.$$slot('_button').dispatchEvent(newEvent);
   }
 
   __setupDelegation() {
@@ -180,7 +185,7 @@ export class LionButton extends DelegateMixin(SlotMixin(LionLitElement)) {
     if (e.keyCode === 32 /* space */ || e.keyCode === 13 /* enter */) {
       e.preventDefault();
       this.shadowRoot.querySelector('.btn').removeAttribute('active');
-      this.$$slot('_button').click();
+      this.shadowRoot.querySelector('.click-area').click();
     }
   }
 

packages/button/test/lion-button.test.js

@@ -1,9 +1,20 @@
-import { expect, fixture, html, aTimeout } from '@open-wc/testing';
+import { expect, fixture, html, aTimeout, oneEvent } from '@open-wc/testing';
 import sinon from 'sinon';
-import { pressEnter, pressSpace } from '@polymer/iron-test-helpers/mock-interactions.js';
+import {
+  makeMouseEvent,
+  pressEnter,
+  pressSpace,
+} from '@polymer/iron-test-helpers/mock-interactions.js';
 
 import '../lion-button.js';
 
+function getTopElement(el) {
+  const { left, top } = el.getBoundingClientRect();
+  // to support elementFromPoint() in polyfilled browsers we have to use document
+  const crossBrowserRoot = el.shadowRoot.elementFromPoint ? el.shadowRoot : document;
+  return crossBrowserRoot.elementFromPoint(left, top);
+}
+
 describe('lion-button', () => {
   it('behaves like native `button` in terms of a11y', async () => {
     const el = await fixture(`<lion-button>foo</lion-button>`);
@@ -99,11 +110,7 @@ describe('lion-button', () => {
       `);
 
       const button = form.querySelector('lion-button');
-      const { left, top } = button.getBoundingClientRect();
-      // to support elementFromPoint() in polyfilled browsers we have to use document
-      const crossBrowserRoot = button.shadowRoot.elementFromPoint ? button.shadowRoot : document;
-      const shadowClickAreaElement = crossBrowserRoot.elementFromPoint(left, top);
-      shadowClickAreaElement.click();
+      getTopElement(button).click();
 
       expect(formSubmitSpy.called).to.be.true;
     });
@@ -138,4 +145,62 @@ describe('lion-button', () => {
       expect(formSubmitSpy.called).to.be.true;
     });
   });
+
+  describe('click event', () => {
+    it('is fired once', async () => {
+      const clickSpy = sinon.spy();
+      const el = await fixture(
+        html`
+          <lion-button @click="${clickSpy}"></lion-button>
+        `,
+      );
+
+      getTopElement(el).click();
+
+      // trying to wait for other possible redispatched events
+      await aTimeout();
+      await aTimeout();
+
+      expect(clickSpy.callCount).to.equal(1);
+    });
+
+    describe('event after redispatching', async () => {
+      async function prepareClickEvent(el, host) {
+        setTimeout(() => {
+          if (host) {
+            // click on host like in native button
+            makeMouseEvent('click', { x: 11, y: 11 }, el);
+          } else {
+            // click on click-area which is then redispatched
+            makeMouseEvent('click', { x: 11, y: 11 }, getTopElement(el));
+          }
+        });
+        return oneEvent(el, 'click');
+      }
+
+      let hostEvent;
+      let redispatchedEvent;
+
+      before(async () => {
+        const el = await fixture('<lion-button></lion-button>');
+        hostEvent = await prepareClickEvent(el, true);
+        redispatchedEvent = await prepareClickEvent(el, false);
+      });
+
+      const sameProperties = [
+        'constructor',
+        'composed',
+        'bubbles',
+        'cancelable',
+        'clientX',
+        'clientY',
+      ];
+
+      sameProperties.forEach(property => {
+        it(`has same value of the property "${property}"`, async () => {
+          expect(redispatchedEvent[property]).to.equal(hostEvent[property]);
+        });
+      });
+    });
+  });
 });