fix(expansion-panel): don't handle enter/space if modifier is pressed (#13790)

Doesn't `preventDefault` and handle the enter and space key presses if the user is pressing any of the modifier keys.

Fixes #13783.

Author: crisbeto

src/cdk/testing/event-objects.ts

@@ -56,11 +56,14 @@ export function createTouchEvent(type: string, pageX = 0, pageY = 0) {
 /** Dispatches a keydown event from an element. */
 export function createKeyboardEvent(type: string, keyCode: number, target?: Element, key?: string) {
   let event = document.createEvent('KeyboardEvent') as any;
-  // Firefox does not support `initKeyboardEvent`, but supports `initKeyEvent`.
-  let initEventFn = (event.initKeyEvent || event.initKeyboardEvent).bind(event);
   let originalPreventDefault = event.preventDefault;
 
-  initEventFn(type, true, true, window, 0, 0, 0, 0, 0, keyCode);
+  // Firefox does not support `initKeyboardEvent`, but supports `initKeyEvent`.
+  if (event.initKeyEvent) {
+    event.initKeyEvent(type, true, true, window, 0, 0, 0, 0, 0, keyCode);
+  } else {
+    event.initKeyboardEvent(type, true, true, window, 0, key, 0, '', false);
+  }
 
   // Webkit Browsers don't set the keyCode when calling the init function.
   // See related bug https://bugs.webkit.org/show_bug.cgi?id=16735

src/lib/expansion/expansion-panel-header.ts

@@ -140,8 +140,11 @@ export class MatExpansionPanelHeader implements OnDestroy, FocusableOption {
       // Toggle for space and enter keys.
       case SPACE:
       case ENTER:
-        event.preventDefault();
-        this._toggle();
+        if (!event.altKey && !event.metaKey && !event.shiftKey && !event.ctrlKey) {
+          event.preventDefault();
+          this._toggle();
+        }
+
         break;
       default:
         if (this.panel.accordion) {

src/lib/expansion/expansion.spec.ts

@@ -4,7 +4,7 @@ import {By} from '@angular/platform-browser';
 import {NoopAnimationsModule} from '@angular/platform-browser/animations';
 import {MatExpansionModule, MatExpansionPanel} from './index';
 import {SPACE, ENTER} from '@angular/cdk/keycodes';
-import {dispatchKeyboardEvent} from '@angular/cdk/testing';
+import {dispatchKeyboardEvent, createKeyboardEvent, dispatchEvent} from '@angular/cdk/testing';
 
 
 describe('MatExpansionPanel', () => {
@@ -139,6 +139,24 @@ describe('MatExpansionPanel', () => {
     expect(event.defaultPrevented).toBe(true);
   });
 
+  it('should not toggle if a modifier key is pressed', () => {
+    const fixture = TestBed.createComponent(PanelWithContent);
+    const headerEl = fixture.nativeElement.querySelector('.mat-expansion-panel-header');
+
+    spyOn(fixture.componentInstance.panel, 'toggle');
+
+    ['altKey', 'metaKey', 'shiftKey', 'ctrlKey'].forEach(modifier => {
+      const event = createKeyboardEvent('keydown', ENTER);
+      Object.defineProperty(event, modifier, {get: () => true});
+
+      dispatchEvent(headerEl, event);
+      fixture.detectChanges();
+
+      expect(fixture.componentInstance.panel.toggle).not.toHaveBeenCalled();
+      expect(event.defaultPrevented).toBe(false);
+    });
+  });
+
   it('should not be able to focus content while closed', fakeAsync(() => {
     const fixture = TestBed.createComponent(PanelWithContent);
     fixture.componentInstance.expanded = true;