refactor(keycodes): add utilities for checking modifier keys

Based off of the conversation in angular#13790, these changes add some utilities for dealing with modifier keys on keyboard events.

src/cdk/keycodes/BUILD.bazel

@@ -1,10 +1,23 @@
 package(default_visibility=["//visibility:public"])
 
-load("//tools:defaults.bzl", "ts_library")
+load("//tools:defaults.bzl", "ng_module", "ng_test_library", "ng_web_test_suite")
 
-ts_library(
+ng_module(
   name = "keycodes",
   module_name = "@angular/cdk/keycodes",
   srcs = glob(["**/*.ts"], exclude=["**/*.spec.ts"]),
-  deps = ["@npm//tslib"],
+)
+
+ng_test_library(
+  name = "keycodes_test_sources",
+  srcs = glob(["**/*.spec.ts"]),
+  deps = [
+    "//src/cdk/testing",
+    ":keycodes",
+  ]
+)
+
+ng_web_test_suite(
+  name = "unit_tests",
+  deps = [":keycodes_test_sources"],
 )

src/cdk/keycodes/modifiers.spec.ts

@@ -0,0 +1,56 @@
+import {createKeyboardEvent} from '@angular/cdk/testing';
+import {hasModifierKey} from './modifiers';
+
+describe('keyboard modifiers', () => {
+  it('should check whether the alt key is pressed', () => {
+    const event = createKeyboardEvent('keydown', 0);
+
+    expect(hasModifierKey(event)).toBe(false);
+    Object.defineProperty(event, 'altKey', {get: () => true});
+    expect(hasModifierKey(event)).toBe(true);
+  });
+
+  it('should check whether the shift key is pressed', () => {
+    const event = createKeyboardEvent('keydown', 0);
+
+    expect(hasModifierKey(event)).toBe(false);
+    Object.defineProperty(event, 'shiftKey', {get: () => true});
+    expect(hasModifierKey(event)).toBe(true);
+  });
+
+  it('should check whether the meta key is pressed', () => {
+    const event = createKeyboardEvent('keydown', 0);
+
+    expect(hasModifierKey(event)).toBe(false);
+    Object.defineProperty(event, 'metaKey', {get: () => true});
+    expect(hasModifierKey(event)).toBe(true);
+  });
+
+  it('should check whether the ctrl key is pressed', () => {
+    const event = createKeyboardEvent('keydown', 0);
+
+    expect(hasModifierKey(event)).toBe(false);
+    Object.defineProperty(event, 'ctrlKey', {get: () => true});
+    expect(hasModifierKey(event)).toBe(true);
+  });
+
+  it('should check if a particular modifier key is pressed', () => {
+    const event = createKeyboardEvent('keydown', 0);
+    Object.defineProperty(event, 'ctrlKey', {get: () => true});
+
+    expect(hasModifierKey(event, 'altKey')).toBe(false);
+    Object.defineProperty(event, 'altKey', {get: () => true});
+    expect(hasModifierKey(event, 'altKey')).toBe(true);
+  });
+
+  it('should check if multiple specific modifier keys are pressed', () => {
+    const event = createKeyboardEvent('keydown', 0);
+    Object.defineProperty(event, 'ctrlKey', {get: () => true});
+
+    expect(hasModifierKey(event, 'altKey', 'shiftKey')).toBe(false);
+    Object.defineProperty(event, 'altKey', {get: () => true});
+    Object.defineProperty(event, 'shiftKey', {get: () => true});
+    expect(hasModifierKey(event, 'altKey', 'shiftKey')).toBe(true);
+  });
+
+});

src/cdk/keycodes/modifiers.ts

@@ -0,0 +1,21 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+type ModifierKey = 'altKey' | 'shiftKey' | 'ctrlKey' | 'metaKey';
+
+/**
+ * Checks whether a modifier key is pressed.
+ * @param event Event to be checked.
+ */
+export function hasModifierKey(event: KeyboardEvent, ...modifiers: ModifierKey[]): boolean {
+  if (modifiers.length) {
+    return modifiers.some(modifier => event[modifier]);
+  }
+
+  return event.altKey || event.shiftKey || event.ctrlKey || event.metaKey;
+}

src/cdk/keycodes/public-api.ts

@@ -7,3 +7,4 @@
  */
 
 export * from './keycodes';
+export * from './modifiers';

src/cdk/stepper/stepper.ts

@@ -9,7 +9,7 @@
 import {FocusableOption, FocusKeyManager} from '@angular/cdk/a11y';
 import {Direction, Directionality} from '@angular/cdk/bidi';
 import {coerceBooleanProperty} from '@angular/cdk/coercion';
-import {END, ENTER, HOME, SPACE} from '@angular/cdk/keycodes';
+import {END, ENTER, HOME, SPACE, hasModifierKey} from '@angular/cdk/keycodes';
 import {
   AfterViewInit,
   ChangeDetectionStrategy,
@@ -442,9 +442,7 @@ export class CdkStepper implements AfterViewInit, OnDestroy {
   }
 
   _onKeydown(event: KeyboardEvent) {
-    // TODO(crisbeto): move into a CDK utility once
-    // the similar PRs for other components are merged in.
-    const hasModifier = event.altKey || event.shiftKey || event.ctrlKey || event.metaKey;
+    const hasModifier = hasModifierKey(event);
     const keyCode = event.keyCode;
     const manager = this._keyManager;
 

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

@@ -7,7 +7,7 @@
  */
 
 import {FocusMonitor, FocusableOption, FocusOrigin} from '@angular/cdk/a11y';
-import {ENTER, SPACE} from '@angular/cdk/keycodes';
+import {ENTER, SPACE, hasModifierKey} from '@angular/cdk/keycodes';
 import {
   ChangeDetectionStrategy,
   ChangeDetectorRef,
@@ -140,7 +140,7 @@ export class MatExpansionPanelHeader implements OnDestroy, FocusableOption {
       // Toggle for space and enter keys.
       case SPACE:
       case ENTER:
-        if (!event.altKey && !event.metaKey && !event.shiftKey && !event.ctrlKey) {
+        if (!hasModifierKey(event)) {
           event.preventDefault();
           this._toggle();
         }