feat(platform-browser): do not throw error when Hammer.js not loaded (#22257)

closes #16992

PR Close #22257

packages/platform-browser/src/dom/events/hammer_gestures.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Inject, Injectable, InjectionToken} from '@angular/core';
+import {Inject, Injectable, InjectionToken, ɵConsole as Console} from '@angular/core';
 
 import {DOCUMENT} from '../dom_tokens';
 
@@ -99,7 +99,8 @@ export class HammerGestureConfig {
 export class HammerGesturesPlugin extends EventManagerPlugin {
   constructor(
       @Inject(DOCUMENT) doc: any,
-      @Inject(HAMMER_GESTURE_CONFIG) private _config: HammerGestureConfig) {
+      @Inject(HAMMER_GESTURE_CONFIG) private _config: HammerGestureConfig,
+      private console: Console) {
     super(doc);
   }
 
@@ -109,7 +110,8 @@ export class HammerGesturesPlugin extends EventManagerPlugin {
     }
 
     if (!(window as any).Hammer) {
-      throw new Error(`Hammer.js is not loaded, can not bind ${eventName} event`);
+      this.console.warn(`Hammer.js is not loaded, can not bind '${eventName}' event.`);
+      return false;
     }
 
     return true;

packages/platform-browser/test/dom/events/hammer_gestures_spec.ts

@@ -10,14 +10,27 @@ import {HammerGestureConfig, HammerGesturesPlugin} from '@angular/platform-brows
 
 {
   describe('HammerGesturesPlugin', () => {
+    let plugin: HammerGesturesPlugin;
+    let mockConsole: any;
     if (isNode) return;
 
-    it('should implement addGlobalEventListener', () => {
-      const plugin = new HammerGesturesPlugin(document, new HammerGestureConfig());
+    beforeEach(() => {
+      mockConsole = {warn: () => {}};
+      plugin = new HammerGesturesPlugin(document, new HammerGestureConfig(), mockConsole);
+    });
 
+    it('should implement addGlobalEventListener', () => {
       spyOn(plugin, 'addEventListener').and.callFake(() => {});
 
       expect(() => plugin.addGlobalEventListener('document', 'swipe', () => {})).not.toThrowError();
     });
+
+    it('shoud warn user and do nothing when Hammer.js not loaeded', () => {
+      spyOn(mockConsole, 'warn');
+
+      expect(plugin.supports('swipe')).toBe(false);
+      expect(mockConsole.warn)
+          .toHaveBeenCalledWith(`Hammer.js is not loaded, can not bind 'swipe' event.`);
+    });
   });
 }