fix(router): router should not swallow "unhandled" errors

closes #12802

modules/@angular/router/src/router.ts

@@ -596,7 +596,9 @@ export class Router {
     const id = ++this.navigationId;
     this.navigations.next({id, rawUrl, prevRawUrl, extras, resolve, reject, promise});
 
-    return promise;
+    // Make sure that the error is propagated even though `processNavigations` catch
+    // handler does not rethrow
+    return promise.catch((e: any) => Promise.reject(e));
   }
 
   private executeScheduledNavigation({id, rawUrl, prevRawUrl, extras, resolve,

modules/@angular/router/test/integration.spec.ts

@@ -7,7 +7,7 @@
  */
 
 import {CommonModule, Location} from '@angular/common';
-import {Component, NgModule, NgModuleFactoryLoader} from '@angular/core';
+import {Component, Injector, NgModule, NgModuleFactoryLoader} from '@angular/core';
 import {ComponentFixture, TestBed, async, fakeAsync, inject, tick} from '@angular/core/testing';
 import {expect} from '@angular/platform-browser/testing/matchers';
 import {Observable} from 'rxjs/Observable';
@@ -620,6 +620,19 @@ describe('Integration', () => {
        expectEvents(recordedEvents, [[NavigationStart, '/invalid'], [NavigationError, '/invalid']]);
      })));
 
+  it('should not swallow errors', fakeAsync(inject([Router], (router: Router) => {
+       const fixture = createRoot(router, RootCmp);
+
+       router.resetConfig([{path: 'simple', component: SimpleCmp}]);
+
+       router.navigateByUrl('/invalid');
+       expect(() => advance(fixture)).toThrow();
+
+       router.navigateByUrl('/invalid2');
+       expect(() => advance(fixture)).toThrow();
+     })));
+
+
   it('should replace state when path is equal to current path',
      fakeAsync(inject([Router, Location], (router: Router, location: Location) => {
        const fixture = createRoot(router, RootCmp);