fix(router): routerLink support of null/undefined (#13380)

Closes #6971

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

@@ -34,7 +34,7 @@ export function createUrlTree(
 }
 
 function isMatrixParams(command: any): boolean {
-  return typeof command === 'object' && !command.outlets && !command.segmentPath;
+  return typeof command === 'object' && command != null && !command.outlets && !command.segmentPath;
 }
 
 function tree(
@@ -70,7 +70,7 @@ class Navigation {
       throw new Error('Root segment cannot have matrix parameters');
     }
 
-    const cmdWithOutlet = commands.find(c => typeof c === 'object' && c.outlets);
+    const cmdWithOutlet = commands.find(c => typeof c === 'object' && c != null && c.outlets);
     if (cmdWithOutlet && cmdWithOutlet !== last(commands)) {
       throw new Error('{outlets:{}} has to be the last command');
     }
@@ -91,7 +91,7 @@ function computeNavigation(commands: any[]): Navigation {
   let isAbsolute = false;
 
   const res: any[] = commands.reduce((res, cmd, cmdIdx) => {
-    if (typeof cmd === 'object') {
+    if (typeof cmd === 'object' && cmd != null) {
       if (cmd.outlets) {
         const outlets: {[k: string]: any} = {};
         forEach(cmd.outlets, (commands: any, name: string) => {
@@ -169,7 +169,9 @@ function createPositionApplyingDoubleDots(
 }
 
 function getPath(command: any): any {
-  if (typeof command === 'object' && command.outlets) return command.outlets[PRIMARY_OUTLET];
+  if (typeof command === 'object' && command != null && command.outlets) {
+    return command.outlets[PRIMARY_OUTLET];
+  }
   return `${command}`;
 }
 
@@ -306,4 +308,4 @@ function stringify(params: {[key: string]: any}): {[key: string]: string} {
 
 function compare(path: string, params: {[key: string]: any}, segment: UrlSegment): boolean {
   return path == segment.path && shallowEqual(params, segment.parameters);
-}
+}

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

@@ -98,15 +98,15 @@ export class RouterLink {
   }
 
   @Input()
-  set routerLink(data: any[]|string) {
-    if (Array.isArray(data)) {
-      this.commands = data;
+  set routerLink(commands: any[]|string) {
+    if (commands != null) {
+      this.commands = Array.isArray(commands) ? commands : [commands];
     } else {
-      this.commands = [data];
+      this.commands = [];
     }
   }
 
-  @HostListener('click', [])
+  @HostListener('click')
   onClick(): boolean {
     const extras = {
       skipLocationChange: attrBoolValue(this.skipLocationChange),
@@ -163,11 +163,11 @@ export class RouterLinkWithHref implements OnChanges, OnDestroy {
   }
 
   @Input()
-  set routerLink(data: any[]|string) {
-    if (Array.isArray(data)) {
-      this.commands = data;
+  set routerLink(commands: any[]|string) {
+    if (commands != null) {
+      this.commands = Array.isArray(commands) ? commands : [commands];
     } else {
-      this.commands = [data];
+      this.commands = [];
     }
   }
 

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

@@ -1022,6 +1022,26 @@ describe('Integration', () => {
          expect(native.getAttribute('href')).toEqual('/home');
        }));
 
+    it('should not throw when commands is null', fakeAsync(() => {
+         @Component({
+           selector: 'someCmp',
+           template:
+               `<router-outlet></router-outlet><a [routerLink]="null">Link</a><button [routerLink]="null">Button</button>`
+         })
+         class CmpWithLink {
+         }
+
+         TestBed.configureTestingModule({declarations: [CmpWithLink]});
+         const router: Router = TestBed.get(Router);
+
+         let fixture: ComponentFixture<CmpWithLink> = createRoot(router, CmpWithLink);
+         router.resetConfig([{path: 'home', component: SimpleCmp}]);
+         const anchor = fixture.nativeElement.querySelector('a');
+         const button = fixture.nativeElement.querySelector('button');
+         expect(() => anchor.click()).not.toThrow();
+         expect(() => button.click()).not.toThrow();
+       }));
+
     it('should update hrefs when query params or fragment change', fakeAsync(() => {
 
          @Component({