fix(router): routerLinkActive should not throw when not initialized (a…

…ngular#13273)

Fixes angular#13270

PR Close angular#13273

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

@@ -6,14 +6,15 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {AfterContentInit, ChangeDetectorRef, ContentChildren, Directive, ElementRef, Input, OnChanges, OnDestroy, QueryList, Renderer} from '@angular/core';
+import {AfterContentInit, ChangeDetectorRef, ContentChildren, Directive, ElementRef, Input, OnChanges, OnDestroy, QueryList, Renderer, SimpleChanges} from '@angular/core';
 import {Subscription} from 'rxjs/Subscription';
 
 import {NavigationEnd, Router} from '../router';
 
 import {RouterLink, RouterLinkWithHref} from './router_link';
 
 
+
 /**
  * @whatItDoes Lets you add a CSS class to an element when the link's route becomes active.
  *
@@ -82,25 +83,28 @@ import {RouterLink, RouterLinkWithHref} from './router_link';
   exportAs: 'routerLinkActive',
 })
 export class RouterLinkActive implements OnChanges,
-  OnDestroy, AfterContentInit {
+    OnDestroy, AfterContentInit {
   @ContentChildren(RouterLink, {descendants: true}) links: QueryList<RouterLink>;
   @ContentChildren(RouterLinkWithHref, {descendants: true})
   linksWithHrefs: QueryList<RouterLinkWithHref>;
 
   private classes: string[] = [];
   private subscription: Subscription;
+  private active: boolean = false;
 
   @Input() routerLinkActiveOptions: {exact: boolean} = {exact: false};
 
-  constructor(private router: Router, private element: ElementRef, private renderer: Renderer) {
+  constructor(
+      private router: Router, private element: ElementRef, private renderer: Renderer,
+      private cdr: ChangeDetectorRef) {
     this.subscription = router.events.subscribe(s => {
       if (s instanceof NavigationEnd) {
         this.update();
       }
     });
   }
 
-  get isActive(): boolean { return this.hasActiveLink(); }
+  get isActive(): boolean { return this.active; }
 
   ngAfterContentInit(): void {
     this.links.changes.subscribe(_ => this.update());
@@ -110,30 +114,33 @@ export class RouterLinkActive implements OnChanges,
 
   @Input()
   set routerLinkActive(data: string[]|string) {
-    this.classes = (Array.isArray(data) ? data : data.split(' ')).filter(c => !!c);
+    const classes = Array.isArray(data) ? data : data.split(' ');
+    this.classes = classes.filter(c => !!c);
   }
 
-  ngOnChanges(changes: {}): void { this.update(); }
+  ngOnChanges(changes: SimpleChanges): void { this.update(); }
   ngOnDestroy(): void { this.subscription.unsubscribe(); }
 
   private update(): void {
     if (!this.links || !this.linksWithHrefs || !this.router.navigated) return;
-
-    const isActive = this.hasActiveLink();
-    this.classes.forEach(c => {
-      if (c) {
-        this.renderer.setElementClass(this.element.nativeElement, c, isActive);
-      }
-    });
+    const hasActiveLinks = this.hasActiveLinks();
+
+    // react only when status has changed to prevent unnecessary dom updates
+    if (this.active !== hasActiveLinks) {
+      this.active = hasActiveLinks;
+      this.classes.forEach(
+          c => this.renderer.setElementClass(this.element.nativeElement, c, hasActiveLinks));
+      this.cdr.detectChanges();
+    }
   }
 
   private isLinkActive(router: Router): (link: (RouterLink|RouterLinkWithHref)) => boolean {
     return (link: RouterLink | RouterLinkWithHref) =>
-      router.isActive(link.urlTree, this.routerLinkActiveOptions.exact);
+               router.isActive(link.urlTree, this.routerLinkActiveOptions.exact);
   }
 
-  private hasActiveLink(): boolean {
+  private hasActiveLinks(): boolean {
     return this.links.some(this.isLinkActive(this.router)) ||
-      this.linksWithHrefs.some(this.isLinkActive(this.router));
+        this.linksWithHrefs.some(this.isLinkActive(this.router));
   }
 }

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

@@ -2096,6 +2096,8 @@ describe('Integration', () => {
          @Component({
            template: `<a routerLink="/team" routerLinkActive #rla="routerLinkActive"></a>
               <p>{{rla.isActive}}</p>
+              <span *ngIf="rla.isActive"></span>
+              <span [ngClass]="{'highlight': rla.isActive}"></span>
               <router-outlet></router-outlet>`
          })
          class ComponentWithRouterLink {
@@ -2115,15 +2117,15 @@ describe('Integration', () => {
            }
          ]);
 
-         const f = TestBed.createComponent(ComponentWithRouterLink);
+         const fixture = TestBed.createComponent(ComponentWithRouterLink);
          router.navigateByUrl('/team');
-         advance(f);
+         expect(() => advance(fixture)).not.toThrow();
 
-         const paragraph = f.nativeElement.querySelector('p');
+         const paragraph = fixture.nativeElement.querySelector('p');
          expect(paragraph.textContent).toEqual('true');
 
          router.navigateByUrl('/otherteam');
-         advance(f);
+         advance(fixture);
 
          expect(paragraph.textContent).toEqual('false');
        }));

tools/public_api_guard/router/index.d.ts

@@ -264,7 +264,7 @@ export declare class RouterLinkActive implements OnChanges, OnDestroy, AfterCont
     };
     constructor(router: Router, element: ElementRef, renderer: Renderer, cdr: ChangeDetectorRef);
     ngAfterContentInit(): void;
-    ngOnChanges(changes: {}): void;
+    ngOnChanges(changes: SimpleChanges): void;
     ngOnDestroy(): void;
 }