refactor(router): Update TitleStrategy to useFactory (#46876)

The implementation of the `DefaultTitleStrategy` was modeled after the
existing strategy patterns in the Router. These patterns were developed
before the `providedIn` syntax for injectables. We can simplify the
model a lot by providing the default in the factory of the abstract
class.

Note that the other strategy patterns aren't touched in this PR due to
how long they've existed. Because they have been there for such a long
time, it's possible there will need to be some adjustments to code
if/when they are refactored to do the same.

PR Close #46876

goldens/public-api/router/index.md

@@ -874,6 +874,10 @@ export abstract class TitleStrategy {
     buildTitle(snapshot: RouterStateSnapshot): string | undefined;
     getResolvedTitleForRoute(snapshot: ActivatedRouteSnapshot): any;
     abstract updateTitle(snapshot: RouterStateSnapshot): void;
+    // (undocumented)
+    static ɵfac: i0.ɵɵFactoryDeclaration<TitleStrategy, never>;
+    // (undocumented)
+    static ɵprov: i0.ɵɵInjectableDeclaration<TitleStrategy>;
 }
 
 // @public

goldens/public-api/router/testing/index.md

@@ -6,7 +6,6 @@
 
 import { ChildrenOutletContexts } from '@angular/router';
 import { Compiler } from '@angular/core';
-import { DefaultTitleStrategy } from '@angular/router';
 import { ExtraOptions } from '@angular/router';
 import * as i0 from '@angular/core';
 import * as i1 from '@angular/router';
@@ -37,7 +36,7 @@ export class RouterTestingModule {
 export function setupTestingRouter(urlSerializer: UrlSerializer, contexts: ChildrenOutletContexts, location: Location_2, compiler: Compiler, injector: Injector, routes: Route[][], opts?: ExtraOptions | UrlHandlingStrategy | null, urlHandlingStrategy?: UrlHandlingStrategy, routeReuseStrategy?: RouteReuseStrategy, titleStrategy?: TitleStrategy): Router;
 
 // @public
-export function setupTestingRouterInternal(urlSerializer: UrlSerializer, contexts: ChildrenOutletContexts, location: Location_2, compiler: Compiler, injector: Injector, routes: Route[][], opts?: ExtraOptions | UrlHandlingStrategy, urlHandlingStrategy?: UrlHandlingStrategy, routeReuseStrategy?: RouteReuseStrategy, defaultTitleStrategy?: DefaultTitleStrategy, titleStrategy?: TitleStrategy): Router;
+export function setupTestingRouterInternal(urlSerializer: UrlSerializer, contexts: ChildrenOutletContexts, location: Location_2, compiler: Compiler, injector: Injector, routes: Route[][], titleStrategy: TitleStrategy, opts?: ExtraOptions | UrlHandlingStrategy, urlHandlingStrategy?: UrlHandlingStrategy, routeReuseStrategy?: RouteReuseStrategy): Router;
 
 // (No @packageDocumentation comment for this package)
 

packages/router/src/page_title_strategy.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {Injectable} from '@angular/core';
+import {inject, Injectable} from '@angular/core';
 import {Title} from '@angular/platform-browser';
 
 import {RouteTitle as TitleKey} from './operators/resolve_data';
@@ -36,6 +36,7 @@ import {PRIMARY_OUTLET} from './shared';
  * @publicApi
  * @see [Page title guide](guide/router#setting-the-page-title)
  */
+@Injectable({providedIn: 'root', useFactory: () => inject(DefaultTitleStrategy)})
 export abstract class TitleStrategy {
   /** Performs the application title update. */
   abstract updateTitle(snapshot: RouterStateSnapshot): void;

packages/router/src/router_module.ts

@@ -18,7 +18,7 @@ import {RouterOutlet} from './directives/router_outlet';
 import {RuntimeErrorCode} from './errors';
 import {Event, NavigationCancel, NavigationCancellationCode, NavigationEnd, NavigationError, stringifyEvent} from './events';
 import {Route, Routes} from './models';
-import {DefaultTitleStrategy, TitleStrategy} from './page_title_strategy';
+import {TitleStrategy} from './page_title_strategy';
 import {RouteReuseStrategy} from './route_reuse_strategy';
 import {ErrorHandler, Router} from './router';
 import {RouterConfigLoader, ROUTES} from './router_config_loader';
@@ -64,9 +64,9 @@ export const ROUTER_PROVIDERS: Provider[] = [
     provide: Router,
     useFactory: setupRouter,
     deps: [
-      UrlSerializer, ChildrenOutletContexts, Location, Injector, Compiler, ROUTES,
-      ROUTER_CONFIGURATION, DefaultTitleStrategy, [TitleStrategy, new Optional()],
-      [UrlHandlingStrategy, new Optional()], [RouteReuseStrategy, new Optional()]
+      UrlSerializer, ChildrenOutletContexts, Location, Injector, Compiler, ROUTES, TitleStrategy,
+      ROUTER_CONFIGURATION, [UrlHandlingStrategy, new Optional()],
+      [RouteReuseStrategy, new Optional()]
     ]
   },
   ChildrenOutletContexts,
@@ -461,9 +461,9 @@ export interface ExtraOptions {
 
 export function setupRouter(
     urlSerializer: UrlSerializer, contexts: ChildrenOutletContexts, location: Location,
-    injector: Injector, compiler: Compiler, config: Route[][], opts: ExtraOptions = {},
-    defaultTitleStrategy: DefaultTitleStrategy, titleStrategy?: TitleStrategy,
-    urlHandlingStrategy?: UrlHandlingStrategy, routeReuseStrategy?: RouteReuseStrategy) {
+    injector: Injector, compiler: Compiler, config: Route[][], titleStrategy: TitleStrategy,
+    opts: ExtraOptions = {}, urlHandlingStrategy?: UrlHandlingStrategy,
+    routeReuseStrategy?: RouteReuseStrategy) {
   const router =
       new Router(null, urlSerializer, contexts, location, injector, compiler, flatten(config));
 
@@ -475,7 +475,7 @@ export function setupRouter(
     router.routeReuseStrategy = routeReuseStrategy;
   }
 
-  router.titleStrategy = titleStrategy ?? defaultTitleStrategy;
+  router.titleStrategy = titleStrategy;
 
   assignExtraOptionsToRouter(opts, router);
 

packages/router/testing/src/router_testing_module.ts

@@ -9,7 +9,7 @@
 import {Location, LocationStrategy} from '@angular/common';
 import {MockLocationStrategy, SpyLocation} from '@angular/common/testing';
 import {Compiler, Injector, ModuleWithProviders, NgModule, Optional} from '@angular/core';
-import {ChildrenOutletContexts, DefaultTitleStrategy, ExtraOptions, NoPreloading, PreloadingStrategy, provideRoutes, Route, Router, ROUTER_CONFIGURATION, RouteReuseStrategy, RouterModule, ROUTES, Routes, TitleStrategy, UrlHandlingStrategy, UrlSerializer, ɵassignExtraOptionsToRouter as assignExtraOptionsToRouter, ɵflatten as flatten, ɵprovidePreloading as providePreloading, ɵROUTER_PROVIDERS as ROUTER_PROVIDERS} from '@angular/router';
+import {ChildrenOutletContexts, ExtraOptions, NoPreloading, provideRoutes, Route, Router, ROUTER_CONFIGURATION, RouteReuseStrategy, RouterModule, ROUTES, Routes, TitleStrategy, UrlHandlingStrategy, UrlSerializer, ɵassignExtraOptionsToRouter as assignExtraOptionsToRouter, ɵflatten as flatten, ɵprovidePreloading as providePreloading, ɵROUTER_PROVIDERS as ROUTER_PROVIDERS} from '@angular/router';
 
 import {EXTRA_ROUTER_TESTING_PROVIDERS} from './extra_router_testing_providers';
 
@@ -25,14 +25,20 @@ function isUrlHandlingStrategy(opts: ExtraOptions|
  * marked as publicApi cleaner (i.e. not having _both_ `TitleStrategy` and `DefaultTitleStrategy`).
  */
 export function setupTestingRouterInternal(
-    urlSerializer: UrlSerializer, contexts: ChildrenOutletContexts, location: Location,
-    compiler: Compiler, injector: Injector, routes: Route[][],
-    opts?: ExtraOptions|UrlHandlingStrategy, urlHandlingStrategy?: UrlHandlingStrategy,
-    routeReuseStrategy?: RouteReuseStrategy, defaultTitleStrategy?: DefaultTitleStrategy,
-    titleStrategy?: TitleStrategy) {
+    urlSerializer: UrlSerializer,
+    contexts: ChildrenOutletContexts,
+    location: Location,
+    compiler: Compiler,
+    injector: Injector,
+    routes: Route[][],
+    titleStrategy: TitleStrategy,
+    opts?: ExtraOptions|UrlHandlingStrategy,
+    urlHandlingStrategy?: UrlHandlingStrategy,
+    routeReuseStrategy?: RouteReuseStrategy,
+) {
   return setupTestingRouter(
       urlSerializer, contexts, location, compiler, injector, routes, opts, urlHandlingStrategy,
-      routeReuseStrategy, titleStrategy ?? defaultTitleStrategy);
+      routeReuseStrategy, titleStrategy);
 }
 
 /**
@@ -112,11 +118,10 @@ export function setupTestingRouter(
         Compiler,
         Injector,
         ROUTES,
+        TitleStrategy,
         ROUTER_CONFIGURATION,
         [UrlHandlingStrategy, new Optional()],
         [RouteReuseStrategy, new Optional()],
-        [DefaultTitleStrategy, new Optional()],
-        [TitleStrategy, new Optional()],
       ]
     },
     providePreloading(NoPreloading),