refactor(router): Simplify router defaults by making the defaults Injectable (#48022)

The router has several default strategy implementations that are either
assigned via `new XStrategy()` property assignements or via the factory
function for the `Router` itself. These can be simplified by providing
the default implementation in the strategy `Injectable`. Custom
implementations can still override the defaults by specifying them in
the `providers` list.

Notably, this change also makes the `UrlHandlingStrategy` and
`RouteReuseStrategy` defaults injectable via DI rather than having to
indirectly grab them by going through the `Router` instance and
accessing the properties.

PR Close #48022

goldens/public-api/router/index.md

@@ -690,6 +690,10 @@ export abstract class RouteReuseStrategy {
     abstract shouldDetach(route: ActivatedRouteSnapshot): boolean;
     abstract shouldReuseRoute(future: ActivatedRouteSnapshot, curr: ActivatedRouteSnapshot): boolean;
     abstract store(route: ActivatedRouteSnapshot, handle: DetachedRouteHandle | null): void;
+    // (undocumented)
+    static ɵfac: i0.ɵɵFactoryDeclaration<RouteReuseStrategy, never>;
+    // (undocumented)
+    static ɵprov: i0.ɵɵInjectableDeclaration<RouteReuseStrategy>;
 }
 
 // @public
@@ -941,6 +945,10 @@ export abstract class UrlHandlingStrategy {
     abstract extract(url: UrlTree): UrlTree;
     abstract merge(newUrlPart: UrlTree, rawUrl: UrlTree): UrlTree;
     abstract shouldProcessUrl(url: UrlTree): boolean;
+    // (undocumented)
+    static ɵfac: i0.ɵɵFactoryDeclaration<UrlHandlingStrategy, never>;
+    // (undocumented)
+    static ɵprov: i0.ɵɵInjectableDeclaration<UrlHandlingStrategy>;
 }
 
 // @public

goldens/size-tracking/integration-payloads.json

@@ -33,7 +33,7 @@
   "cli-hello-world-lazy": {
     "uncompressed": {
       "runtime": 2835,
-      "main": 225113,
+      "main": 225766,
       "polyfills": 33842,
       "src_app_lazy_lazy_routes_ts": 487
     }

packages/core/test/bundling/router/bundle.golden_symbols.json

@@ -125,9 +125,15 @@
   {
     "name": "DefaultIfEmptySubscriber"
   },
+  {
+    "name": "DefaultRouteReuseStrategy"
+  },
   {
     "name": "DefaultTitleStrategy"
   },
+  {
+    "name": "DefaultUrlHandlingStrategy"
+  },
   {
     "name": "DefaultUrlSerializer"
   },
@@ -464,6 +470,9 @@
   {
     "name": "RootViewRef"
   },
+  {
+    "name": "RouteReuseStrategy"
+  },
   {
     "name": "RouteTitleKey"
   },
@@ -617,6 +626,9 @@
   {
     "name": "UnsubscriptionError"
   },
+  {
+    "name": "UrlHandlingStrategy"
+  },
   {
     "name": "UrlParser"
   },
@@ -1088,6 +1100,9 @@
   {
     "name": "getFactoryDef"
   },
+  {
+    "name": "getFactoryOf"
+  },
   {
     "name": "getFirstLContainer"
   },
@@ -1346,6 +1361,9 @@
   {
     "name": "isEnvironmentProviders"
   },
+  {
+    "name": "isForwardRef"
+  },
   {
     "name": "isFunction"
   },
@@ -1526,6 +1544,9 @@
   {
     "name": "noMatch2"
   },
+  {
+    "name": "noSideEffects"
+  },
   {
     "name": "nodeChildrenAsMap"
   },

packages/router/src/route_reuse_strategy.ts

@@ -6,7 +6,7 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
-import {ComponentRef} from '@angular/core';
+import {ComponentRef, inject, Injectable} from '@angular/core';
 
 import {OutletContext} from './router_outlet_context';
 import {ActivatedRoute, ActivatedRouteSnapshot} from './router_state';
@@ -38,6 +38,7 @@ export type DetachedRouteHandleInternal = {
  *
  * @publicApi
  */
+@Injectable({providedIn: 'root', useFactory: () => inject(DefaultRouteReuseStrategy)})
 export abstract class RouteReuseStrategy {
   /** Determines if this route (and its subtree) should be detached to be reused later */
   abstract shouldDetach(route: ActivatedRouteSnapshot): boolean;
@@ -110,4 +111,6 @@ export abstract class BaseRouteReuseStrategy implements RouteReuseStrategy {
   }
 }
 
-export class DefaultRouteReuseStrategy extends BaseRouteReuseStrategy {}
+@Injectable({providedIn: 'root'})
+export class DefaultRouteReuseStrategy extends BaseRouteReuseStrategy {
+}

packages/router/src/router.ts

@@ -23,14 +23,14 @@ import {checkGuards} from './operators/check_guards';
 import {recognize} from './operators/recognize';
 import {resolveData} from './operators/resolve_data';
 import {switchTap} from './operators/switch_tap';
-import {DefaultTitleStrategy, TitleStrategy} from './page_title_strategy';
-import {DefaultRouteReuseStrategy, RouteReuseStrategy} from './route_reuse_strategy';
+import {TitleStrategy} from './page_title_strategy';
+import {RouteReuseStrategy} from './route_reuse_strategy';
 import {ErrorHandler, ExtraOptions, ROUTER_CONFIGURATION} from './router_config';
 import {RouterConfigLoader, ROUTES} from './router_config_loader';
 import {ChildrenOutletContexts} from './router_outlet_context';
 import {ActivatedRoute, ActivatedRouteSnapshot, createEmptyState, RouterState, RouterStateSnapshot} from './router_state';
 import {Params} from './shared';
-import {DefaultUrlHandlingStrategy, UrlHandlingStrategy} from './url_handling_strategy';
+import {UrlHandlingStrategy} from './url_handling_strategy';
 import {containsTree, IsActiveMatchOptions, isUrlTree, UrlSerializer, UrlTree} from './url_tree';
 import {flatten} from './utils/collection';
 import {standardizeConfig, validateConfig} from './utils/config';
@@ -325,23 +325,9 @@ export function setupRouter() {
   const compiler = inject(Compiler);
   const config = inject(ROUTES, {optional: true}) ?? [];
   const opts = inject(ROUTER_CONFIGURATION, {optional: true}) ?? {};
-  const defaultTitleStrategy = inject(DefaultTitleStrategy);
-  const titleStrategy = inject(TitleStrategy, {optional: true});
-  const urlHandlingStrategy = inject(UrlHandlingStrategy, {optional: true});
-  const routeReuseStrategy = inject(RouteReuseStrategy, {optional: true});
   const router =
       new Router(null, urlSerializer, contexts, location, injector, compiler, flatten(config));
 
-  if (urlHandlingStrategy) {
-    router.urlHandlingStrategy = urlHandlingStrategy;
-  }
-
-  if (routeReuseStrategy) {
-    router.routeReuseStrategy = routeReuseStrategy;
-  }
-
-  router.titleStrategy = titleStrategy ?? defaultTitleStrategy;
-
   assignExtraOptionsToRouter(opts, router);
 
   return router;
@@ -475,17 +461,17 @@ export class Router {
    * A strategy for extracting and merging URLs.
    * Used for AngularJS to Angular migrations.
    */
-  urlHandlingStrategy: UrlHandlingStrategy = new DefaultUrlHandlingStrategy();
+  urlHandlingStrategy = inject(UrlHandlingStrategy);
 
   /**
    * A strategy for re-using routes.
    */
-  routeReuseStrategy: RouteReuseStrategy = new DefaultRouteReuseStrategy();
+  routeReuseStrategy = inject(RouteReuseStrategy);
 
   /**
    * A strategy for setting the title based on the `routerState`.
    */
-  titleStrategy?: TitleStrategy;
+  titleStrategy?: TitleStrategy = inject(TitleStrategy);
 
   /**
    * How to handle a navigation request to the current URL. One of:

packages/router/src/url_handling_strategy.ts

@@ -6,6 +6,8 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {inject, Injectable} from '@angular/core';
+
 import {UrlTree} from './url_tree';
 
 /**
@@ -15,6 +17,7 @@ import {UrlTree} from './url_tree';
  *
  * @publicApi
  */
+@Injectable({providedIn: 'root', useFactory: () => inject(DefaultUrlHandlingStrategy)})
 export abstract class UrlHandlingStrategy {
   /**
    * Tells the router if this URL should be processed.
@@ -41,6 +44,7 @@ export abstract class UrlHandlingStrategy {
 /**
  * @publicApi
  */
+@Injectable({providedIn: 'root'})
 export class DefaultUrlHandlingStrategy implements UrlHandlingStrategy {
   shouldProcessUrl(url: UrlTree): boolean {
     return true;