refactor(router): move internal router properties to transition handler where appropriate (#48475)

Working towards removing the backwards dependency on router from the
navigation transition handler, this change moves `rootComponentType` and
`afterPreactivation` to the transition handler since that is the only
location those properties are used.

PR Close #48475

packages/router/src/navigation_transition.ts

@@ -270,7 +270,6 @@ interface InternalRouterInterface {
   errorHandler: ErrorHandler;
   titleStrategy?: TitleStrategy;
   navigated: boolean;
-  afterPreactivation: () => Observable<void>;
   urlHandlingStrategy: UrlHandlingStrategy;
   routeReuseStrategy: RouteReuseStrategy;
   onSameUrlNavigation: 'reload'|'ignore';
@@ -278,7 +277,6 @@ interface InternalRouterInterface {
   urlUpdateStrategy: 'deferred'|'eager';
   serializeUrl(url: UrlTree): string;
   config: Routes;
-  rootComponentType: Type<any>|null;
   setBrowserUrl(url: UrlTree, t: NavigationTransition): void;
   restoreHistory(t: NavigationTransition, restoringFromCaughtError?: boolean): void;
   scheduleNavigation(
@@ -301,6 +299,15 @@ export class NavigationTransitions {
     return this.navigationId !== 0;
   }
   private transitions?: BehaviorSubject<NavigationTransition>;
+  /**
+   * Hook that enables you to pause navigation after the preactivation phase.
+   * Used by `RouterModule`.
+   *
+   * @internal
+   */
+  afterPreactivation: () => Observable<void> = () => of(void 0);
+  /** @internal */
+  rootComponentType: Type<any>|null = null;
 
   constructor() {
     const onLoadStart = (r: Route) => this.events.next(new RouteConfigLoadStart(r));
@@ -437,7 +444,7 @@ export class NavigationTransitions {
 
                                  // Recognize
                                  recognize(
-                                     this.environmentInjector, router.rootComponentType,
+                                     this.environmentInjector, this.rootComponentType,
                                      router.config, this.urlSerializer,
                                      router.paramsInheritanceStrategy),
 
@@ -472,7 +479,7 @@ export class NavigationTransitions {
                                  restoredState);
                              this.events.next(navStart);
                              const targetSnapshot =
-                                 createEmptyState(extractedUrl, router.rootComponentType).snapshot;
+                                 createEmptyState(extractedUrl, this.rootComponentType).snapshot;
 
                              overallTransitionState = {
                                ...t,
@@ -614,7 +621,7 @@ export class NavigationTransitions {
                                .pipe(defaultIfEmpty(), take(1));
                          }),
 
-                         switchTap(() => router.afterPreactivation()),
+                         switchTap(() => this.afterPreactivation()),
 
                          map((t: NavigationTransition) => {
                            const targetRouterState = createRouterState(

packages/router/src/provide_router.ts

@@ -358,7 +358,7 @@ export function withEnabledBlockingInitialNavigation(): EnabledBlockingInitialNa
                 resolve(true);
               });
 
-              router.afterPreactivation = () => {
+              injector.get(NavigationTransitions).afterPreactivation = () => {
                 // Unblock APP_INITIALIZER once we get to `afterPreactivation`. At this point, we
                 // assume activation will complete successfully (even though this is not
                 // guaranteed).

packages/router/src/router.ts

@@ -204,14 +204,6 @@ export class Router {
   navigated: boolean = false;
   private lastSuccessfulId: number = -1;
 
-  /**
-   * Hook that enables you to pause navigation after the preactivation phase.
-   * Used by `RouterModule`.
-   *
-   * @internal
-   */
-  afterPreactivation: () => Observable<void> = () => of(void 0);
-
   /**
    * A strategy for extracting and merging URLs.
    * Used for AngularJS to Angular migrations.
@@ -317,9 +309,6 @@ export class Router {
   private readonly urlSerializer = inject(UrlSerializer);
   private readonly location = inject(Location);
 
-  /** @internal */
-  rootComponentType: Type<any>|null = null;
-
   constructor() {
     this.isNgZoneEnabled = inject(NgZone) instanceof NgZone && NgZone.isInAngularZone();
 
@@ -328,7 +317,7 @@ export class Router {
     this.rawUrlTree = this.currentUrlTree;
     this.browserUrlTree = this.currentUrlTree;
 
-    this.routerState = createEmptyState(this.currentUrlTree, this.rootComponentType);
+    this.routerState = createEmptyState(this.currentUrlTree, null);
 
     this.navigationTransitions.setupNavigations(this).subscribe(
         t => {
@@ -342,10 +331,10 @@ export class Router {
 
   /** @internal */
   resetRootComponentType(rootComponentType: Type<any>): void {
-    this.rootComponentType = rootComponentType;
     // TODO: vsavkin router 4.0 should make the root component set to null
     // this will simplify the lifecycle of the router.
-    this.routerState.root.component = this.rootComponentType;
+    this.routerState.root.component = rootComponentType;
+    this.navigationTransitions.rootComponentType = rootComponentType;
   }
 
   /**