fix(router-outlet): attach entering view before first change detection (#18821)

angular/test/test-app/src/app/alert/alert.component.html

@@ -1,10 +1,10 @@
 <ion-header>
   <ion-toolbar>
     <ion-title>
-      Modal test
+      Alert test
     </ion-title>
   </ion-toolbar>
 </ion-header>
 <ion-content padding>
-  <ion-button (click)="openAlert()" id="action-button">Open Alert</ion-button>
+  <p>Change Detections: <span id="counter">{{counter()}}</span></p>
 </ion-content>

angular/test/test-app/src/app/alert/alert.component.ts

@@ -8,10 +8,17 @@ import { NavComponent } from '../nav/nav.component';
 })
 export class AlertComponent {
 
+  changes = 0;
+
   constructor(
     private alertCtrl: AlertController
   ) { }
 
+  counter() {
+    this.changes++;
+    return Math.floor(this.changes / 2);
+  }
+
   async openAlert() {
     const alert = await this.alertCtrl.create({
       header: 'Hello',

angular/test/test-app/src/app/router-link-page/router-link-page.component.html

@@ -9,6 +9,7 @@
 
 <ion-content padding>
   <p>ngOnInit: <span id="ngOnInit">{{onInit}}</span></p>
+  <p>canGoBack: <span id="canGoBack">{{canGoBack}}</span></p>
   <p>ionViewWillEnter: <span id="ionViewWillEnter">{{willEnter}}</span></p>
   <p>ionViewDidEnter: <span id="ionViewDidEnter">{{didEnter}}</span></p>
   <p>ionViewWillLeave: <span id="ionViewWillLeave">{{willLeave}}</span></p>

angular/test/test-app/src/app/router-link-page/router-link-page.component.ts

@@ -1,4 +1,5 @@
 import { Component, OnInit, NgZone } from '@angular/core';
+import { IonRouterOutlet } from '@ionic/angular';
 
 @Component({
   selector: 'app-router-link-page',
@@ -11,9 +12,15 @@ export class RouterLinkPageComponent implements OnInit {
   didEnter = 0;
   willLeave = 0;
   didLeave = 0;
+  canGoBack: boolean = null;
+
+  constructor(
+    private ionRouterOutlet: IonRouterOutlet
+  ) {}
 
   ngOnInit() {
     NgZone.assertInAngularZone();
+    this.canGoBack = this.ionRouterOutlet.canGoBack();
     this.onInit++;
   }
 
@@ -21,10 +28,16 @@ export class RouterLinkPageComponent implements OnInit {
     if (this.onInit !== 1) {
       throw new Error('ngOnInit was not called');
     }
+    if (this.canGoBack !== this.ionRouterOutlet.canGoBack()) {
+      throw new Error('canGoBack() changed');
+    }
     NgZone.assertInAngularZone();
     this.willEnter++;
   }
   ionViewDidEnter() {
+    if (this.canGoBack !== this.ionRouterOutlet.canGoBack()) {
+      throw new Error('canGoBack() changed');
+    }
     NgZone.assertInAngularZone();
     this.didEnter++;
   }