fix(@angular/ssr): handle platform destruction during rendering

Fixes crash when platform/app destroys itself during the bootstrapping and
stabilization phase. Previously, the code would call `applicationRef.injector`
without checking if the platform was destroyed, resulting in:
"Error: Injector has already been destroyed"

This can occur when:
- Component constructor calls `inject(PlatformRef).destroy()`
- AbortSignal triggers during request handling
- APP_INITIALIZER rejects and causes cleanup
- Custom guard/resolver logic destroys the platform

Solution: Check `applicationRef.destroyed` after `whenStable()` and return error
state instead of accessing destroyed injector.

Test: Added test case that destroys app in component constructor to
verify graceful handling of this edge case.

Author: arturovt

packages/angular/ssr/src/utils/ng.ts

@@ -100,6 +100,19 @@ export async function renderAngular(
     // Block until application is stable.
     await applicationRef.whenStable();
 
+    // This code protect againsts app destruction during bootstrapping which is a
+    // valid case. We should not assume the `applicationRef` is not in destroyed state.
+    // Calling `envInjector.get` would throw `NG0205: Injector has already been destroyed`.
+    if (applicationRef.destroyed) {
+      return {
+        hasNavigationError,
+        redirectTo: undefined,
+        // TODO(alanagius): let's think on the content?
+        // or should we use `Promise.resolve('...')`?
+        content: () => Promise.reject(new Error('Application was destroyed during bootstrapping')),
+      };
+    }
+
     // TODO(alanagius): Find a way to avoid rendering here especially for redirects as any output will be discarded.
     const envInjector = applicationRef.injector;
     const routerIsProvided = !!envInjector.get(ActivatedRoute, null);

packages/angular/ssr/test/app_spec.ts

@@ -12,8 +12,8 @@ import '@angular/compiler';
 /* eslint-enable import/no-unassigned-import */
 
 import { APP_BASE_HREF } from '@angular/common';
-import { Component, REQUEST, RESPONSE_INIT, inject } from '@angular/core';
-import { CanActivateFn, Router } from '@angular/router';
+import { Component, PlatformRef, REQUEST, RESPONSE_INIT, inject } from '@angular/core';
+import { ActivatedRoute, CanActivateFn, Router } from '@angular/router';
 import { AngularServerApp } from '../src/app';
 import { RenderMode } from '../src/routes/route-config';
 import { setAngularAppTestingManifest } from './testing-utils';
@@ -26,7 +26,13 @@ describe('AngularServerApp', () => {
       selector: 'app-home',
       template: `Home works`,
     })
-    class HomeComponent {}
+    class HomeComponent {
+      constructor() {
+        if (inject(ActivatedRoute).snapshot.data['destroyApp']) {
+          inject(PlatformRef).destroy();
+        }
+      }
+    }
 
     @Component({
       selector: 'app-redirect',
@@ -65,7 +71,7 @@ describe('AngularServerApp', () => {
         { path: 'home-ssg', component: HomeComponent },
         { path: 'page-with-headers', component: HomeComponent },
         { path: 'page-with-status', component: HomeComponent },
-
+        { path: 'page-destroy-app', component: HomeComponent, data: { destroyApp: true } },
         { path: 'redirect', redirectTo: 'home' },
         { path: 'redirect-via-navigate', component: RedirectComponent },
         {
@@ -227,6 +233,13 @@ describe('AngularServerApp', () => {
         expect(response?.status).toBe(201);
       });
 
+      it('should not throw an error when app destroys itself', async () => {
+        const response = await app.handle(new Request('http://localhost/page-destroy-app'));
+        // The test expects response to be null, which is reasonable - if the app destroys
+        // itself, there's nothing to render.
+        expect(response).toBeNull();
+      });
+
       it('should return static `index.csr.html` for routes with CSR rendering mode', async () => {
         const response = await app.handle(new Request('http://localhost/home-csr'));
         const content = await response?.text();