fix: enable strict mode, honest HTTP boundary, and add routing

Three fixes to the parts of the template that contradicted its own
"illegal states unrepresentable" claim:

- tsconfig: turn on strict + strictTemplates (measured zero fallout —
  the codebase already typechecked cleanly, it just wasn't enforced).
- RemoteData<T> drops its unused error type parameter (Resource.error
  is always Error) and Failure now carries a real Error. Pages read the
  union with @let instead of re-deriving from the resource, which
  deletes the non-null assertion strictNullChecks would otherwise flag.
- users.adapter.ts never checked response.ok, so an HTTP error resolved
  as a garbage Success and crashed instead of reaching RemoteData's
  Failure branch. New shared/infrastructure/http.ts adds the status
  check plus hand-written parse guards and abortSignal forwarding; the
  six fetch stubs across the test suite (which encoded the missing
  check) and adapter spec now cover the Failure and Empty paths.

Also adds real routing (@angular/router was a dependency with zero
imports and a fake "Back" button): /users and /users/:id are now
deep-linkable via withComponentInputBinding(), tested with
RouterTestingHarness driving real navigation.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/app.config.ts

@@ -1,5 +1,10 @@
 import { ApplicationConfig, provideBrowserGlobalErrorListeners } from '@angular/core';
+import { provideRouter, withComponentInputBinding } from '@angular/router';
+import { routes } from './app.routes';
 
 export const appConfig: ApplicationConfig = {
-  providers: [provideBrowserGlobalErrorListeners()],
+  providers: [
+    provideBrowserGlobalErrorListeners(),
+    provideRouter(routes, withComponentInputBinding()),
+  ],
 };

src/app/app.html

@@ -1 +1 @@
-<app-users-page />
+<router-outlet />

src/app/app.routes.ts

@@ -0,0 +1,9 @@
+import { Routes } from '@angular/router';
+
+export const routes: Routes = [
+  {
+    path: 'users',
+    loadChildren: () => import('@users/ui/users.routes').then((m) => m.usersRoutes),
+  },
+  { path: '', redirectTo: 'users', pathMatch: 'full' },
+];

src/app/app.spec.ts

@@ -1,14 +1,25 @@
-import { describe, expect, it, vi } from 'vitest';
+import { afterEach, describe, expect, it, vi } from 'vitest';
 import { TestBed } from '@angular/core/testing';
-import { App } from './app';
+import { provideRouter, withComponentInputBinding } from '@angular/router';
+import { RouterTestingHarness } from '@angular/router/testing';
+import { routes } from './app.routes';
 
-describe('App', () => {
-  it('renders the users page heading', async () => {
-    vi.stubGlobal('fetch', vi.fn().mockResolvedValue({ json: () => Promise.resolve([]) }));
-    await TestBed.configureTestingModule({ imports: [App] }).compileComponents();
-    const fixture = TestBed.createComponent(App);
-    fixture.detectChanges();
-    expect(fixture.nativeElement.querySelector('h1')?.textContent).toBe('Users');
-    vi.unstubAllGlobals();
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe('App routes', () => {
+  it('redirects to /users and renders the page heading', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn().mockResolvedValue({ ok: true, status: 200, json: () => Promise.resolve([]) }),
+    );
+    TestBed.configureTestingModule({
+      providers: [provideRouter(routes, withComponentInputBinding())],
+    });
+    const harness = await RouterTestingHarness.create('/');
+    await harness.fixture.whenStable();
+    harness.detectChanges();
+    expect(harness.routeNativeElement?.querySelector('h1')?.textContent).toBe('Users');
   });
 });

src/app/app.ts

@@ -1,10 +1,9 @@
 import { Component } from '@angular/core';
-import { UsersPage } from '@users/ui/users.page';
+import { RouterOutlet } from '@angular/router';
 
 @Component({
   selector: 'app-root',
-  imports: [UsersPage],
+  imports: [RouterOutlet],
   templateUrl: './app.html',
-  styleUrl: './app.css',
 })
 export class App {}

src/app/shared/application/remote-data.ts

@@ -4,18 +4,19 @@ import type { Resource } from '@angular/core';
  * Four mutually exclusive async states — the data lives ON the state, so e.g.
  * "success with no value" or "error with a stale value" is unrepresentable.
  */
-export type RemoteData<E, T> =
+export type RemoteData<T> =
   | { tag: 'Loading' }
   | { tag: 'Empty' }
-  | { tag: 'Failure'; error: E }
+  | { tag: 'Failure'; error: Error }
   | { tag: 'Success'; value: T };
 
 /** Project Angular's own resource() into a RemoteData value. */
 export function fromResource<T>(
   r: Resource<T>,
   isEmpty: (v: T) => boolean = () => false,
-): RemoteData<unknown, T> {
-  if (r.status() === 'error') return { tag: 'Failure', error: r.error() };
+): RemoteData<T> {
+  const error = r.error();
+  if (error) return { tag: 'Failure', error };
   if (r.hasValue()) {
     const v = r.value();
     return isEmpty(v) ? { tag: 'Empty' } : { tag: 'Success', value: v };

src/app/shared/infrastructure/http.ts

@@ -0,0 +1,34 @@
+export const API_BASE_URL = 'https://jsonplaceholder.typicode.com';
+
+/** Server answered, but not with a 2xx. */
+export class HttpError extends Error {
+  constructor(
+    readonly status: number,
+    path: string,
+  ) {
+    super(`HTTP ${status} for ${path}`);
+    this.name = 'HttpError';
+  }
+}
+
+/** Server answered 2xx, but the body isn't the shape we asked for. */
+export class ParseError extends Error {
+  constructor(what: string) {
+    super(`Malformed response: expected ${what}`);
+    this.name = 'ParseError';
+  }
+}
+
+/**
+ * GET + status check + parse, in that order. Throws HttpError or ParseError —
+ * resource() turns a thrown error into RemoteData's Failure branch.
+ */
+export async function getJson<T>(
+  path: string,
+  parse: (value: unknown) => T,
+  abortSignal?: AbortSignal,
+): Promise<T> {
+  const response = await fetch(`${API_BASE_URL}${path}`, { signal: abortSignal });
+  if (!response.ok) throw new HttpError(response.status, path);
+  return parse(await response.json());
+}

src/app/shared/ui/molecules/async.component.spec.ts

@@ -13,11 +13,11 @@ import type { RemoteData } from '@shared/application/remote-data';
   `,
 })
 class HostComponent {
-  data: RemoteData<unknown, string> = { tag: 'Loading' };
+  data: RemoteData<string> = { tag: 'Loading' };
   retried = false;
 }
 
-function render(data: RemoteData<unknown, string>) {
+function render(data: RemoteData<string>) {
   const fixture = TestBed.createComponent(HostComponent);
   fixture.componentInstance.data = data;
   fixture.detectChanges();

src/app/shared/ui/molecules/async.component.ts

@@ -24,7 +24,7 @@ import type { RemoteData } from '@shared/application/remote-data';
   `,
 })
 export class AsyncComponent<T> {
-  data = input.required<RemoteData<unknown, T>>();
+  data = input.required<RemoteData<T>>();
   emptyText = input('No data.');
   errorText = input('Something went wrong.');
   retryText = input('Retry');

src/app/users/application/user-detail.resource.ts

@@ -2,4 +2,7 @@ import { resource } from '@angular/core';
 import { fetchUserById } from '@users/infrastructure/users.adapter';
 
 export const userDetailResource = (userId: () => number) =>
-  resource({ params: userId, loader: ({ params }) => fetchUserById(params) });
+  resource({
+    params: userId,
+    loader: ({ params, abortSignal }) => fetchUserById(params, abortSignal),
+  });

src/app/users/application/users.resource.ts

@@ -1,4 +1,5 @@
 import { resource } from '@angular/core';
 import { fetchUsers } from '@users/infrastructure/users.adapter';
 
-export const usersResource = () => resource({ loader: fetchUsers });
+export const usersResource = () =>
+  resource({ loader: ({ abortSignal }) => fetchUsers(abortSignal) });

src/app/users/infrastructure/users.adapter.spec.ts

@@ -0,0 +1,71 @@
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { HttpError, ParseError } from '@shared/infrastructure/http';
+import { fetchUserById, fetchUsers, parseUser, parseUserDetail, parseUsers } from './users.adapter';
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+});
+
+describe('fetchUsers', () => {
+  it('resolves with the parsed list on a 200 response', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn().mockResolvedValue({
+        ok: true,
+        status: 200,
+        json: () => Promise.resolve([{ id: 1, name: 'Ada' }]),
+      }),
+    );
+    await expect(fetchUsers()).resolves.toEqual([{ id: 1, name: 'Ada' }]);
+  });
+
+  it('rejects with HttpError when the server answers with a non-2xx status', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockResolvedValue({ ok: false, status: 404 }));
+    await expect(fetchUsers()).rejects.toBeInstanceOf(HttpError);
+  });
+});
+
+describe('fetchUserById', () => {
+  it('resolves with the parsed user on a 200 response', async () => {
+    vi.stubGlobal(
+      'fetch',
+      vi.fn().mockResolvedValue({
+        ok: true,
+        status: 200,
+        json: () => Promise.resolve({ id: 1, name: 'Ada', email: 'ada@example.com' }),
+      }),
+    );
+    await expect(fetchUserById(1)).resolves.toEqual({
+      id: 1,
+      name: 'Ada',
+      email: 'ada@example.com',
+    });
+  });
+
+  it('rejects with HttpError when the server answers with a non-2xx status', async () => {
+    vi.stubGlobal('fetch', vi.fn().mockResolvedValue({ ok: false, status: 500 }));
+    await expect(fetchUserById(1)).rejects.toBeInstanceOf(HttpError);
+  });
+});
+
+describe('parseUsers', () => {
+  it('throws ParseError when the response is not an array', () => {
+    expect(() => parseUsers({})).toThrow(ParseError);
+  });
+
+  it('throws ParseError when a list item is missing a name', () => {
+    expect(() => parseUsers([{ id: 1 }])).toThrow(ParseError);
+  });
+});
+
+describe('parseUser', () => {
+  it('throws ParseError when id is not a number', () => {
+    expect(() => parseUser({ id: '1', name: 'Ada' })).toThrow(ParseError);
+  });
+});
+
+describe('parseUserDetail', () => {
+  it('throws ParseError when email is missing', () => {
+    expect(() => parseUserDetail({ id: 1, name: 'Ada' })).toThrow(ParseError);
+  });
+});

src/app/users/infrastructure/users.adapter.ts

@@ -1,7 +1,32 @@
+import { getJson, ParseError } from '@shared/infrastructure/http';
 import type { User, UserDetail } from '@users/domain/user';
 
-export const fetchUsers = (): Promise<User[]> =>
-  fetch('https://jsonplaceholder.typicode.com/users').then((r) => r.json());
+const isRecord = (value: unknown): value is Record<string, unknown> =>
+  typeof value === 'object' && value !== null;
 
-export const fetchUserById = (id: number): Promise<UserDetail> =>
-  fetch(`https://jsonplaceholder.typicode.com/users/${id}`).then((r) => r.json());
+export function parseUser(value: unknown): User {
+  if (!isRecord(value)) throw new ParseError('a user');
+  const { id, name } = value;
+  if (typeof id !== 'number' || typeof name !== 'string') throw new ParseError('a user');
+  return { id, name };
+}
+
+export function parseUserDetail(value: unknown): UserDetail {
+  if (!isRecord(value)) throw new ParseError('a user detail');
+  const { id, name, email } = value;
+  if (typeof id !== 'number' || typeof name !== 'string' || typeof email !== 'string') {
+    throw new ParseError('a user detail');
+  }
+  return { id, name, email };
+}
+
+export function parseUsers(value: unknown): User[] {
+  if (!Array.isArray(value)) throw new ParseError('a user list');
+  return value.map(parseUser);
+}
+
+export const fetchUsers = (abortSignal?: AbortSignal): Promise<User[]> =>
+  getJson('/users', parseUsers, abortSignal);
+
+export const fetchUserById = (id: number, abortSignal?: AbortSignal): Promise<UserDetail> =>
+  getJson(`/users/${id}`, parseUserDetail, abortSignal);

src/app/users/ui/organisms/user-detail.component.spec.ts

@@ -11,6 +11,8 @@ describe('UserDetailComponent', () => {
     vi.stubGlobal(
       'fetch',
       vi.fn().mockResolvedValue({
+        ok: true,
+        status: 200,
         json: () => Promise.resolve({ id: 1, name: 'Ada', email: 'ada@example.com' }),
       }),
     );
@@ -27,6 +29,8 @@ describe('UserDetailComponent', () => {
     vi.stubGlobal(
       'fetch',
       vi.fn().mockResolvedValue({
+        ok: true,
+        status: 200,
         json: () => Promise.resolve({ id: 1, name: 'Ada', email: 'a@x.com' }),
       }),
     );

src/app/users/ui/organisms/user-detail.component.ts

@@ -7,9 +7,10 @@ import { userDetailResource } from '@users/application/user-detail.resource';
   selector: 'app-user-detail',
   imports: [AsyncComponent],
   template: `
-    <app-async [data]="data()" (retry)="detailResource.reload()">
-      @if (detailResource.value(); as u) {
-        <p>{{ u.name }} — {{ u.email }}</p>
+    @let detail = data();
+    <app-async [data]="detail" (retry)="detailResource.reload()">
+      @if (detail.tag === 'Success' && detail.value) {
+        <p>{{ detail.value.name }} — {{ detail.value.email }}</p>
       }
     </app-async>
     <button type="button" (click)="close.emit()">Back</button>

src/app/users/ui/users.page.spec.ts

@@ -1,21 +1,55 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
 import { TestBed } from '@angular/core/testing';
-import { UsersPage } from './users.page';
+import { provideRouter, withComponentInputBinding } from '@angular/router';
+import { RouterTestingHarness } from '@angular/router/testing';
+import { usersRoutes } from './users.routes';
 
 function stubFetch() {
   vi.stubGlobal(
     'fetch',
     vi.fn((url: string) => {
       if (url.endsWith('/users')) {
-        return Promise.resolve({ json: () => Promise.resolve([{ id: 1, name: 'Ada' }]) });
+        return Promise.resolve({
+          ok: true,
+          status: 200,
+          json: () => Promise.resolve([{ id: 1, name: 'Ada' }]),
+        });
       }
       return Promise.resolve({
+        ok: true,
+        status: 200,
         json: () => Promise.resolve({ id: 1, name: 'Ada', email: 'ada@example.com' }),
       });
     }),
   );
 }
 
+function stubFetchFailure() {
+  vi.stubGlobal(
+    'fetch',
+    vi.fn().mockResolvedValue({ ok: false, status: 500, json: () => Promise.resolve({}) }),
+  );
+}
+
+function stubFetchEmpty() {
+  vi.stubGlobal(
+    'fetch',
+    vi.fn().mockResolvedValue({ ok: true, status: 200, json: () => Promise.resolve([]) }),
+  );
+}
+
+async function renderUsersAt(url: string) {
+  TestBed.configureTestingModule({
+    providers: [
+      provideRouter([{ path: 'users', children: usersRoutes }], withComponentInputBinding()),
+    ],
+  });
+  const harness = await RouterTestingHarness.create(url);
+  await harness.fixture.whenStable();
+  harness.detectChanges();
+  return harness;
+}
+
 afterEach(() => {
   vi.unstubAllGlobals();
 });
@@ -23,44 +57,50 @@ afterEach(() => {
 describe('UsersPage', () => {
   it('renders the fetched users as a list', async () => {
     stubFetch();
-    await TestBed.configureTestingModule({ imports: [UsersPage] }).compileComponents();
-    const fixture = TestBed.createComponent(UsersPage);
-    fixture.detectChanges();
-    await fixture.whenStable();
-    fixture.detectChanges();
-    expect(fixture.nativeElement.textContent).toContain('Ada');
+    const harness = await renderUsersAt('/users');
+    expect(harness.routeNativeElement?.textContent).toContain('Ada');
+  });
+
+  it('shows the failure state when the request fails', async () => {
+    stubFetchFailure();
+    const harness = await renderUsersAt('/users');
+    expect(harness.routeNativeElement?.querySelector('[role="alert"]')).toBeTruthy();
+  });
+
+  it('shows the empty state when there are no users', async () => {
+    stubFetchEmpty();
+    const harness = await renderUsersAt('/users');
+    expect(harness.routeNativeElement?.textContent).toContain('No data.');
   });
 
   it("shows a user's details after clicking their name", async () => {
     stubFetch();
-    await TestBed.configureTestingModule({ imports: [UsersPage] }).compileComponents();
-    const fixture = TestBed.createComponent(UsersPage);
-    fixture.detectChanges();
-    await fixture.whenStable();
-    fixture.detectChanges();
-    fixture.nativeElement.querySelector('button').click();
-    fixture.detectChanges();
-    await fixture.whenStable();
-    fixture.detectChanges();
-    expect(fixture.nativeElement.textContent).toContain('ada@example.com');
+    const harness = await renderUsersAt('/users');
+    harness.routeNativeElement!.querySelector('button')!.click();
+    await harness.fixture.whenStable();
+    harness.detectChanges();
+    expect(harness.routeNativeElement?.textContent).toContain('ada@example.com');
   });
 
   it('returns to the list when the detail view is closed', async () => {
     stubFetch();
-    await TestBed.configureTestingModule({ imports: [UsersPage] }).compileComponents();
-    const fixture = TestBed.createComponent(UsersPage);
-    fixture.detectChanges();
-    await fixture.whenStable();
-    fixture.detectChanges();
-    fixture.nativeElement.querySelector('button').click();
-    fixture.detectChanges();
-    await fixture.whenStable();
-    fixture.detectChanges();
-    const backButton = Array.from(fixture.nativeElement.querySelectorAll('button')).find(
+    const harness = await renderUsersAt('/users');
+    harness.routeNativeElement!.querySelector('button')!.click();
+    await harness.fixture.whenStable();
+    harness.detectChanges();
+    const backButton = Array.from(harness.routeNativeElement!.querySelectorAll('button')).find(
       (b) => (b as HTMLElement).textContent === 'Back',
     ) as HTMLElement;
     backButton.click();
-    fixture.detectChanges();
-    expect(fixture.nativeElement.querySelector('app-user-detail')).toBeFalsy();
+    await harness.fixture.whenStable();
+    harness.detectChanges();
+    expect(harness.routeNativeElement?.querySelector('app-user-detail')).toBeFalsy();
+    expect(harness.routeNativeElement?.textContent).toContain('Ada');
+  });
+
+  it('deep-links directly to a user detail view', async () => {
+    stubFetch();
+    const harness = await renderUsersAt('/users/1');
+    expect(harness.routeNativeElement?.textContent).toContain('ada@example.com');
   });
 });

src/app/users/ui/users.page.ts

@@ -1,4 +1,5 @@
-import { Component, computed, signal } from '@angular/core';
+import { Component, computed, inject, input } from '@angular/core';
+import { Router } from '@angular/router';
 import { PageShellComponent } from '@shared/ui/templates/page-shell.component';
 import { AsyncComponent } from '@shared/ui/molecules/async.component';
 import { fromResource } from '@shared/application/remote-data';
@@ -13,11 +14,12 @@ import { isEmptyUserList } from '@users/domain/user';
   template: `
     <app-page-shell heading="Users">
       @if (selectedUserId(); as id) {
-        <app-user-detail [userId]="id" (close)="selectedUserId.set(null)" />
+        <app-user-detail [userId]="id" (close)="router.navigate(['/users'])" />
       } @else {
-        <app-async [data]="listData()" (retry)="usersResource.reload()">
-          @if (usersResource.hasValue()) {
-            <app-user-list [users]="usersResource.value()!" (select)="selectedUserId.set($event)" />
+        @let list = listData();
+        <app-async [data]="list" (retry)="usersResource.reload()">
+          @if (list.tag === 'Success' && list.value) {
+            <app-user-list [users]="list.value" (select)="router.navigate(['/users', $event])" />
           }
         </app-async>
       }
@@ -25,7 +27,12 @@ import { isEmptyUserList } from '@users/domain/user';
   `,
 })
 export class UsersPage {
-  protected selectedUserId = signal<number | null>(null);
+  protected router = inject(Router);
+  userId = input<string>();
+  protected selectedUserId = computed(() => {
+    const id = this.userId();
+    return id ? Number(id) : null;
+  });
   protected usersResource = usersResource();
   protected listData = computed(() => fromResource(this.usersResource, isEmptyUserList));
 }

src/app/users/ui/users.routes.ts

@@ -0,0 +1,7 @@
+import { Routes } from '@angular/router';
+import { UsersPage } from './users.page';
+
+export const usersRoutes: Routes = [
+  { path: '', component: UsersPage },
+  { path: ':userId', component: UsersPage },
+];

src/index.html

@@ -1,13 +1,13 @@
 <!doctype html>
 <html lang="en">
-<head>
-  <meta charset="utf-8">
-  <title>NgSignalsTemplate</title>
-  <base href="/">
-  <meta name="viewport" content="width=device-width, initial-scale=1">
-  <link rel="icon" type="image/x-icon" href="favicon.ico">
-</head>
-<body>
-  <app-root></app-root>
-</body>
+  <head>
+    <meta charset="utf-8" />
+    <title>NgSignalsTemplate</title>
+    <base href="/" />
+    <meta name="viewport" content="width=device-width, initial-scale=1" />
+    <link rel="icon" type="image/x-icon" href="favicon.ico" />
+  </head>
+  <body>
+    <app-root></app-root>
+  </body>
 </html>

tsconfig.app.json

@@ -5,10 +5,6 @@
   "compilerOptions": {
     "types": []
   },
-  "include": [
-    "src/**/*.ts"
-  ],
-  "exclude": [
-    "src/**/*.spec.ts"
-  ]
+  "include": ["src/**/*.ts"],
+  "exclude": ["src/**/*.spec.ts"]
 }

tsconfig.json

@@ -3,6 +3,7 @@
 {
   "compileOnSave": false,
   "compilerOptions": {
+    "strict": true,
     "noImplicitOverride": true,
     "noPropertyAccessFromIndexSignature": true,
     "noImplicitReturns": true,
@@ -21,6 +22,7 @@
     }
   },
   "angularCompilerOptions": {
+    "strictTemplates": true,
     "enableI18nLegacyMessageIdFormat": false,
     "strictInjectionParameters": true,
     "strictInputAccessModifiers": true

tsconfig.spec.json

@@ -3,12 +3,7 @@
 {
   "extends": "./tsconfig.json",
   "compilerOptions": {
-    "types": [
-      "vitest/globals"
-    ]
+    "types": ["vitest/globals"]
   },
-  "include": [
-    "src/**/*.d.ts",
-    "src/**/*.spec.ts"
-  ]
+  "include": ["src/**/*.d.ts", "src/**/*.spec.ts"]
 }