fix(@schematics/angular): don't show server routing prompt when using browser builder

The new routing APIs don't support `browser` builder, but calling `ng add @angular/ssr` with a `browser` builder would still prompt the user to add them. If the user said "Yes", it would actually ignore that answer and not enable the new APIs.

With this change, `ng add @angular/ssr` when using `browser` builder does not show the prompt and assumes the answer is "No". It also throws an error if the user runs `ng add @angular/ssr --server-routing`.

I'm not aware of a built-in prompting mechanism in schematics beyond `x-prompt`, which can't be used here, so instead I just called Inquirer directly. Unfortunately testing the prompt is a little awkward, as Inquirier does not provide useful APIs in this space. I evaluated `@inquirer/testing`, but ultimately decided that was more intended for testing custom Inquirer prompts, not mocking usage of standard prompts. Schematics APIs do not provide a useful way to inject additional data like a mock, so instead I had to do this through a `setPrompterForTestOnly` function. I'm not a huge fan of it, but I don't see a more straightforward way of solving the problem.

Author: dgp1130

packages/schematics/angular/BUILD.bazel

@@ -84,6 +84,7 @@ ts_library(
         "//packages/angular_devkit/schematics",
         "//packages/angular_devkit/schematics/tasks",
         "//packages/schematics/angular/third_party/github.com/Microsoft/TypeScript",
+        "@npm//@inquirer/prompts",
         "@npm//@types/node",
         "@npm//browserslist",
         "@npm//jsonc-parser",

packages/schematics/angular/application/index_spec.ts

@@ -32,6 +32,7 @@ describe('Application Schematic', () => {
   const defaultOptions: ApplicationOptions = {
     name: 'foo',
     skipPackageJson: false,
+    serverRouting: false,
   };
 
   let workspaceTree: UnitTestTree;

packages/schematics/angular/ssr/index.ts

@@ -85,7 +85,7 @@ async function getApplicationBuilderOutputPaths(
   const { outputPath } = architectTarget.options;
   if (outputPath === null || outputPath === undefined) {
     throw new SchematicsException(
-      `outputPath for ${projectName} ${target} target is undeined or null.`,
+      `outputPath for ${projectName} ${target} target is undefined or null.`,
     );
   }
 
@@ -361,19 +361,20 @@ function addServerFile(
   };
 }
 
-export default function (options: SSROptions): Rule {
+export default function (inputOptions: SSROptions): Rule {
   return async (host, context) => {
-    const browserEntryPoint = await getMainFilePath(host, options.project);
+    const browserEntryPoint = await getMainFilePath(host, inputOptions.project);
     const isStandalone = isStandaloneApp(host, browserEntryPoint);
 
     const workspace = await getWorkspace(host);
-    const clientProject = workspace.projects.get(options.project);
+    const clientProject = workspace.projects.get(inputOptions.project);
     if (!clientProject) {
       throw targetBuildNotFoundError();
     }
 
     const isUsingApplicationBuilder = usingApplicationBuilder(clientProject);
-
+    const serverRouting = await isServerRoutingEnabled(isUsingApplicationBuilder, inputOptions);
+    const options = { ...inputOptions, serverRouting };
     const sourceRoot = clientProject.sourceRoot ?? posix.join(clientProject.root, 'src');
 
     return chain([
@@ -404,3 +405,44 @@ function usingApplicationBuilder(project: ProjectDefinition) {
 
   return isUsingApplicationBuilder;
 }
+
+// Wrap inquirer in a `prompt` function.
+export type Prompt = (message: string, defaultValue: boolean) => Promise<boolean>;
+const defaultPrompter: Prompt = async (message, defaultValue) => {
+  const { confirm } = await import('@inquirer/prompts');
+  return await confirm({
+    message,
+    default: defaultValue,
+  });
+};
+
+// Allow the prompt functionality to be overridden to facilitate testing.
+let prompt = defaultPrompter;
+export function setPrompterForTestOnly(prompter?: Prompt): void {
+  prompt = prompter ?? defaultPrompter;
+}
+
+/** Returns whether or not server routing is enabled, potentially prompting the user if necessary. */
+async function isServerRoutingEnabled(
+  isUsingApplicationBuilder: boolean,
+  options: SSROptions,
+): Promise<boolean> {
+  if (!isUsingApplicationBuilder) {
+    if (options.serverRouting) {
+      throw new SchematicsException(
+        'Server routing APIs can only be added to a project using `application` builder.',
+      );
+    } else {
+      return false;
+    }
+  }
+
+  // Use explicit option if provided.
+  if (options.serverRouting !== undefined) return options.serverRouting;
+
+  // Prompt the user if no option was provided.
+  return await prompt(
+    'Would you like to use the Server Routing and App Engine APIs (Developer Preview) for this server application?',
+    /* defaultValue */ false,
+  );
+}

packages/schematics/angular/ssr/index_spec.ts

@@ -10,10 +10,12 @@ import { SchematicTestRunner, UnitTestTree } from '@angular-devkit/schematics/te
 
 import { join } from 'node:path';
 import { Schema as ServerOptions } from './schema';
+import { Prompt, setPrompterForTestOnly } from './index';
 
 describe('SSR Schematic', () => {
   const defaultOptions: ServerOptions = {
     project: 'test-app',
+    serverRouting: false,
   };
 
   const schematicRunner = new SchematicTestRunner(
@@ -30,6 +32,10 @@ describe('SSR Schematic', () => {
   };
 
   beforeEach(async () => {
+    setPrompterForTestOnly((message) => {
+      return fail(`Unmocked prompt: ${message}`) as never;
+    });
+
     appTree = await schematicRunner.runExternalSchematic(
       '@schematics/angular',
       'workspace',
@@ -150,6 +156,56 @@ describe('SSR Schematic', () => {
         server: 'node-server',
       });
     });
+
+    it('generates server routing configuration when enabled', async () => {
+      const tree = await schematicRunner.runSchematic(
+        'ssr',
+        { ...defaultOptions, serverRouting: true },
+        appTree,
+      );
+
+      expect(tree.exists('/projects/test-app/src/app/app.routes.server.ts')).toBeTrue();
+    });
+
+    it('does not generate server routing configuration when disabled', async () => {
+      const tree = await schematicRunner.runSchematic(
+        'ssr',
+        { ...defaultOptions, serverRouting: false },
+        appTree,
+      );
+
+      expect(tree.exists('/projects/test-app/src/app/app.routes.server.ts')).toBeFalse();
+    });
+
+    it('generates server routing configuration when prompt is accepted by the user', async () => {
+      const prompter = jasmine.createSpy<Prompt>('prompt').and.callFake(async () => true);
+      setPrompterForTestOnly(prompter);
+
+      const tree = await schematicRunner.runSchematic(
+        'ssr',
+        { ...defaultOptions, serverRouting: undefined },
+        appTree,
+      );
+
+      expect(prompter).toHaveBeenCalledTimes(1);
+
+      expect(tree.exists('/projects/test-app/src/app/app.routes.server.ts')).toBeTrue();
+    });
+
+    it('does not generate server routing configuration when prompt is rejected by the user', async () => {
+      const prompter = jasmine.createSpy<Prompt>('prompt').and.callFake(async () => false);
+      setPrompterForTestOnly(prompter);
+
+      const tree = await schematicRunner.runSchematic(
+        'ssr',
+        { ...defaultOptions, serverRouting: undefined },
+        appTree,
+      );
+
+      expect(prompter).toHaveBeenCalledTimes(1);
+
+      expect(tree.exists('/projects/test-app/src/app/app.routes.server.ts')).toBeFalse();
+    });
   });
 
   describe('Legacy browser builder', () => {
@@ -216,5 +272,26 @@ describe('SSR Schematic', () => {
       const content = tree.readContent('/projects/test-app/src/server.ts');
       expect(content).toContain(`const distFolder = join(process.cwd(), 'dist/test-app/browser');`);
     });
+
+    it('throws an exception when used with `serverRouting`', async () => {
+      await expectAsync(
+        schematicRunner.runSchematic('ssr', { ...defaultOptions, serverRouting: true }, appTree),
+      ).toBeRejectedWithError(/Server routing APIs.*`application` builder/);
+    });
+
+    it('automatically disables `serverRouting` and does not prompt for it', async () => {
+      const prompter = jasmine.createSpy<Prompt>('prompt').and.resolveTo(false);
+      setPrompterForTestOnly(prompter);
+
+      const tree = await schematicRunner.runSchematic(
+        'ssr',
+        { ...defaultOptions, serverRouting: undefined },
+        appTree,
+      );
+
+      expect(prompter).not.toHaveBeenCalled();
+
+      expect(tree.exists('/projects/test-app/src/app/app.routes.server.ts')).toBeFalse();
+    });
   });
 });

packages/schematics/angular/ssr/schema.json

@@ -18,9 +18,7 @@
     },
     "serverRouting": {
       "description": "Creates a server application using the Server Routing and App Engine APIs (Developer Preview).",
-      "x-prompt": "Would you like to use the Server Routing and App Engine APIs (Developer Preview) for this server application?",
-      "type": "boolean",
-      "default": false
+      "type": "boolean"
     }
   },
   "required": ["project"],