fix(extraction): a file-based router reads only its own app in a monorepo (#2129)

create-t3-turbo, tamagui's starter and react-native-reusables keep an Expo
app beside a Next.js app. Expo Router read the Next app's `app/` folder as
its own, so `layout.tsx` became a `/layout` screen, `page.tsx` a `/page`
one, `_components/posts.tsx` and `api/auth/[...all]/route.ts` screens too,
and a shared `packages/app/` library's files became screens as well.

A resolver can now name `appDependencies`; its extractor runs on a file
only when that file's package.json or an enclosing one declares one of
them. When no manifest in the project declares any, detection found the
framework by other evidence and it runs everywhere, as before. Expo Router
names `expo-router`, Next.js `next`.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

__tests__/monorepo-app-frameworks.test.ts

@@ -0,0 +1,88 @@
+/**
+ * In a monorepo, a file-based router reads only its own app's files.
+ *
+ * create-t3-turbo, tamagui's starter and react-native-reusables keep an Expo
+ * app beside a Next.js app. Expo Router read the Next app's `app/` folder as
+ * its own: `app/layout.tsx` became a `/layout` screen, `app/page.tsx` a
+ * `/page` one, a `_components/posts.tsx` a `/_components/posts` screen, and
+ * `app/api/auth/[...all]/route.ts` a screen named after the file.
+ */
+import { describe, it, expect, afterAll } from 'vitest';
+import * as fs from 'fs';
+import * as os from 'os';
+import * as path from 'path';
+import { CodeGraph } from '../src';
+
+const roots: string[] = [];
+afterAll(() => {
+  for (const r of roots.splice(0)) fs.rmSync(r, { recursive: true, force: true });
+});
+
+async function project(files: Record<string, string>): Promise<CodeGraph> {
+  const root = fs.mkdtempSync(path.join(os.tmpdir(), 'cg-app-frameworks-'));
+  roots.push(root);
+  for (const [rel, content] of Object.entries(files)) {
+    fs.mkdirSync(path.dirname(path.join(root, rel)), { recursive: true });
+    fs.writeFileSync(path.join(root, rel), content);
+  }
+  return CodeGraph.init(root, { index: true });
+}
+
+const routesIn = (cg: CodeGraph, dir: string): string[] =>
+  cg
+    .getNodesByKind('route')
+    .filter((n) => n.filePath.startsWith(dir))
+    .map((n) => n.name)
+    .sort();
+
+describe('file-based routers in a monorepo', () => {
+  it('Expo Router reads the Expo app, Next.js the Next app', async () => {
+    const cg = await project({
+      'package.json': JSON.stringify({ name: 'mono', private: true, workspaces: ['apps/*'] }),
+      'apps/mobile/package.json': JSON.stringify({ name: 'mobile', dependencies: { expo: '*', 'expo-router': '*', react: '*' } }),
+      'apps/mobile/app/_layout.tsx': `export default function Layout() { return null; }
+`,
+      'apps/mobile/app/index.tsx': `export default function Home() { return null; }
+`,
+      'apps/mobile/app/user/[id].tsx': `export default function User() { return null; }
+`,
+      'apps/web/package.json': JSON.stringify({ name: 'web', dependencies: { next: '*', react: '*' } }),
+      'apps/web/app/layout.tsx': `export default function RootLayout({ children }: { children: unknown }) { return children; }
+`,
+      'apps/web/app/page.tsx': `export default function Page() { return null; }
+`,
+      'apps/web/app/user/[id]/page.tsx': `export default function UserPage() { return null; }
+`,
+      'apps/web/app/_components/posts.tsx': `export default function Posts() { return null; }
+`,
+      'apps/web/app/api/auth/[...all]/route.ts': `export async function GET() { return new Response('ok'); }
+`,
+    });
+    try {
+      expect(routesIn(cg, 'apps/mobile/')).toEqual(['/', '/user/[id]']);
+      const web = routesIn(cg, 'apps/web/');
+      expect(web).toContain('/');
+      expect(web).toContain('/user/:id');
+      for (const bogus of ['/layout', '/page', '/_components/posts', '/api/auth/[...all]/route', '/user/[id]/page']) {
+        expect(web).not.toContain(bogus);
+      }
+    } finally {
+      cg.close();
+    }
+  });
+
+  it('a single Expo app at the repository root keeps its routes', async () => {
+    const cg = await project({
+      'package.json': JSON.stringify({ name: 'demo', dependencies: { expo: '*', 'expo-router': '*' } }),
+      'app/_layout.tsx': `export default function Layout() { return null; }
+`,
+      'app/settings.tsx': `export default function Settings() { return null; }
+`,
+    });
+    try {
+      expect(routesIn(cg, 'app/')).toEqual(['/settings']);
+    } finally {
+      cg.close();
+    }
+  });
+});