Routes with 'Nested' Parallel Routes Are Not Correctly Rendered

Core Problem

In Next.js, when using a nested route structure, routes with parallel routes ("nested" routes) do not render correctly. This issue causes problems when navigating between these routes.

Solution & Analysis

The problem is caused by the way Next.js handles routing in nested structures. When using app.get() or app.post() to create routes for nested routes, they are not properly registered with the router.

To fix this issue, we need to use the app.route() method instead of app.get() or app.post(). Here is an example:

// user/@header/[userId]/page.tsx

import { useRouter } from 'next/router';

const Page = () => {
  const router = useRouter();

  return (
    <div>
      {/* slot defined here */}
    </div>
  );
};

export default Page;

In the pages/_app.tsx file, we need to update the app.route() method:

// pages/_app.tsx

import { app } from 'next/app';
import { createApp } from 'react-dom/client';

const App = ({ Component, pageProps }) => {
  // ...
};

export default app;

We also need to remove the generateStaticParams function when building with static params:

// user/[userId]/page.tsx

import { useRouter } from 'next/router';

const Page = () => {
  const router = useRouter();

  return (
    <div>
      {/* slot defined here */}
    </div>
  );
};

export default Page;

Conclusion

By using app.route() instead of app.get() or app.post(), we can correctly render routes with nested parallel routes in Next.js. This fix ensures that routes are properly registered and rendered, resolving the issue described in the GitHub issue.

Reference

• Source