fix(turbopack): restrict default pattern to app directory to prevent middleware crashes

[lars-hagen]

Summary

This PR addresses the Turbopack middleware crash issue with code-inspector plugin.

• Changes default pattern from **/*.{jsx,tsx,js,ts,mjs,mts} to **/app/**/*.{jsx,tsx,js,ts,mjs,mts}
• Restricts code-inspector to only process files in app directories
• Naturally excludes middleware files (typically at root/src level), preventing Turbopack crashes

Related Issues

• Next.js/Turbopack issue: Turbopack loaders don't work with middleware vercel/next.js#79592
• Code Inspector issue: nextjs15.4 turbopack runtime error #357

Configuration Workaround

Users can also fix this issue immediately in their next.config.ts without waiting for this PR:

const nextConfig: NextConfig = {
  turbopack: {
    rules: {
      '**/app/**/*.{jsx,tsx,js,ts,mjs,mts}': Object.values(codeInspectorPlugin({ bundler: 'turbopack' }))[0]
    } as any
  },
};

Test Plan

• Tested with Next.js 15 demo app containing middleware
• No crashes with middleware present
• Code inspector works correctly for app directory files

This is a temporary workaround until Turbopack resolves the underlying issue.

[lars-hagen]

🎉 Configuration-Level Workaround Available!

While testing this PR, I discovered users can fix this issue immediately without any package changes!

Immediate fix

Add this to your next.config.ts:

import { codeInspectorPlugin } from 'code-inspector-plugin';
import type { NextConfig } from 'next';

const nextConfig: NextConfig = {
  turbopack: {
    rules: {
      '**/app/**/*.{jsx,tsx,js,ts,mjs,mts}': Object.values(codeInspectorPlugin({ bundler: 'turbopack' }))[0]
    } as any
  },
};

export default nextConfig;

You can customize the pattern to match your project structure (e.g., **/src/**/*.{jsx,tsx}, etc.).

About this PR

While the config workaround solves the immediate problem, this PR could still add value by providing a better out-of-the-box experience. However, I wanted to share this workaround for anyone who needs a fix right now!

Related issues:

• Next.js/Turbopack: Turbopack loaders don't work with middleware vercel/next.js#79592
• Code Inspector: nextjs15.4 turbopack runtime error #357

[zh-lx]

This is great! Thanks very much!

[lars-hagen]

Hi @zh-lx! Thanks for merging this PR. After testing with real Next.js 15 projects, I found the current pattern **/app/** misses common directories like components, lib, hooks, etc.

I'd like to propose a follow-up PR with this improved pattern:

'**/*.{jsx,tsx,js,mjs,mts}'

Why this is better:

• Covers the entire codebase (not just /app)
• Naturally excludes middleware.ts since .ts files don't contain JSX
• Aligns perfectly with code-inspector's purpose (JSX element inspection)
• Much simpler and more intuitive

Since code-inspector adds click-to-source functionality to JSX elements, excluding .ts files makes perfect sense - they're typically utility/config files without JSX.

What do you think? Happy to submit a follow-up PR!

[zh-lx]

@lars-hagen Thank you for your follow-up and supplementation.
Since maybe middleware is middleware.js, I think it is safer to only do it for . jsx and .tsx. But according to nextjs routing files, some jsx files may also be . js files, so I added a PR: #399

[lars-hagen]

@zh-lx Thanks for the quick reply!
I agree I think the best pattern for now is also **/*.{jsx,tsx}.