Error during dev and warning at build in middleware.ts with --turbo flag

[sommeeeer]

Link to the code that reproduces this issue

https://github.com/sommeeeer/next-middleware-edge-turbo-node

To Reproduce

1. start the dev server with pnpm dev
2. open up http://localhost:3000 and look for the request header: hello-from-function.
3. close the dev server and now run it with --turbo flag: pnpm devturbo

Current vs. Expected behavior

So the src/lib/node-native.ts exports two functions. One is for the middleware.ts and the other one is a random async hi() function that dynamically imports a native Node.js API from fs/promises.

Since we are not using this function in the middleware it should not be flagged. I think it should work the same way as normal next dev without the --turbo flag.

Can note that next build works but with warnings.

Provide environment information

Operating System:
  Platform: linux
  Arch: x64
  Version: #47~22.04.1-Ubuntu SMP PREEMPT_DYNAMIC Wed Oct  2 16:16:55 UTC 2
  Available memory (MB): 14800
  Available CPU cores: 16
Binaries:
  Node: 20.18.0
  npm: 10.9.1
  Yarn: 1.22.19
  pnpm: 9.15.4
Relevant Packages:
  next: 15.1.6 // Latest available version is detected (15.1.6).
  eslint-config-next: 15.1.6
  react: 19.0.0
  react-dom: 19.0.0
  typescript: 5.7.3
Next.js Config:
  output: N/A

Which area(s) are affected? (Select all that apply)

Turbopack, Middleware

Which stage(s) are affected? (Select all that apply)

next dev (local), next build (local)

Additional context

No response

[samcx]

@sommeeeer Thank you for submitting an issue!

Taking a look 👁