Tree shaking in middleware doesn't work

[amannn]

Link to the code that reproduces this issue

amannn/nextjs-bug-repro-middleware@6c442b0

To Reproduce

1. Run pnpm i && pnpm build
2. See console output and analyzer output

Current vs. Expected behavior

Console output:

ƒ Middleware                             1.07 MB

I'd expect getMessages to not be bundled into the middleware as it's not used there.

See also the analyzer output:

Provide environment information

Operating System:
  Platform: darwin
  Arch: x64
  Version: Darwin Kernel Version 23.6.0: Mon Jul 29 21:13:00 PDT 2024; root:xnu-10063.141.2~1/RELEASE_X86_64
  Available memory (MB): 16384
  Available CPU cores: 12
Binaries:
  Node: 20.11.1
  npm: 10.2.4
  Yarn: 1.22.22
  pnpm: 9.15.4
Relevant Packages:
  next: 15.1.5 // Latest available version is detected (15.1.5).
  eslint-config-next: N/A
  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)

Middleware

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

next build (local)

Additional context

No response