Link to the code that reproduces this issue

https://github.com/hsucherng/nextjs-genstaticparams-output-export-issue

To Reproduce

1. Run npm run dev.

Current vs. Expected behavior

Current behaviour: When I try to view http://localhost:3000/en, an error occurs: Error: Page "/[lang]/page" is missing exported function "generateStaticParams()", which is required with "output: export" config.

Expected behaviour: I should be able to view http://localhost:3000/en without any errors.

Provide environment information

Operating System:
  Platform: win32
  Arch: x64
  Version: Windows 11 Pro
  Available memory (MB): 32503
  Available CPU cores: 8
Binaries:
  Node: 18.18.0
  npm: N/A
  Yarn: N/A
  pnpm: n?A
Relevant Packages:
  next: 14.3.0-canary.18 // Latest available version is detected (14.3.0-canary.18).
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: 5.1.3
Next.js Config:
  output: export

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

Output (export/standalone)

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

next dev (local)

Additional context

I've tried with 14.1.3 and 14.2.2. The issue happens on both versions.

npm run dev works fine until output: "export" is added into the Next config.

A side note that npm run build works as intended. It is npm run dev that does not work as expected.