In web worker, typeof window === 'undefined' is falsely bundled to true

[yf-yang]

Link to the code that reproduces this issue

https://github.com/yf-yang/next-webworker-bug

To Reproduce

1. pnpm i
2. pnpm dev
3. open the window, click the button

Current vs. Expected behavior

Expected:
Web worker started, then debugjs can log a message "worker started" (console log level should be "verbose")
Current:
Error: Uncaught ReferenceError: window is not defined

Provide environment information

Operating System:
  Platform: darwin
  Arch: x64
  Version: Darwin Kernel Version 22.3.0: Mon Jan 30 20:42:11 PST 2023; root:xnu-8792.81.3~2/RELEASE_X86_64
Binaries:
  Node: 20.9.0
  npm: 10.1.0
  Yarn: 1.22.19
  pnpm: 8.14.3
Relevant Packages:
  next: 14.1.1-canary.45 // Latest available version is detected (14.1.1-canary.45).
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0
  typescript: N/A
Next.js Config:
  output: N/A

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

SWC transpilation

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

next dev (local)

Additional context

The error is this line in debug.js:
https://github.com/debug-js/debug/blob/f66cb2d9f729e1a592e72d3698e3b75329d75a25/src/browser.js#L119-L121

if (typeof window !== 'undefined' && window.process ...) {
  ...
}

In the bundled output file .next/static/chunks/_app-pages-browser_app_worker_js.js, this line is transpiled to

if (true && window.process ...) {
  ...
}

The bundled output is wrong, because in web worker, window does not exist.

NOTE: This bug does not exist in next@13.5.6

Operating System:
Platform: darwin
Arch: x64
Version: Darwin Kernel Version 22.3.0: Mon Jan 30 20:42:11 PST 2023; root:xnu-8792.81.3~2/RELEASE_X86_64
Binaries:
Node: 20.9.0
npm: 10.1.0
Yarn: 1.22.19
pnpm: 8.14.3
Relevant Packages:
next: 13.5.6
eslint-config-next: N/A
react: 18.2.0
react-dom: 18.2.0
typescript: N/A
Next.js Config:
output: N/A

_NEXT-2418

[yf-yang]

@kdy1 Is it a swc issue?

[kdy1]

No, it's not

[kdy1]

And this is duplicate

[yf-yang]

Ah, sorry for that.

#60644 (I think the issue may be incorrect because window should be undefined in web worker)

[yf-yang]

Also duplicates #61740
The same behavior: 14.0.5-canary.19 is OK, 14.0.5-canary.20 is broken.

I think both #60644 and #61740 does not address the issue correctly. window should be undefined, but typeof window !== 'undefined' should be false in a web worker context. (Or, does webpack create a window variable for workers?)

[yf-yang]

@huozhi Is it related to #59569?

[yf-yang]

I highly suspect #59569 is the root cause. isAppBrowserLayer does not imply this is the browser, it could be the web worker, where window object is not available. If I got it right, swc-loader is not configured correctly due to the problem.

See also: https://developer.mozilla.org/en-US/docs/Web/API/Web_Workers_API/Using_web_workers#web_workers_api
The first paragraph.

[hiromaily]

I'm using web worker and loaded worker code depends on other 3rd party library which checks window object.
It used to be working without any problems at Next.js version 14.0.4 or older. However it failed after upgrading next.js to 14.1.0. This error occurs both production and dev.

minimal.js:28 Uncaught ReferenceError: window is not defined
    at eval (webpack-internal:///(app-pages-browser)/./node_modules/protobufjs/src/util/minimal.js:28:68)

[huozhi]

We should disable the swc optimizer for the node_modules in app browser layer. I filled a PR for fixing it

[yf-yang]

Thanks and happy new year :)

[github-actions]

This closed issue has been automatically locked because it had no new activity for 2 weeks. If you are running into a similar issue, please create a new issue with the steps to reproduce. Thank you.