[appDir] Next.js appDir can not resolve virtual CSS files injected by webpack-virtual-modules

[SukkaW]

Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
  Platform: darwin
  Arch: x64
  Version: Darwin Kernel Version 22.2.0: Tue Nov  8 21:14:46 PST 2022; root:xnu-8792.60.55.131.1~1/RELEASE_X86_64
Binaries:
  Node: 18.12.1
  npm: 8.19.3
  Yarn: 1.22.19
  pnpm: 7.18.1
Relevant packages:
  next: 13.0.8-canary.4
  eslint-config-next: N/A
  react: 18.2.0
  react-dom: 18.2.0

Which area(s) of Next.js are affected? (leave empty if unsure)

App directory (appDir: true)

Link to the code that reproduces this issue

https://github.com/SukkaW/nextjs-issue-virtual-css

To Reproduce

git clone https://github.com/SukkaW/nextjs-issue-virtual-css
cd nextjs-issue-virtual-css
npm run dev

Open https://localhost:3001

Describe the Bug

Next.js' fails to collect CSS injected by webpack-virtual-modules from appDir, resulting in a Module not found error:

https://github.com/SukkaW/nextjs-issue-virtual-css/blob/a191e1cc9a0afcae2331b691dd6b11066940679a/next.config.js

---

I am porting a CSS-in-JS Next.js plugin to Next.js appDir (johanholmerin/style9#83). And it is common for CSS-in-JS to utilize webpack-virtual-modules to emit virtual CSS files (E.g. WindiCSS).

However, Next.js 13 can not collect virtual CSS from appDir. Which would break all existing AoT CSS-in-JS plugins. And I have created a minimal re-production above.

cc @shuding

Expected Behavior

The emitted virtual CSS files should be collected and resolved, just like the pages dir.

Which browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

[asos-tomp]

Try disabling the SWC compiler, using:

{
  "presets": ["next/babel"]
}

...which appears to allow webpack-virtual-modules to function.