Error: Cannot find module './readBuffer' when Experimental option "babelMultiThread" is enabled

Bug report

When experimental option “babelMultiThread” is enabled, dev version does not start, giving error

internal/modules/cjs/loader.js:960
  throw err;
  ^

Error: Cannot find module './readBuffer'
Require stack:
- C:\Users\khades\projects\CODEr\node_modules\next\dist\compiled\thread-loader\worker.js
    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:957:15)
    at Function.Module._load (internal/modules/cjs/loader.js:840:27)
    at Module.require (internal/modules/cjs/loader.js:1019:19)
    at require (internal/modules/cjs/helpers.js:77:18)
    at Object.<anonymous> (C:\Users\khades\projects\CIWD-CorpSites\Frontend\site-editor\node_modules\next\dist\compiled\thread-loader\worker.js:19:19)
    at Module._compile (internal/modules/cjs/loader.js:1133:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1153:10)
    at Module.load (internal/modules/cjs/loader.js:977:32)
    at Function.Module._load (internal/modules/cjs/loader.js:877:14)
    at Function.executeUserEntryPoint [as runMain] (internal/modules/run_main.js:74:12) {
  code: 'MODULE_NOT_FOUND',
  requireStack: [
    'C:\\Users\\khades\\projects\\CODE\\node_modules\\next\\dist\\compiled\\thread-loader\\worker.js'
  ]
}

Describe the bug

I have project with lots of dynamic modules, that recompilation time was too long, looked through code and found that “babelMultiThread” experimental option enables cache-loader (which i really need).

So i enabled it while using next 9.3.3, it worked. I upgraded to latest canary - it broke.

To Reproduce

Steps to reproduce the behavior, please provide code snippets or a repository:

1. Do any project with latest canary next.js
2. Enable babelMultiThread

 experimental: { babelMultiThread: true },

in next.config.js 3. Start dev version

Expected behavior

It works, like in nextJS 9.3.3

System information

• OS: Widnows 10
• Browser (if applies) [e.g. chrome, safari]
• Version of Next.js: ^9.3.7-canary.12
• Version of Node.js: v12.16.3

[timneutkens]

This option no longer exists and Babel was superseded by SWC so I’m going to close this issue 👍

[github-actions[bot]]

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