node 20.1.0 --loader seems trigger beforeExit when use await import

[wacdev]

Version

20.1.0

Platform

macos

What do you see instead?

My module will close the redis connection at the time of beforeExit, and the await import module (19.9.0) will not trigger beforeExit before.

In addition, the exit event is not triggered when use await import module

[MoLow]

also reported here - with a minimal repro

// file.js
process.on('beforeExit', () => {
  console.log('beforeExit')
})
import('./anyfile.js')
console.log('THIS CONSOLE LOG IS PREINTED')

./node  file.js                                                                                              ✔
THIS CONSOLE LOG IS PREINTED
beforeExit

./node --experimental-loader="data:text/javascript,export default true"  file.js                             ✔
(node:62415) ExperimentalWarning: Custom ESM Loaders is an experimental feature and might change at any time
(Use `node --trace-warnings ...` to show where the warning was created)
THIS CONSOLE LOG IS PREINTED
beforeExit
beforeExit
beforeExit

[targos]

This is probably because the ESM loader uses process.on('beforeExit') in a way that asynchronous work is scheduled in the callback. We should probably refactor that part anyway, I don't like that the internals use a public API that can be tampered with (for example with process.removeAllListeners('beforeExit');)

Refs: https://nodejs.org/dist/latest-v20.x/docs/api/process.html#event-beforeexit

/cc @aduh95

[aduh95]

The underlying issue being that Atomics.waitAsync does not keep the event loop alive, which has been reported to them already. That being said, we should be able to work around this without triggering beforeExit events on the main thread (on the loader thread though, I don’t think we can work around it, and calling process.removeAllListeners('beforeExit') from the loader thread needs to be forbidden probably.