[Bug]: processChild fails to initialize under certain conditions when a custom ESM loader is present

[kherock]

Version

27.3.1

Steps to reproduce

1. Clone https://github.com/kherock/jest-worker-spawn-bug
   • please look through the README for additional context!
   • this repo is using Yarn 3, however I can confirm that this issue isn't Yarn-specific.
2. Run the example worker script with the custom ESM loader:

yarn install
yarn worker-with-loader

Expected behavior

The worker should initialize and run the procedure.

Actual behavior

The worker misses the initialization message and hangs until something requests for it to be killed.

Additional context

This appears to be a timing-sensitive issue. I'll try to test this on some other platforms when I have time. Also, since this uses --experimental-loader, I suspect this might be a Node.js bug/quirk. However, the current use of ChildProcess.send feels unsound.

I've also written up some more context in the reproduction repo readme:

https://github.com/kherock/jest-worker-spawn-bug/blob/main/README.md

Environment

System:
    OS: macOS 11.5.2
    CPU: (12) x64 Intel(R) Core(TM) i7-9750H CPU @ 2.60GHz
  Binaries:
    Node: 14.18.1 - ~/.volta/tools/image/node/14.18.1/bin/node
    Yarn: 3.2.0-rc.3.git.20211110.hash-83311e1d4 - ~/.volta/tools/image/yarn/1.22.11/bin/yarn
    npm: 6.14.15 - ~/.volta/tools/image/node/14.18.1/bin/npm

[merceyz]

This seems to be a known issue in Node.js nodejs/node#39140 / nodejs/node#37782 with a solution in nodejs/node#37782 (comment)

[merceyz]

Looks like nodejs/node#41221 will fix the issue in Node.js itself

[merceyz]

nodejs/node#41221 has shipped in Node.js v16.14 and v17.4

[kherock]

I'm closing this since I've confirmed that everything behaves properly with Node v16.14.

[github-actions]

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