[BUG]: Dangling processes on exit with --watch-stdin and multiple configurations

[LostKobrakai]

Bug report

What is the current behavior?
Starting webpack with --watch-stdin doesn't properly cleanup after itself. My webpack config returns a function, which returns two configuration objects. When starting webpack via my backend it starts 5 node processes, but when stopping the backend it leaves one node process running. It works when only one configuration object is returned by the function.

If the current behavior is a bug, please provide the steps to reproduce.

• Use a webpack config returning two configurations
• Start webpack with --watch-stdin
• Close stdin

What is the expected behavior?
All processes to be properly stopped without any dangling processes, like it does for only a single configuration.

Other relevant information:
webpack version: 4.31.0
Node.js version: 11.9.0
Operating System: MacOS X
Additional tools:

[hiroppy]

Could you submit the reproducible repo?

[LostKobrakai]

https://github.com/LostKobrakai/webpack-issue-reproduction

[evenstensberg]

I don't think it's going to be a priority fixing this for the v3 version, but will leave open as this might be an upcoming issue with v4

[alexander-akait]

Fixed in master, please use --watch-options-stdin, fixed for serve too