Add support for Process.close() method (added in CPython 3.7)

[millerdev]

gipc processes started with proc = start_process(...) always error on proc.close():

ValueError: Cannot close a process while it is still running. You should first call join() or terminate().

The problem is that _GProcess patches _popen.poll to return None:

https://github.com/jgehrcke/gipc/blob/e79845d6af4f6c574eb344b1c7d3aa2c421d255b/gipc/gipc.py#L448

This breaks the implementation of multiprocessing.Process.close, which raises an error if _popen.poll() returns None.

[jgehrcke]

Thank you for reporting this. Which Python version did you use to run into this? CPython 3.8, on Linux?

[millerdev]

CPython 3.7 on macOS. The close() method was added in 3.7

[jgehrcke]

Gotcha, thanks, I'll look into that!

Edit: so far on MacOS CI tests:

Mac OS X tests (all with gevent 1.3.x):
pyenv Python builds: CPython 2.7, 3.6, PyPy3
system CPython

That's one reason how we didn't notice this so far.

Will need to change that, too, obviously.

[jgehrcke]

I felt free to rename this issue. Did a bit of CI maintenance work (https://github.com/jgehrcke/gipc/pull/91) that will allow for confidently adding support for the close() method to gipc.

We cannot call the original .close() method, as outlined in the gipc code base, because that will invoke a wait()-like system call -- which would conflict with the libev child watcher's mechanism.

My plan is, I think, to provide a close() implementation very close to what the original does.

[jgehrcke]

Working on this in https://github.com/jgehrcke/gipc/pull/93

[jgehrcke]

@millerdev I just released gipc 1.1.0 which should resolve this. If you can, please give it a quick test! Thank you!

https://pypi.org/project/gipc/