Parallelize removing deps in poetry intall --sync

[adriangb]

Issue Kind

Change in current behaviour

Description

Currently poetry install --sync removes dependencies one by one. It's also somewhat slow for each one (~1s, I'd think it should me ms). Uninstalling should be done in parallel and hopefully can be sped up.

Impact

This enables a workflow where you cache all of the dependencies for a monorepo and then uninstall the ones you don't need in each services' Docker layer.

Workarounds

None that I know of. Just don't use the pattern.

[adriangb]

I see now that the source of this is #2658, but is seems like that was never fully investigated and a lot has changed in the internals of poetry since 2020 (e.g. not calling pip via subprocess, I think?). It seems prime candidate to re-evaluate.

[dimbleby]

This was certainly not an accident.

poetry/src/poetry/installation/executor.py

Lines 190 to 192 in bd029ac

	# Some operations are unsafe, we must execute them serially in a group
	# https://github.com/python-poetry/poetry/issues/3086
	# https://github.com/python-poetry/poetry/issues/2658

Uninstall is one of the few places where poetry does still call pip via a subprocess. I expect a pull request to reimplement uninstallation more directly would be desirable - but more work than just "don't act serially"

[adriangb]

Yeah I saw those lines, I was just hoping that "reimplement uninstallation more directly" had already been done so this would be easy. I guess not. Seems like that's what this issue is asking for then.