pex: --preserve-pip-download-log

[jake-normal]

During python lockfile generation, it would be nice to include the pex3 --preserve-pip-download-log flag. When included, the pex process will print out the path to a temporary file that contains the realtime download log of the pip process. This file can then be tailed. This is useful for debugging issues like catastrophic backtracking during dependency resolution.

[telekid]

Note to self: would add around here.

[telekid]

Eh, created #21980 just in case this feature is deemed useful. Untested locally, I don't have pants set up for local development 😢 .

[jsirois]

Untested locally, I don't have pants set up for local development

So... I am not a Pants dev any longer, but I would like to call this out as generally bogus for any Python code ... since its Python code! You could make that edit directly in the Pants venv which is presumably somewhere under <user cache dir>/nce/... somewhere. You have the live Python source available for editing even if you are not "set up for local development".

[jake-normal]

Ah, what I meant was I hadn't yet had the chance to look at https://www.pantsbuild.org/2.18/docs/contributions/development/setting-up-pants. Looks simple after a quick scan, just not quite at the top of my stack :)

[jsirois]

Aha. I fell for your alias as some 3rdparty yolo cowboy who swooped in and tried a fix without testing. Apparently "jake-normal" == "telekid"

[jake-normal]

Ahaha no, that's my bad. The alias is confusing. And you're totally right to call that out, I appreciate deeply the maintainer's burden.

[sureshjoshi]

I just fell for that too - I came back to check who that was.

One question: Is there any perf hit of note for adding that in by default? Or is it something that would be better passed in with some of the extra-args?

[jsirois]

No perf hit. Pex needs to capture the Pip log in full already to create a universal lock. The flag with no arg just skips a tempdir teardown.