I know that there are 2 different methods of process execution in the Pants codebase called

Process

(which executes external processes) and

VenvPexProcess

(which runs inside a virtual environment + PEX). Is there a way to run a OS-level process inside the venv, but NOT using PEX?

That's not quite right. There is only really Process. A VenvPexProcess just ensures a venv is built from a PEX (instead of running the PEX directly), and then the Process runs inside that built venv; so Pex is not involved at that point.

Ah okay, got it. I’m trying to run

ruff

from the command line inside a venv and was trying to go through the Pants internals to see how it works; it uses

VenvPexProcess

internally and I see that there is an open issue on Github here on what seems like the same thing: https://github.com/pantsbuild/pants/issues/19270 https://github.com/pantsbuild/pants/blob/main/src/python/pants/backend/python/lint/ruff/rules.py#L72

Gotcha. Yeah, super strange the ruff rules got written that way!

I’m happy to tackle that issue as well since it is very related to what I’m trying to do - but I was trying to work out how to build the necessary venv from a lockfile (located in that same directory) and then execute a process inside that venv. But from what you described above, it seems like that’s pretty much what

VenvPexProcess

does?

Well you don't want to run ruff in a venv IIUC. You want to run the ruff native binary pointed at a venv. Is that right? In other words, you can install ruff on a machine and then run it against many and arbitrary venvs, correct?

Yup that’s right

@better-van-82973 the issue you point to is just a perf optimization in the end, the current ruff support should already do what you describe.

Okay, sounds good - thanks! I’ll keep playing around with it and see if I run into any issues