Defer finding uv binary to shutil

[ulucs]

Summary

Currently the find_uv_binary function searches some amount of pre-defined locations. Finding the binary itself can be achieved in a simpler way by deferring the logic to shutil.which, which does the following for us for free:

• handle exe extension logic in Windows
• search user/system-installed paths
• search virtualenv paths

In addition, leaving the location logic to PATH and shutil.which has the additional advantage of being compatible with tools that expose binaries via PATH (ie Nix), and any other package managers that work in ways we don't expect

Test Plan

No new functions -- previously written tests should cover correctness. Marked as Draft until all tests pass

[zanieb]

Hi! I don't think we want this behavior - it's only the intent of the script to find the uv binary associated with the Python module not another one on the system. If people want to find any uv binary, yeah which is a good option to call directly. See the discussion at #4451 for more context.

Perhaps we just need to clarify the documentation here instead.

[ulucs]

All good! Is there any interest in configuring uv to play well with Nix? One other option is to do something similar to

import os

def up(file_path, times = 1):
    for i in range(times):
        file_path = os.path.dirname(file_path)
    return file_path

os.path.join(up(__file__, 5), "bin", "uv")

in order to target $ROOT/bin/uv from $ROOT/lib/pythonXX/site-packages/uv/__init__.py. The current approach is targeting $ROOT/lib/pythonXX/site-packages/bin/uv which is something I'm not sure exists

[zanieb]

It'd be nice to support Nix but I don't think it makes sense for us to scan in arbitrary locations (i.e. up five levels) for the bin. Why doesn't Nix use one of the Python standard locations for the executable?

[ulucs]

It does do that, by initializing the library root at nix/store/$(derivation-hash)-$(python+ver)-$(package+ver), putting the binaries at $ROOT/bin and the library files at $ROOT/lib/pythonXX/site-packages

The problems for this case start when Python allows package location declarations via site and PYTHONPATH and disregards the binary paths. The previous version of this file had the same problem with pip install --target too, which was then solved by looking 2 directories up

[ulucs]

Hello! Following up.

Is there any interest in supporting the python library being pulled in via PYTHONPATH? Or is that considered to be an unsupported use-case?

[zanieb]

Hi! Sorry I'm not entirely understanding what you're proposing now. Can you clarify?