Use uv for session.install with conda backend about nox

[henryiii]

Can't you install "uv" then use that? Or even do shutil.which("uv"), and then install it if that returns None, otherwise use the external one?

Not saying having an installer option, and then having venv's default to the right thing but making it settable is bad. But it does complicate things.

[jayqi]

I did end up making a workaround with shutil.which("uv") based on the find_uv function that I saw in nox's source code.

In noxfile.py global namespace:

def find_uv() -> tuple[bool, str]:
    # Inspired by:
    # https://github.com/wntrblm/nox/blob/08813c3c6b0d2171c280bbfcf219d089a16d1ac2/nox/virtualenv.py#L42
    uv = shutil.which("uv")
    if uv is not None:
        return True, uv
    return False, "uv"


HAS_UV, UV = find_uv()

Then in the session:

    if HAS_UV:
        session.run(UV, "pip", "install", "-r", "requirements/dev.txt", external=True)
    else:
        session.install("-r", "requirements/dev.txt")

Kind of messy but seems to work well enough.