Enable uv as an alternative to pip installation with --install-types

[cthoyt]

Currently, if you want to use mypy with mypy --install-types, it requires pip to be installed.

In my case, I am using tox with the tox-uv backend that creates all virtual environments without pip, since uv pip install is a drop-in replacement for pip install. I'm calling mypy in these environments, so I would like to have the possibility to specify the installer used.

The main code that would need to be changed is the following:

mypy/mypy/main.py

Line 1576 in fa01a07

cmd = [options.python_executable, "-m", "pip", "install"] + packages

where it might be nice to have the ability to pass in to the enclosing function install_types() an additional keyword called "installer" (or synonym) that would enable changing it to something like:

if installer == "pip":
    assert options.python_executable, "Python executable required to install types with pip"
    cmd = [options.python_executable, "-m", "pip", "install"] + packages
elif installer == "uv":
    import shutil

    # there are two possibilities here, since there might be a globally
    # installed uv that is not managed by the current python environment
    if shutil.which("uv"):  
        cmd = ["uv", "pip", "install"] + packages
    else:
        assert options.python_executable, "Python executable required to install types with uv"
        cmd = [options.python_executable, "-m", "uv", "pip", "install"] + packages
else:
    raise ValueError(f"Unknown installer: {installer}")

This is just a quick, self-contained mockup - there are other patterns that could be used to make this a bit more extensible in case there are other installers desired.

I've got a working demo in master...cthoyt:mypy:uv-installer that I could pull request, but it's not clear to me what is the best way to test this within MyPy's CI

[sobolevn]

I don't think that mypy should support different package managers for this use-case.

You can use any other package manager and install types manually. But, I think that exposing the list of types to install might be a great feature. Something like --list-install-types

[hauntsaninja]

Yeah, I think --install-types was a bit of a mistake. It can effectively make mypy take like twice as long, fails in situations involving cache and packaging is complicated enough that mypy shouldn't get in between users and installation. A --generate-stub-requirements like sobolevn proposes would be much better. See also #10600 and others

[cthoyt]

Thanks for the feedback. I think sobolevn's proposal is nice.

If there were a --list-install-types, then you could do something like mypy --list-install-types | xargs uv pip install.

If you don't think this my specific suggestion is something that could be considered for MyPy, then feel free to close this issue. At least it'll be tracked in #10600!

[sobolevn]

See my proposal in #10600 (comment)

Going to close this! Thanks for the idea :)