resolver: requiring PyQt5 produces non-portable locks

[neutrinoceros]

Ok this is a weird one. Let's start with what uv 0.5.9 does (or older versions too, as far as I could check):

mkdir test
cd test
uv init
uv add PyQt5

and let's look at the relevant portion of the resulting lock file. For context, PyQt5-Qt5 is a dependency to PyQt5:

[[package]]
name = "pyqt5-qt5"
version = "5.15.15"
source = { registry = "https://pypi.org/simple" }
wheels = [
    { url = "https://files.pythonhosted.org/packages/4a/6e/a5789bac6310208756fc6a36fd7e01caa86ea6ae7abbb5922dcea003a215/PyQt5_Qt5-5.15.15-py3-none-macosx_10_13_x86_64.whl", hash = "sha256:eb74072935958a830887115b1de1ff26341fc2d5881b28129de39612b10a260e", size = 39147807 },
    { url = "https://files.pythonhosted.org/packages/92/4c/c9026ca280f2cd4bef562cfb0a5050eb23f1e7fe1b85aa8455eb6ea437bf/PyQt5_Qt5-5.15.15-py3-none-macosx_11_0_arm64.whl", hash = "sha256:f8b174725fbe29c1a22f8acce5798933a65c8a083f1d9833ff212479ec2b3c14", size = 36953104 },
    { url = "https://files.pythonhosted.org/packages/95/70/1ba9b828387f42e0812b496ed637a950bf57a5d59b844d034841e8f9fb4f/PyQt5_Qt5-5.15.15-py3-none-manylinux2014_x86_64.whl", hash = "sha256:611505d04ffb06a5e5bcf98f5ff0e4e15ba7785565ccbe7bd3b2e40642ea3bdd", size = 59827278 },
]

It is evident that the version that uv selected (the current latest) doesn't have wheels for windows. Unfortunately there a no source distribution either, so this lock file just doesn't port to windows.
Looking at https://pypi.org/simple/pyqt5-qt5/

PyQt5_Qt5-5.15.2-py3-none-macosx_10_13_intel.whl
PyQt5_Qt5-5.15.2-py3-none-manylinux2014_x86_64.whl
PyQt5_Qt5-5.15.2-py3-none-win32.whl
PyQt5_Qt5-5.15.2-py3-none-win_amd64.whl
PyQt5_Qt5-5.15.11-1-py3-none-macosx_11_0_arm64.whl
PyQt5_Qt5-5.15.11-py3-none-macosx_10_13_x86_64.whl
PyQt5_Qt5-5.15.11-py3-none-macosx_11_0_arm64.whl
PyQt5_Qt5-5.15.12-py3-none-macosx_10_13_x86_64.whl
PyQt5_Qt5-5.15.12-py3-none-macosx_11_0_arm64.whl
PyQt5_Qt5-5.15.13-py3-none-macosx_10_13_x86_64.whl
PyQt5_Qt5-5.15.13-py3-none-macosx_11_0_arm64.whl
PyQt5_Qt5-5.15.14-py3-none-macosx_10_13_x86_64.whl
PyQt5_Qt5-5.15.14-py3-none-macosx_11_0_arm64.whl
PyQt5_Qt5-5.15.14-py3-none-manylinux2014_x86_64.whl
PyQt5_Qt5-5.15.15-py3-none-macosx_10_13_x86_64.whl
PyQt5_Qt5-5.15.15-py3-none-macosx_11_0_arm64.whl
PyQt5_Qt5-5.15.15-py3-none-manylinux2014_x86_64.whl

we can see that there are wheels for older versions on Windows (PyQt5-Qt5==5.15.2). Unfortunately no single version has wheels for all major platforms: PyQt5-Qt5==5.15.2 misses a wheel for macosx + arm64.

My expectation would be that uv's resolver could detect this problem and fork the requirements automatically, but it doesn't.
Admittedly this is an exceptional setup, and I would understand that it falls out of scope somehow, especially considering that it could be resolved downstream if PyQt5-Qt5 just shipped more wheels. I just thought it was similar (at least in spirit) to the problem solved by #9827, so I figured it was worth a shot.

Meanwhile, a usable workaround for me is to manually write the fork in my requirements as

"PyQt5-Qt5==5.15.2 ; platform_system == 'Windows'",
"PyQt5-Qt5>=5.15.14 ; platform_system != 'Windows'",

which I can hide away from users into a dependency group (where a user-visible requirement would be much more inconvenient).

[charliermarsh]

Thanks! This is another case of #9711: for packages that lack source distributions, we can end up with "incomplete" resolutions.

[neutrinoceros]

Oh, sorry I missed it ! Of course, feel free to close this one as a dup'
Thanks !

[charliermarsh]

I'll merge into that issue. I'm thinking about that problem now.