Can't install pypi package dtale

[kjyv]

Hey there,
I'm trying to install dtale with a simple pyproject.toml running uv sync (.venv deleted, .cache/uv deleted). Even if it is the only package, I see this error:
error: distribution kaleido==0.2.1.post1 @ registry+https://pypi.org/simple can't be installed because it doesn't have a source distribution or wheel for the current platform

Installing with uv pip install dtale work fine though and the same package combination works well with pipenv.
I'm on macOS 15.0, uv 0.4.16.

[konstin]

This is caused by a difference in how uv sync and uv pip install handle unavailable wheel. The tl;dr fix for you problem is adding the following to your pyproject.toml:

[tool.uv]
constraint-dependencies = ["kaleido!=0.2.1.post1"]

The longer explanation: There are two recent versions of dtale, 0.2.1 and 0.2.1.post1. The former has a source distribution and wheels for all sorts of platforms (https://pypi.org/project/kaleido/0.2.1/#files), the latter only has an armv7l wheel for linux (https://pypi.org/project/kaleido/0.2.1.post1/#files); I think the authors wanted to add the missing wheel to the release, but instead created a new release. When using uv pip install, the resolver skips over 0.2.1.post1 because it wants to find something that works for the current platform and uses 0.2.1 instead. uv sync on the other hand attempts a universal resolution that is the same independent from which platform you run it, so it can't skip releases due to missing source distributions or platforms. It then locks 0.2.1.post1 and subsequently fails to install. The constraint we're adding says that if the resolver is trying to pick a version for kaleido, it should skip that post-release, but without making kaleido a dependency of your project.

[kjyv]

Ok, thank you for the detailed explanation. So the contraint fixes our problem but I guess it's not ideal if users like me run into this and the error message is not saying much about how to go forward. Rather than changing the resolver for the sync which I guess is tricky for all platforms with such packages, could this case be detected by uv and a more specific error message shown?