🤖 Upstream testing failure (2026-08-27)

[github-actions]

Upstream testing failure

Workflow: CI Upstream
Run: 33048658064
Date: Thu Aug 27 07:12:46 UTC 2026

Upstream testing has failed.

Please check the workflow run for details.

This issue was automatically generated from the CI Upstream workflow.

[dylannelson]

Comments on the logs:

• It appears to be a Cython 3.3.0 regression test failing through cartopy's main branch
• Cython 3.3.0 shipped 2026-08-22 — three days before this run
  • Update includes: "Declared container item types (e.g. list[float] or tuple[atype, ...]) are now used by the type system" from pypi.org/project/Cython/
• cartopy's pyproject.toml requires Cython >= 3.0 (pip in installing the latest, so this updated version)

Relevant log lines:

Repeated 4 times:

Error compiling Cython file:
...
Cannot convert 'list[T]' to Python object

line about failing to compile:

Cython.Compiler.Errors.CompileError: lib/cartopy/trace.pyx

it appears to be the fault of Cythonizing cartopy's lib/cartopy/trace.pyx

Correct me if I'm wrong but this may be out of our hands for now? as it seems to be a problem with cython and cartopy interacting, which is a dependency. The cython update was only 3 days ago so it may just need some time to get patched by cartopy? I could create an issue over at cartopy if this is the case, there doesn't seem to be any at the moment.

[Sevans711]

@dylannelson If this looks like a cartopy issue then creating an issue report upstream there sounds like the right call, thank you for digging into this!

[dylannelson]

created and issue at cartopy and found an issue there that is likely related (they may close my issue in favor of this one saying it's solved):
github.com/SciTools/cartopy/issues/2715

Though this issue above is closed, and we're still seeing this as of today, so not sure how they'll react. This may also be a cython issue that I'm looking into as well