Missing tomli dependency

[AckslD]

This is probably not an issue with maturin but wondering if anyone seen something similar or have any thoughts what's going wrong. Let me know if this is not the correct place to ask this type of question.

I've been using maturin (which is awesome btw 🚀) for a while for a project. But recently, without changes to my own code (so I'm suspecting that it's caused by the latest version but could also be something else or that I'm doing something wrong) my build in CI is now failing due to missing tomli.

I have the following pyproject.toml:

[project]
name = "XXX"
dynamic = ['version']
dependencies = [
  "typing-extensions",
  "pydantic",
]

[build-system]
requires = ["maturin>=1.0,<2.0"]
build-backend = "maturin"

[tool.maturin]
python-source = "src"
module-name = "XXX.XXX"

and my pipelines are now failing with:

.pkg: install_requires> python -I -m pip install 'maturin<2.0,>=1.0'
.pkg: _optional_hooks> python /pyenv_root/pyenv/versions/3.10-dev/lib/python3.10/site-packages/pyproject_api/_backend.py True maturin
cov: packaging backend failed (code=-5), with FailedToStart: could not start backend
failed to start backend
Traceback (most recent call last):
  File "/builds/XXX/.tox/.pkg/lib/python3.10/site-packages/maturin/__init__.py", line 25, in <module>
    import tomllib
ModuleNotFoundError: No module named 'tomllib'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
  File "/pyenv_root/pyenv/versions/3.10-dev/lib/python3.10/site-packages/pyproject_api/_backend.py", line 132, in <module>
    sys.exit(run(sys.argv[1:]))
  File "/pyenv_root/pyenv/versions/3.10-dev/lib/python3.10/site-packages/pyproject_api/_backend.py", line 63, in run
    backend_proxy = BackendProxy(argv[1], None if len(argv) == 2 else argv[2])
  File "/pyenv_root/pyenv/versions/3.10-dev/lib/python3.10/site-packages/pyproject_api/_backend.py", line 23, in __init__
    backend = importlib.import_module(self.backend_module)
  File "/pyenv_root/pyenv/versions/3.10-dev/lib/python3.10/importlib/__init__.py", line 126, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 1050, in _gcd_import
  File "<frozen importlib._bootstrap>", line 1027, in _find_and_load
  File "<frozen importlib._bootstrap>", line 1006, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 688, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 883, in exec_module
  File "<frozen importlib._bootstrap>", line 241, in _call_with_frames_removed
  File "/builds/XXX/.tox/.pkg/lib/python3.10/site-packages/maturin/__init__.py", line 27, in <module>
    import tomli as tomllib  # type: ignore
ModuleNotFoundError: No module named 'tomli'

Any ideas? Manually adding tomli as a requirement to the build-backend works but that should already be a dependency of maturin so not sure why that's not installed as well. The above is part of a tox job and I cannot reproduce locally.

[konstin]

maturin declares tomli>=1.1.0 ; python_version<'3.11', so the missing tomli sounds like either a bug with the build frontend, which didn't install tomli, or there's some mixing of different python interpreters/venv in your setup.

[AckslD]

Thanks, it's difficult to debug as it only happens in CI, but I'll add some logging/verbose flags and see if I can understand what's happening.

[AckslD]

Seems like an issue with tox, at least upgrading from 4.11.3 to 4.24.1 makes it work again.