Race condition when running pytest-cov in parallel

[madig]

Summary

Setting up a tox.ini to run pytest-cov in parallel for different Pythons like described in https://pytest-cov.readthedocs.io/en/latest/tox.html leads to crashes sometimes.

Expected vs actual result

There should be no crash.

However, see this failed Windows job: https://github.com/daltonmaag/statmake/actions/runs/12891149682/job/35942412517#step:5:69.

Here's the output from Ubuntu 24.04 on WSL, on the occasion that it crashes:

❯ tox -q -p
clean-cov: OK ✔ in 0.2 seconds
lint: OK ✔ in 0.37 seconds
py310-cov: FAIL ✖ in 1.61 seconds
================================================= test session starts ==================================================
platform linux -- Python 3.10.15, pytest-8.3.4, pluggy-1.5.0
cachedir: .tox/py310-cov/.pytest_cache
rootdir: /home/user/statmake
configfile: pyproject.toml
plugins: cov-6.0.0
collected 31 items

tests/test_cli.py .....                                                                                          [ 16%]
tests/test_make_stat.py .........................                                                                [ 96%]
tests/test_serialize.py .
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/sqlitedb.py", line 115, in _execute
INTERNALERROR>     return self.con.execute(sql, parameters)    # type: ignore[arg-type]
INTERNALERROR> sqlite3.OperationalError: no such table: file
INTERNALERROR>
INTERNALERROR> During handling of the above exception, another exception occurred:
INTERNALERROR>
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/sqlitedb.py", line 120, in _execute
INTERNALERROR>     return self.con.execute(sql, parameters)    # type: ignore[arg-type]
INTERNALERROR> sqlite3.OperationalError: no such table: file
INTERNALERROR>
INTERNALERROR> The above exception was the direct cause of the following exception:
INTERNALERROR>
INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/_pytest/main.py", line 283, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/_pytest/main.py", line 337, in _main
INTERNALERROR>     config.hook.pytest_runtestloop(session=session)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/pluggy/_hooks.py", line 513, in __call__
INTERNALERROR>     return self._hookexec(self.name, self._hookimpls.copy(), kwargs, firstresult)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/pluggy/_manager.py", line 120, in _hookexec
INTERNALERROR>     return self._inner_hookexec(hook_name, methods, kwargs, firstresult)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/pluggy/_callers.py", line 156, in _multicall
INTERNALERROR>     teardown[0].send(outcome)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/pytest_cov/plugin.py", line 329, in pytest_runtestloop
INTERNALERROR>     self.cov_controller.finish()
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/pytest_cov/engine.py", line 54, in ensure_topdir_wrapper
INTERNALERROR>     return meth(self, *args, **kwargs)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/pytest_cov/engine.py", line 279, in finish
INTERNALERROR>     self.cov.combine()
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/control.py", line 841, in combine
INTERNALERROR>     combine_parallel_data(
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/data.py", line 186, in combine_parallel_data
INTERNALERROR>     data.update(new_data, map_path=map_path)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/sqldata.py", line 679, in update
INTERNALERROR>     with con.execute("select path from file") as cur:
INTERNALERROR>   File "/home/user/.local/share/uv/python/cpython-3.10.15-linux-x86_64-gnu/lib/python3.10/contextlib.py", line 135, in __enter__
INTERNALERROR>     return next(self.gen)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/sqlitedb.py", line 150, in execute
INTERNALERROR>     cur = self._execute(sql, parameters)
INTERNALERROR>   File "/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/coverage/sqlitedb.py", line 138, in _execute
INTERNALERROR>     raise DataError(f"Couldn't use data file {self.filename!r}: {msg}") from exc
INTERNALERROR> coverage.exceptions.DataError: Couldn't use data file '/home/user/statmake/.coverage.DM1257.117674.XLffsVlx.c': no such table: file

================================================== 31 passed in 1.08s ==================================================
py310-cov: exit 3 (1.55 seconds) /home/user/statmake> pytest --cov --cov-append --cov-report=term-missing pid=117701
py38-cov: OK ✔ in 1.62 seconds
py39-cov: OK ✔ in 1.64 seconds
py311-cov: OK ✔ in 1.7 seconds
py313-cov: OK ✔ in 2.07 seconds
py312-cov: OK ✔ in 2.16 seconds
pypy310-cov: OK ✔ in 6.97 seconds
pypy39-cov: OK ✔ in 7.65 seconds
pypy38-cov: OK ✔ in 8.52 seconds
  lint: OK (0.36 seconds)
  clean-cov: OK (0.20 seconds)
  py38-cov: OK (1.62 seconds)
  py39-cov: OK (1.64 seconds)
  py310-cov: FAIL code 3 (1.61 seconds)
  py311-cov: OK (1.70 seconds)
  py312-cov: OK (2.16 seconds)
  py313-cov: OK (2.07 seconds)
  pypy38-cov: OK (8.52 seconds)
  pypy39-cov: OK (7.65 seconds)
  pypy310-cov: OK (6.97 seconds)
  report-cov: OK (0.24 seconds)
  evaluation failed :( (8.82 seconds)
/home/user/statmake/.tox/py310-cov/lib/python3.10/site-packages/_pytest/main.py:337: PluggyTeardownRaisedWarning: A plugin raised an exception during an old-style hookwrapper teardown.
Plugin: _cov, Hook: pytest_runtestloop
DataError: Couldn't use data file '/home/user/statmake/.coverage.DM1257.117674.XLffsVlx.c': no such table: file
For more information see https://pluggy.readthedocs.io/en/stable/api_reference.html#pluggy.PluggyTeardownRaisedWarning
  config.hook.pytest_runtestloop(session=session)

Reproducer

1. Clone https://github.com/daltonmaag/statmake
2. Repeatedly run tox -q -p until you get a crash

Versions

Running tox with tox-uv via Python 3.13.1, both installed by uv.

Package       Version
------------- -------
cachetools    5.5.1
chardet       5.2.0
colorama      0.4.6
distlib       0.3.9
filelock      3.17.0
packaging     24.2
platformdirs  4.3.6
pluggy        1.5.0
pyproject-api 1.9.0
tox           4.24.1
tox-uv        1.20.0
uv            0.5.22
virtualenv    20.29.1

pytest-cov is pinned to v6.0.0 in the statmake's lockfile for Py >= 3.9 and to v5.0.0 below.

Config

See https://github.com/daltonmaag/statmake/blob/master/tox.ini, https://github.com/daltonmaag/statmake/blob/master/.coveragerc and https://github.com/daltonmaag/statmake/blob/master/pyproject.toml.