ImportPathMismatchError on WindowsPath

[jaraco]

I'm running pytest in a Windows 2019 Docker image on macOS 11 with the project under test mounted from the host file system at C:\src.

When I run pytest under tox the first time, the tests run as expected.

When I run them a second time, pytest fails early with an ImportError:

PS C:\src> tox -- -k test_ls --pdb
GLOB sdist-make: C:\src\setup.py
python inst-nodeps: C:\tox\.tmp\package\1\cmdix-0.2.1.dev87+gd3e3450.d20201126.zip
python installed: appdirs==1.4.4,atomicwrites==1.4.0,attrs==20.3.0,black==20.8b1,click==7.1.2,cmdix @ file:///C:/tox/.tmp/package/1/cmdix-0.2.1.dev87%2Bgd3e3450.d20201126.zip,colorama==0.4.4,coverage==5.3,docutils==0.16,filelock==3.0.12,flake8==3.8.4,importlib-metadata==3.1.0,importlib-resources==3.3.0,iniconfig==1.1.1,jaraco.apt==2.0,jaraco.classes==3.1.0,jaraco.collections==3.0.0,jaraco.context==3.0.0,jaraco.functools==3.0.1,jaraco.test==4.0.1,jaraco.text==3.2.0,mccabe==0.6.1,more-itertools==8.6.0,mypy==0.790,mypy-extensions==0.4.3,packaging==20.4,pathspec==0.8.1,pluggy==0.13.1,py==1.9.0,pycodestyle==2.6.0,pyflakes==2.2.0,pyparsing==2.4.7,pytest==6.1.2,pytest-black==0.3.12,pytest-checkdocs==2.1.1,pytest-cov==2.10.1,pytest-flake8==1.0.6,pytest-mypy==0.8.0,pytz==2020.4,regex==2020.11.13,six==1.15.0,tempora==4.0.1,toml==0.10.2,typed-ast==1.4.1,typing-extensions==3.7.4.3,yg.lockfile==2.3,zc.lockfile==2.0,zipp==3.4.0
python run-test-pre: PYTHONHASHSEED='641'
python run-test: commands[0] | pytest -k test_ls --pdb
ImportError while loading conftest 'C:\src\conftest.py'.
_pytest.pathlib.ImportPathMismatchError: ('conftest', 'C:\\src\\conftest.py', WindowsPath('C:/src/conftest.py'))
ERROR: InvocationError for command 'C:\tox\python\Scripts\pytest.EXE' -k test_ls --pdb (exited with code 4)
_____________________________________________________________ summary _____________________________________________________________ 
ERROR:   python: commands failed

It appears that pytest is somehow detecting that C:\src\conftest.py is not the same file as C:/src/conftest.py. I'm not sure what library is generating the wrong slashes.

Deleting the tox work dir at C:\tox and re-running tox allows the tests to run once again, so whatever is caching path with the funny slashes is caching it in the tox work dir.

[nicoddemus]

Hi @jaraco,

Sorry for the delay.

Seems that the problem is not really the forward/backward slashes:

>>> import os.path
>>> os.path.samefile('d:\\projects', 'd:/projects')
True

(That exception is raised when that samefile call returns False).

I suspect it is the same problem as in #7678.

[jaraco]

Agreed these issues are very similar. It's not a UNC path, but it is a mounted path, so likely going through similar underlying APIs that may be failing on samefile. I'll try with your branch and see how it goes.

[jaraco]

I've confirmed the issue was still occurring on pytest stable, then remedied by using the candidate commit above. I was careful to run the tox tests twice in each configuration (because the issue only occurred on subsequent invocations) and clean between the two experiments.

So I'm pleased to say this issue is a confirmed duplicate and the proposed fix works as intended.

[nicoddemus]

Awesome, thanks for testing it out @jaraco. 👍