"ERROR collecting tests" - backslash vs forward slash on Mingw32

While testing PyCairo [1] on Mingw32, “ERROR collecting tests” was triggered [2]

Most of the errors are because the __file__ attribute of test files has backslashes as the directory separators beyond the test root directory, while it’s expecting all forward slashes:

_________________ ERROR collecting tests/test_textextents.py __________________
import file mismatch:
imported module 'tests.test_textextents' has this __file__ attribute:
  D:/a/1/s\tests\test_textextents.py
which is not the same as the test file we want to collect:
  D:/a/1/s/tests/test_textextents.py

Longer log

##[section]Starting: Test
==============================================================================
Task         : Command line
Description  : Run a command line script using Bash on Linux and macOS and cmd.exe on Windows
Version      : 2.151.2
Author       : Microsoft Corporation
Help         : https://docs.microsoft.com/azure/devops/pipelines/tasks/utility/command-line
==============================================================================
Generating script.
========================== Starting Command Output ===========================
##[command]"C:\windows\system32\cmd.exe" /D /E:ON /V:OFF /S /C "CALL "d:\a\_temp\dcc6be11-cb7c-4f24-9554-70225cf9e5bf.cmd""
+ set -e
+ export MSYS2_FC_CACHE_SKIP=1
+ MSYS2_FC_CACHE_SKIP=1
+ export PYTHONPYCACHEPREFIX=/home/VssAdministrator/.cache/i686-python3/
+ PYTHONPYCACHEPREFIX=/home/VssAdministrator/.cache/i686-python3/
+ mkdir -p /home/VssAdministrator/.cache/i686-python3/
+ pacman --noconfirm -Suy
[snipped]
+ pacman --noconfirm -S --needed mingw-w64-i686-cairo mingw-w64-i686-python3 mingw-w64-i686-python3-pip mingw-w64-i686-toolchain git
[snipped]
============================= test session starts =============================
platform win32 -- Python 3.8.0, pytest-5.3.1, py-1.8.0, pluggy-0.13.1
rootdir: D:/a/1/s
plugins: hypothesis-4.50.6
collected 0 items / 18 errors / 2 skipped

[snipped]
=================================== ERRORS ====================================
_____________________ ERROR collecting tests/test_api.py ______________________
import file mismatch:
imported module 'tests.test_api' has this __file__ attribute:
  D:/a/1/s\tests\test_api.py
which is not the same as the test file we want to collect:
  D:/a/1/s/tests/test_api.py
HINT: remove __pycache__ / .pyc files and/or use a unique basename for your test file modules

[1] Pycairo on github https://github.com/pygobject/pycairo

[2] Build log on Azure https://dev.azure.com/pygobject/pycairo/_build/results?buildId=249

[lazka]

I think this is mainly a MSYS2 bug, see https://github.com/msys2/MINGW-packages/issues/6035 I’ll look into it (on the MSYS2 side) when I have some time.

[RonnyPfannschmidt]

i suspect its a difference in normalization between assertion rewriting and pylib py.path.local i cant investigate myself before the weekend, but we might want to investigate using pathlib + own code instead of pylibs import helper