`python_files=*.py` breaks with Python 3.10

[trehn]

Consider this simple setup (no other files in the directory):

# setup.cfg
[tool:pytest]
python_files=*.py

# broken.py
from requests import certs

def test_foo():
    print(certs.where())

This has worked fine for previous versions of Python. Since 3.10, I'm getting this:

> py.test .
======================================= test session starts =======================================
platform linux -- Python 3.10.0, pytest-6.2.5, py-1.10.0, pluggy-1.0.0
rootdir: /home/trehn/git/aur/python310/venv/frob, configfile: setup.cfg
collected 0 items / 1 error                                                                       

============================================= ERRORS ==============================================
_____________________________________ ERROR collecting broken.py __________________________________
broken.py:1: in <module>
    from requests import certs
<frozen importlib._bootstrap>:1027: in _find_and_load
    ???
<frozen importlib._bootstrap>:1006: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:688: in _load_unlocked
    ???
../lib/python3.10/site-packages/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
../lib/python3.10/site-packages/requests/__init__.py:133: in <module>
    from . import utils
<frozen importlib._bootstrap>:1027: in _find_and_load
    ???
<frozen importlib._bootstrap>:1006: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:688: in _load_unlocked
    ???
../lib/python3.10/site-packages/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
../lib/python3.10/site-packages/requests/utils.py:41: in <module>
    DEFAULT_CA_BUNDLE_PATH = certs.where()
../lib/python3.10/site-packages/certifi/core.py:37: in where
    _CACERT_PATH = str(_CACERT_CTX.__enter__())
/usr/lib/python3.10/contextlib.py:135: in __enter__
    return next(self.gen)
/usr/lib/python3.10/importlib/_common.py:88: in _tempfile
    fd, raw_path = tempfile.mkstemp(suffix=suffix)
/usr/lib/python3.10/tempfile.py:337: in mkstemp
    return _mkstemp_inner(dir, prefix, suffix, flags, output_type)
/usr/lib/python3.10/tempfile.py:249: in _mkstemp_inner
    file = _os.path.join(dir, pre + name + suf)
E   TypeError: can only concatenate str (not "method") to str
----------------------------------------- Captured stdout -----------------------------------------
<class 'method'> <bound method DegenerateFiles.Path.name of <importlib._adapters.DegenerateFiles.Path object at 0x7f1860f59420>>
===================================== short test summary info =====================================
ERROR broken.py - TypeError: can only concatenate str (not "method") to str
!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
======================================== 1 error in 0.29s =========================================

When changing python_files in setup.cfg to anything other than *.py (e.g. b*.py), things work as expected again.

I tried digging into why this happens, but it seems rather involved. The method mentioned in the TypeError is this one:

https://github.com/python/cpython/blob/67148254146948041a77d8a2989f41b88cdb2f99/Lib/importlib/_adapters.py#L49

I'm not sure what DegenerateFiles is and under which circumstances it is used. Also note that it has been removed from Python's main branch in this commit:

python/cpython@aaa83cd

If python_files=*.py is problematic in general, pytest should throw a better error message. But of course I'd prefer it to be fixed since it lets me use shorter filenames when all my tests live in a dedicated directory.

Thanks!

[The-Compiler]

What happens if you run that broken.py with Python 3.10, without pytest involved?

[trehn]

It works and prints lib/python3.10/site-packages/certifi/cacert.pem (I just added test_foo() to the file)

[RonnyPfannschmidt]

Does it work with --assert=plain?

[trehn]

It does!

[asottile]

I think your python_files may be misconfigured -- it's causing the assertion rewriting to rewrite things inside your site-packages which are unrelated to your tests. that said, I also think there's some sort of regression in importlib-resources itself so it may be worth a https://bugs.python.org issue for that

[RonnyPfannschmidt]

@jaraco i believe its a bug in the degraded files in import-lib, at first glance name is a method instead of a property,

[jaraco]

Agreed. The TypeError appears to be a bug, and a bug that's only present in importlib_resources 5.0.x and importlib.resources as found on CPython 3.10. I'm confident that making DegenerateFiles.Path.name a property will correct the proximate error, but correcting that error leads to another proximate failure:

Details

____________________________________________________________________ ERROR collecting broken.py _____________________________________________________________________
broken.py:2: in <module>
    from requests import certs
<frozen importlib._bootstrap>:1027: in _find_and_load
    ???
<frozen importlib._bootstrap>:1006: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:688: in _load_unlocked
    ???
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-2jazv_1w/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-2jazv_1w/requests/__init__.py:133: in <module>
    from . import utils
<frozen importlib._bootstrap>:1027: in _find_and_load
    ???
<frozen importlib._bootstrap>:1006: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:688: in _load_unlocked
    ???
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-2jazv_1w/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-2jazv_1w/requests/utils.py:41: in <module>
    DEFAULT_CA_BUNDLE_PATH = certs.where()
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-2jazv_1w/certifi/core.py:37: in where
    _CACERT_PATH = str(_CACERT_CTX.__enter__())
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py:135: in __enter__
    return next(self.gen)
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/_common.py:89: in _tempfile
    os.write(fd, reader())
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/abc.py:371: in read_bytes
    with self.open('rb') as strm:
E   TypeError: DegenerateFiles.Path.open() takes 1 positional argument but 2 were given
====================================================================== short test summary info ======================================================================
ERROR broken.py - TypeError: DegenerateFiles.Path.open() takes 1 positional argument but 2 were given
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Correcting that issue leads to a new failure, this one intended:

____________________________________________________________________ ERROR collecting broken.py _____________________________________________________________________
broken.py:2: in <module>
    from requests import certs
<frozen importlib._bootstrap>:1027: in _find_and_load
    ???
<frozen importlib._bootstrap>:1006: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:688: in _load_unlocked
    ???
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-_f1ljnq3/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-_f1ljnq3/requests/__init__.py:133: in <module>
    from . import utils
<frozen importlib._bootstrap>:1027: in _find_and_load
    ???
<frozen importlib._bootstrap>:1006: in _find_and_load_unlocked
    ???
<frozen importlib._bootstrap>:688: in _load_unlocked
    ???
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-_f1ljnq3/_pytest/assertion/rewrite.py:170: in exec_module
    exec(co, module.__dict__)
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-_f1ljnq3/requests/utils.py:41: in <module>
    DEFAULT_CA_BUNDLE_PATH = certs.where()
/var/folders/c6/v7hnmq453xb6p2dbz1gqc6rr0000gn/T/pip-run-_f1ljnq3/certifi/core.py:37: in where
    _CACERT_PATH = str(_CACERT_CTX.__enter__())
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/contextlib.py:135: in __enter__
    return next(self.gen)
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/_common.py:89: in _tempfile
    os.write(fd, reader())
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/abc.py:371: in read_bytes
    with self.open('rb') as strm:
/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/importlib/_adapters.py:54: in open
    raise ValueError()
E   ValueError

The ValueError here is indicating that DegenerateFiles is not expected to be encountered. Something about pytest is causing the resources of certifi not to resolve.

[jaraco]

I can confirm the issue was fixed in main:

draft $ cat broken.py
# broken.py
from requests import certs


def test_foo():
    print(certs.where())
draft $ cat setup.cfg
[tool:pytest]
python_files=*.py
draft $ pip-run -q requests git+https://github.com/pytest-dev/pytest -- -m pytest
======================================================================== test session starts ========================================================================
platform darwin -- Python 3.10.0, pytest-6.3.0.dev775+g14a879b6d, py-1.10.0, pluggy-1.0.0
rootdir: /Users/jaraco/draft, configfile: setup.cfg
collected 1 item                                                                                                                                                    

broken.py .                                                                                                                                                   [100%]

========================================================================= 1 passed in 0.23s =========================================================================

I'll take care of reporting and fixing the interface issues with DegenerateFiles.Path.

[jaraco]

Filed bpo-45419 to track the identified interface issue.

[nicoddemus]

Thanks @jaraco and everyone.

Closing this then as it is not something actionable on pytest. 👍

[trehn]

The fix for bpo-45419 just does what @jaraco already did in #9174 (comment), leaving this unresolved:

The ValueError here is indicating that DegenerateFiles is not expected to be encountered. Something about pytest is causing the resources of certifi not to resolve.

I'm still not sure if that's a Python issue, a certifi issue or a pytest issue. But right now the problem isn't gone, it's just producing a different error.