pytest with importlib & dataclass & __future__ annotations crash #7856
Description
I'm transitioning from pytest regular imports to --import-mode=importlib imports due to namespace collisions in tests. And I'm getting the following crash, no plugins installed, pytest 6.1.1 CPython 3.8.6, the issue reproduces on Mac & Linux.
File names test_xx.py:
from __future__ import annotations
from dataclasses import dataclass
@dataclass
class TestHelper:
value: strrunning pytest --import-mode=importlib test_xx.py and I get the following crash:
==================================================== test session starts ====================================================
platform darwin -- Python 3.8.5, pytest-6.1.1, py-1.9.0, pluggy-0.13.1
rootdir: /private/tmp/qwer/dir
collected 0 items / 1 error
========================================================== ERRORS ===========================================================
________________________________________________ ERROR collecting test_xx.py ________________________________________________
test_xx.py:6: in <module>
class TestHelper:
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:1019: in dataclass
return wrap(cls)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:1011: in wrap
return _process_class(cls, init, repr, eq, order, unsafe_hash, frozen)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:861: in _process_class
cls_fields = [_get_field(cls, name, type)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:861: in <listcomp>
cls_fields = [_get_field(cls, name, type)
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:712: in _get_field
and _is_type(f.type, cls, typing, typing.ClassVar,
/usr/local/opt/python@3.8/Frameworks/Python.framework/Versions/3.8/lib/python3.8/dataclasses.py:658: in _is_type
ns = sys.modules.get(cls.__module__).__dict__
E AttributeError: 'NoneType' object has no attribute '__dict__'
================================================== short test summary info ==================================================
ERROR test_xx.py - AttributeError: 'NoneType' object has no attribute '__dict__'
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 error during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
===================================================== 1 error in 0.28s ======================================================
pip list:
Package Version
---------- -------
attrs 20.2.0
iniconfig 1.0.1
packaging 20.4
pip 20.1.1
pluggy 0.13.1
py 1.9.0
pyparsing 2.4.7
pytest 6.1.1
setuptools 50.3.0
six 1.15.0
toml 0.10.1
wheel 0.35.1