Feedback about --import-mode=importlib in pytest 6.0

[nicoddemus]

This issue is a placeholder to gather feedback from users about the new --import-mode=importlib introduced in pytest 6.0.

It is our intention to change the default to importlib in future versions, and perhaps even eliminate the other --import-mode options (prepend and append).

[The-Compiler]

It looks like the pytest-bdd plugin is incompatible with --import-mode=importlib:

_______________________________ ERROR collecting tests/end2end/features/test_backforward_bdd.py _______________________________
tests/end2end/features/test_backforward_bdd.py:21: in <module>
    bdd.scenarios('backforward.feature')
.tox/py38-pyqt515/lib/python3.8/site-packages/pytest_bdd/scenario.py:296: in scenarios
    features_base_dir = get_features_base_dir(module)
.tox/py38-pyqt515/lib/python3.8/site-packages/pytest_bdd/scenario.py:241: in get_features_base_dir
    default_base_dir = os.path.dirname(caller_module.__file__)
E   AttributeError: 'NoneType' object has no attribute '__file__'

Relevant code:

def scenarios(*feature_paths, **kwargs):
    frame = inspect.stack()[1]
    module = inspect.getmodule(frame[0])    # <- this is None

    features_base_dir = kwargs.get("features_base_dir")
    if features_base_dir is None:
        features_base_dir = get_features_base_dir(module)

Any idea why this could be happening?

[nicoddemus]

I think bdd.scenarios assumes the module given as arguments are available in sys.path, which is not the case when --import-mode=importlib.

Perhaps this will work (untested):

  module = inspect.getmodule(frame[0])
+ if module is None:
+     module = __import__(frame[0])

[schperplata]

Maybe this issue should be transfered here?

[nicoddemus]

Thanks @schperplata, but it seems that's a different issue however (I replied there).

[graingert]

refs: pytest-dev/py#203 (comment)

for me relative imports are broken when using --import-mode=importlib https://github.com/graingert/relative-imports-import-mode-importlib/blob/default/tests/test_foo.py#L1

============================================================================================================================== test session starts ===============================================================================================================================
platform linux -- Python 3.8.2, pytest-6.0.1, py-1.9.0, pluggy-0.13.1
rootdir: /home/graingert/projects/relative-imports-import-mode-importlib, configfile: pytest.ini
plugins: forked-1.3.0, cov-2.9.0, xdist-1.34.0, case-1.5.3, timeout-1.4.2
collected 0 items / 1 error                                                                                                                                                                                                                                                      

===================================================================================================================================== ERRORS =====================================================================================================================================
_______________________________________________________________________________________________________________________ ERROR collecting tests/test_foo.py _______________________________________________________________________________________________________________________
ImportError while importing test module '/home/graingert/projects/relative-imports-import-mode-importlib/tests/test_foo.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
tests/test_foo.py:1: in <module>
    from . import utils
E   ImportError: attempted relative import with no known parent package

when doing inline tests, I often use relative imports:

https://github.com/graingert/relative-imports-import-mode-importlib/blob/default/graingertspkg/tests/test_business_logic.py#L1

ImportError while importing test module '/home/graingert/projects/relative-imports-import-mode-importlib/graingertspkg/tests/test_business_logic.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
graingertspkg/tests/test_business_logic.py:1: in <module>
    from .. import business_logic
E   ImportError: attempted relative import with no known parent package

[nicoddemus]

for me relative imports are broken

Not sure they are broken, imports using importlib by design won't add modules to sys.modules or change sys.path, which explains why it doesn't work for your use case.

This however brings an important point, that importlib is not recommended for tests included with package code if one wants to use relative imports.

We should consider that as documentation, and also weight this use case in an eventual future decision of changing the default --importmode.