[prerelease] pytest-isort and `if session is None: assert parent is None`

[The-Compiler]

Another one from #9415 - I don't quite understand what's going on and would like some help here.

When running the tests of pytest-isort, they fail with pytest 7.0.0rc1, but they fail in three different ways when bisecting things:

After 22dad53:

pytest_isort/__init__.py:67: in pytest_collect_file
    return IsortItem.from_parent(parent, fspath=path)
../../../proj/pytest/src/_pytest/nodes.py:587: in from_parent
    return super().from_parent(parent=parent, fspath=fspath, path=path, **kw)
../../../proj/pytest/src/_pytest/nodes.py:237: in from_parent
    return cls._create(parent=parent, **kw)
../../../proj/pytest/src/_pytest/nodes.py:128: in _create
    return super().__call__(*k, **kw)
pytest_isort/__init__.py:175: in __init__
    super(IsortItem, self).__init__(name=path, parent=parent, **kwargs)
../../../proj/pytest/src/_pytest/nodes.py:621: in __init__
    super().__init__(name, parent, config, session, nodeid=nodeid)
../../../proj/pytest/src/_pytest/nodes.py:549: in __init__
    path, fspath = _imply_path(path, fspath=fspath)
../../../proj/pytest/src/_pytest/nodes.py:100: in _imply_path
    raise ValueError(
E   ValueError: Path(local('/home/florian/tmp/pytest-bisect/pytest-isort/pytest_isort/__init__.py')) != <Session pytest-isort exitstatus=<ExitCode.OK: 0> testsfailed=0 testscollected=0>
E   if both path and fspath are given they need to be equal

After d7b0e17:

pytest_isort/__init__.py:67: in pytest_collect_file
    return IsortItem.from_parent(parent, fspath=path)
../../../proj/pytest/src/_pytest/nodes.py:622: in from_parent
    return super().from_parent(parent=parent, fspath=fspath, path=path, **kw)
../../../proj/pytest/src/_pytest/nodes.py:254: in from_parent
    return cls._create(parent=parent, **kw)
../../../proj/pytest/src/_pytest/nodes.py:131: in _create
    return super().__call__(*k, **kw)
pytest_isort/__init__.py:175: in __init__
    super(IsortItem, self).__init__(name=path, parent=parent, **kwargs)
../../../proj/pytest/src/_pytest/nodes.py:671: in __init__
    super().__init__(
../../../proj/pytest/src/_pytest/nodes.py:576: in __init__
    path, fspath = _imply_path(path, fspath=fspath)
../../../proj/pytest/src/_pytest/nodes.py:112: in _imply_path
    assert fspath is not None
E   AssertionError
===================

After f87df9c (also needs 63899c7):

/home/florian/tmp/pytest-bisect/pytest-isort/tests/test_plugin.py:187: in test_init
    test_obj = IsortItem.from_parent(parent, fspath=path)
/home/florian/proj/pytest/src/_pytest/nodes.py:623: in from_parent
    return super().from_parent(parent=parent, fspath=fspath, path=path, **kw)
/home/florian/proj/pytest/src/_pytest/nodes.py:256: in from_parent
    return cls._create(parent=parent, **kw)
/home/florian/proj/pytest/src/_pytest/nodes.py:140: in _create
    return super().__call__(*k, **kw)
/home/florian/tmp/pytest-bisect/pytest-isort/pytest_isort/__init__.py:175: in __init__
    super(IsortItem, self).__init__(name=path, parent=parent, **kwargs)
/home/florian/proj/pytest/src/_pytest/nodes.py:676: in __init__
    super().__init__(
/home/florian/proj/pytest/src/_pytest/nodes.py:592: in __init__
    assert parent is not None
E   AssertionError

Note that you will need pytest-isort master (with stephrdev/pytest-isort#39 in).

This might be caused by something pytest-isort does (see its source), but honestly I'm pretty lost...

cc @RonnyPfannschmidt @bluetech @stephrdev @hroncok

[RonnyPfannschmidt]

It's likely related to the item + file inheritance

[stephrdev]

If there is something we can fix in pytest-isort, I'm willing to do whatever is needed maintaining backwards compatibility for at least 5 and 6.

[bluetech]

The model for the fixes needed for File+Item inheritance and path/fspath issues is pytest-pyflakes: https://github.com/asmeurer/pytest-flakes/blob/master/pytest_flakes.py

I can submit a PR for pytest-isort when I get a chance (and if someone else does feel free to ping me for review).

[The-Compiler]

One thing I'm wondering about is if we need a better/nicer error output in pytest for this case? Then again we did't see the same kind of failure in any other projects, so I suppose it could be okay as-is.

[The-Compiler]

Seems like nobody picked this up so far, so I guess we'll just live with this for 7.0.0. I guess that's acceptable given that it only seems to affect one plugin, at least from what @hroncok tested in Fedora.

If someone can take a look at fixing the underlying issue in pytest-isort, that'd be great though!

[nicoddemus]

Opened stephrdev/pytest-isort#40 for this. 👍

[stephrdev]

Perfect, will look into this tonight.

[nicoddemus]

@stephrdev if you can go to the page earlier than that to at least let the CI run, it would be great. 👍

[nicoddemus]

Fixed in stephrdev/pytest-isort#40