Regression since 1.3.1 with Python 3

[jd]

Hey there,

We used to have everything working with Python 3.3 and now it's broken.

Full log is at http://logs.openstack.org/28/74728/4/check/gate-oslo-incubator-python33/fcccbc2/console.html

The error we see is:

2014-03-11 14:45:38.808 | ======================================================================
2014-03-11 14:45:38.808 | ERROR: Failure: TypeError (__class__ assignment: 'UnboundSelf' object layout differs from 'TestException')
2014-03-11 14:45:38.808 | ----------------------------------------------------------------------
2014-03-11 14:45:38.808 | Traceback (most recent call last):
2014-03-11 14:45:38.808 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/failure.py", line 39, in runTest
2014-03-11 14:45:38.808 |     raise self.exc_val.with_traceback(self.tb)
2014-03-11 14:45:38.809 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/loader.py", line 516, in makeTest
2014-03-11 14:45:38.809 |     return self._makeTest(obj, parent)
2014-03-11 14:45:38.809 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/loader.py", line 565, in _makeTest
2014-03-11 14:45:38.809 |     return self.loadTestsFromTestClass(obj)
2014-03-11 14:45:38.809 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/loader.py", line 509, in loadTestsFromTestClass
2014-03-11 14:45:38.809 |     for case in filter(wanted, dir(cls))]
2014-03-11 14:45:38.809 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/loader.py", line 508, in <listcomp>
2014-03-11 14:45:38.809 |     cases = [self.makeTest(getattr(cls, case), cls)
2014-03-11 14:45:38.809 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/loader.py", line 504, in wanted
2014-03-11 14:45:38.809 |     item = unbound_method(cls, item)
2014-03-11 14:45:38.809 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/pyversion.py", line 131, in unbound_method
2014-03-11 14:45:38.810 |     return UnboundMethod(cls, func)
2014-03-11 14:45:38.810 |   File "/home/jenkins/workspace/gate-oslo-incubator-python33/.tox/py33/lib/python3.3/site-packages/nose/pyversion.py", line 92, in __init__
2014-03-11 14:45:38.810 |     self.__self__.__class__ = cls
2014-03-11 14:45:38.810 | TypeError: __class__ assignment: 'UnboundSelf' object layout differs from 'TestException'
2014-03-11 14:45:38.810 | 

[sileht]

The regression was introduce by:
c51ff6f

[jszakmeister]

Can you provide more information about the test case that fails? Is the source for the test available somewhere? Can it be reduced to a small test case?

[jd]

It seems to be from that file:

https://git.openstack.org/cgit/openstack/oslo-incubator/tree/tests/unit/test_policy.py

That's where TestException is defined. Didn't get deeper yet.

[jszakmeister]

Can you try adding __test__ = False to your TestException class?

class TestException(Exception):
    __test__ = False

    def __init__(self, *args, **kwargs):
        self.args = args
        self.kwargs = kwargs

Or you can try renaming it. I think the issue here is that Nose is trying to collect the class because of the name (it's starts with Test), and it's not liking how we're wrapping it up. Perhaps we need to take a different approach, but I'm curious if that alleviates your issue.

[jd]

@jszakmeister adding __test__ = False or renaming the exception both works.

[jszakmeister]

Just to have it cross-referenced: the original issue being fixed was #728.

[cjw296]

This is also a problem for me as I said on the list.
@takluyver: What's the valid use case for having a static method on a test suite?

[takluyver]

I believe it was a piece of test machinery we had in IPython to do a variant of parametric tests. We've since ripped it out as it was more complexity than it was worth, but the code was here: https://github.com/ipython/ipython/blob/1.x/IPython/testing/_paramtestpy3.py

[cjw296]

So could the "fix" in #728 be reverted? maybe the docs should just be updated to say that staticmethods aren't supported on test suite classes?

[takluyver]

I think it would be sufficient to just put that line of code inside an if not PY3: block.

[takluyver]

I think #728 was a genuine bug, so it shouldn't be reverted, but I don't think the fix is needed in Python 3, so it should be simple.

[jszakmeister]

@cjw296 No, I don't think it should be reverted. I believe there's another way we can approach the problem.

[takluyver]

@jszakmeister I'm pretty sure the fix in c51ff6f was only necessary for Python 2, the equivalent in Python 3 is already set via UnboundSelf.__class__. So I think it can just do this:

if not PY3:
    self.im_class = cls

[Arfrever]

@jszakmeister: Are you planning Nose 1.3.2 release soon?

[jszakmeister]

That's my intention. Can you test master and see that it works better for you?

[Arfrever]

All tests now pass for me with CPython 2.7, 3.1, 3.2, 3.3, 3.4.