Tests fail with Python 3.9

[mgorny]

This is via running tox -e py39 on git master, with Python 3.9.0b1.

Full log: py39.log

==================================================================== FAILURES =====================================================================
______________________________________________ TestCallingOuterClassMethod.test_class_call_function _______________________________________________

self = <test_outer_classmethod.TestCallingOuterClassMethod testMethod=test_class_call_function>

    def test_class_call_function(self):
        # Test calling classmethod. The instance and class passed to the
        # wrapper will both be None because our decorator is surrounded
        # by the classmethod decorator. The classmethod decorator
        # doesn't bind the method and treats it like a normal function,
        # explicitly passing the class as the first argument with the
        # actual arguments following that.
    
        _args = (1, 2)
        _kwargs = {'one': 1, 'two': 2}
    
        @wrapt.decorator
        def _decorator(wrapped, instance, args, kwargs):
            self.assertEqual(instance, None)
            self.assertEqual(args, (Class,)+_args)
            self.assertEqual(kwargs, _kwargs)
            self.assertEqual(wrapped.__module__, _function.__module__)
            self.assertEqual(wrapped.__name__, _function.__name__)
            return wrapped(*args, **kwargs)
    
        @_decorator
        def _function(*args, **kwargs):
            return args, kwargs
    
        class Class(object):
            @classmethod
            @_decorator
            def _function(cls, *args, **kwargs):
                return (args, kwargs)
    
>       result = Class._function(*_args, **_kwargs)

tests/test_outer_classmethod.py:153: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
tests/test_outer_classmethod.py:136: in _decorator
    self.assertEqual(instance, None)
E   AssertionError: <class 'test_outer_classmethod.TestCallin[54 chars]ass'> != None
_____________________________________________ TestCallingOuterClassMethod.test_instance_call_function _____________________________________________

self = <test_outer_classmethod.TestCallingOuterClassMethod testMethod=test_instance_call_function>

    def test_instance_call_function(self):
        # Test calling classmethod via class instance. The instance
        # and class passed to the wrapper will both be None because our
        # decorator is surrounded by the classmethod decorator. The
        # classmethod decorator doesn't bind the method and treats it
        # like a normal function, explicitly passing the class as the
        # first argument with the actual arguments following that.
    
        _args = (1, 2)
        _kwargs = {'one': 1, 'two': 2}
    
        @wrapt.decorator
        def _decorator(wrapped, instance, args, kwargs):
            self.assertEqual(instance, None)
            self.assertEqual(args, (Class,)+_args)
            self.assertEqual(kwargs, _kwargs)
            self.assertEqual(wrapped.__module__, _function.__module__)
            self.assertEqual(wrapped.__name__, _function.__name__)
            return wrapped(*args, **kwargs)
    
        @_decorator
        def _function(*args, **kwargs):
            return args, kwargs
    
        class Class(object):
            @classmethod
            @_decorator
            def _function(cls, *args, **kwargs):
                return (args, kwargs)
    
>       result = Class()._function(*_args, **_kwargs)

tests/test_outer_classmethod.py:187: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
tests/test_outer_classmethod.py:170: in _decorator
    self.assertEqual(instance, None)
E   AssertionError: <class 'test_outer_classmethod.TestCallin[57 chars]ass'> != None
______________________________________________ TestSynchronized.test_synchronized_outer_classmethod _______________________________________________

self = <test_synchronized_lock.TestSynchronized testMethod=test_synchronized_outer_classmethod>

    def test_synchronized_outer_classmethod(self):
        # XXX If all was good, this would be detected as a class
        # method call, but the classmethod decorator doesn't bind
        # the wrapped function to the class before calling and
        # just calls it direct, explicitly passing the class as
        # first argument. This screws things up. Would be nice if
        # Python were fixed, but that isn't likely to happen.
    
        #_lock0 = getattr(C4, '_synchronized_lock', None)
        _lock0 = getattr(C4.function2, '_synchronized_lock', None)
        self.assertEqual(_lock0, None)
    
        c4.function2()
    
        #_lock1 = getattr(C4, '_synchronized_lock', None)
        _lock1 = getattr(C4.function2, '_synchronized_lock', None)
>       self.assertNotEqual(_lock1, None)
E       AssertionError: None == None

tests/test_synchronized_lock.py:175: AssertionError
-------------------------------------------------------------- Captured stdout call ---------------------------------------------------------------
function2

[GrahamDumpleton]

Both tests seem to relate to what has been a long standing bug in Python that I reported many many years ago related to the classmethod decorator. The tests would be expecting the broken behaviour. It is possible that the bug have finally been fixed.

[mgorny]

bpo-19072: The classmethod decorator can now wrap other descriptors such as property objects. Adapted from a patch written by Graham Dumpleton.

I guess that's you ;-).

[GrahamDumpleton]

First reported in 2013. Patch was even provided. But as a non Python core contributor who knew nothing about what was required to submit patches to core, the response I got was very off putting. Never wanted to get involved with Python core work after that.

[mgorny]

Yeah, from what I've seen a lot of very old patches have suddenly made it to 3.9, when their authors haven't looked at them in years (and might have not agreed with the final solution after all).

[mgorny]

Does this mean that the test failure is safe to ignore?

[GrahamDumpleton]

I don't know. It was late at night when you reported it. I need to make time to look properly at it.

[mgorny]

Well, the way I read https://wrapt.readthedocs.io/en/latest/decorators.html#decorating-class-methods it says that it might be fixed one day and that users shouldn't do this. I'm going to make a PR with the assumption that Py3.9 behavior is correct.

[mgorny]

Sorry, clicked the wrong button.

[WildCard65]

@GrahamDumpleton @mgorny Bumping this to inject when the issue was marked resolved: python/cpython#8405

[GrahamDumpleton]

These tests are fixed up with version 1.13.0 of wrapt.