145 lines
4.7 KiB
Python
145 lines
4.7 KiB
Python
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# Tests some corner cases with isinstance() and issubclass(). While these
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# tests use new style classes and properties, they actually do whitebox
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# testing of error conditions uncovered when using extension types.
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import unittest
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import test_support
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class TestIsInstanceWhitebox(unittest.TestCase):
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# Test to make sure that an AttributeError when accessing the instance's
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# class's bases is masked. This was actually a bug in Python 2.2 and
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# 2.2.1 where the exception wasn't caught but it also wasn't being cleared
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# (leading to an "undetected error" in the debug build). Set up is,
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# isinstance(inst, cls) where:
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#
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# - inst isn't an InstanceType
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# - cls isn't a ClassType, a TypeType, or a TupleType
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# - cls has a __bases__ attribute
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# - inst has a __class__ attribute
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# - inst.__class__ as no __bases__ attribute
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#
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# Sounds complicated, I know, but this mimics a situation where an
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# extension type raises an AttributeError when its __bases__ attribute is
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# gotten. In that case, isinstance() should return False.
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def test_class_has_no_bases(self):
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class I(object):
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def getclass(self):
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# This must return an object that has no __bases__ attribute
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return None
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__class__ = property(getclass)
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class C(object):
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def getbases(self):
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return ()
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__bases__ = property(getbases)
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self.assertEqual(False, isinstance(I(), C()))
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# Like above except that inst.__class__.__bases__ raises an exception
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# other than AttributeError
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def test_bases_raises_other_than_attribute_error(self):
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class E(object):
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def getbases(self):
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raise RuntimeError
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__bases__ = property(getbases)
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class I(object):
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def getclass(self):
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return E()
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__class__ = property(getclass)
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class C(object):
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def getbases(self):
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return ()
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__bases__ = property(getbases)
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self.assertRaises(RuntimeError, isinstance, I(), C())
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# Here's a situation where getattr(cls, '__bases__') raises an exception.
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# If that exception is not AttributeError, it should not get masked
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def test_dont_mask_non_attribute_error(self):
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class I: pass
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class C(object):
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def getbases(self):
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raise RuntimeError
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__bases__ = property(getbases)
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self.assertRaises(RuntimeError, isinstance, I(), C())
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# Like above, except that getattr(cls, '__bases__') raises an
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# AttributeError, which /should/ get masked as a TypeError
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def test_mask_attribute_error(self):
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class I: pass
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class C(object):
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def getbases(self):
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raise AttributeError
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__bases__ = property(getbases)
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self.assertRaises(TypeError, isinstance, I(), C())
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# These tests are similar to above, but tickle certain code paths in
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# issubclass() instead of isinstance() -- really PyObject_IsSubclass()
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# vs. PyObject_IsInstance().
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class TestIsSubclassWhitebox(unittest.TestCase):
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def test_dont_mask_non_attribute_error(self):
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class C(object):
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def getbases(self):
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raise RuntimeError
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__bases__ = property(getbases)
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class S(C): pass
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self.assertRaises(RuntimeError, issubclass, C(), S())
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def test_mask_attribute_error(self):
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class C(object):
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def getbases(self):
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raise AttributeError
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__bases__ = property(getbases)
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class S(C): pass
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self.assertRaises(TypeError, issubclass, C(), S())
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# Like above, but test the second branch, where the __bases__ of the
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# second arg (the cls arg) is tested. This means the first arg must
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# return a valid __bases__, and it's okay for it to be a normal --
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# unrelated by inheritance -- class.
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def test_dont_mask_non_attribute_error_in_cls_arg(self):
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class B: pass
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class C(object):
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def getbases(self):
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raise RuntimeError
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__bases__ = property(getbases)
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self.assertRaises(RuntimeError, issubclass, B, C())
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def test_mask_attribute_error_in_cls_arg(self):
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class B: pass
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class C(object):
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def getbases(self):
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raise AttributeError
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__bases__ = property(getbases)
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self.assertRaises(TypeError, issubclass, B, C())
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def test_main():
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suite = unittest.TestSuite()
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suite.addTest(unittest.makeSuite(TestIsInstanceWhitebox))
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suite.addTest(unittest.makeSuite(TestIsSubclassWhitebox))
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test_support.run_suite(suite)
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if __name__ == '__main__':
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test_main()
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