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