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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 sys
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import typing
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from test import support
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class TestIsInstanceExceptions(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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# - cls isn't a type, or a tuple
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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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# check that we don't mask non AttributeErrors
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# see: http://bugs.python.org/issue1574217
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def test_isinstance_dont_mask_non_attribute_error(self):
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class C(object):
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def getclass(self):
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raise RuntimeError
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__class__ = property(getclass)
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c = C()
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self.assertRaises(RuntimeError, isinstance, c, bool)
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# test another code path
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class D: pass
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self.assertRaises(RuntimeError, isinstance, c, D)
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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 TestIsSubclassExceptions(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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# meta classes for creating abstract classes and instances
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class AbstractClass(object):
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def __init__(self, bases):
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self.bases = bases
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def getbases(self):
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return self.bases
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__bases__ = property(getbases)
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def __call__(self):
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return AbstractInstance(self)
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class AbstractInstance(object):
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def __init__(self, klass):
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self.klass = klass
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def getclass(self):
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return self.klass
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__class__ = property(getclass)
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# abstract classes
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AbstractSuper = AbstractClass(bases=())
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AbstractChild = AbstractClass(bases=(AbstractSuper,))
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# normal classes
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class Super:
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pass
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class Child(Super):
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pass
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class TestIsInstanceIsSubclass(unittest.TestCase):
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# Tests to ensure that isinstance and issubclass work on abstract
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# classes and instances. Before the 2.2 release, TypeErrors were
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# raised when boolean values should have been returned. The bug was
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# triggered by mixing 'normal' classes and instances were with
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# 'abstract' classes and instances. This case tries to test all
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# combinations.
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def test_isinstance_normal(self):
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# normal instances
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self.assertEqual(True, isinstance(Super(), Super))
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self.assertEqual(False, isinstance(Super(), Child))
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self.assertEqual(False, isinstance(Super(), AbstractSuper))
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self.assertEqual(False, isinstance(Super(), AbstractChild))
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self.assertEqual(True, isinstance(Child(), Super))
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self.assertEqual(False, isinstance(Child(), AbstractSuper))
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def test_isinstance_abstract(self):
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# abstract instances
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self.assertEqual(True, isinstance(AbstractSuper(), AbstractSuper))
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self.assertEqual(False, isinstance(AbstractSuper(), AbstractChild))
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self.assertEqual(False, isinstance(AbstractSuper(), Super))
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self.assertEqual(False, isinstance(AbstractSuper(), Child))
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self.assertEqual(True, isinstance(AbstractChild(), AbstractChild))
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self.assertEqual(True, isinstance(AbstractChild(), AbstractSuper))
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self.assertEqual(False, isinstance(AbstractChild(), Super))
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self.assertEqual(False, isinstance(AbstractChild(), Child))
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def test_isinstance_with_or_union(self):
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self.assertTrue(isinstance(Super(), Super | int))
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self.assertFalse(isinstance(None, str | int))
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self.assertTrue(isinstance(3, str | int))
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self.assertTrue(isinstance("", str | int))
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self.assertTrue(isinstance([], typing.List | typing.Tuple))
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self.assertTrue(isinstance(2, typing.List | int))
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self.assertFalse(isinstance(2, typing.List | typing.Tuple))
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self.assertTrue(isinstance(None, int | None))
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self.assertFalse(isinstance(3.14, int | str))
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with self.assertRaises(TypeError):
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isinstance(2, list[int])
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with self.assertRaises(TypeError):
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isinstance(2, list[int] | int)
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with self.assertRaises(TypeError):
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isinstance(2, int | str | list[int] | float)
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def test_subclass_normal(self):
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# normal classes
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self.assertEqual(True, issubclass(Super, Super))
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self.assertEqual(False, issubclass(Super, AbstractSuper))
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self.assertEqual(False, issubclass(Super, Child))
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self.assertEqual(True, issubclass(Child, Child))
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self.assertEqual(True, issubclass(Child, Super))
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self.assertEqual(False, issubclass(Child, AbstractSuper))
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self.assertTrue(issubclass(typing.List, typing.List|typing.Tuple))
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self.assertFalse(issubclass(int, typing.List|typing.Tuple))
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def test_subclass_abstract(self):
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# abstract classes
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self.assertEqual(True, issubclass(AbstractSuper, AbstractSuper))
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self.assertEqual(False, issubclass(AbstractSuper, AbstractChild))
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self.assertEqual(False, issubclass(AbstractSuper, Child))
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self.assertEqual(True, issubclass(AbstractChild, AbstractChild))
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self.assertEqual(True, issubclass(AbstractChild, AbstractSuper))
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self.assertEqual(False, issubclass(AbstractChild, Super))
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self.assertEqual(False, issubclass(AbstractChild, Child))
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def test_subclass_tuple(self):
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# test with a tuple as the second argument classes
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self.assertEqual(True, issubclass(Child, (Child,)))
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self.assertEqual(True, issubclass(Child, (Super,)))
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self.assertEqual(False, issubclass(Super, (Child,)))
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self.assertEqual(True, issubclass(Super, (Child, Super)))
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self.assertEqual(False, issubclass(Child, ()))
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self.assertEqual(True, issubclass(Super, (Child, (Super,))))
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self.assertEqual(True, issubclass(int, (int, (float, int))))
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self.assertEqual(True, issubclass(str, (str, (Child, str))))
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def test_subclass_recursion_limit(self):
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# make sure that issubclass raises RecursionError before the C stack is
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# blown
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with support.infinite_recursion():
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self.assertRaises(RecursionError, blowstack, issubclass, str, str)
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def test_isinstance_recursion_limit(self):
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# make sure that issubclass raises RecursionError before the C stack is
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# blown
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with support.infinite_recursion():
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self.assertRaises(RecursionError, blowstack, isinstance, '', str)
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def test_subclass_with_union(self):
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self.assertTrue(issubclass(int, int | float | int))
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self.assertTrue(issubclass(str, str | Child | str))
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self.assertFalse(issubclass(dict, float|str))
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self.assertFalse(issubclass(object, float|str))
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with self.assertRaises(TypeError):
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issubclass(2, Child | Super)
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with self.assertRaises(TypeError):
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issubclass(int, list[int] | Child)
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def test_issubclass_refcount_handling(self):
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# bpo-39382: abstract_issubclass() didn't hold item reference while
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# peeking in the bases tuple, in the single inheritance case.
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class A:
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@property
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def __bases__(self):
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return (int, )
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class B:
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def __init__(self):
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# setting this here increases the chances of exhibiting the bug,
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# probably due to memory layout changes.
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self.x = 1
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@property
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def __bases__(self):
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return (A(), )
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self.assertEqual(True, issubclass(B(), int))
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def test_infinite_recursion_in_bases(self):
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class X:
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@property
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def __bases__(self):
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return self.__bases__
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with support.infinite_recursion():
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self.assertRaises(RecursionError, issubclass, X(), int)
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self.assertRaises(RecursionError, issubclass, int, X())
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self.assertRaises(RecursionError, isinstance, 1, X())
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def test_infinite_recursion_via_bases_tuple(self):
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"""Regression test for bpo-30570."""
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class Failure(object):
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def __getattr__(self, attr):
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return (self, None)
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with support.infinite_recursion():
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with self.assertRaises(RecursionError):
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issubclass(Failure(), int)
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def test_infinite_cycle_in_bases(self):
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"""Regression test for bpo-30570."""
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class X:
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@property
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def __bases__(self):
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return (self, self, self)
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with support.infinite_recursion():
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self.assertRaises(RecursionError, issubclass, X(), int)
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def test_infinitely_many_bases(self):
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"""Regression test for bpo-30570."""
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class X:
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def __getattr__(self, attr):
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self.assertEqual(attr, "__bases__")
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class A:
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pass
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class B:
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pass
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A.__getattr__ = B.__getattr__ = X.__getattr__
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return (A(), B())
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with support.infinite_recursion():
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self.assertRaises(RecursionError, issubclass, X(), int)
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def blowstack(fxn, arg, compare_to):
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# Make sure that calling isinstance with a deeply nested tuple for its
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# argument will raise RecursionError eventually.
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tuple_arg = (compare_to,)
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for cnt in range(sys.getrecursionlimit()+5):
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tuple_arg = (tuple_arg,)
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fxn(arg, tuple_arg)
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if __name__ == '__main__':
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unittest.main()
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