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1# Tests some corner cases with isinstance() and issubclass().  While these
2# tests use new style classes and properties, they actually do whitebox
3# testing of error conditions uncovered when using extension types.
4
5import unittest
6import sys
7
8
9
10class TestIsInstanceExceptions(unittest.TestCase):
11    # Test to make sure that an AttributeError when accessing the instance's
12    # class's bases is masked.  This was actually a bug in Python 2.2 and
13    # 2.2.1 where the exception wasn't caught but it also wasn't being cleared
14    # (leading to an "undetected error" in the debug build).  Set up is,
15    # isinstance(inst, cls) where:
16    #
17    # - cls isn't a type, or a tuple
18    # - cls has a __bases__ attribute
19    # - inst has a __class__ attribute
20    # - inst.__class__ as no __bases__ attribute
21    #
22    # Sounds complicated, I know, but this mimics a situation where an
23    # extension type raises an AttributeError when its __bases__ attribute is
24    # gotten.  In that case, isinstance() should return False.
25    def test_class_has_no_bases(self):
26        class I(object):
27            def getclass(self):
28                # This must return an object that has no __bases__ attribute
29                return None
30            __class__ = property(getclass)
31
32        class C(object):
33            def getbases(self):
34                return ()
35            __bases__ = property(getbases)
36
37        self.assertEqual(False, isinstance(I(), C()))
38
39    # Like above except that inst.__class__.__bases__ raises an exception
40    # other than AttributeError
41    def test_bases_raises_other_than_attribute_error(self):
42        class E(object):
43            def getbases(self):
44                raise RuntimeError
45            __bases__ = property(getbases)
46
47        class I(object):
48            def getclass(self):
49                return E()
50            __class__ = property(getclass)
51
52        class C(object):
53            def getbases(self):
54                return ()
55            __bases__ = property(getbases)
56
57        self.assertRaises(RuntimeError, isinstance, I(), C())
58
59    # Here's a situation where getattr(cls, '__bases__') raises an exception.
60    # If that exception is not AttributeError, it should not get masked
61    def test_dont_mask_non_attribute_error(self):
62        class I: pass
63
64        class C(object):
65            def getbases(self):
66                raise RuntimeError
67            __bases__ = property(getbases)
68
69        self.assertRaises(RuntimeError, isinstance, I(), C())
70
71    # Like above, except that getattr(cls, '__bases__') raises an
72    # AttributeError, which /should/ get masked as a TypeError
73    def test_mask_attribute_error(self):
74        class I: pass
75
76        class C(object):
77            def getbases(self):
78                raise AttributeError
79            __bases__ = property(getbases)
80
81        self.assertRaises(TypeError, isinstance, I(), C())
82
83    # check that we don't mask non AttributeErrors
84    # see: http://bugs.python.org/issue1574217
85    def test_isinstance_dont_mask_non_attribute_error(self):
86        class C(object):
87            def getclass(self):
88                raise RuntimeError
89            __class__ = property(getclass)
90
91        c = C()
92        self.assertRaises(RuntimeError, isinstance, c, bool)
93
94        # test another code path
95        class D: pass
96        self.assertRaises(RuntimeError, isinstance, c, D)
97
98
99# These tests are similar to above, but tickle certain code paths in
100# issubclass() instead of isinstance() -- really PyObject_IsSubclass()
101# vs. PyObject_IsInstance().
102class TestIsSubclassExceptions(unittest.TestCase):
103    def test_dont_mask_non_attribute_error(self):
104        class C(object):
105            def getbases(self):
106                raise RuntimeError
107            __bases__ = property(getbases)
108
109        class S(C): pass
110
111        self.assertRaises(RuntimeError, issubclass, C(), S())
112
113    def test_mask_attribute_error(self):
114        class C(object):
115            def getbases(self):
116                raise AttributeError
117            __bases__ = property(getbases)
118
119        class S(C): pass
120
121        self.assertRaises(TypeError, issubclass, C(), S())
122
123    # Like above, but test the second branch, where the __bases__ of the
124    # second arg (the cls arg) is tested.  This means the first arg must
125    # return a valid __bases__, and it's okay for it to be a normal --
126    # unrelated by inheritance -- class.
127    def test_dont_mask_non_attribute_error_in_cls_arg(self):
128        class B: pass
129
130        class C(object):
131            def getbases(self):
132                raise RuntimeError
133            __bases__ = property(getbases)
134
135        self.assertRaises(RuntimeError, issubclass, B, C())
136
137    def test_mask_attribute_error_in_cls_arg(self):
138        class B: pass
139
140        class C(object):
141            def getbases(self):
142                raise AttributeError
143            __bases__ = property(getbases)
144
145        self.assertRaises(TypeError, issubclass, B, C())
146
147
148
149# meta classes for creating abstract classes and instances
150class AbstractClass(object):
151    def __init__(self, bases):
152        self.bases = bases
153
154    def getbases(self):
155        return self.bases
156    __bases__ = property(getbases)
157
158    def __call__(self):
159        return AbstractInstance(self)
160
161class AbstractInstance(object):
162    def __init__(self, klass):
163        self.klass = klass
164
165    def getclass(self):
166        return self.klass
167    __class__ = property(getclass)
168
169# abstract classes
170AbstractSuper = AbstractClass(bases=())
171
172AbstractChild = AbstractClass(bases=(AbstractSuper,))
173
174# normal classes
175class Super:
176    pass
177
178class Child(Super):
179    pass
180
181class TestIsInstanceIsSubclass(unittest.TestCase):
182    # Tests to ensure that isinstance and issubclass work on abstract
183    # classes and instances.  Before the 2.2 release, TypeErrors were
184    # raised when boolean values should have been returned.  The bug was
185    # triggered by mixing 'normal' classes and instances were with
186    # 'abstract' classes and instances.  This case tries to test all
187    # combinations.
188
189    def test_isinstance_normal(self):
190        # normal instances
191        self.assertEqual(True, isinstance(Super(), Super))
192        self.assertEqual(False, isinstance(Super(), Child))
193        self.assertEqual(False, isinstance(Super(), AbstractSuper))
194        self.assertEqual(False, isinstance(Super(), AbstractChild))
195
196        self.assertEqual(True, isinstance(Child(), Super))
197        self.assertEqual(False, isinstance(Child(), AbstractSuper))
198
199    def test_isinstance_abstract(self):
200        # abstract instances
201        self.assertEqual(True, isinstance(AbstractSuper(), AbstractSuper))
202        self.assertEqual(False, isinstance(AbstractSuper(), AbstractChild))
203        self.assertEqual(False, isinstance(AbstractSuper(), Super))
204        self.assertEqual(False, isinstance(AbstractSuper(), Child))
205
206        self.assertEqual(True, isinstance(AbstractChild(), AbstractChild))
207        self.assertEqual(True, isinstance(AbstractChild(), AbstractSuper))
208        self.assertEqual(False, isinstance(AbstractChild(), Super))
209        self.assertEqual(False, isinstance(AbstractChild(), Child))
210
211    def test_subclass_normal(self):
212        # normal classes
213        self.assertEqual(True, issubclass(Super, Super))
214        self.assertEqual(False, issubclass(Super, AbstractSuper))
215        self.assertEqual(False, issubclass(Super, Child))
216
217        self.assertEqual(True, issubclass(Child, Child))
218        self.assertEqual(True, issubclass(Child, Super))
219        self.assertEqual(False, issubclass(Child, AbstractSuper))
220
221    def test_subclass_abstract(self):
222        # abstract classes
223        self.assertEqual(True, issubclass(AbstractSuper, AbstractSuper))
224        self.assertEqual(False, issubclass(AbstractSuper, AbstractChild))
225        self.assertEqual(False, issubclass(AbstractSuper, Child))
226
227        self.assertEqual(True, issubclass(AbstractChild, AbstractChild))
228        self.assertEqual(True, issubclass(AbstractChild, AbstractSuper))
229        self.assertEqual(False, issubclass(AbstractChild, Super))
230        self.assertEqual(False, issubclass(AbstractChild, Child))
231
232    def test_subclass_tuple(self):
233        # test with a tuple as the second argument classes
234        self.assertEqual(True, issubclass(Child, (Child,)))
235        self.assertEqual(True, issubclass(Child, (Super,)))
236        self.assertEqual(False, issubclass(Super, (Child,)))
237        self.assertEqual(True, issubclass(Super, (Child, Super)))
238        self.assertEqual(False, issubclass(Child, ()))
239        self.assertEqual(True, issubclass(Super, (Child, (Super,))))
240
241        self.assertEqual(True, issubclass(int, (int, (float, int))))
242        self.assertEqual(True, issubclass(str, (str, (Child, str))))
243
244    def test_subclass_recursion_limit(self):
245        # make sure that issubclass raises RecursionError before the C stack is
246        # blown
247        self.assertRaises(RecursionError, blowstack, issubclass, str, str)
248
249    def test_isinstance_recursion_limit(self):
250        # make sure that issubclass raises RecursionError before the C stack is
251        # blown
252        self.assertRaises(RecursionError, blowstack, isinstance, '', str)
253
254def blowstack(fxn, arg, compare_to):
255    # Make sure that calling isinstance with a deeply nested tuple for its
256    # argument will raise RecursionError eventually.
257    tuple_arg = (compare_to,)
258    for cnt in range(sys.getrecursionlimit()+5):
259        tuple_arg = (tuple_arg,)
260        fxn(arg, tuple_arg)
261
262
263if __name__ == '__main__':
264    unittest.main()
265