summaryrefslogtreecommitdiff
path: root/Lib/test/test_isinstance.py
blob: dc2d07467aa7fa889f142adf8bcf4cd1b1527fe2 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
# 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
from test import support
import sys



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:
    #
    # - cls isn't a a type, or a tuple
    # - 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())

    # check that we don't mask non AttributeErrors
    # see: http://bugs.python.org/issue1574217
    def test_isinstance_dont_mask_non_attribute_error(self):
        class C(object):
            def getclass(self):
                raise RuntimeError
            __class__ = property(getclass)

        c = C()
        self.assertRaises(RuntimeError, isinstance, c, bool)

        # test another code path
        class D: pass
        self.assertRaises(RuntimeError, isinstance, c, D)


# 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

# new-style classes
class NewSuper(object):
    pass

class NewChild(NewSuper):
    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_subclass_tuple(self):
        # test with a tuple as the second argument classes
        self.assertEqual(True, issubclass(Child, (Child,)))
        self.assertEqual(True, issubclass(Child, (Super,)))
        self.assertEqual(False, issubclass(Super, (Child,)))
        self.assertEqual(True, issubclass(Super, (Child, Super)))
        self.assertEqual(False, issubclass(Child, ()))
        self.assertEqual(True, issubclass(Super, (Child, (Super,))))

        self.assertEqual(True, issubclass(NewChild, (NewChild,)))
        self.assertEqual(True, issubclass(NewChild, (NewSuper,)))
        self.assertEqual(False, issubclass(NewSuper, (NewChild,)))
        self.assertEqual(True, issubclass(NewSuper, (NewChild, NewSuper)))
        self.assertEqual(False, issubclass(NewChild, ()))
        self.assertEqual(True, issubclass(NewSuper, (NewChild, (NewSuper,))))

        self.assertEqual(True, issubclass(int, (int, (float, int))))
        self.assertEqual(True, issubclass(str, (str, (Child, NewChild, str))))

    def test_subclass_recursion_limit(self):
        # make sure that issubclass raises RuntimeError before the C stack is
        # blown
        self.assertRaises(RuntimeError, blowstack, issubclass, str, str)

    def test_isinstance_recursion_limit(self):
        # make sure that issubclass raises RuntimeError before the C stack is
        # blown
        self.assertRaises(RuntimeError, blowstack, isinstance, '', str)

def blowstack(fxn, arg, compare_to):
    # Make sure that calling isinstance with a deeply nested tuple for its
    # argument will raise RuntimeError eventually.
    tuple_arg = (compare_to,)
    for cnt in range(sys.getrecursionlimit()+5):
        tuple_arg = (tuple_arg,)
        fxn(arg, tuple_arg)


def test_main():
    support.run_unittest(
        TestIsInstanceExceptions,
        TestIsSubclassExceptions,
        TestIsInstanceIsSubclass
    )


if __name__ == '__main__':
    test_main()