summaryrefslogtreecommitdiff
path: root/Lib/test/test_dynamic.py
blob: 3ae090fd66ae25e41c99f1bd435f0afed67d6fa4 (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
# Test the most dynamic corner cases of Python's runtime semantics.

import builtins
import unittest

from test.support import swap_item, swap_attr


class RebindBuiltinsTests(unittest.TestCase):

    """Test all the ways that we can change/shadow globals/builtins."""

    def configure_func(self, func, *args):
        """Perform TestCase-specific configuration on a function before testing.

        By default, this does nothing. Example usage: spinning a function so
        that a JIT will optimize it. Subclasses should override this as needed.

        Args:
            func: function to configure.
            *args: any arguments that should be passed to func, if calling it.

        Returns:
            Nothing. Work will be performed on func in-place.
        """
        pass

    def test_globals_shadow_builtins(self):
        # Modify globals() to shadow an entry in builtins.
        def foo():
            return len([1, 2, 3])
        self.configure_func(foo)

        self.assertEqual(foo(), 3)
        with swap_item(globals(), "len", lambda x: 7):
            self.assertEqual(foo(), 7)

    def test_modify_builtins(self):
        # Modify the builtins module directly.
        def foo():
            return len([1, 2, 3])
        self.configure_func(foo)

        self.assertEqual(foo(), 3)
        with swap_attr(builtins, "len", lambda x: 7):
            self.assertEqual(foo(), 7)

    def test_modify_builtins_while_generator_active(self):
        # Modify the builtins out from under a live generator.
        def foo():
            x = range(3)
            yield len(x)
            yield len(x)
        self.configure_func(foo)

        g = foo()
        self.assertEqual(next(g), 3)
        with swap_attr(builtins, "len", lambda x: 7):
            self.assertEqual(next(g), 7)

    def test_modify_builtins_from_leaf_function(self):
        # Verify that modifications made by leaf functions percolate up the
        # callstack.
        with swap_attr(builtins, "len", len):
            def bar():
                builtins.len = lambda x: 4

            def foo(modifier):
                l = []
                l.append(len(range(7)))
                modifier()
                l.append(len(range(7)))
                return l
            self.configure_func(foo, lambda: None)

            self.assertEqual(foo(bar), [7, 4])

    def test_cannot_change_globals_or_builtins_with_eval(self):
        def foo():
            return len([1, 2, 3])
        self.configure_func(foo)

        # Note that this *doesn't* change the definition of len() seen by foo().
        builtins_dict = {"len": lambda x: 7}
        globals_dict = {"foo": foo, "__builtins__": builtins_dict,
                        "len": lambda x: 8}
        self.assertEqual(eval("foo()", globals_dict), 3)

        self.assertEqual(eval("foo()", {"foo": foo}), 3)

    def test_cannot_change_globals_or_builtins_with_exec(self):
        def foo():
            return len([1, 2, 3])
        self.configure_func(foo)

        globals_dict = {"foo": foo}
        exec("x = foo()", globals_dict)
        self.assertEqual(globals_dict["x"], 3)

        # Note that this *doesn't* change the definition of len() seen by foo().
        builtins_dict = {"len": lambda x: 7}
        globals_dict = {"foo": foo, "__builtins__": builtins_dict,
                        "len": lambda x: 8}

        exec("x = foo()", globals_dict)
        self.assertEqual(globals_dict["x"], 3)

    def test_cannot_replace_builtins_dict_while_active(self):
        def foo():
            x = range(3)
            yield len(x)
            yield len(x)
        self.configure_func(foo)

        g = foo()
        self.assertEqual(next(g), 3)
        with swap_item(globals(), "__builtins__", {"len": lambda x: 7}):
            self.assertEqual(next(g), 3)

    def test_cannot_replace_builtins_dict_between_calls(self):
        def foo():
            return len([1, 2, 3])
        self.configure_func(foo)

        self.assertEqual(foo(), 3)
        with swap_item(globals(), "__builtins__", {"len": lambda x: 7}):
            self.assertEqual(foo(), 3)

    def test_eval_gives_lambda_custom_globals(self):
        globals_dict = {"len": lambda x: 7}
        foo = eval("lambda: len([])", globals_dict)
        self.configure_func(foo)

        self.assertEqual(foo(), 7)


if __name__ == "__main__":
    unittest.main()