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138 lines
4.3 KiB
Python
138 lines
4.3 KiB
Python
# Test the most dynamic corner cases of Python's runtime semantics.
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import builtins
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import unittest
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from test.support import swap_item, swap_attr
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class RebindBuiltinsTests(unittest.TestCase):
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"""Test all the ways that we can change/shadow globals/builtins."""
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def configure_func(self, func, *args):
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"""Perform TestCase-specific configuration on a function before testing.
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By default, this does nothing. Example usage: spinning a function so
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that a JIT will optimize it. Subclasses should override this as needed.
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Args:
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func: function to configure.
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*args: any arguments that should be passed to func, if calling it.
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Returns:
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Nothing. Work will be performed on func in-place.
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"""
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pass
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def test_globals_shadow_builtins(self):
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# Modify globals() to shadow an entry in builtins.
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def foo():
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return len([1, 2, 3])
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self.configure_func(foo)
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self.assertEqual(foo(), 3)
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with swap_item(globals(), "len", lambda x: 7):
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self.assertEqual(foo(), 7)
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def test_modify_builtins(self):
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# Modify the builtins module directly.
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def foo():
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return len([1, 2, 3])
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self.configure_func(foo)
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self.assertEqual(foo(), 3)
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with swap_attr(builtins, "len", lambda x: 7):
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self.assertEqual(foo(), 7)
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def test_modify_builtins_while_generator_active(self):
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# Modify the builtins out from under a live generator.
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def foo():
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x = range(3)
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yield len(x)
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yield len(x)
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self.configure_func(foo)
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g = foo()
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self.assertEqual(next(g), 3)
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with swap_attr(builtins, "len", lambda x: 7):
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self.assertEqual(next(g), 7)
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def test_modify_builtins_from_leaf_function(self):
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# Verify that modifications made by leaf functions percolate up the
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# callstack.
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with swap_attr(builtins, "len", len):
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def bar():
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builtins.len = lambda x: 4
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def foo(modifier):
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l = []
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l.append(len(range(7)))
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modifier()
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l.append(len(range(7)))
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return l
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self.configure_func(foo, lambda: None)
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self.assertEqual(foo(bar), [7, 4])
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def test_cannot_change_globals_or_builtins_with_eval(self):
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def foo():
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return len([1, 2, 3])
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self.configure_func(foo)
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# Note that this *doesn't* change the definition of len() seen by foo().
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builtins_dict = {"len": lambda x: 7}
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globals_dict = {"foo": foo, "__builtins__": builtins_dict,
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"len": lambda x: 8}
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self.assertEqual(eval("foo()", globals_dict), 3)
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self.assertEqual(eval("foo()", {"foo": foo}), 3)
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def test_cannot_change_globals_or_builtins_with_exec(self):
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def foo():
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return len([1, 2, 3])
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self.configure_func(foo)
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globals_dict = {"foo": foo}
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exec("x = foo()", globals_dict)
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self.assertEqual(globals_dict["x"], 3)
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# Note that this *doesn't* change the definition of len() seen by foo().
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builtins_dict = {"len": lambda x: 7}
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globals_dict = {"foo": foo, "__builtins__": builtins_dict,
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"len": lambda x: 8}
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exec("x = foo()", globals_dict)
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self.assertEqual(globals_dict["x"], 3)
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def test_cannot_replace_builtins_dict_while_active(self):
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def foo():
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x = range(3)
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yield len(x)
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yield len(x)
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self.configure_func(foo)
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g = foo()
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self.assertEqual(next(g), 3)
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with swap_item(globals(), "__builtins__", {"len": lambda x: 7}):
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self.assertEqual(next(g), 3)
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def test_cannot_replace_builtins_dict_between_calls(self):
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def foo():
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return len([1, 2, 3])
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self.configure_func(foo)
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self.assertEqual(foo(), 3)
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with swap_item(globals(), "__builtins__", {"len": lambda x: 7}):
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self.assertEqual(foo(), 3)
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def test_eval_gives_lambda_custom_globals(self):
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globals_dict = {"len": lambda x: 7}
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foo = eval("lambda: len([])", globals_dict)
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self.configure_func(foo)
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self.assertEqual(foo(), 7)
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if __name__ == "__main__":
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unittest.main()
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