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gh-125783: Add tests to prevent regressions with the combination of ctypes and metaclasses. #125881

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merged 5 commits into from
Oct 25, 2024
Merged

gh-125783: Add tests to prevent regressions with the combination of ctypes and metaclasses. #125881

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80deddb
Add a test.
junkmd Oct 24, 2024
cf81f03
Add a test.
junkmd Oct 24, 2024
6903277
Remove the `_` prefix from local names.
junkmd Oct 24, 2024
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junkmd Oct 25, 2024
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junkmd Oct 25, 2024
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78 changes: 78 additions & 0 deletions Lib/test/test_ctypes/test_c_simple_type_meta.py
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Original file line number Diff line number Diff line change
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import unittest
import ctypes
from ctypes import POINTER, c_void_p

from ._support import PyCSimpleType


class PyCSimpleTypeAsMetaclassTest(unittest.TestCase):
def tearDown(self):
# to not leak references, we must clean _pointer_type_cache
ctypes._reset_cache()

def test_early_return_in_dunder_new_1(self):
# Such an implementation is used in `IUnknown` of `comtypes`.

class _ct_meta(type):
def __new__(cls, name, bases, namespace):
self = super().__new__(cls, name, bases, namespace)
if bases == (c_void_p,):
return self
if issubclass(self, _PtrBase):
return self
if bases == (object,):
_ptr_bases = (self, _PtrBase)
else:
_ptr_bases = (self, POINTER(bases[0]))
p = _p_meta(f"POINTER({self.__name__})", _ptr_bases, {})
ctypes._pointer_type_cache[self] = p
return self

class _p_meta(PyCSimpleType, _ct_meta):
pass

class _PtrBase(c_void_p, metaclass=_p_meta):
pass

class _CtBase(object, metaclass=_ct_meta):
pass

class _Sub(_CtBase):
pass

class _Sub2(_Sub):
pass

self.assertIsInstance(POINTER(_Sub2), _p_meta)
self.assertTrue(issubclass(POINTER(_Sub2), _Sub2))
self.assertTrue(issubclass(POINTER(_Sub2), POINTER(_Sub)))
self.assertTrue(issubclass(POINTER(_Sub), POINTER(_CtBase)))

def test_early_return_in_dunder_new_2(self):
# Such an implementation is used in `CoClass` of `comtypes`.
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class _ct_meta(type):
def __new__(cls, name, bases, namespace):
self = super().__new__(cls, name, bases, namespace)
if isinstance(self, _p_meta):
return self
p = _p_meta(
f"POINTER({self.__name__})", (self, c_void_p), {}
)
ctypes._pointer_type_cache[self] = p
return self

class _p_meta(PyCSimpleType, _ct_meta):
pass

class _Core(object):
pass

class _CtBase(_Core, metaclass=_ct_meta):
pass

class _Sub(_CtBase):
pass

self.assertIsInstance(POINTER(_Sub), _p_meta)
self.assertTrue(issubclass(POINTER(_Sub), _Sub))
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