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gh-93627: Align copy module behaviour with pickle module #109498

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1535893
Align copy module behaviour with pickle module
eendebakpt Sep 16, 2023
30d6b97
📜🤖 Added by blurb_it.
blurb-it[bot] Sep 16, 2023
c97105f
align behaviour of __replace__
eendebakpt Sep 16, 2023
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Merge branch 'pickle_copy' of github.com:eendebakpt/cpython into pick…
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Merge branch 'main' into pickle_copy
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Align copy module behaviour with pickle module
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@eendebakpt
eendebakpt committed Sep 16, 2023
commit 1535893ec9a0f17c52cc86ff77f4875166b46306
30 changes: 16 additions & 14 deletions Lib/copy.py
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Original file line number Diff line number Diff line change
Expand Up @@ -56,6 +56,8 @@ class Error(Exception):
pass
error = Error # backward compatibility

_NoValue = object()

__all__ = ["Error", "copy", "deepcopy"]

def copy(x):
Expand All @@ -74,20 +76,20 @@ def copy(x):
# treat it as a regular class:
return _copy_immutable(x)

copier = getattr(cls, "__copy__", None)
if copier is not None:
copier = getattr(cls, "__copy__", _NoValue)
if copier is not _NoValue:
return copier(x)

reductor = dispatch_table.get(cls)
if reductor is not None:
reductor = dispatch_table.get(cls, _NoValue)
if reductor is not _NoValue:
rv = reductor(x)
else:
reductor = getattr(x, "__reduce_ex__", None)
if reductor is not None:
reductor = getattr(x, "__reduce_ex__", _NoValue)
if reductor is not _NoValue:
rv = reductor(4)
else:
reductor = getattr(x, "__reduce__", None)
if reductor:
reductor = getattr(x, "__reduce__", _NoValue)
if reductor is not _NoValue:
rv = reductor()
else:
raise Error("un(shallow)copyable object of type %s" % cls)
Expand Down Expand Up @@ -138,20 +140,20 @@ def deepcopy(x, memo=None, _nil=[]):
if issubclass(cls, type):
y = _deepcopy_atomic(x, memo)
else:
copier = getattr(x, "__deepcopy__", None)
if copier is not None:
copier = getattr(x, "__deepcopy__", _NoValue)
if copier is not _NoValue:
y = copier(memo)
else:
reductor = dispatch_table.get(cls)
if reductor:
rv = reductor(x)
else:
reductor = getattr(x, "__reduce_ex__", None)
if reductor is not None:
reductor = getattr(x, "__reduce_ex__", _NoValue)
if reductor is not _NoValue:
rv = reductor(4)
else:
reductor = getattr(x, "__reduce__", None)
if reductor:
reductor = getattr(x, "__reduce__", _NoValue)
if reductor is not _NoValue:
rv = reductor()
else:
raise Error(
Expand Down
20 changes: 20 additions & 0 deletions Lib/test/test_copy.py
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Original file line number Diff line number Diff line change
Expand Up @@ -68,6 +68,26 @@ def __reduce__(self):
self.assertIs(y, x)
self.assertEqual(c, [1])

def test_copy_invalid_reduction_methods(self):
class C(object):
__copy__ = None
x = C()
with self.assertRaises(TypeError):
copy.copy(x)

class C(object):
__reduce_ex__ = None
x = C()
with self.assertRaises(TypeError):
copy.copy(x)

class C(object):
__reduce_ex__ = copy._NoValue
__reduce__ = None
x = C()
with self.assertRaises(TypeError):
copy.copy(x)

def test_copy_reduce(self):
class C(object):
def __reduce__(self):
Expand Down