IntFlag Enum - broken after py3.11

提供されたテストを Python 3.11–3.13 で再現し、その後 cloudpickle/cloudpickle.py の 1177 行目付近にある _class_setstate と、traceback に示されている Enum の動作を調査します。IntFlag の値がメンバー再代入エラーなしに cloudpickle を介してラウンドトリップし、既存の Enum の動作が引き続き成功すれば完了です。

Hi!
cloudpickling for IntFlag Enum seems to be broken after python 3.11

cloudpickle version : 3.1.1

Test Code

import enum
import cloudpickle
import pickle
import sys
print(sys.version)

class EnumClass(enum.Enum):
    RANK_0 = 11
    RANK_1 = 37
    RANK_2 = 389


class IntFlagClass(enum.IntFlag):
    RANK_0 = 11
    RANK_1 = 37
    RANK_2 = 389

    
def test(pickler, value):
    print(f"testing {pickler} for {value} ... ", end="")
    
    pickled = pickler.dumps(value)
    unpickled = pickler.loads(pickled)
    assert(unpickled == value)
    
    print(f" success.")

for mod in [pickle, cloudpickle]:
    for val in [EnumClass.RANK_1, IntFlagClass.RANK_1]:
        test(mod, val)

Results for python 3.8 to 3.10, which is fine

3.8.20 (default, Oct  3 2024, 10:22:23)
[Clang 14.0.6 ]
testing <module 'pickle' from '~/test/py3.8/lib/python3.8/pickle.py'> for EnumClass.RANK_1 ...  success.
testing <module 'pickle' from '~/test/py3.8/lib/python3.8/pickle.py'> for 37 ...  success.
testing <module 'cloudpickle' from '~/test/py3.8/lib/python3.8/site-packages/cloudpickle/__init__.py'> for EnumClass.RANK_1 ...  success.
testing <module 'cloudpickle' from '~/test/py3.8/lib/python3.8/site-packages/cloudpickle/__init__.py'> for 37 ...  success.

3.9.21 (main, Dec 11 2024, 10:21:40)
[Clang 14.0.6 ]
testing <module 'pickle' from '~/test/py3.9/lib/python3.9/pickle.py'> for EnumClass.RANK_1 ...  success.
testing <module 'pickle' from '~/test/py3.9/lib/python3.9/pickle.py'> for 37 ...  success.
testing <module 'cloudpickle' from '~/test/py3.9/lib/python3.9/site-packages/cloudpickle/__init__.py'> for EnumClass.RANK_1 ...  success.
testing <module 'cloudpickle' from '~/test/py3.9/lib/python3.9/site-packages/cloudpickle/__init__.py'> for 37 ...  success.

3.10.16 (main, Dec 11 2024, 10:22:29) [Clang 14.0.6 ]
testing <module 'pickle' from '~/test/py3.10/lib/python3.10/pickle.py'> for EnumClass.RANK_1 ...  success.
testing <module 'pickle' from '~/test/py3.10/lib/python3.10/pickle.py'> for 37 ...  success.
testing <module 'cloudpickle' from '~/test/py3.10/lib/python3.10/site-packages/cloudpickle/__init__.py'> for EnumClass.RANK_1 ...  success.
testing <module 'cloudpickle' from '~/test/py3.10/lib/python3.10/site-packages/cloudpickle/__init__.py'> for 37 ...  success.

We get same error for python 3.11 to 3.13

3.11.11 (main, Dec 11 2024, 10:25:04) [Clang 14.0.6 ]
testing <module 'pickle' from '~/test/py3.11/lib/python3.11/pickle.py'> for EnumClass.RANK_1 ...  success.
testing <module 'pickle' from '~/test/py3.11/lib/python3.11/pickle.py'> for 37 ...  success.
testing <module 'cloudpickle' from '~/test/py3.11/lib/python3.11/site-packages/cloudpickle/__init__.py'> for EnumClass.RANK_1 ...  success.
testing <module 'cloudpickle' from '~/test/py3.11/lib/python3.11/site-packages/cloudpickle/__init__.py'> for 37 ... Traceback (most recent call last):
  File "/Users/ekrem/Desktop/work/test/pickle_test.py", line 30, in <module>
    test(mod, val)
  File "/Users/ekrem/Desktop/work/test/pickle_test.py", line 23, in test
    unpickled = pickler.loads(pickled)
                ^^^^^^^^^^^^^^^^^^^^^^
  File "~/test/py3.11/lib/python3.11/site-packages/cloudpickle/cloudpickle.py", line 1177, in _class_setstate
    setattr(obj, attrname, attr)
  File "~/test/py3.11/lib/python3.11/enum.py", line 838, in __setattr__
    raise AttributeError('cannot reassign member %r' % (name, ))
AttributeError: cannot reassign member 'RANK_0'



3.12.9 | packaged by Anaconda, Inc. | (main, Feb  6 2025, 12:55:12) [Clang 14.0.6 ]
testing <module 'pickle' from '~/test/py3.12/lib/python3.12/pickle.py'> for EnumClass.RANK_1 ...  success.
testing <module 'pickle' from '~/test/py3.12/lib/python3.12/pickle.py'> for 37 ...  success.
testing <module 'cloudpickle' from '~/test/py3.12/lib/python3.12/site-packages/cloudpickle/__init__.py'> for EnumClass.RANK_1 ...  success.
testing <module 'cloudpickle' from '~/test/py3.12/lib/python3.12/site-packages/cloudpickle/__init__.py'> for 37 ... Traceback (most recent call last):
  File "/Users/ekrem/Desktop/work/test/pickle_test.py", line 30, in <module>
    test(mod, val)
  File "/Users/ekrem/Desktop/work/test/pickle_test.py", line 23, in test
    unpickled = pickler.loads(pickled)
                ^^^^^^^^^^^^^^^^^^^^^^
  File "~/test/py3.12/lib/python3.12/site-packages/cloudpickle/cloudpickle.py", line 1177, in _class_setstate
    setattr(obj, attrname, attr)
  File "~/test/py3.12/lib/python3.12/enum.py", line 854, in __setattr__
    raise AttributeError('cannot reassign member %r' % (name, ))
AttributeError: cannot reassign member 'RANK_0'



3.13.2 | packaged by Anaconda, Inc. | (main, Feb  6 2025, 12:55:35) [Clang 14.0.6 ]
testing <module 'pickle' from '~/test/py3.13/lib/python3.13/pickle.py'> for EnumClass.RANK_1 ...  success.
testing <module 'pickle' from '~/test/py3.13/lib/python3.13/pickle.py'> for 37 ...  success.
testing <module 'cloudpickle' from '~/test/py3.13/lib/python3.13/site-packages/cloudpickle/__init__.py'> for EnumClass.RANK_1 ...  success.
testing <module 'cloudpickle' from '~/test/py3.13/lib/python3.13/site-packages/cloudpickle/__init__.py'> for 37 ... Traceback (most recent call last):
  File "/Users/ekrem/Desktop/work/test/pickle_test.py", line 30, in <module>
    test(mod, val)
    ~~~~^^^^^^^^^^
  File "/Users/ekrem/Desktop/work/test/pickle_test.py", line 23, in test
    unpickled = pickler.loads(pickled)
  File "~/test/py3.13/lib/python3.13/site-packages/cloudpickle/cloudpickle.py", line 1177, in _class_setstate
    setattr(obj, attrname, attr)
    ~~~~~~~^^^^^^^^^^^^^^^^^^^^^
  File "~/test/py3.13/lib/python3.13/enum.py", line 835, in __setattr__
    raise AttributeError('cannot reassign member %r' % (name, ))
AttributeError: cannot reassign member 'RANK_0'