python 3.9.2 seems to break enumfields

[jadedarko]

After upgrading to python 3.9.2 I am now unable to import from the enumfields package

3.9.2 changed the way subclassing and multiple inheritance works so it might be related?

Python 3.9.2 (default, Feb 20 2021, 20:59:40) 
[GCC 5.4.0 20160609] on linux
Type "help", "copyright", "credits" or "license" for more information.

>>> from enumfields import EnumIntegerField
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/__init__.py", line 1, in <module>
    from .enums import Enum, IntEnum
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/enums.py", line 28, in <module>
    class Enum(EnumMeta('Enum', (BaseEnum,), _EnumDict())):
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/enums.py", line 18, in __new__
    obj = BaseEnumMeta.__new__(mcs, name, bases, attrs)
  File "/usr/lib/python3.9/enum.py", line 212, in __new__
    classdict['__doc__'] = 'An enumeration.'
  File "/usr/lib/python3.9/enum.py", line 97, in __setitem__
    if _is_private(self._cls_name, key):
AttributeError: '_EnumDict' object has no attribute '_cls_name'

>>> from enumfields import EnumField
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/__init__.py", line 1, in <module>
    from .enums import Enum, IntEnum
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/enums.py", line 28, in <module>
    class Enum(EnumMeta('Enum', (BaseEnum,), _EnumDict())):
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/enums.py", line 18, in __new__
    obj = BaseEnumMeta.__new__(mcs, name, bases, attrs)
  File "/usr/lib/python3.9/enum.py", line 212, in __new__
    classdict['__doc__'] = 'An enumeration.'
  File "/usr/lib/python3.9/enum.py", line 97, in __setitem__
    if _is_private(self._cls_name, key):
AttributeError: '_EnumDict' object has no attribute '_cls_name'

>>> import enumfields
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/__init__.py", line 1, in <module>
    from .enums import Enum, IntEnum
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/enums.py", line 28, in <module>
    class Enum(EnumMeta('Enum', (BaseEnum,), _EnumDict())):
  File "/var/www/.venv/lib/python3.9/site-packages/enumfields/enums.py", line 18, in __new__
    obj = BaseEnumMeta.__new__(mcs, name, bases, attrs)
  File "/usr/lib/python3.9/enum.py", line 212, in __new__
    classdict['__doc__'] = 'An enumeration.'
  File "/usr/lib/python3.9/enum.py", line 97, in __setitem__
    if _is_private(self._cls_name, key):
AttributeError: '_EnumDict' object has no attribute '_cls_name'

[jadedarko]

From what I can tell, EnumMeta.__prepare__ doesn't seem to be used to generate the attrs dict enumfields uses

A hack to bypass this is to set attrs._cls_name to cls before invoking __new__, but that's obviously not ideal?

[jadedarko]

ah, that's exactly what django-enumfields does:

hzdg/django-enumfields@8a54ab6

Sorry for the noise, I'll swap to using that package.

[Swamii]

Closing this since it doesn't seem related to our package