Cannot pickle graphene.Enum

[kazhuravlev]

Environment

Mac OS

$ sw_vers -productVersion 
10.14

$ python -V
Python 3.6.3

$ python -c 'import graphene; print(graphene.__version__)'
2.1.3

Reproduce

import graphene
import pickle

class ExampleEnum(graphene.Enum):
    CAT = 1
    DOG = 2

print(pickle.dumps(ExampleEnum.CAT))

Traceback (most recent call last):
  File "/Users/exanpleuser/scratches/scratch.py", line 9, in <module>
    print(pickle.dumps(ExampleEnum.CAT))
_pickle.PicklingError: Can't pickle <enum 'EnumMeta'>: attribute lookup ExampleEnum on graphene.types.enum failed

Expected

Pickle can perform dumps and loads on graphene.Enum objects

[avivey]

(I think #879 also makes this stuff work)

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[senseysensor]

any fix for this...?

[senseysensor]

Don't have idea why this gets closed and won't be fixed,
however, fix is very small. This can be both fixed in library source code or if create enums using custom metaclass.

from graphene.types.enum import EnumMeta as GrEnumMeta
import graphene.types.enum


class MyMeta(GrEnumMeta):
    def __new__(cls, name_, bases, classdict, **options):
        obj = super().__new__(cls, name_, bases, classdict, **options)
        setattr(graphene.types.enum, name_, obj.__enum__)
        return obj


class MyEnum(GrEnum, metaclass=MyMeta):
    A = 'a'
    B = 1


gr_enum = MyEnum.B
pickled = pickle.dumps(gr_enum)
restored = pickle.loads(pickled)
assert type(gr_enum) is type(restored)
assert gr_enum == restored

[erikwrede]

@senseysensor nice fix, if you send in a PR including tests I can review & test 🙂

[senseysensor]

Sorry, unfortunately that solution above appeared to have some limitations. In order pickle.dumps() works fine with such approach, declared Enum names in runtime must be unique, otherwise pickle fails with another error. It's easy to submit similar fix for library code (my first commit in PR), at least that will resolve part of cases (which in case of our project will be acceptable).