marhsmallow auto generated field using enum.Enum raises error on load

[joaquimvl]

Hi,

When I define SQLAlchemy columns using enum.Enum the auto generated marshmallow field fails validation when I try to load:

import enum
import marshmallow as ma
import sqlalchemy as sa
from marshmallow_sqlalchemy import SQLAlchemyAutoSchema
from sqlalchemy.orm import declarative_base, scoped_session, sessionmaker

engine = sa.create_engine("sqlite:///:memory:")
session = scoped_session(sessionmaker(bind=engine))
Base = declarative_base()

class ColorEnum(str, enum.Enum):
    RED = 1
    GREEN = 2
    BLUE = 3

class Item(Base):
    __tablename__ = 'items'
    id = sa.Column(sa.Integer, primary_key=True)
    color = sa.Column(sa.Enum(ColorEnum))

class ItemSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Item
        load_instance = True

data = {'color': 'RED'}
item = ItemSchema().load(data, session=session) 

This raises marshmallow.exceptions.ValidationError: {'color': ['Must be one of: RED, GREEN, BLUE.']}

If I define a Enum field explicitly on ItemSchema:

color = ma.fields.Enum(ColorEnum)

It loads correctly.

Also works if I define the enum using sa.Enum with strings on Item:

color = sa.Column(sa.Enum("RED", "GREEN", "BLUE"))

After #611, if I understood correctly, I shouldn't need to define the field explicitly, or is there something I'm missing?
Thank you!

[AbdealiLoKo]

From my debugging, it looks like this validator is interfering with the checks that fields.Enum does by default.

And validators are run AFTER deserialization.

So, this is basically doing a validator check for: 1 in {"RED", "GREEN", "BLUE"} when we use sa.Enum(ColorEnum)

[sloria]

i unfortunately don't have time to dig into this in the next few weeks. would definitely appreciate a PR from a kind soul