validation issue with Enum column

[bitfusion-brian]

I use the serializer.load() function to validate my data and instantiate the SQLAlchemy object. If I try to set the Enum field as an Integer and load, then it throws:

venv/lib/python2.7/site-packages/marshmallow_sqlalchemy/schema.py:186: in load
    ret = super(ModelSchema, self).load(data, *args, **kwargs)
venv/lib/python2.7/site-packages/marshmallow/schema.py:568: in load
    result, errors = self._do_load(data, many, partial=partial, postprocess=True)
venv/lib/python2.7/site-packages/marshmallow/schema.py:648: in _do_load
    index_errors=self.opts.index_errors,
venv/lib/python2.7/site-packages/marshmallow/marshalling.py:295: in deserialize
    index=(index if index_errors else None)
venv/lib/python2.7/site-packages/marshmallow/marshalling.py:68: in call_and_store
    value = getter_func(data)
venv/lib/python2.7/site-packages/marshmallow/marshalling.py:288: in <lambda>
    data
venv/lib/python2.7/site-packages/marshmallow/fields.py:266: in deserialize
    self._validate(output)
venv/lib/python2.7/site-packages/marshmallow/fields.py:196: in _validate
    r = validator(value)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <Length(min=None, max=9, equal=None, error=None)>, value = 123

    def __call__(self, value):
>       length = len(value)
E       TypeError: object of type 'int' has no len()

I assume this should instead just return the normal error instead of throwing an exception.

Here is my model class. I use the Node.create() method to to the validation/instantiation:

from marshmallow_sqlalchemy import ModelSchema

# SQLAlchemy session provider
from app import db

class Node(db.Model):
  id = db.Column(db.Integer, primary_key=True)
  state = db.Column(db.Enum('allocated', 'free', 'error'), default='free')

  @staticmethod
  def create(data):
    return NodeSerializer.load(data, session=db.session)


class NodeSchema(ModelSchema):
  class Meta:
    model = Node


NodeSerializer = NodeSchema()

Example failing code using above model class

data = {'state': 123}
node, err = Node.create(data) # Raises TypeError

[jonasschalck]

Did you find a solution for this?

[uhnomoli]

I ran into this issue as well. If you want to serialize by name, I used:

import enum

from flask import Flask
from flask_marshmallow import Marshmallow
from flask_sqlalchemy import SQLAlchemy
from marshmallow_sqlalchemy import ModelConverter as _ModelConverter
import sqlalchemy as sa
from sqlalchemy.dialects import mysql

app = Flask(__name__)

db = SQLAlchemy(app)
ma = Marshmallow(app)

class Enum(ma.Field):
    default_error_messages = {
        'invalid_type': 'Invalid type for value.',
        'one_of': 'Must be one of: {choices}.'}

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        self.enum = self.metadata.get('enum', None)

        if not self.enum:
            raise ValueError('Enum type not set.')

        if not issubclass(self.enum, enum.Enum):
            raise TypeError('Invalid type for enum.')

    def _deserialize(self, value, *args, **kwargs):
        return self._validated(value)

    def _serialize(self, value, *args, **kwargs):
        if not isinstance(value, self.enum):
            raise self.make_error('invalid_type')

        return value.name

    def _validate(self, value, *args, **kwargs):
        if not isinstance(value, self.num):
            super()._validate(value, *args, **kwargs)
        else:
            super()._validate(value.name, *args, **kwargs)

    def _validated(self, value):
        if value is None:
            return None

        if isinstance(value, self.enum):
            return value

        try:
            return getattr(self.enum, value)
        except AttributeError:
            choices = ', '.join(value.name for value in self.enum)

            raise self.make_error('one_of', choices=choices)

class ModelConverter(_ModelConverter):
    SQLA_TYPE_MAPPING = dict(
        list(_ModelConverter.SQLA_TYPE_MAPPING.items()) +
        [(sa.Enum, Enum), (mysql.ENUM, Enum)])

class PetType(enum.Enum):
    bird = 1
    cat = 2
    dog = 3

class Pet(db.model):
    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.Enum(PetType), nullable=False)

class PetSchema(ma.SQLAlchemyAutoSchema):
    class Meta:
        model_converter = ModelConverter

    type = ma.auto_field(enum=PetType)

The largest issue was with enum.Enum not being serializable by default, SQLAlchemy serializing by name, and Marshmallow serializing by value. I wanted my enums to serialize by name and ended up with the above. If you want to serialize by value, you'll need to make some modifications.