Raise an exception if no SQLAlchemy session was set

I just inherited from the wrong class, so no session attribute was set. Instead of a clear excetption, the code failed implicitly when the object was tried to be added to the session.

It would be a nice convenience feature to raise a ValueError or similiar.

Proof of concept:

from factory.alchemy import SQLAlchemyModelFactory as Factory
from factory.fuzzy import FuzzyText
from flask.ext.sqlalchemy import SQLAlchemy
from sqlalchemy import (Column, String)

db = SQLAlchemy()


class Traffic(db.Model):
    traffic_id = Column(String(15), nullable=False, index=True, primary_key=True)


class TrafficFactory(Factory):
    class Meta:
        model = Traffic
        # this was missing:
        # session = db.session

    traffic_id = FuzzyText()


if __name__ == '__main__':
    assert TrafficFactory()

Returns:

AttributeError: 'NoneType' object has no attribute 'add'

The place where it fails is alchemy.py:46. Adding if not session: raise ValueError("No session provided") before that line should be sufficient.

[rbarrois]

Just a note here: the session inheritance is handled in factory.base.FactoryOptions.

For this case, it might be simpler to put the check with the SQLAlchemyModelFactory._create code, just before accessing the session.

This ways, you don’t have to worry about the way sessions are passed across the stack, nor handling the abstract=True factories in that chain.

[jeffwidman]

Fixed by #339