Got "AttributeError: uselist" when using association proxy and deriving from ConcreteBase

I saw a similar-looking issue here: https://bitbucket.org/zzzeek/sqlalchemy/issues/3397/association-proxy-any-on-o2m-non-object. But that one was resolved, and upon closer inspection the problem seems different. Here's my error:

Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "<string>", line 4, in __init__
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/orm/state.py", line 306, in _initialize_instance
    manager.dispatch.init_failure(self, args, kwargs)
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/util/compat.py", line 184, in reraise
    raise value
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/orm/state.py", line 303, in _initialize_instance
    return manager.original_init(*mixed[1:], **kwargs)
  File "/home/brian/code/pwm/flask-permissions-ex/ex/database.py", line 28, in __init__
    UserMixin.__init__(self, roles)
  File "<string>", line 6, in __init__
  File "/home/brian/code/pwm/flask-permissions/flask_permissions/models.py", line 125, in __init__
    self.roles = [default_role]
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/ext/associationproxy.py", line 272, in __set__
    if self.scalar:
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 754, in __get__
    obj.__dict__[self.__name__] = result = self.fget(obj)
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/ext/associationproxy.py", line 232, in scalar
    scalar = not self._get_property().uselist
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 840, in __getattr__
    return self._fallback_getattr(key)
  File "/home/brian/.virtualenvs/flask-permissions-ex/lib/python3.4/site-packages/sqlalchemy/util/langhelpers.py", line 818, in _fallback_getattr
    raise AttributeError(key)
AttributeError: uselist

And here's the class deriving from ConcreteBase:

class UserMixin(db.Model, ConcreteBase):

    """
    Subclass this for your user class
    """
    __tablename__ = 'fp_user'
    id = db.Column(db.Integer, primary_key=True)
    _roles = db.relationship(
        'Role', secondary=user_role_table, backref='users', uselist=True)
    type = db.Column(db.String(50))

    roles = association_proxy('_roles', 'name', creator=_role_find_or_create)

    __mapper_args__ = {
        'polymorphic_identity': 'usermixin',
        'polymorphic_on': type
        'concrete': True
    }

    def __init__(self, roles=None, default_role='user'):
        # If only a string is passed for roles, convert it to a list containing
        # that string
        if roles and isinstance(roles, basestring):
            roles = [roles]

        # If a sequence is passed for roles (or if roles has been converted to
        # a sequence), fetch the corresponding database objects and make a list
        # of those.
        if roles and is_sequence(roles):
            self.roles = roles
        # Otherwise, assign the default 'user' role. Create that role if it
        # doesn't exist.
        elif default_role:
            self.roles = [default_role]

I tried specifying uselist=True as shown above, and that didn't make a difference.

Comments (6)