[Sqlalchemy-tickets] Issue #3505: join targeting broken for joined-inh-> joined-inh w/ secondary (zzzeek/sqlalchemy)

[Mike B. <iss...@bi...>]

New issue 3505: join targeting broken for joined-inh-> joined-inh w/ secondary
https://bitbucket.org/zzzeek/sqlalchemy/issues/3505/join-targeting-broken-for-joined-inh

Mike Bayer:

unfortunately the patch in #3366 does not resolve

```
#!python

from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import Session, relationship
from sqlalchemy import Column, String, Integer
from sqlalchemy.schema import ForeignKey

Base = declarative_base()


class Object(Base):
    """ Object ORM """
    __tablename__ = 'object'

    type = Column(String(30))
    __mapper_args__ = {
        'polymorphic_identity': 'object',
        'polymorphic_on': type
    }

    id = Column(Integer, primary_key=True)
    name = Column(String(256))


class A(Object):
    __tablename__ = 'a'

    __mapper_args__ = {
        'polymorphic_identity': 'a',
    }

    id = Column(Integer, ForeignKey('object.id'), primary_key=True)

    b_list = relationship(
        'B',
        secondary='a_b_association',
        backref='a_list'
    )


class B(Object):
    __tablename__ = 'b'

    __mapper_args__ = {
        'polymorphic_identity': 'b',
    }

    id = Column(Integer, ForeignKey('object.id'), primary_key=True)


class ABAssociation(Base):
    __tablename__ = 'a_b_association'

    a_id = Column(Integer, ForeignKey('a.id'), primary_key=True)
    b_id = Column(Integer, ForeignKey('b.id'), primary_key=True)


class X(Base):
    __tablename__ = 'x'

    id = Column(Integer, primary_key=True)
    name = Column(String(30))

    obj_id = Column(Integer, ForeignKey('object.id'))
    obj = relationship('Object', backref='x_list')


s = Session()

# works
q = s.query(B).\
    join(B.a_list, 'x_list').filter(X.name == 'x1')

print q


# fails
q = s.query(B).\
    join(B.a_list, A.x_list).filter(X.name == 'x1')

print q

```