[Sqlalchemy-tickets] Issue #3240: using an __abstract__ interferes with declarative determining inherits (zzzeek/sqlalchemy)

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

New issue 3240: using an __abstract__ interferes with declarative determining inherits
https://bitbucket.org/zzzeek/sqlalchemy/issue/3240/using-an-__abstract__-interferes-with

Mike Bayer:


```
#!python

from sqlalchemy import Integer, Column, ForeignKey
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class A(Base):
    __tablename__ = 'a'
    id = Column(Integer, primary_key=True)


class AAbs(A):
    __abstract__ = True


class B1(A):
    __tablename__ = 'b1'
    id = Column(ForeignKey('a.id'), primary_key=True)


class B2(AAbs):
    __tablename__ = 'b2'
    id = Column(ForeignKey('a.id'), primary_key=True)


assert B1.__mapper__.inherits is A.__mapper__  # passes

assert B2.__mapper__.inherits is A.__mapper__  # fails

```