[Sqlalchemy-tickets] Issue #4350: synonym + single inheritance + mixins (zzzeek/sqlalchemy)

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

New issue 4350: synonym + single inheritance + mixins
https://bitbucket.org/zzzeek/sqlalchemy/issues/4350/synonym-single-inheritance-mixins

Michael Bayer:

this shouldn't seem to need @cascading though it at least works when we do that, but synonyms are inheritable.  if the superclass has the synonym it should be getting mapped or at least warning there's a problem:

```
#!python


from sqlalchemy import *
from sqlalchemy.orm import *
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.ext.declarative import declared_attr


Base = declarative_base()


class A(Base):
    __tablename__ = 'a'

    id = Column(Integer, primary_key=True)
    type = Column(String)
    __mapper_options__ = {
        'polymorphic_on': type
    }
    data = Column(String)


class Mixin:
    @declared_attr
    def data_syn(cls):
        return synonym("data")

    @declared_attr.cascading
    def data_syn_cascading(cls):
        return synonym("data")


class B(Mixin, A):
    __mapper_options__ = {
        'polymorphic_identity': "B"
    }


class C(B):
    __mapper_options__ = {
        'polymorphic_identity': "C"
    }

s = Session()

# yes
print(s.query(B.data).filter(B.data == 'foo'))

# yes
print(s.query(B.data_syn_cascading).filter(B.data_syn_cascading == 'foo'))

# yes
print(s.query(B.data_syn).filter(B.data_syn == 'foo'))


# yes
print(s.query(C.data).filter(C.data == 'foo'))

# yes
print(s.query(C.data_syn_cascading).filter(C.data_syn_cascading == 'foo'))

# no, there's an unmapped C.data_syn property sitting there blocking it
print(s.query(C.data_syn).filter(C.data_syn == 'foo'))
```