[Sqlalchemy-tickets] Issue #4133: configure_mappers does not refresh all_orm_descriptors (zzzeek/sqlalchemy)

[dima-starosud <iss...@bi...>]

New issue 4133: configure_mappers does not refresh all_orm_descriptors
https://bitbucket.org/zzzeek/sqlalchemy/issues/4133/configure_mappers-does-not-refresh

dima-starosud:

This is using sqlalchemy 1.2.0b3.

I've faced weird behavior shown in following code snippet. Assertion in that test fails. But if you comment either `#1` or `#2` or both it will pass.

```
#!python
        Base = declarative_base()

        class Target(Base):
            __tablename__ = 'target'
            id = Column(Integer, primary_key=True)

        descriptors = lambda: inspect(Target).all_orm_descriptors.keys()

        # these two calls make test fail
        configure_mappers()  #1
        descriptors()        #2

        Target.value = hybrid_property(lambda _: 'Hello!')
        configure_mappers()
        assert 'value' in descriptors()
```

Please let me know if I get it wrong.

Thanks a lot in advance!