[Sqlalchemy-tickets] Issue #3778: Mapper property all_orm_descriptors memoized even after new attributes get added (zzzeek/sqlalchemy)

[Konsta V. <iss...@bi...>]

New issue 3778: Mapper property all_orm_descriptors memoized even after new attributes get added
https://bitbucket.org/zzzeek/sqlalchemy/issues/3778/mapper-property-all_orm_descriptors

Konsta Vesterinen:

The following code should outline the issue:


```
#!python

import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base, synonym_for

Base = declarative_base()


class Article(Base):
    __tablename__ = 'article'
    id = sa.Column(sa.Integer, primary_key=True)


Article.__mapper__.all_orm_descriptors

Article.name = sa.Column(sa.String)

Article.__mapper__.all_orm_descriptors.keys()
```

I would expect the last line to return a list containing ``'name'``, but currently it only returns ``['id', '__mapper__']``. Even calling ``sa.orm.configure_mappers()`` won't help here.

I noticed this problem when I had SQLAlchemy mapper configuration listeners that were accessing ``Mapper.all_orm_descriptors``.