[Sqlalchemy-tickets] Issue #3486: Property all_orm_descriptors doesn't contain backref attributes (zzzeek/sqlalchemy)

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

New issue 3486: Property all_orm_descriptors doesn't contain backref attributes
https://bitbucket.org/zzzeek/sqlalchemy/issues/3486/property-all_orm_descriptors-doesnt

Konsta Vesterinen:

I don't know if its desired behaviour but currently the `Mapper.all_orm_descriptors` doesn't contain relationship backref attributes. Atleast I think the docs should clearly state that `all_orm_descriptors` doesn't contain these. Consider the following model definition:

```python
import sqlalchemy as sa

Base = sa.ext.declarative.declarative_base()


group_user = sa.Table(
    'group_user',
    Base.metadata,
    sa.Column('user_id', sa.Integer, sa.ForeignKey('user.id')),
    sa.Column('group_id', sa.Integer, sa.ForeignKey('group.id'))
)

class Group(Base):
    __tablename__ = 'group'
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String)


class User(Base):
    __tablename__ = 'user'
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String)
    groups = sa.orm.relationship(
        'Group',
        secondary=group_user,
        backref='users'
    )
```

```python
User.__mapper__.attrs.keys()
# ['groups', 'id', 'name']
Group.__mapper__.attrs.keys()
# ['users', 'id', 'name']
User.__mapper__.all_orm_descriptors.keys()
# ['groups', 'id', 'name', '__mapper__']

Group.__mapper__.all_orm_descriptors.keys()
# ['id', 'name', '__mapper__'] <- Doesn't contain 'users'
```

I have some situations where I need to inspect all model descriptors. Currently I need to use all_orm_descriptors and combine those with backref relationships of given model.