Changing renderer for ManyToMany field is not possible

[tahajahangir]

For simple fields, we can use Column.info for attaching FA-related metdata to columns. For ManyToOne fields, we can change info for related ForeignKey column. But for ManyToMany fields, there is not a simple way.

Suppose this schema: (simple ManyToMany relation)

class Item(Base):
    __tablename__ = 'items'
    id = Column(Integer, primary_key=True)
    name = Column(Unicode(255))

model_items_table = Table('model_items', Base.metadata,
                          Column('item_id', Integer, ForeignKey(Item.id), primary_key=True),
                          Column('model_id', Integer, ForeignKey('models.id'), primary_key=True))

class MyModel(Base):
    __tablename__ = 'models'
    id = Column(Integer, primary_key=True)
    name = Column(Unicode(255))
    many_to_many = relationship(Item, secondary=model_items_table)

We want to change ManyToMany renderer by adding info={'renderer: ...} keyword argument for a Column, but which Column?

The right Column should be one of columns in intermediate table(model_items), but adding this doesn't work for either of those two columns.

Default implementation of AttributeField.info() only checks info attribute of Item.id which is not sufficient.