_dependency_processor Attribute Error Bug in orm.dependency with viewonly many to many relationships

[Former user]

It appears that orm.properties.RelationProperty. _post_init does not create a _dependency_processor attribute if the relation is viewonly.

Line1016:

        if not self.viewonly:
            self._dependency_processor = dependency.create_dependency_processor(self)

This causes orm.dependency._check_reverse_action to fail as the attribute does not exist.

The patch I applied is to add attribute existence verification:

Line 142:

        for r in self.prop._reverse_property:
            if hasattr(r, '_dependency_processor') :
                if (r._dependency_processor, action, parent, child) in uowcommit.attributes:
                    return True
        return False

Here's a test case that reproduces the bug:

from sqlalchemy import Table, create_engine, MetaData, Column, Integer, String, ForeignKey
from sqlalchemy.orm import sessionmaker, scoped_session, relation, mapper, backref

engine = create_engine(<engine params>)
metadata = MetaData(bind=engine)
scoped_sess = scoped_session(sessionmaker(autoflush=False))

owner_table = Table('owners', metadata,
                    Column('id', Integer, primary_key=True),
                    Column('name', String(50), nullable=False))

pet_table = Table('pets', metadata,
                  Column('id', Integer, primary_key=True),
                  Column('name', String(50), nullable=False))

owner_to_pet_table = Table('owner_to_pets', metadata,
                           Column('owner_id', Integer, ForeignKey('owners.id')),
                           Column('pet_id', Integer, ForeignKey('pets.id')))


metadata.create_all(engine)

class Pet(object) :
    pass

pet_mapper = mapper(Pet, pet_table)



class Owner(object) :
    pass

owner_mapper = mapper(Owner, owner_table,
                      properties=
                      {
                         'pets':relation(Pet,
                                 secondary=owner_to_pet_table,
                                 primaryjoin=owner_table.c.id == owner_to_pet_table.c.owner_id,
                                 secondaryjoin=owner_to_pet_table.c.pet_id == pet_table.c.id,
                                 backref=backref('owners', viewonly=True))
                      })

session = scoped_sess()


owner = Owner()
owner.id=1
owner.name='George'

pet = Pet()
pet.id=1
pet.name = 'Ruffles'

owner.pets.append(pet)

session.add(owner)
session.flush()

[Mike Bayer]

this is the patch:

Index: lib/sqlalchemy/orm/dependency.py
===================================================================
--- lib/sqlalchemy/orm/dependency.py    (revision 6287)
+++ lib/sqlalchemy/orm/dependency.py    (working copy)
@@ -131,7 +131,7 @@

         """
         raise NotImplementedError()
-
+        
     def _check_reverse_action(self, uowcommit, parent, child, action):
         """Determine if an action has been performed by the 'reverse' property of this property.

@@ -140,7 +140,7 @@

         """
         for r in self.prop._reverse_property:
-            if (r._dependency_processor, action, parent, child) in uowcommit.attributes:
+            if not r.viewonly and (r._dependency_processor, action, parent, child) in uowcommit.attributes:
                 return True
         return False

unit test should go into orm/test_relationships.py or orm/test_manytomany.py.

[Mike Bayer]

31f26e561cc1aeb3475e6e662839b07a60412c36 02059bcde55bc68dfefd345457bfa9c8221a8c93

[Mike Bayer]

Removing milestone: 0.5.6 (automated comment)