Commits

Mike Bayer committed 6c8db1c

- Improved checking for an existing backref name conflict during
mapper configuration; will now test for name conflicts on
superclasses and subclasses, in addition to the current mapper,
as these conflicts break things just as much. This is new for
0.8, but see below for a warning that will also be triggered
in 0.7.11.
- Improved the error message emitted when a "backref loop" is detected,
that is when an attribute event triggers a bidirectional
assignment between two other attributes with no end.
This condition can occur not just when an object of the wrong
type is assigned, but also when an attribute is mis-configured
to backref into an existing backref pair. Also in 0.7.11.
- A warning is emitted when a MapperProperty is assigned to a mapper
that replaces an existing property, if the properties in question
aren't plain column-based properties. Replacement of relationship
properties is rarely (ever?) what is intended and usually refers to a
mapper mis-configuration. Also in 0.7.11.
[ticket:2674]

Comments (0)

Files changed (8)

doc/build/changelog/changelog_07.rst

       Fixed an import of "logging" in test_execute which was not
       working on some linux platforms.
 
+    .. change::
+        :tags: bug, orm
+        :tickets: 2674
+
+      Improved the error message emitted when a "backref loop" is detected,
+      that is when an attribute event triggers a bidirectional
+      assignment between two other attributes with no end.
+      This condition can occur not just when an object of the wrong
+      type is assigned, but also when an attribute is mis-configured
+      to backref into an existing backref pair.
+
+    .. change::
+      :tags: bug, orm
+      :tickets: 2674
+
+      A warning is emitted when a MapperProperty is assigned to a mapper
+      that replaces an existing property, if the properties in question
+      aren't plain column-based properties.   Replacement of relationship
+      properties is rarely (ever?) what is intended and usually refers to a
+      mapper mis-configuration.   This will also warn if a backref configures
+      itself on top of an existing one in an inheritance relationship
+      (which is an error in 0.8).
+
 .. changelog::
     :version: 0.7.10
     :released: Thu Feb 7 2013

doc/build/changelog/changelog_08.rst

       * :ref:`metadata_create_drop_tables`
 
     .. change::
+        :tags: bug, orm
+        :tickets: 2674
+
+      Improved checking for an existing backref name conflict during
+      mapper configuration; will now test for name conflicts on
+      superclasses and subclasses, in addition to the current mapper,
+      as these conflicts break things just as much.  This is new for
+      0.8, but see below for a warning that will also be triggered
+      in 0.7.11.
+
+    .. change::
+        :tags: bug, orm
+        :tickets: 2674
+
+      Improved the error message emitted when a "backref loop" is detected,
+      that is when an attribute event triggers a bidirectional
+      assignment between two other attributes with no end.
+      This condition can occur not just when an object of the wrong
+      type is assigned, but also when an attribute is mis-configured
+      to backref into an existing backref pair.  Also in 0.7.11.
+
+    .. change::
+      :tags: bug, orm
+      :tickets: 2674
+
+      A warning is emitted when a MapperProperty is assigned to a mapper
+      that replaces an existing property, if the properties in question
+      aren't plain column-based properties.   Replacement of relationship
+      properties is rarely (ever?) what is intended and usually refers to a
+      mapper mis-configuration.   Also in 0.7.11.
+
+    .. change::
         :tags: feature, orm
 
       Can set/change the "cascade" attribute on a :func:`.relationship`

lib/sqlalchemy/orm/attributes.py

 
         self.expire_missing = expire_missing
 
+    def __str__(self):
+        return "%s.%s" % (self.class_.__name__, self.key)
+
     def _get_active_history(self):
         """Backwards compat for impl.active_history"""
 
 
     parent_token = attribute.impl.parent_token
 
-    def _acceptable_key_err(child_state, initiator):
+    def _acceptable_key_err(child_state, initiator, child_impl):
         raise ValueError(
-            "Object %s not associated with attribute of "
-            "type %s" % (orm_util.state_str(child_state),
-                    manager_of_class(initiator.class_)[initiator.key]))
+            "Bidirectional attribute conflict detected: "
+            'Passing object %s to attribute "%s" '
+            'triggers a modify event on attribute "%s" '
+            'via the backref "%s".' % (
+                orm_util.state_str(child_state),
+                initiator.parent_token,
+                child_impl.parent_token,
+                attribute.impl.parent_token
+            )
+        )
 
     def emit_backref_from_scalar_set_event(state, child, oldchild, initiator):
         if oldchild is child:
             child_impl = child_state.manager[key].impl
             if initiator.parent_token is not parent_token and \
                 initiator.parent_token is not child_impl.parent_token:
-                _acceptable_key_err(state, initiator)
+                _acceptable_key_err(state, initiator, child_impl)
             child_impl.append(
                                 child_state,
                                 child_dict,
         child_state, child_dict = instance_state(child), \
                                     instance_dict(child)
         child_impl = child_state.manager[key].impl
+
+        print initiator.parent_token, parent_token, child_impl.parent_token
         if initiator.parent_token is not parent_token and \
             initiator.parent_token is not child_impl.parent_token:
-            _acceptable_key_err(state, initiator)
+            _acceptable_key_err(state, initiator, child_impl)
         child_impl.append(
                                 child_state,
                                 child_dict,

lib/sqlalchemy/orm/mapper.py

                 # initialized; check for 'readonly'
                 if hasattr(self, '_readonly_props') and \
                     (not hasattr(col, 'table') or
-                    col.table not in self._cols_by_table):
+                        col.table not in self._cols_by_table):
                         self._readonly_props.add(prop)
 
             else:
                         "%r for column %r" % (syn, key, key, syn)
                     )
 
+        if key in self._props and \
+                not isinstance(prop, properties.ColumnProperty) and \
+                not isinstance(self._props[key], properties.ColumnProperty):
+            util.warn("Property %s on %s being replaced with new "
+                            "property %s; the old property will be discarded" % (
+                            self._props[key],
+                            self,
+                            prop,
+                        ))
+
         self._props[key] = prop
 
         if not self.non_primary:

lib/sqlalchemy/orm/properties.py

                 adapt_source=adapt_source)
 
     def __str__(self):
-        return str(self.parent.class_.__name__) + "." + self.key
+        if self.parent:
+            return str(self.parent.class_.__name__) + "." + self.key
+        else:
+            return "." + self.key
 
     def merge(self,
                     session,
             else:
                 backref_key, kwargs = self.backref
             mapper = self.mapper.primary_mapper()
-            if mapper.has_property(backref_key):
-                raise sa_exc.ArgumentError("Error creating backref "
-                        "'%s' on relationship '%s': property of that "
-                        "name exists on mapper '%s'" % (backref_key,
-                        self, mapper))
+
+            check = set(mapper.iterate_to_root()).\
+                        union(mapper.self_and_descendants)
+            for m in check:
+                if m.has_property(backref_key):
+                    raise sa_exc.ArgumentError("Error creating backref "
+                            "'%s' on relationship '%s': property of that "
+                            "name exists on mapper '%s'" % (backref_key,
+                            self, m))
 
             # determine primaryjoin/secondaryjoin for the
             # backref.  Use the one we had, so that

test/orm/test_attributes.py

         b1 = B()
         assert_raises_message(
             ValueError,
-            "Object <B at .*> not associated with attribute of type C.a",
+            'Bidirectional attribute conflict detected: '
+            'Passing object <B at .*> to attribute "C.a" '
+            'triggers a modify event on attribute "C.b" '
+            'via the backref "B.c".',
             setattr, c1, 'a', b1
         )
 
         b1 = B()
         assert_raises_message(
             ValueError,
-            "Object <B at .*> not associated with attribute of type C.a",
+            'Bidirectional attribute conflict detected: '
+            'Passing object <B at .*> to attribute "C.a" '
+            'triggers a modify event on attribute "C.b" '
+            'via the backref "B.c".',
             c1.a.append, b1
         )
 
+
     def _scalar_fixture(self):
         class A(object):
             pass
 
         return A, B, C
 
+    def _broken_collection_fixture(self):
+        class A(object):
+            pass
+        class B(object):
+            pass
+        instrumentation.register_class(A)
+        instrumentation.register_class(B)
+
+        attributes.register_attribute(A, 'b', backref='a1', useobject=True)
+        attributes.register_attribute(B, 'a1', backref='b', useobject=True,
+                                                uselist=True)
+
+        attributes.register_attribute(B, 'a2', backref='b', useobject=True,
+                                                uselist=True)
+
+        return A, B
+
+    def test_broken_collection_assertion(self):
+        A, B = self._broken_collection_fixture()
+        b1 = B()
+        a1 = A()
+        assert_raises_message(
+            ValueError,
+            'Bidirectional attribute conflict detected: '
+            'Passing object <A at .*> to attribute "B.a2" '
+            'triggers a modify event on attribute "B.a1" '
+            'via the backref "A.b".',
+            b1.a2.append, a1
+        )
+
 class PendingBackrefTest(fixtures.ORMTest):
     def setup(self):
         global Post, Blog, called, lazy_load

test/orm/test_compile.py

         b = Table('b', meta, Column('id', Integer, primary_key=True),
                                 Column('a_id', Integer, ForeignKey('a.id')))
 
-        class A(object):pass
-        class B(object):pass
+        class A(object):
+            pass
+        class B(object):
+            pass
 
         mapper(A, a, properties={
             'b':relationship(B, backref='a')
             configure_mappers
         )
 
+    def test_conflicting_backref_subclass(self):
+        meta = MetaData()
+
+        a = Table('a', meta, Column('id', Integer, primary_key=True))
+        b = Table('b', meta, Column('id', Integer, primary_key=True),
+                                Column('a_id', Integer, ForeignKey('a.id')))
+
+        class A(object):
+            pass
+        class B(object):
+            pass
+        class C(B):
+            pass
+
+        mapper(A, a, properties={
+            'b': relationship(B, backref='a'),
+            'c': relationship(C, backref='a')
+        })
+        mapper(B, b)
+        mapper(C, None, inherits=B)
+
+        assert_raises_message(
+            sa_exc.ArgumentError,
+            "Error creating backref",
+            configure_mappers
+        )

test/orm/test_mapper.py

         assert hasattr(User, 'addresses')
         assert "addresses" in [p.key for p in m1._polymorphic_properties]
 
-    def test_replace_property(self):
+    def test_replace_col_prop_w_syn(self):
         users, User = self.tables.users, self.classes.User
 
         m = mapper(User, users)
         u.name = 'jacko'
         assert m._columntoproperty[users.c.name] is m.get_property('_name')
 
+    def test_replace_rel_prop_with_rel_warns(self):
+        users, User = self.tables.users, self.classes.User
+        addresses, Address = self.tables.addresses, self.classes.Address
+
+        m = mapper(User, users, properties={
+                "addresses": relationship(Address)
+            })
+        mapper(Address, addresses)
+
+        assert_raises_message(
+            sa.exc.SAWarning,
+            "Property User.addresses on Mapper|User|users being replaced "
+            "with new property User.addresses; the old property will "
+            "be discarded",
+            m.add_property,
+            "addresses", relationship(Address)
+        )
+
     def test_add_column_prop_deannotate(self):
         User, users = self.classes.User, self.tables.users
         Address, addresses = self.classes.Address, self.tables.addresses