- merged r4841 from 0.4 branch (enable_typechecks lockdown)

CHANGES

@@ -80,6 +80,12 @@ user_defined_state
 
     - fixed bug preventing merge() from functioning in 
       conjunction with a comparable_property()
+
+    - the enable_typechecks=False setting on relation()
+      now only allows subtypes with inheriting mappers.  
+      Totally unrelated types, or subtypes not set up with
+      mapper inheritance against the target mapper are 
+      still not allowed.
       
 - mysql
     - Added 'CALL' to the list of SQL keywords which return

lib/sqlalchemy/orm/dependency.py

@@ -107,11 +107,12 @@ class DependencyProcessor(object):
         raise NotImplementedError()
 
     def _verify_canload(self, state):
-        if not self.enable_typechecks:
-            return
-        if state is not None and not self.mapper._canload(state):
-            raise exc.FlushError("Attempting to flush an item of type %s on collection '%s', which is handled by mapper '%s' and does not load items of that type.  Did you mean to use a polymorphic mapper for this relationship ?  Set 'enable_typechecks=False' on the relation() to disable this exception.  Mismatched typeloading may cause bi-directional relationships (backrefs) to not function properly." % (state.class_, self.prop, self.mapper))
-
+        if state is not None and not self.mapper._canload(state, allow_subtypes=not self.enable_typechecks):
+            if self.mapper._canload(state, allow_subtypes=True):
+                raise exc.FlushError("Attempting to flush an item of type %s on collection '%s', which is not the expected type %s.  Configure mapper '%s' to load this subtype polymorphically, or set enable_typechecks=False to allow subtypes.  Mismatched typeloading may cause bi-directional relationships (backrefs) to not function properly." % (state.class_, self.prop, self.mapper.class_, self.mapper))
+            else:
+                raise exc.FlushError("Attempting to flush an item of type %s on collection '%s', whose mapper does not inherit from that of %s." % (state.class_, self.prop, self.mapper.class_))
+            
     def _synchronize(self, state, child, associationrow, clearkeys, uowcommit):
         """Called during a flush to synchronize primary key identifier
         values between a parent/child object, as well as to an

lib/sqlalchemy/orm/mapper.py

@@ -826,9 +826,9 @@ class Mapper(object):
 
         return self.base_mapper is other.base_mapper
 
-    def _canload(self, state):
+    def _canload(self, state, allow_subtypes):
         s = self.primary_mapper()
-        if s.polymorphic_on:
+        if self.polymorphic_on or allow_subtypes:
             return _state_mapper(state).isa(s)
         else:
             return _state_mapper(state) is s
@@ -942,7 +942,6 @@ class Mapper(object):
     def _primary_key_from_state(self, state):
         return [self._get_state_attr_by_column(state, column) for column in self.primary_key]
 
-
     def _get_col_to_prop(self, column):
         try:
             return self._columntoproperty[column]