fixes, but still unsure of things

doc/build/reference/sqlalchemy/event.rst

@@ -0,0 +1,7 @@
+Events
+------
+
+.. automodule:: sqlalchemy.event
+   :members:
+
+

lib/sqlalchemy/event.py

@@ -146,6 +146,9 @@ class Listeners(_ExecEvent):
         return bool(self.listeners or self.parent_listeners)
         
     def append(self, obj, target):
+        # this will be needed, but not 
+        # sure why we don't seem to need it yet
+ #       if obj not in self.listeners:
         self.listeners.append(obj)
 
 class dispatcher(object):

lib/sqlalchemy/orm/attributes.py

@@ -104,9 +104,6 @@ class QueryableAttribute(interfaces.PropComparator):
         self.comparator = comparator
         self.parententity = parententity
 
-    # TODO: this can potentially be moved to AttributeImpl,
-    # have Sphinx document the "events" class directly, implement an 
-    # accept_with() that checks for QueryableAttribute
     class events(event.Events):
         """Events for ORM attributes.
 
@@ -123,6 +120,12 @@ class QueryableAttribute(interfaces.PropComparator):
         
         active_history = False
         
+        # TODO: what to do about subclasses !!
+        # a shared approach will be needed.   listeners can be placed
+        # before subclasses are created.   new attrs on subclasses
+        # can pull them from the superclass attr.  listeners
+        # should be auto-propagated to existing subclasses.
+        
         @classmethod
         def listen(cls, fn, identifier, target, active_history=False):
             if active_history:
@@ -347,7 +350,10 @@ class AttributeImpl(object):
         else:
             self.is_equal = compare_function
         
-        attr = getattr(class_, key)
+        # TODO: pass in the manager here
+        # instead of doing a lookup
+        attr = manager_of_class(class_)[key]
+        
         for ext in util.to_list(extension or []):
             ext._adapt_listener(attr, ext)
             
@@ -356,7 +362,6 @@ class AttributeImpl(object):
             
         self.expire_missing = expire_missing
 
-    
     def hasparent(self, state, optimistic=False):
         """Return the boolean value of a `hasparent` flag attached to 
         the given state.
@@ -1011,6 +1016,14 @@ class ClassManager(dict):
     def mapper(self):
         raise exc.UnmappedClassError(self.class_)
         
+    def _attr_has_impl(self, key):
+        """Return True if the given attribute is fully initialized.
+        
+        i.e. has an impl.
+        """
+        
+        return key in self and self[key].impl is not None
+        
     def _configure_create_arguments(self, 
                             _source=None, 
                             deferred_scalar_loader=None):
@@ -1504,6 +1517,7 @@ def register_attribute_impl(class_, key,
     manager[key].impl = impl
     
     manager.post_configure_attribute(key)
+
     
 def register_descriptor(class_, key, proxy_property=None, comparator=None, 
                                 parententity=None, property_=None, doc=None):

lib/sqlalchemy/orm/interfaces.py

@@ -482,7 +482,7 @@ class MapperProperty(object):
 
     _compile_started = False
     _compile_finished = False
-
+    
     def init(self):
         """Called after all mappers are created to assemble
         relationships between mappers and perform other post-mapper-creation
@@ -647,7 +647,7 @@ class StrategizedProperty(MapperProperty):
     ``StrategizedOption`` objects via the Query.options() method.
     
     """
-
+    
     def _get_context_strategy(self, context, path):
         cls = context.attributes.get(('loaderstrategy',
                 _reduce_path(path)), None)
@@ -683,9 +683,10 @@ class StrategizedProperty(MapperProperty):
         self.strategy = self.__init_strategy(self.strategy_class)
 
     def post_instrument_class(self, mapper):
-        if self.is_primary():
+        if self.is_primary() and \
+            not mapper.class_manager._attr_has_impl(self.key):
             self.strategy.init_class_attribute(mapper)
-
+        
 def build_path(entity, key, prev=None):
     if prev:
         return prev + (entity, key)

lib/sqlalchemy/util.py

@@ -907,7 +907,10 @@ class OrderedSet(set):
 
     def __iter__(self):
         return iter(self._list)
-
+    
+    def __add__(self, other):
+        return self.union(other)
+        
     def __repr__(self):
         return '%s(%r)' % (self.__class__.__name__, self._list)