- basic idea of "session.merge()" actually implemented. needs more testing.

3 files changed, 41 insertions, 22 deletions

diff --git a/lib/sqlalchemy/orm/interfaces.py b/lib/sqlalchemy/orm/interfaces.py
index 0c0ad2a72..4e9fe55f4 100644
--- a/lib/sqlalchemy/orm/interfaces.py
+++ b/lib/sqlalchemy/orm/interfaces.py
@@ -55,7 +55,10 @@ class MapperProperty(object):
         This flag is used to indicate that the MapperProperty can define attribute instrumentation
         for the class at the class level (as opposed to the individual instance level.)"""
         return self.parent._is_primary_mapper()
-
+    def merge(self, session, source, dest):
+        """merges the attribute represented by this MapperProperty from source to destination object"""
+        raise NotImplementedError()
+        
 class StrategizedProperty(MapperProperty):
     """a MapperProperty which uses selectable strategies to affect loading behavior.
     There is a single default strategy selected, and alternate strategies can be selected
diff --git a/lib/sqlalchemy/orm/properties.py b/lib/sqlalchemy/orm/properties.py
index cdab5464a..888ac0442 100644
--- a/lib/sqlalchemy/orm/properties.py
+++ b/lib/sqlalchemy/orm/properties.py
@@ -39,6 +39,8 @@ class SynonymProperty(MapperProperty):
                     return s
                 return getattr(obj, self.name)
         setattr(self.parent.class_, self.key, SynonymProp())
+    def merge(self, session, source, dest):
+        pass
         
 class ColumnProperty(StrategizedProperty):
     """describes an object attribute that corresponds to a table column."""
@@ -60,6 +62,8 @@ class ColumnProperty(StrategizedProperty):
         setattr(object, self.key, value)
     def get_history(self, obj, passive=False):
         return sessionlib.attribute_manager.get_history(obj, self.key, passive=passive)
+    def merge(self, session, source, dest):
+        setattr(dest, self.key, getattr(source, self.key, None))
         
 ColumnProperty.logger = logging.class_logger(ColumnProperty)
         
@@ -118,6 +122,20 @@ class PropertyLoader(StrategizedProperty):
             
     def __str__(self):
         return self.__class__.__name__ + " " + str(self.parent) + "->" + self.key + "->" + str(self.mapper)
+
+    def merge(self, session, source, dest):
+        if not "merge" in self.cascade:
+            return
+        childlist = sessionlib.attribute_manager.get_history(source, self.key, passive=True)
+        if childlist is None:
+            return
+        if self.uselist:
+            # sets a blank list according to the correct list class
+            dest_list = getattr(self.parent.class_, self.key).initialize(dest)
+            for current in list(childlist):
+                dest_list.append(session.merge(current))
+        else:
+            setattr(dest, self.key, session.merge(current))
         
     def cascade_iterator(self, type, object, recursive, halt_on=None):
         if not type in self.cascade:
diff --git a/lib/sqlalchemy/orm/session.py b/lib/sqlalchemy/orm/session.py
index 113341e17..829220688 100644
--- a/lib/sqlalchemy/orm/session.py
+++ b/lib/sqlalchemy/orm/session.py
@@ -324,29 +324,27 @@ class Session(object):
             self.uow.register_deleted(c)
 
     def merge(self, object, entity_name=None):
-        """merge the object into a newly loaded or existing instance from this Session.
+        """copy the state of the given object onto the persistent object with the same identifier. 
         
-        note: this method is currently not completely implemented."""
-        instance = None
-        for obj in [object] + list(_object_mapper(object).cascade_iterator('merge', object)):
-            key = getattr(obj, '_instance_key', None)
-            if key is None:
-                mapper = _object_mapper(object)
-                ident = mapper.identity(object)
-                for k in ident:
-                    if k is None:
-                        raise exceptions.InvalidRequestError("Instance '%s' does not have a full set of identity values, and does not represent a saved entity in the database.  Use the add() method to add unsaved instances to this Session." % repr(obj))
-                key = mapper.identity_key(ident)
-            u = self.uow
-            if u.identity_map.has_key(key):
-                # TODO: copy the state of the given object into this one.  tricky !
-                inst = u.identity_map[key]
+        If there is no persistent instance currently associated with the session, it will be loaded. 
+        Return the persistent instance. If the given instance is unsaved, save a copy of and return it as 
+        a newly persistent instance. The given instance does not become associated with the session. 
+        This operation cascades to associated instances if the association is mapped with cascade="merge".
+        """
+        mapper = _object_mapper(object)
+        key = getattr(object, '_instance_key', None)
+        if key is None:
+            merged = mapper._create_instance(self)
+        else:
+            if key in self.identity_map:
+                merged = self.identity_map[key]
             else:
-                inst = self.get(object.__class__, key[1])
-            if obj is object:
-                instance = inst
-                
-        return instance
+                merged = self.get(mapper.class_, key[1])
+        for prop in mapper.props.values():
+            prop.merge(self, object, merged)
+        if key is None:
+            self.save(merged)
+        return merged
                     
     def _save_impl(self, object, **kwargs):
         if hasattr(object, '_instance_key'):