- added standalone "query" class attribute generated

by a scoped_session.  This provides MyClass.query
without using Session.mapper.  Use via:

MyClass.query = Session.query_property()

2 files changed, 30 insertions, 3 deletions

diff --git a/lib/sqlalchemy/orm/mapper.py b/lib/sqlalchemy/orm/mapper.py
index 07075efd0..d9dc70a58 100644
--- a/lib/sqlalchemy/orm/mapper.py
+++ b/lib/sqlalchemy/orm/mapper.py
@@ -1578,7 +1578,7 @@ def object_mapper(object, entity_name=None, raiseerror=True):
             return None
     return mapper
 
-def class_mapper(class_, entity_name=None, compile=True):
+def class_mapper(class_, entity_name=None, compile=True, raiseerror=True):
     """Given a class and optional entity_name, return the primary Mapper associated with the key.
 
     If no mapper can be located, raises ``InvalidRequestError``.
@@ -1587,7 +1587,10 @@ def class_mapper(class_, entity_name=None, compile=True):
     try:
         mapper = class_._class_state.mappers[entity_name]
     except (KeyError, AttributeError):
-        raise exceptions.InvalidRequestError("Class '%s' entity name '%s' has no mapper associated with it" % (class_.__name__, entity_name))
+        if raiseerror:
+            raise exceptions.InvalidRequestError("Class '%s' entity name '%s' has no mapper associated with it" % (class_.__name__, entity_name))
+        else:
+            return None
     if compile:
         return mapper.compile()
     else:
diff --git a/lib/sqlalchemy/orm/scoping.py b/lib/sqlalchemy/orm/scoping.py
index 19cd44884..479b2f737 100644
--- a/lib/sqlalchemy/orm/scoping.py
+++ b/lib/sqlalchemy/orm/scoping.py
@@ -1,5 +1,5 @@
 from sqlalchemy.util import ScopedRegistry, to_list, get_cls_kwargs
-from sqlalchemy.orm import MapperExtension, EXT_CONTINUE, object_session
+from sqlalchemy.orm import MapperExtension, EXT_CONTINUE, object_session, class_mapper
 from sqlalchemy.orm.session import Session
 from sqlalchemy import exceptions
 import types
@@ -69,6 +69,30 @@ class ScopedSession(object):
         
         self.session_factory.configure(**kwargs)
 
+    def query_property(self):
+        """return a class property which produces a `Query` object against the
+        class when called.
+        
+        e.g.::
+            Session = scoped_session(sessionmaker())
+            
+            class MyClass(object):
+                query = Session.query_property()
+                
+            # after mappers are defined
+            result = MyClass.query.filter(MyClass.name=='foo').all()
+        
+        """
+        
+        class query(object):
+            def __get__(s, instance, owner):
+                mapper = class_mapper(owner, raiseerror=False)
+                if mapper:
+                    return self.registry().query(mapper)
+                else:
+                    return None
+        return query()
+        
 def instrument(name):
     def do(self, *args, **kwargs):
         return getattr(self.registry(), name)(*args, **kwargs)