- Some refinements to the :class:`.AliasedClass` construct with regards

to descriptors, like hybrids, synonyms, composites, user-defined
descriptors, etc.  The attribute
adaptation which goes on has been made more robust, such that if a descriptor
returns another instrumented attribute, rather than a compound SQL
expression element, the operation will still proceed.
Addtionally, the "adapted" operator will retain its class; previously,
a change in class from ``InstrumentedAttribute`` to ``QueryableAttribute``
(a superclass) would interact with Python's operator system such that
an expression like ``aliased(MyClass.x) > MyClass.x`` would reverse itself
to read ``myclass.x < myclass_1.x``.   The adapted attribute will also
refer to the new :class:`.AliasedClass` as its parent which was not
always the case before. [ticket:2872]

1 files changed, 7 insertions, 1 deletions

diff --git a/lib/sqlalchemy/orm/attributes.py b/lib/sqlalchemy/orm/attributes.py
index 6071b565d..e3c6a3512 100644
--- a/lib/sqlalchemy/orm/attributes.py
+++ b/lib/sqlalchemy/orm/attributes.py
@@ -149,6 +149,12 @@ class QueryableAttribute(interfaces._MappedAttribute,
 
         return self.comparator._query_clause_element()
 
+    def adapt_to_entity(self, adapt_to_entity):
+        assert not self._of_type
+        return self.__class__(adapt_to_entity.entity, self.key, impl=self.impl,
+                           comparator=self.comparator.adapt_to_entity(adapt_to_entity),
+                           parententity=adapt_to_entity)
+
     def of_type(self, cls):
         return QueryableAttribute(
                     self.class_,
@@ -270,7 +276,7 @@ def create_proxied_attribute(descriptor):
             return self._comparator
 
         def adapt_to_entity(self, adapt_to_entity):
-            return self.__class__(self.class_, self.key, self.descriptor,
+            return self.__class__(adapt_to_entity.entity, self.key, self.descriptor,
                                        self._comparator,
                                        adapt_to_entity)