Search through mapper superclass hierarchy for owner

Fixed regression caused by fix for issue :ticket:`4116` affecting versions
1.2.2 as well as 1.1.15, which had the effect of mis-calculation of the
"owning class" of an :class:`.AssociationProxy` as the ``NoneType`` class
in some declarative mixin/inheritance situations as well as if the
association proxy were accessed off of an un-mapped class.  The "figure out
the owner" logic has been replaced by an in-depth routine that searches
through the complete mapper hierarchy assigned to the class or subclass to
determine the correct (we hope) match; will not assign the owner if no
match is found.  An exception is now raised if the proxy is used
against an un-mapped instance.

Change-Id: I611b590df2babe077ce6c19bea89e84251d1a7f4
Fixes: #4185

1 files changed, 35 insertions, 0 deletions

diff --git a/lib/sqlalchemy/orm/instrumentation.py b/lib/sqlalchemy/orm/instrumentation.py
index 5a96c57cf..d5422b0d0 100644
--- a/lib/sqlalchemy/orm/instrumentation.py
+++ b/lib/sqlalchemy/orm/instrumentation.py
@@ -115,6 +115,41 @@ class ClassManager(dict):
         # raises unless self.mapper has been assigned
         raise exc.UnmappedClassError(self.class_)
 
+    def _locate_owning_manager(self, attribute):
+        """Scan through all instrumented classes in our hierarchy
+        searching for the given object as an attribute, and return
+        the bottommost owner.
+
+        E.g.::
+
+            foo = foobar()
+
+            class Parent:
+                attr = foo
+
+            class Child(Parent):
+                pass
+
+        Child.manager._locate_owning_manager(foo) would
+        give us Parent.
+
+        Needed by association proxy to correctly figure out the
+        owning class when the attribute is accessed.
+
+        """
+
+        stack = [None]
+        for supercls in self.class_.__mro__:
+            mgr = manager_of_class(supercls)
+            if not mgr:
+                continue
+            for key in set(supercls.__dict__):
+                val = supercls.__dict__[key]
+                if val is attribute:
+                    stack.append(mgr)
+                    continue
+        return stack[-1]
+
     def _all_sqla_attributes(self, exclude=None):
         """return an iterator of all classbound attributes that are
         implement :class:`.InspectionAttr`.