- Fixed bug where using an ``__abstract__`` mixin in the middle

of a declarative inheritance hierarchy would prevent attributes
and configuration being correctly propagated from the base class
to the inheriting class.
fixes #3219 fixes #3240

1 files changed, 21 insertions, 0 deletions

diff --git a/lib/sqlalchemy/ext/declarative/base.py b/lib/sqlalchemy/ext/declarative/base.py
index e35ae085a..7d4020b24 100644
--- a/lib/sqlalchemy/ext/declarative/base.py
+++ b/lib/sqlalchemy/ext/declarative/base.py
@@ -35,6 +35,21 @@ def _declared_mapping_info(cls):
         return None
 
 
+def _resolve_for_abstract(cls):
+    if cls is object:
+        return None
+
+    if _get_immediate_cls_attr(cls, '__abstract__'):
+        for sup in cls.__bases__:
+            sup = _resolve_for_abstract(sup)
+            if sup is not None:
+                return sup
+        else:
+            return None
+    else:
+        return cls
+
+
 def _get_immediate_cls_attr(cls, attrname):
     """return an attribute of the class that is either present directly
     on the class, e.g. not on a superclass, or is from a superclass but
@@ -46,6 +61,9 @@ def _get_immediate_cls_attr(cls, attrname):
     inherit from.
 
     """
+    if not issubclass(cls, object):
+        return None
+
     for base in cls.__mro__:
         _is_declarative_inherits = hasattr(base, '_decl_class_registry')
         if attrname in base.__dict__:
@@ -389,6 +407,9 @@ class _MapperConfig(object):
         table_args = self.table_args
         declared_columns = self.declared_columns
         for c in cls.__bases__:
+            c = _resolve_for_abstract(c)
+            if c is None:
+                continue
             if _declared_mapping_info(c) is not None and \
                     not _get_immediate_cls_attr(
                         c, '_sa_decl_prepare_nocascade'):