Merge "Resolve AliasedClass when determining owning class of association proxy"

3 files changed, 47 insertions, 1 deletions

diff --git a/doc/build/changelog/unreleased_11/4116.rst b/doc/build/changelog/unreleased_11/4116.rst
new file mode 100644
index 000000000..f4cf1f47c
--- /dev/null
+++ b/doc/build/changelog/unreleased_11/4116.rst
@@ -0,0 +1,9 @@
+.. change::
+    :tags: bug, orm, ext
+    :tickets: 4116
+    :versions: 1.2.0b4
+
+    Fixed bug where the association proxy would inadvertently link itself
+    to an :class:`.AliasedClass` object if it were called first with
+    the :class:`.AliasedClass` as a parent, causing errors upon subsequent
+    usage.
\ No newline at end of file
diff --git a/lib/sqlalchemy/ext/associationproxy.py b/lib/sqlalchemy/ext/associationproxy.py
index 16a4f3540..c0dbb538e 100644
--- a/lib/sqlalchemy/ext/associationproxy.py
+++ b/lib/sqlalchemy/ext/associationproxy.py
@@ -19,6 +19,7 @@ import weakref
 from .. import exc, orm, util
 from ..orm import collections, interfaces
 from ..sql import not_, or_
+from .. import inspect
 
 
 def association_proxy(target_collection, attr, **kw):
@@ -245,7 +246,17 @@ class AssociationProxy(interfaces.InspectionAttrInfo):
 
     def __get__(self, obj, class_):
         if self.owning_class is None:
-            self.owning_class = class_ and class_ or type(obj)
+            try:
+                insp = inspect(class_)
+            except exc.NoInspectionAvailable:
+                pass
+            else:
+                if hasattr(insp, 'mapper'):
+                    self.owning_class = insp.mapper.class_
+
+            if self.owning_class is None:
+                self.owning_class = type(obj)
+
         if obj is None:
             return self
 
diff --git a/test/ext/test_associationproxy.py b/test/ext/test_associationproxy.py
index 4653fdf83..28eb7a712 100644
--- a/test/ext/test_associationproxy.py
+++ b/test/ext/test_associationproxy.py
@@ -14,6 +14,7 @@ from sqlalchemy import testing
 from sqlalchemy.testing.schema import Table, Column
 from sqlalchemy.testing.mock import Mock, call
 from sqlalchemy.testing.assertions import expect_warnings
+from sqlalchemy.ext.declarative import declarative_base
 
 
 class DictCollection(dict):
@@ -1847,6 +1848,31 @@ class DictOfTupleUpdateTest(fixtures.TestBase):
         )
 
 
+class AttributeAccessTest(fixtures.TestBase):
+    def test_resolve_aliased_class(self):
+        Base = declarative_base()
+
+        class A(Base):
+            __tablename__ = 'a'
+            id = Column(Integer, primary_key=True)
+            value = Column(String)
+
+        class B(Base):
+            __tablename__ = 'b'
+            id = Column(Integer, primary_key=True)
+            a_id = Column(Integer, ForeignKey(A.id))
+            a = relationship(A)
+            a_value = association_proxy('a', 'value')
+
+        spec = aliased(B).a_value
+
+        is_(spec.owning_class, B)
+
+        spec = B.a_value
+
+        is_(spec.owning_class, B)
+
+
 class InfoTest(fixtures.TestBase):
     def test_constructor(self):
         assoc = association_proxy('a', 'b', info={'some_assoc': 'some_value'})