Consult is_attrbute flag to determine descriptor; enable for assoc proxy

Fixed bug where the :attr:`.Mapper.all_orm_descriptors` accessor would
return an entry for the :class:`.Mapper` itself under the declarative
``__mapper___`` key, when this is not a descriptor.  The ``.is_attribute``
flag that's present on all :class:`.InspectionAttr` objects is now
consulted, which has also been modified to be ``True`` for an association
proxy, as it was erroneously set to False for this object.

Fixes: #4729
Change-Id: Ia02388cc25d004e32d337140b62a587f3e5a0b7b

5 files changed, 30 insertions, 3 deletions

diff --git a/doc/build/changelog/unreleased_13/4729.rst b/doc/build/changelog/unreleased_13/4729.rst
new file mode 100644
index 000000000..3fa55b667
--- /dev/null
+++ b/doc/build/changelog/unreleased_13/4729.rst
@@ -0,0 +1,10 @@
+.. change::
+    :tags: bug, orm
+    :tickets: 4729
+
+    Fixed bug where the :attr:`.Mapper.all_orm_descriptors` accessor would
+    return an entry for the :class:`.Mapper` itself under the declarative
+    ``__mapper___`` key, when this is not a descriptor.  The ``.is_attribute``
+    flag that's present on all :class:`.InspectionAttr` objects is now
+    consulted, which has also been modified to be ``True`` for an association
+    proxy, as it was erroneously set to False for this object.
diff --git a/lib/sqlalchemy/ext/associationproxy.py b/lib/sqlalchemy/ext/associationproxy.py
index 9a8294f3c..32dee79c6 100644
--- a/lib/sqlalchemy/ext/associationproxy.py
+++ b/lib/sqlalchemy/ext/associationproxy.py
@@ -93,7 +93,7 @@ ASSOCIATION_PROXY = util.symbol("ASSOCIATION_PROXY")
 class AssociationProxy(interfaces.InspectionAttrInfo):
     """A descriptor that presents a read/write view of an object attribute."""
 
-    is_attribute = False
+    is_attribute = True
     extension_type = ASSOCIATION_PROXY
 
     def __init__(
diff --git a/lib/sqlalchemy/orm/instrumentation.py b/lib/sqlalchemy/orm/instrumentation.py
index 7cf46227f..ee0cc0600 100644
--- a/lib/sqlalchemy/orm/instrumentation.py
+++ b/lib/sqlalchemy/orm/instrumentation.py
@@ -143,7 +143,10 @@ class ClassManager(dict):
             for key in set(supercls.__dict__).difference(exclude):
                 exclude.add(key)
                 val = supercls.__dict__[key]
-                if isinstance(val, interfaces.InspectionAttr):
+                if (
+                    isinstance(val, interfaces.InspectionAttr)
+                    and val.is_attribute
+                ):
                     yield key, val
 
     def _get_class_attr_mro(self, key, default=None):
diff --git a/test/ext/declarative/test_basic.py b/test/ext/declarative/test_basic.py
index b6c911813..935e6f431 100644
--- a/test/ext/declarative/test_basic.py
+++ b/test/ext/declarative/test_basic.py
@@ -1337,6 +1337,15 @@ class DeclarativeTest(DeclarativeTestBase):
 
         eq_(Foo.__mapper__.CHECK, True)
 
+    def test_no_change_to_all_descriptors(self):
+        base = decl.declarative_base()
+
+        class Foo(base):
+            __tablename__ = "foo"
+            id = Column(Integer, primary_key=True)
+
+        eq_(Foo.__mapper__.all_orm_descriptors.keys(), ["id"])
+
     def test_oops(self):
 
         with testing.expect_warnings(
diff --git a/test/orm/test_inspect.py b/test/orm/test_inspect.py
index 48d69b6ed..e99d46672 100644
--- a/test/orm/test_inspect.py
+++ b/test/orm/test_inspect.py
@@ -11,6 +11,7 @@ from sqlalchemy.orm import Session
 from sqlalchemy.orm import synonym
 from sqlalchemy.orm.attributes import instance_state
 from sqlalchemy.orm.attributes import NO_VALUE
+from sqlalchemy.orm.base import InspectionAttr
 from sqlalchemy.orm.util import identity_key
 from sqlalchemy.testing import assert_raises_message
 from sqlalchemy.testing import eq_
@@ -402,9 +403,13 @@ class TestORMInspection(_fixtures.FixtureTest):
         assert "name" in u1.__dict__
 
     def test_attrs_props_prop_added_after_configure(self):
-        class AnonClass(object):
+        class Thing(InspectionAttr):
             pass
 
+        class AnonClass(object):
+            __foo__ = "bar"
+            __bat__ = Thing()
+
         from sqlalchemy.orm import mapper, column_property
         from sqlalchemy.ext.hybrid import hybrid_property