Add change note and tests for omitted owner in proxy descriptor binding

docs/changes.rst

@@ -63,6 +63,18 @@ Version 2.4.2
   attribute of a ``PartialCallableObjectProxy`` which was initialized, but
   with no keyword arguments, continues to be an empty dictionary.
 
+* Calling ``__get__()`` on an ``AutoObjectProxy`` or ``LazyObjectProxy``
+  wrapping a descriptor, with only the ``instance`` argument supplied,
+  failed with a ``TypeError`` as the ``owner`` argument was required. The
+  descriptor protocol makes ``owner`` optional, and builtin descriptors
+  such as functions and ``property`` accept the one argument form, so
+  manual binding through the proxy did not behave the same as manual
+  binding of the wrapped descriptor. The ``owner`` argument now defaults
+  to ``None``, consistent with ``__get__()`` on function wrappers, and
+  ``None`` is what the wrapped descriptor is passed when it is omitted.
+  Normal attribute lookup was not affected as Python always supplies both
+  arguments in that case.
+
 Version 2.4.1
 -------------
 

tests/core/test_auto_object_proxy.py

@@ -187,6 +187,25 @@ def method(instance):
                     proxy.__get__(None, object), descriptor.__get__(None, object)
                 )
 
+    def test_descriptor_optional_owner_required_by_wrapped(self):
+        # A descriptor implemented in Python can require the owner argument,
+        # as Python always supplies it on attribute lookup. When the owner
+        # is omitted in a manual call through the proxy, it is None which
+        # must be passed to the wrapped descriptor.
+
+        class Descriptor:
+            def __get__(self, instance, owner):
+                return (instance, owner)
+
+        instance = object()
+
+        proxy = wrapt.AutoObjectProxy(Descriptor())
+
+        self.assertEqual(proxy.__get__(instance), (instance, None))
+        self.assertEqual(proxy.__get__(instance, None), (instance, None))
+        self.assertEqual(proxy.__get__(instance, object), (instance, object))
+        self.assertEqual(proxy.__get__(None, object), (None, object))
+
     def test_descriptor(self):
         class Descriptor:
             def __init__(self, value):
@@ -409,6 +428,7 @@ def __get__(self, instance, owner):
         self.assertFalse(hasattr(proxy, "__get__"))
         proxy.__wrapped__ = Descriptor()
         self.assertTrue(hasattr(proxy, "__get__"))
+        self.assertEqual(proxy.__get__(object()), 42)
 
     def test_get_removed_on_reassignment(self):
         class Descriptor:

tests/core/test_lazy_object_proxy.py

@@ -42,6 +42,25 @@ def method(instance):
                     proxy.__get__(None, object), descriptor.__get__(None, object)
                 )
 
+    def test_descriptor_optional_owner_required_by_wrapped(self):
+        # A descriptor implemented in Python can require the owner argument,
+        # as Python always supplies it on attribute lookup. When the owner
+        # is omitted in a manual call through the proxy, it is None which
+        # must be passed to the wrapped descriptor.
+
+        class Descriptor:
+            def __get__(self, instance, owner):
+                return (instance, owner)
+
+        instance = object()
+
+        proxy = wrapt.LazyObjectProxy(Descriptor, interface=Descriptor)
+
+        self.assertEqual(proxy.__get__(instance), (instance, None))
+        self.assertEqual(proxy.__get__(instance, None), (instance, None))
+        self.assertEqual(proxy.__get__(instance, object), (instance, object))
+        self.assertEqual(proxy.__get__(None, object), (None, object))
+
     def test_lazy_import(self):
         if "sched" in sys.modules:
             del sys.modules["sched"]