Issue #26750: unittest.mock.create_autospec() now works properly

for subclasses of property() and other data descriptors.

Lib/unittest/mock.py

@@ -64,12 +64,20 @@ class _slotted(object):
     __slots__ = ['a']
 
 
+# Do not use this tuple.  It was never documented as a public API.
+# It will be removed.  It has no obvious signs of users on github.
 DescriptorTypes = (
     type(_slotted.a),
     property,
 )
 
 
+def _is_data_descriptor(obj):
+    # Data descriptors are Properties, slots, getsets and C data members.
+    return ((hasattr(obj, '__set__') or hasattr(obj, '__del__')) and
+            hasattr(obj, '__get__'))
+
+
 def _get_signature_object(func, as_instance, eat_self):
     """
     Given an arbitrary, possibly callable object, try to create a suitable
@@ -2130,7 +2138,7 @@ def create_autospec(spec, spec_set=False, instance=False, _parent=None,
     _kwargs.update(kwargs)
 
     Klass = MagicMock
-    if type(spec) in DescriptorTypes:
+    if _is_data_descriptor(spec):
         # descriptors don't have a spec
         # because we don't know what type they return
         _kwargs = {}