gh-89519: Remove classmethod descriptor chaining, deprecated since 3.11 (gh-110163)

3 files changed, 19 insertions, 32 deletions

diff --git a/Doc/howto/descriptor.rst b/Doc/howto/descriptor.rst
index 1d9424c..024c1eb 100644
--- a/Doc/howto/descriptor.rst
+++ b/Doc/howto/descriptor.rst
@@ -1141,6 +1141,16 @@ roughly equivalent to:
             obj = self.__self__
             return func(obj, *args, **kwargs)
 
+        def __getattribute__(self, name):
+            "Emulate method_getset() in Objects/classobject.c"
+            if name == '__doc__':
+                return self.__func__.__doc__
+            return object.__getattribute__(self, name)
+
+        def __getattr__(self, name):
+            "Emulate method_getattro() in Objects/classobject.c"
+            return getattr(self.__func__, name)
+
 To support automatic creation of methods, functions include the
 :meth:`__get__` method for binding methods during attribute access.  This
 means that functions are non-data descriptors that return bound methods
@@ -1420,10 +1430,6 @@ Using the non-data descriptor protocol, a pure Python version of
         def __get__(self, obj, cls=None):
             if cls is None:
                 cls = type(obj)
-            if hasattr(type(self.f), '__get__'):
-                # This code path was added in Python 3.9
-                # and was deprecated in Python 3.11.
-                return self.f.__get__(cls, cls)
             return MethodType(self.f, cls)
 
 .. testcode::
@@ -1436,11 +1442,6 @@ Using the non-data descriptor protocol, a pure Python version of
             "Class method that returns a tuple"
             return (cls.__name__, x, y)
 
-        @ClassMethod
-        @property
-        def __doc__(cls):
-            return f'A doc for {cls.__name__!r}'
-
 
 .. doctest::
     :hide:
@@ -1453,10 +1454,6 @@ Using the non-data descriptor protocol, a pure Python version of
     >>> t.cm(11, 22)
     ('T', 11, 22)
 
-    # Check the alternate path for chained descriptors
-    >>> T.__doc__
-    "A doc for 'T'"
-
     # Verify that T uses our emulation
     >>> type(vars(T)['cm']).__name__
     'ClassMethod'
@@ -1481,24 +1478,6 @@ Using the non-data descriptor protocol, a pure Python version of
     ('T', 11, 22)
 
 
-The code path for ``hasattr(type(self.f), '__get__')`` was added in
-Python 3.9 and makes it possible for :func:`classmethod` to support
-chained decorators.  For example, a classmethod and property could be
-chained together.  In Python 3.11, this functionality was deprecated.
-
-.. testcode::
-
-    class G:
-        @classmethod
-        @property
-        def __doc__(cls):
-            return f'A doc for {cls.__name__!r}'
-
-.. doctest::
-
-    >>> G.__doc__
-    "A doc for 'G'"
-
 The :func:`functools.update_wrapper` call in ``ClassMethod`` adds a
 ``__wrapped__`` attribute that refers to the underlying function.  Also
 it carries forward the attributes necessary to make the wrapper look
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index a5f580c..a72f779 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -285,7 +285,7 @@ are always available.  They are listed here in alphabetical order.
       ``__name__``, ``__qualname__``, ``__doc__`` and ``__annotations__``) and
       have a new ``__wrapped__`` attribute.
 
-   .. versionchanged:: 3.11
+   .. deprecated-removed:: 3.11 3.13
       Class methods can no longer wrap other :term:`descriptors <descriptor>` such as
       :func:`property`.
 
diff --git a/Doc/whatsnew/3.13.rst b/Doc/whatsnew/3.13.rst
index 1053aa5..34dd3ea 100644
--- a/Doc/whatsnew/3.13.rst
+++ b/Doc/whatsnew/3.13.rst
@@ -1228,6 +1228,14 @@ Deprecated
 Removed
 -------
 
+* Removed chained :class:`classmethod` descriptors (introduced in
+  :issue:`19072`).  This can no longer be used to wrap other descriptors
+  such as :class:`property`.  The core design of this feature was flawed
+  and caused a number of downstream problems.  To "pass-through" a
+  :class:`classmethod`, consider using the :attr:`!__wrapped__`
+  attribute that was added in Python 3.10.  (Contributed by Raymond
+  Hettinger in :gh:`89519`.)
+
 * Remove many APIs (functions, macros, variables) with names prefixed by
   ``_Py`` or ``_PY`` (considered as private API). If your project is affected
   by one of these removals and you consider that the removed API should remain