Fix #16832 - expose cache validity checking support in ABCMeta

1 files changed, 17 insertions, 0 deletions

diff --git a/Doc/library/abc.rst b/Doc/library/abc.rst
index 27abb60..1f21b57 100644
--- a/Doc/library/abc.rst
+++ b/Doc/library/abc.rst
@@ -58,6 +58,10 @@ This module provides the following classes:
       .. versionchanged:: 3.3
          Returns the registered subclass, to allow usage as a class decorator.
 
+      .. versionchanged:: 3.4
+         To detect calls to :meth:`register`, you can use the
+         :func:`get_cache_token` function.
+
    You can also override this method in an abstract base class:
 
    .. method:: __subclasshook__(subclass)
@@ -308,6 +312,19 @@ The :mod:`abc` module also provides the following decorators:
        :func:`abstractmethod`, making this decorator redundant.
 
 
+The :mod:`abc` module also provides the following functions:
+
+.. function:: get_cache_token()
+
+   Returns the current abstract base class cache token.
+
+   The token is an opaque integer identifying the current version of the
+   abstract base class cache for virtual subclasses. This number changes
+   with every call to :meth:`ABCMeta.register` on any ABC.
+
+   .. versionadded:: 3.4
+
+
 .. rubric:: Footnotes
 
 .. [#] C++ programmers should note that Python's virtual base class