Don't store singledispatch in the registry

python · JelleZijlstra · Apr 16, 2022 · Mar 6, 2022 · Mar 7, 2022 · Mar 7, 2022
commit fc6a92579b30aa21e586f0423630b7c233f6804c
diff --git a/Doc/library/functools.rst b/Doc/library/functools.rst
@@ -536,7 +536,7 @@ The :mod:`functools` module defines the following functions:
      The :func:`register` attribute now supports using type annotations.

   .. versionchanged:: 3.11
-      Implementation functions are now registered using :func:`register_variant`.
+      Implementation functions can now be retrieved using :func:`get_variants`.

 .. class:: singledispatchmethod(func)


diff --git a/Lib/functools.py b/Lib/functools.py
@@ -16,7 +16,8 @@

 from abc import get_cache_token
 from collections import namedtuple
-# import types, weakref  # Deferred to single_dispatch()
+import types
+# import weakref  # Deferred to single_dispatch()
 from reprlib import recursive_repr
 from _thread import RLock
 from types import GenericAlias
@@ -670,7 +671,21 @@ def register_variant(func, variant):
 def get_variants(func):
    """Get all function variants for the given function."""
    key = _get_key_for_callable(func)
-    return _variant_registry.get(key, [])
+    variants = list(_variant_registry.get(key, []))
+
+    # We directly retrieve variants from the singledispatch
+    # and singledispatchmethod registries.
+    if isinstance(func, singledispatchmethod):
+        variants += func.dispatcher.registry.values()
+    else:
+        try:
+            registry = func.registry
+        except AttributeError:
+            pass
+        else:
+            if isinstance(registry, types.MappingProxyType):
+                variants += registry.values()
+    return variants


 def clear_variants(func=None):
@@ -852,7 +867,7 @@ def singledispatch(func):
    # There are many programs that use functools without singledispatch, so we
    # trade-off making singledispatch marginally slower for the benefit of
    # making start-up of such applications slightly faster.
-    import types, weakref
+    import weakref

    registry = {}
    dispatch_cache = weakref.WeakKeyDictionary()
@@ -934,11 +949,6 @@ def register(cls, func=None):
                        f"{cls!r} is not a class."
                    )

-        try:
-            register_variant(outer_func, func)
-        except AttributeError:
-            pass
-
        if _is_union_type(cls):
            from typing import get_args