gh-92810: Automatically add ABC registry entries to cache

Author: dolfinus

Lib/_py_abc.py

@@ -66,7 +66,10 @@ def register(cls, subclass):
         if issubclass(cls, subclass):
             # This would create a cycle, which is bad for the algorithm below
             raise RuntimeError("Refusing to create an inheritance cycle")
+        # Add registry entry
         cls._abc_registry.add(subclass)
+        # Automatically include cache entry
+        cls._abc_cache.add(subclass)
         ABCMeta._abc_invalidation_counter += 1  # Invalidate negative cache
         return subclass
 

Modules/_abc.c

@@ -613,10 +613,16 @@ _abc__abc_register_impl(PyObject *module, PyObject *self, PyObject *subclass)
     if (impl == NULL) {
         return NULL;
     }
+    // Add registry entry
     if (_add_to_weak_set(impl, &impl->_abc_registry, subclass) < 0) {
         Py_DECREF(impl);
         return NULL;
     }
+    // Automatically include cache entry
+    if (_add_to_weak_set(impl, &impl->_abc_cache, subclass) < 0) {
+        Py_DECREF(impl);
+        return NULL;
+    }
     Py_DECREF(impl);
 
     /* Invalidate negative cache */