Register Scalar/MessageMapContainerTypes as virtual subclasses of

MutableMapping instead of inheriting directly in python cpp extension.

This prevents these from using abc.ABCMeta metaclass to avoid deprecation warning:
DeprecationWarning: Type google.protobuf.internal.cpp._message.MessageMapContainer uses PyType_Spec with a metaclass that has custom tp_new. This is deprecated and will no longer be allowed in Python 3.14.
PiperOrigin-RevId: 734302096

Author: anandolee

python/google/protobuf/pyext/map_container.cc

@@ -9,6 +9,9 @@
 
 #include "google/protobuf/pyext/map_container.h"
 
+#include <Python.h>
+
+#include <cstddef>
 #include <cstdint>
 #include <memory>
 #include <string>
@@ -30,7 +33,7 @@ namespace python {
 class MapReflectionFriend {
  public:
   // Methods that are in common between the map types.
-  static PyObject* Contains(PyObject* _self, PyObject* key);
+  static int Contains(PyObject* _self, PyObject* key);
   static Py_ssize_t Length(PyObject* _self);
   static PyObject* GetIterator(PyObject* _self);
   static PyObject* IterNext(PyObject* _self);
@@ -328,7 +331,7 @@ PyObject* MapReflectionFriend::MergeFrom(PyObject* _self, PyObject* arg) {
   Py_RETURN_NONE;
 }
 
-PyObject* MapReflectionFriend::Contains(PyObject* _self, PyObject* key) {
+int MapReflectionFriend::Contains(PyObject* _self, PyObject* key) {
   MapContainer* self = GetMap(_self);
 
   const Message* message = self->parent->message;
@@ -337,14 +340,14 @@ PyObject* MapReflectionFriend::Contains(PyObject* _self, PyObject* key) {
   MapKey map_key;
 
   if (!PythonToMapKey(self, key, &map_key, &map_key_string)) {
-    return nullptr;
+    return -1;
   }
 
   if (reflection->ContainsMapKey(*message, self->parent_field_descriptor,
                                  map_key)) {
-    Py_RETURN_TRUE;
+    return 1;
   } else {
-    Py_RETURN_FALSE;
+    return 0;
   }
 }
 
@@ -450,11 +453,11 @@ static PyObject* ScalarMapSetdefault(PyObject* self, PyObject* args) {
     return nullptr;
   }
 
-  ScopedPyObjectPtr is_present(MapReflectionFriend::Contains(self, key));
-  if (is_present == nullptr) {
+  int is_present = MapReflectionFriend::Contains(self, key);
+  if (is_present < 0) {
     return nullptr;
   }
-  if (PyObject_IsTrue(is_present.get())) {
+  if (is_present) {
     return MapReflectionFriend::ScalarMapGetItem(self, key);
   }
 
@@ -476,12 +479,12 @@ static PyObject* ScalarMapGet(PyObject* self, PyObject* args,
     return nullptr;
   }
 
-  ScopedPyObjectPtr is_present(MapReflectionFriend::Contains(self, key));
-  if (is_present.get() == nullptr) {
+  int is_present = MapReflectionFriend::Contains(self, key);
+  if (is_present < 0) {
     return nullptr;
   }
 
-  if (PyObject_IsTrue(is_present.get())) {
+  if (is_present) {
     return MapReflectionFriend::ScalarMapGetItem(self, key);
   } else {
     if (default_value != nullptr) {
@@ -534,8 +537,6 @@ static void ScalarMapDealloc(PyObject* _self) {
 }
 
 static PyMethodDef ScalarMapMethods[] = {
-    {"__contains__", MapReflectionFriend::Contains, METH_O,
-     "Tests whether a key is a member of the map."},
     {"clear", (PyCFunction)Clear, METH_NOARGS,
      "Removes all elements from the map."},
     {"setdefault", (PyCFunction)ScalarMapSetdefault, METH_VARARGS,
@@ -561,6 +562,7 @@ static PyType_Slot ScalarMapContainer_Type_slots[] = {
     {Py_mp_length, (void*)MapReflectionFriend::Length},
     {Py_mp_subscript, (void*)MapReflectionFriend::ScalarMapGetItem},
     {Py_mp_ass_subscript, (void*)MapReflectionFriend::ScalarMapSetItem},
+    {Py_sq_contains, (void*)MapReflectionFriend::Contains},
     {Py_tp_methods, (void*)ScalarMapMethods},
     {Py_tp_iter, (void*)MapReflectionFriend::GetIterator},
     {Py_tp_repr, (void*)MapReflectionFriend::ScalarMapToStr},
@@ -727,12 +729,12 @@ PyObject* MessageMapGet(PyObject* self, PyObject* args, PyObject* kwargs) {
     return nullptr;
   }
 
-  ScopedPyObjectPtr is_present(MapReflectionFriend::Contains(self, key));
-  if (is_present.get() == nullptr) {
+  int is_present = MapReflectionFriend::Contains(self, key);
+  if (is_present < 0) {
     return nullptr;
   }
 
-  if (PyObject_IsTrue(is_present.get())) {
+  if (is_present) {
     return MapReflectionFriend::MessageMapGetItem(self, key);
   } else {
     if (default_value != nullptr) {
@@ -757,8 +759,6 @@ static void MessageMapDealloc(PyObject* _self) {
 }
 
 static PyMethodDef MessageMapMethods[] = {
-    {"__contains__", (PyCFunction)MapReflectionFriend::Contains, METH_O,
-     "Tests whether the map contains this element."},
     {"clear", (PyCFunction)Clear, METH_NOARGS,
      "Removes all elements from the map."},
     {"setdefault", (PyCFunction)MessageMapSetdefault, METH_VARARGS,
@@ -786,6 +786,7 @@ static PyType_Slot MessageMapContainer_Type_slots[] = {
     {Py_mp_length, (void*)MapReflectionFriend::Length},
     {Py_mp_subscript, (void*)MapReflectionFriend::MessageMapGetItem},
     {Py_mp_ass_subscript, (void*)MapReflectionFriend::MessageMapSetItem},
+    {Py_sq_contains, (void*)MapReflectionFriend::Contains},
     {Py_tp_methods, (void*)MessageMapMethods},
     {Py_tp_iter, (void*)MapReflectionFriend::GetIterator},
     {Py_tp_repr, (void*)MapReflectionFriend::MessageMapToStr},
@@ -910,6 +911,30 @@ PyTypeObject MapIterator_Type = {
     nullptr,                        //  tp_init
 };
 
+PyTypeObject* Py_AddClassWithRegister(PyType_Spec* spec, PyObject* virtual_base,
+                                      const char** methods) {
+  PyObject* type = PyType_FromSpec(spec);
+  PyObject* ret1 = PyObject_CallMethod(virtual_base, "register", "O", type);
+  if (!ret1) {
+    Py_XDECREF(type);
+    return nullptr;
+  }
+  for (size_t i = 0; methods[i] != nullptr; i++) {
+    PyObject* method = PyObject_GetAttrString(virtual_base, methods[i]);
+    if (!method) {
+      Py_XDECREF(type);
+      return nullptr;
+    }
+    int ret2 = PyObject_SetAttrString(type, methods[i], method);
+    if (ret2 < 0) {
+      Py_XDECREF(type);
+      return nullptr;
+    }
+  }
+
+  return (PyTypeObject*)type;
+}
+
 bool InitMapContainers() {
   // ScalarMapContainer_Type derives from our MutableMapping type.
   ScopedPyObjectPtr abc(PyImport_ImportModule("collections.abc"));
@@ -923,21 +948,20 @@ bool InitMapContainers() {
     return false;
   }
 
-  Py_INCREF(mutable_mapping.get());
-  ScopedPyObjectPtr bases(PyTuple_Pack(1, mutable_mapping.get()));
-  if (bases == nullptr) {
-    return false;
-  }
+  const char* methods[] = {"keys", "items",   "values", "__eq__", "__ne__",
+                           "pop",  "popitem", "update", nullptr};
 
-  ScalarMapContainer_Type = reinterpret_cast<PyTypeObject*>(
-      PyType_FromSpecWithBases(&ScalarMapContainer_Type_spec, bases.get()));
+  ScalarMapContainer_Type =
+      reinterpret_cast<PyTypeObject*>(Py_AddClassWithRegister(
+          &ScalarMapContainer_Type_spec, mutable_mapping.get(), methods));
 
   if (PyType_Ready(&MapIterator_Type) < 0) {
     return false;
   }
 
-  MessageMapContainer_Type = reinterpret_cast<PyTypeObject*>(
-      PyType_FromSpecWithBases(&MessageMapContainer_Type_spec, bases.get()));
+  MessageMapContainer_Type =
+      reinterpret_cast<PyTypeObject*>(Py_AddClassWithRegister(
+          &MessageMapContainer_Type_spec, mutable_mapping.get(), methods));
   return true;
 }