5 files changed, 18 insertions, 15 deletions
diff --git a/python/google/protobuf/pyext/cpp_message.py b/python/google/protobuf/pyext/cpp_message.py
index b215211e..fc8eb32d 100644
--- a/python/google/protobuf/pyext/cpp_message.py
+++ b/python/google/protobuf/pyext/cpp_message.py
@@ -48,9 +48,9 @@ class GeneratedProtocolMessageType(_message.MessageMeta):
   classes at runtime, as in this example:
 
   mydescriptor = Descriptor(.....)
-  class MyProtoClass(Message):
-    __metaclass__ = GeneratedProtocolMessageType
-    DESCRIPTOR = mydescriptor
+  factory = symbol_database.Default()
+  factory.pool.AddDescriptor(mydescriptor)
+  MyProtoClass = factory.GetPrototype(mydescriptor)
   myproto_instance = MyProtoClass()
   myproto.foo_field = 23
   ...
diff --git a/python/google/protobuf/pyext/map_container.cc b/python/google/protobuf/pyext/map_container.cc
index 90438df1..0987b898 100644
--- a/python/google/protobuf/pyext/map_container.cc
+++ b/python/google/protobuf/pyext/map_container.cc
@@ -348,9 +348,10 @@ PyObject* MapReflectionFriend::Contains(PyObject* _self, PyObject* key) {
 }
 
 // Initializes the underlying Message object of "to" so it becomes a new parent
-// repeated scalar, and copies all the values from "from" to it. A child scalar
+// map container, and copies all the values from "from" to it. A child map
 // container can be released by passing it as both from and to (e.g. making it
 // the recipient of the new parent message and copying the values from itself).
+// In fact, this is the only supported use at the moment.
 static int InitializeAndCopyToParentContainer(MapContainer* from,
                                               MapContainer* to) {
   // For now we require from == to, re-evaluate if we want to support deep copy
diff --git a/python/google/protobuf/pyext/message.cc b/python/google/protobuf/pyext/message.cc
index a9261f20..5535338d 100644
--- a/python/google/protobuf/pyext/message.cc
+++ b/python/google/protobuf/pyext/message.cc
@@ -1041,7 +1041,12 @@ int InternalDeleteRepeatedField(
 }
 
 // Initializes fields of a message. Used in constructors.
-int InitAttributes(CMessage* self, PyObject* kwargs) {
+int InitAttributes(CMessage* self, PyObject* args, PyObject* kwargs) {
+  if (args != NULL && PyTuple_Size(args) != 0) {
+    PyErr_SetString(PyExc_TypeError, "No positional arguments allowed");
+    return -1;
+  }
+
   if (kwargs == NULL) {
     return 0;
   }
@@ -1167,7 +1172,7 @@ int InitAttributes(CMessage* self, PyObject* kwargs) {
       }
       CMessage* cmessage = reinterpret_cast<CMessage*>(message.get());
       if (PyDict_Check(value)) {
-        if (InitAttributes(cmessage, value) < 0) {
+        if (InitAttributes(cmessage, NULL, value) < 0) {
           return -1;
         }
       } else {
@@ -1245,12 +1250,7 @@ static PyObject* New(PyTypeObject* cls,
 // The __init__ method of Message classes.
 // It initializes fields from keywords passed to the constructor.
 static int Init(CMessage* self, PyObject* args, PyObject* kwargs) {
-  if (PyTuple_Size(args) != 0) {
-    PyErr_SetString(PyExc_TypeError, "No positional arguments allowed");
-    return -1;
-  }
-
-  return InitAttributes(self, kwargs);
+  return InitAttributes(self, args, kwargs);
 }
 
 // ---------------------------------------------------------------------
diff --git a/python/google/protobuf/pyext/message.h b/python/google/protobuf/pyext/message.h
index 8b399e05..c44a2ae2 100644
--- a/python/google/protobuf/pyext/message.h
+++ b/python/google/protobuf/pyext/message.h
@@ -237,7 +237,9 @@ PyObject* HasFieldByDescriptor(
 PyObject* HasField(CMessage* self, PyObject* arg);
 
 // Initializes values of fields on a newly constructed message.
-int InitAttributes(CMessage* self, PyObject* kwargs);
+// Note that positional arguments are disallowed: 'args' must be NULL or the
+// empty tuple.
+int InitAttributes(CMessage* self, PyObject* args, PyObject* kwargs);
 
 PyObject* MergeFrom(CMessage* self, PyObject* arg);
 
diff --git a/python/google/protobuf/pyext/repeated_composite_container.cc b/python/google/protobuf/pyext/repeated_composite_container.cc
index 4f339e77..bb2f6db2 100644
--- a/python/google/protobuf/pyext/repeated_composite_container.cc
+++ b/python/google/protobuf/pyext/repeated_composite_container.cc
@@ -146,7 +146,7 @@ static PyObject* AddToAttached(RepeatedCompositeContainer* self,
   cmsg->owner = self->owner;
   cmsg->message = sub_message;
   cmsg->parent = self->parent;
-  if (cmessage::InitAttributes(cmsg, kwargs) < 0) {
+  if (cmessage::InitAttributes(cmsg, args, kwargs) < 0) {
     Py_DECREF(cmsg);
     return NULL;
   }
@@ -166,7 +166,7 @@ static PyObject* AddToReleased(RepeatedCompositeContainer* self,
 
   // Create a new Message detached from the rest.
   PyObject* py_cmsg = PyEval_CallObjectWithKeywords(
-      self->child_message_class->AsPyObject(), NULL, kwargs);
+      self->child_message_class->AsPyObject(), args, kwargs);
   if (py_cmsg == NULL)
     return NULL;