Nextgen Proto Pythonic API: “Add-on” proto for serialize/parse

- add google.protobuf.proto module
- wrap generated SerializeToString and ParseFromString to the new module:

def serialize(message: Message, deterministic: bool=None) -> bytes:
        """Return the serialized proto."""
def parse(message_class: typing.Type[Message], payload: bytes) -> Message:
        """Given a serialized proto, deserialize it into a Message."""

PiperOrigin-RevId: 632223409

python/google/protobuf/internal/proto_test.py

@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+"""Tests Nextgen Pythonic protobuf APIs."""
+
+import unittest
+
+from google.protobuf import proto
+
+from google.protobuf.internal import test_util
+from google.protobuf.internal import testing_refleaks
+from google.protobuf.internal import _parameterized
+from google.protobuf import unittest_pb2
+from google.protobuf import unittest_proto3_arena_pb2
+
+@_parameterized.named_parameters(('_proto2', unittest_pb2),
+                                ('_proto3', unittest_proto3_arena_pb2))
+@testing_refleaks.TestCase
+class ProtoTest(unittest.TestCase):
+
+  def testSerializeParse(self, message_module):
+    msg = message_module.TestAllTypes()
+    test_util.SetAllFields(msg)
+    serialized_data = proto.serialize(msg)
+    parsed_msg = proto.parse(message_module.TestAllTypes, serialized_data)
+    self.assertEqual(msg, parsed_msg)
+
+if __name__ == '__main__':
+  unittest.main()

python/google/protobuf/proto.py

@@ -0,0 +1,39 @@
+# Protocol Buffers - Google's data interchange format
+# Copyright 2008 Google Inc.  All rights reserved.
+#
+# Use of this source code is governed by a BSD-style
+# license that can be found in the LICENSE file or at
+# https://developers.google.com/open-source/licenses/bsd
+
+"""Contains the Nextgen Pythonic protobuf APIs."""
+
+import typing
+
+from google.protobuf.message import Message
+
+def serialize(message: Message, deterministic: bool=None) -> bytes:
+  """Return the serialized proto.
+
+  Args:
+    message: The proto message to be serialized.
+    deterministic: If true, requests deterministic serialization
+        of the protobuf, with predictable ordering of map keys.
+
+  Returns:
+    A binary bytes representation of the message.
+  """
+  return message.SerializeToString(deterministic=deterministic)
+
+def parse(message_class: typing.Type[Message], payload: bytes) -> Message:
+  """Given a serialized data in binary form, deserialize it into a Message.
+
+  Args:
+    message_class: The message meta class.
+    payload: A serialized bytes in binary form.
+
+  Returns:
+    A new message deserialized from payload.
+  """
+  new_message = message_class()
+  new_message.ParseFromString(payload)
+  return new_message