Protobuf unnecessarily serializes default values when passed directly about protobuf HOT 2 OPEN

@anandolee can you take a look?

from protobuf.

Replying to myself after a little docs reading session.

It looks this is on purpose, and the "expected semantics" solving the above issue are the "no presence" ones.
Relevant extract:

Presence disciplines define the semantics for translating between the API representation and the serialized representation. The no presence discipline relies upon the field value itself to make decisions at (de)serialization time, while the explicit presence discipline relies upon the explicit tracking state instead.

AFAICT "no presence" works only on proto3, so by modifying my previous example to use proto3 and removing the optional:

syntax = "proto3";

message Person {
  string name = 1;
  int32 id = 2;
  bool alive = 3;
}

Everything works "as expected":

>>> from test_pb2 import Person
>>> str(Person(name='', id=0, alive=False))
''
>>> Person(name='', id=0, alive=False).SerializeToString()
b''
>>> Person() == Person(name='', id=0, alive=False)
True

Unless I missed something else, this can be closed. It would be nice to have some kind of flag to force the "no presence" semantics for proto2 though.

from protobuf.