Default value change contadicts proto3 spec

[staticgears]

Version of protoc (protoc --version)

3.3.2

Version of ProtocolBuffers.framework

3.0.22

.proto file to reproduce

syntax = "proto3";
package protocol;

message Example {
  uint64 user_id         = 1;
}

Description

This is in the same spirit as #142 however this time it is a much more significant breaking change
Related to commit 20db367

The generated code has changed so that primitives no longer default to the "appropriate zero", but now are force unwrapped optionals. This behaviour does not play well with other protobuf implementations which do not send values which match the default. It also differs from Google's proto3 specification.

Here is the specification for proto3 default values:
https://developers.google.com/protocol-buffers/docs/proto3#default

The impact of this change is that when serializing this object in java (with the value 0) and then deserializing it in swift will result in a nil NOT the desired 0. The painful way to get the old behaviour is to change all instances of:

let myVal = proto.userId
to
let myVal = proto.userId ?? 0

I also tried this was a work around without success:

uint64 user_id = 1 [default = 0];
Issue.proto: Explicit default values are not allowed in proto3.

[shinma]

I'm also interested in fixing this issue.