Support for proto3 syntax

[vanvlack]

I was wondering if this is on the release plan for 1.8.0 or at some point in the future.

With proto3, certain keywords are no longer supported required and implied on each field optional. Currently, wire will fail if a proto3 is inputted into it.

12:52:55 {master} ~/Development/vanvlack/test $ java -jar wire-compiler-1.8.0-SNAPSHOT-jar-with-dependencies.jar --proto_path=. --java_out=out src/main/proto/test.proto --service_writer=com.squareup.wire.SimpleServiceWriter
Exception in thread "main" java.lang.IllegalStateException: Syntax error in ./src/main/proto/test.proto at 13:10: unexpected label: fixed64
    at com.squareup.protoparser.ProtoParser.unexpected(ProtoParser.java:904)
    at com.squareup.protoparser.ProtoParser.readDeclaration(ProtoParser.java:197)
    at com.squareup.protoparser.ProtoParser.readMessage(ProtoParser.java:219)
    at com.squareup.protoparser.ProtoParser.readDeclaration(ProtoParser.java:153)
    at com.squareup.protoparser.ProtoParser.readProtoFile(ProtoParser.java:92)
    at com.squareup.protoparser.ProtoParser.parse(ProtoParser.java:56)
    at com.squareup.wire.IO$FileIO.parse(IO.java:41)
    at com.squareup.wire.WireCompiler.compile(WireCompiler.java:176)
    at com.squareup.wire.WireCompiler.main(WireCompiler.java:98)

syntax = "proto3";

package test;

service ExampleService {
  /* Gets all example data. */
  rpc GetAllExampleData (ExampleRequest) returns (ExampleResponse);
}

message ExampleRequest {}

message ExampleResponse {
  fixed64 id = 1;
  string data = 2;
}

https://developers.google.com/protocol-buffers/docs/proto3#simple

[JakeWharton]

This was tentatively slated for v2 along with some other architectural changes. Work probably won't begin until more into the summer. ProtoParser was already updated with full proto3 syntax support though.

[vanvlack]

@JakeWharton thanks

I'm guessing moving from JavaWriter to JavaPoet is also slated for v2?

[JakeWharton]

Yes. I'm working on releasing 1.8.0 this weekend so we can start this work!

[swankjesse]

Moving this into #279.