cucumber-messages: Use pure-Ruby protobuf implementation (experimental)

[mvz]

Summary

Replace google-protobuf gem with protobuf, a pure-Ruby implementation that should work on all Ruby platforms.

Details

• Replace google-protobuf dependency with protobuf.
• Use protobuf gem's custom generator.
• Update messages.proto to make the generator emit Cucumber::Messages instead of Io::Cucumber::Messages. This is a bit of a hack. The protobuf gem should use the ruby_package option.

Motivation and Context

JRuby support is lacking in google-protobuf, and the signs are not encouraging that this will get better soon.

How Has This Been Tested?

I ran the specs, and I have backported this change to cucumber-messages 6.0.x and tested it with cucumber 4.0.0.pre.3.

Types of changes

• Bug fix (non-breaking change which fixes an issue).
• New feature (non-breaking change which adds functionality).
• Breaking change (fix or feature that would cause existing functionality to not work as expected).

Checklist:

• The change has been ported to Java.
• The change has been ported to Ruby.
• The change has been ported to JavaScript.
• The change has been ported to Go.
• The change has been ported to .NET.
• I've added tests for my code.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.

Still to do

• Update the Ndjson specs to actually check the generated json instead of just round-tripping.
• Update protobuf to honor the ruby_package option.
• Fix the build on CircleCI.

[aslakhellesoy]

This looks promising! The package states it's protobuf 2.x while the rest of the monorepo uses protobuf 3.x. If the build is green I am fine with this - I think the wire format for 2 and 3 are the same.

[aslakhellesoy]

This bug must be fixed before we can use the native ruby protobuf library: ruby-protobuf/protobuf#408

[aslakhellesoy]

I've submitted a PR to fix the issue in ruby-protobuf: ruby-protobuf/protobuf#408

[aslakhellesoy]

I've also submitted ruby-protobuf/protobuf#411 - another fix that is required

[mvz]

Thanks for working on this, @aslakhellesoy.