[gabetax]

You can implement emptiness with the wrapper message types, e.g. StringValue: https://github.com/protocolbuffers/protobuf/blob/master/src/...

and sometimes defining your own, e.g. nullable lists.

It's not elegant, but it is simple.

[m0zg]

But the point is, proto2 had this feature, and it worked without any hacks.