> Protocol Buffers implement default zero values (https://developers.google.com/protocol-buffers/docs/proto3#d...) and there's no way of discerning whether something is "false" or "unset", the empty-string or unset, etc.

This was one of the significant changes from proto2 to proto3.

This was also met with much opposition internally, and recently changed as of v3.12 (released last year).

https://github.com/protocolbuffers/protobuf/blob/master/docs...

https://github.com/protocolbuffers/protobuf/releases/tag/v3....