I had the same need, and got the same error. I do not believe this is possible. Here is the relevant BNF definitions from the language specification. https://developers.google.com/protocol-buffers/docs/reference/proto3-spec messageType = [ “.” ] { ident “.” } messageName mapField = “map” “<” keyType “,” type “>” mapName “=” fieldNumber [ “[“fieldOptions “]” ] “;” type … Read more
Protocol Buffers does not support inheritance. Instead, consider using composition: message Foo { Bar bar = 1; string id = 2; } However, that said, there is a trick you can use which is like inheritance — but which is an ugly hack, so you should only use it with care. If you define your … Read more
Since protobuf release 3.15, proto3 supports using the optional keyword (just as in proto2) to give a scalar field presence information. syntax = “proto3”; message Foo { int32 bar = 1; optional int32 baz = 2; } A has_baz()/hasBaz() method is generated for the optional field above, just as it was in proto2. Under the … Read more