[libprotobuf ERROR google/protobuf/message_lite.cc:118] Can't parse message of type "RegisterWatcherResponse" because it is missing required fields: rc

[yihao yang]

I updated a proto file from proto2 to proto3 as follows.

   

Previous proto2:

message RegisterWatcherResponse {
 required int32 rc = 1;
 optional uint64 sendTime = 2;
}

Now proto3:

message RegisterWatcherResponse {
  int32 rc = 1;
  optional uint64 sendTime = 2;
}

I tested compatibility by using old version client with using proto2 RegisterWatcherResponse and receiving responses from a server using proto3 RegisterWatcherResponse.

It turns out clients got failure message like follows:

[libprotobuf ERROR google/protobuf/message_lite.cc:118] Can't parse message of type "RegisterWatcherResponse" because it is missing required fields: rc

I'm sure the server side responses have rc filed.

Can anyone help me why I got this error? Is proto3 compatible with proto2 in this scenario?

What can I do to make it work?

Thanks,

Yihao

[Marc Gravell]

(I'm assumig the "optional" isn't there in the real example)

You can't simply change between proto2 and proto3. In proto3 everything is optional with an implicit zero default. This is fundamentally incompatible with consumers who have a "required" expectation **unless** you happen to never send the value zero. Because whenever your value is zero, it will be omitted and the consumer will complain about a missing required field.

Options:

- update the consumers **first** so that they don't have a "required" expectation

- never send zero in that field

- don't change to proto3

Marc

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