I've an RPC server with this interface:
syntax = "proto3";import "google/protobuf/descriptor.proto";
import "google/protobuf/empty.proto";
option csharp_namespace = "RpcVersioningClient.Services";
service MachineService {
rpc GetCounters (google.protobuf.Empty) returns (CountersMessage);
}
message CountersMessage {
int32 module_counter = 1;
}
Suppose I have a client with a newer version and it's not possible to
update the server. The client has a new field in CountersMessage:
syntax = "proto3";import "google/protobuf/descriptor.proto";
import "google/protobuf/empty.proto";
option csharp_namespace = "RpcVersioningClient.Services";
service MachineService {
rpc GetCounters (google.protobuf.Empty) returns (CountersMessage);
}
message CountersMessage {
int32 module_counter = 1;
int32 new_module_counter = 2;
}
The field defaults to '0' and since proto3 doesn't allow to specify default
values, I can't use the value to find out if the server supports the field.
By analyzing the generated message class, I found out, that there is a
private field _unknownFields that sounds like the information that I
needed. After all new_module_counter is an known field for the server.
Since the generated message class is partial, I can make a second partial
class with public getter 'UnknownFields'.
public partial class CountersMessage
{
public UnknownFieldSet UnknownFields => return _unknownFields;
}
Unfortunately, the field is null after receiving the contents of the older
server. Does anybody know what is the intention of this field?
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