JSON transcoding has backwards incompatible change in 1.27.0, due to json_name field always populated by protoc

[C0mbatwombat]

Hi,

In #5193 functionality was added so that if a user sets the json_name field in the .proto file explicitly, it is used to resolve the path & query params when doing transcoding. This makes perfect sense, if it weren't for a bug in protoc: the proto compiler always populates the json_name field since 3.1.0.

This means that to retain our existing behaviour (using the original field which might contain underscores) we have to add json_name = <field_name> to all our proto definitions.

The Protobuf code base also acknowledges it as a bug and has a workaround to deal with it.

I suppose Armeria needs to use the same workaround as the protobuf codebase: if the json_name that is set is the same as the default calculated one, assume it was not set explicitly by the user.

Thanks!

[mbgit2]

Any update on this? I'm currently stuck on 1.26.4 due to this.

[ikhoon]

I suppose Armeria needs to use the same workaround as the protobuf codebase: if the json_name that is set is the same as the default calculated one, assume it was not set explicitly by the user.

It makes sense. We may provide a new option to ignore json_name. Let us handle it in the next version.

[ikhoon]

I've compiled a proto file with protoc 3.25.1 and json_name was empty if it is not set.

armeria/dependencies.toml

Line 119 in 683bd74

protobuf = "3.25.1"

Was that bug fixed in recent versions or am I missing something to reproduce the problem?

[mbgit2]

For us it doesn't seem fixed. We have a custom interceptor, but this now gets a complete empty (ReqT message) argument when using transcoding.

[berendjan]

Hi @ikhoon,
we're also encountering the problem but only when using plugins. As noted in the code base:
"json_name option is not allowed on extension fields. Note that the json_name field in FieldDescriptorProto is always populated by protoc when it sends descriptor data to plugins"

If you add a plugin you will see the filled in json_name.
In our setup we use https://github.com/bufbuild/protoc-gen-validate leading to the same problem

Thanks!

[ikhoon]

I failed to reproduce the problem by configuring https://github.com/bufbuild/protoc-gen-validate. Would you provide a minimal reproducible example? The example should be useful for preventing regression and ensuring compatibility.

[mbgit2]

Issue: explicitly need to set json_name in proto file to enable trancoding.

I've made a minimal repo that reproduces the issue. Note it is build using bazel, but with all previously specified versions as per this issue.

syntax = "proto3";

package hello.service.v1;

import "hello/v1/hello.proto";
import "google/api/annotations.proto";

option java_package = "com.example.myproject.service.hello.v1";
option java_multiple_files = true;


service HelloService {
  rpc Hello (hello.v1.HelloRequest) returns (hello.v1.HelloReply){
    option (google.api.http) = {
      get: "/v1/hello/{name_input}"
    };
  }
}

message HelloRequest {
  string name_input = 1;// [json_name="name_input"];
}

message HelloReply {
  string message = 1;
}

This proto compiled to java and then used by armeria:1.26 with transcoding results in the following service printing "Hello, mbgit2!". However with all the same in armeria:1.30 it prints "Hello, !". The incoming HelloRequest is empty, unless we specify the json_name, see the commented line in the proto file.

public class HelloService extends HelloServiceGrpc.HelloServiceImplBase {

    @Override
    public void hello(HelloRequest req, StreamObserver<HelloReply> responseObserver) {
        HelloReply reply = HelloReply.newBuilder()
                .setMessage("Hello, " + req.getNameInput() + '!')
                .build();
        responseObserver.onNext(reply);
        responseObserver.onCompleted();
    }
}

    ServerBuilder sb = Server.builder();
    GrpcServiceBuilder grpcBuilder = GrpcService.builder();
    grpcBuilder.enableHttpJsonTranscoding(true);
    sb.service(grpcBuilder.addService(new HelloService()).build());

We would really like to have the 1.26 behavior such that it is not necessary to put the json_name everywhere explicitly. Thanks for your time.