How to get params serialized as object, when argument is null?

[prodigy]

I am writing a client for the deribit.com JSON-RPC server. It expects params to always be an object. They do not use positional parameters. So when sending a request for a method that does not expect any parameters, StreamJsonRpc currently serializes as an empty array. But this server requires it to be an empty object. How would I achieve that using StreamJsonRpc?

trace Information: 8 : {"id":2,"method":"public/get_time"}
trace Verbose: 8 : Sent: {
  "jsonrpc": "2.0",
  "id": 2,
  "method": "public/get_time",
  "params": []
}
trace Information: 7 : {"id":2,"error":{"code":11050,"message":"bad_request"}}
trace Verbose: 7 : Received: {
  "jsonrpc": "2.0",
  "id": 2,
  "error": {
    "message": "bad_request",
    "code": 11050
  },
  "usIn": 1712668905757776,
  "usOut": 1712668905757838,
  "usDiff": 62,
  "testnet": false
}
trace Warning: 12 : Received error response for request 2: 11050 "bad_request"

[AArnott]

What API are you using to invoke the RPC request? You can use the JsonRpc.InvokeWithParameterObjectAsync method to enforce an object be sent. If null as the parameter object still produces an array, that may be a bug. But it may be one you can workaround by passing in an object with no properties (or an empty dictionary IIRC).

[prodigy]

Thank you for your reply. JsonRpc.InvokeWithParameterObjectAsync sent an array as well just as you said. Possibly this is a bug.

I then tried using .Attach<>() with a custom server interface with the settings set to ServerRequiresNamedArguments to true.

This then didn't produce any arguments although they were passed as method arguments. It continued generating empty arrays, even with arguments present.

My current workaround actually is a bugfix I guess. After looking through the code of StreamJsonRpc and identifying the code that decides whether to send an object or an array, I came up with this class deriving from JsonMessageFormatter...

public class ObjectOnlyJsonRpcFormatter : JsonMessageFormatter, IJsonRpcMessageFormatter
{
    void IJsonRpcMessageFormatter.Serialize(IBufferWriter<byte> bufferWriter, JsonRpcMessage message)
    {
        if (message is JsonRpcRequest { ArgumentsList.Count: 0 } request)
        {
            request.ArgumentsList = null;
            request.NamedArguments = new Dictionary<string, object?>();
            request.NamedArgumentDeclaredTypes = new Dictionary<string, Type>();
        }
        
        base.Serialize(bufferWriter, message);
    }
}