rpc module: register_async_method only allows Copy closures

[Code0x2]

Im creating a method that will take the values, send it into a channel, and then await its response, by using register_async_method. However, it doesnt let me utilize the mpsc::UnboundedSender because it doesnt implement copy, which is a bound on the register_async_method callback. Is there some other way I can go about sending values down a channel?

I tried register_method, but i can send that message into a channel just fine. But the problem is i want to await its response from the other end of the channel and i dont want to use a blocking recv method to do so.

[niklasad1]

hey @Code0x2

Can you give an example what you are trying to do?
We have this bound on the closure that may you way run into.

I think it should work if you clone the sender and move into closure by async move but I could be wrong.

[niklasad1]

Yeah, alright seems like we need to change the bound to Clone instead of Copy of the closure for that to work.

However, you could move that mpsc::UnboundedSender to the RpcModule or use the proc macros and then implement that trait for a type that has the mpsc::UnboundedSender as field.

Example with proc macros:

use std::net::SocketAddr;

use futures::SinkExt;
use jsonrpsee::core::{async_trait, Error};
use jsonrpsee::proc_macros::rpc;
use jsonrpsee::server::ServerBuilder;

#[rpc(server, client, namespace = "state")]
pub trait Rpc {
	/// Async method call example.
	#[method(name = "getKeys")]
	async fn say_hello(&self) -> Result<u32, Error>;
}

pub struct RpcServerImpl {
	sender: futures::channel::mpsc::UnboundedSender<()>,
}

#[async_trait]
impl RpcServer for RpcServerImpl {
	async fn say_hello(&self) -> Result<u32, Error> {
		self.sender.clone().send(()).await.unwrap();
		Ok(11)
	}
}

#[tokio::main]
async fn main() -> anyhow::Result<()> {
	let _ = run_server().await?;

	loop {}
}

async fn run_server() -> anyhow::Result<SocketAddr> {
	let server = ServerBuilder::default().build("127.0.0.1:0").await?;

	let (tx, rx) = futures::channel::mpsc::unbounded();

	let addr = server.local_addr()?;
	let handle = server.start(RpcServer::into_rpc(RpcServerImpl { sender: tx }))?;

	tokio::spawn(handle.stopped());

	Ok(addr)
}

[Code0x2]

Great this fixes the problem. Thanks for the quick fix and merge!