Lib.rs

A helper trait to assist with passing error types through return tonic::Status messages.

Usage

This works with the thiserror crates, but using that is not required. If you are not using thiserror then at the moment you will need to manually implement std::fmt::Display for your type. Your error type will also need to derive serde::{Serialize, Deserialize}.

In order to use this, you will need to #[derive(TonicError)] on your error type.

#[derive(Debug, Error, TonicError, Serialize, Deserialize)]
pub enum MathsError {
    #[error("division by zero for inputs: a={0} b={1}")]
    DivByZero(i32, i32),
}

The TonicError trait provides implementations of std::convert::TryFrom for your type, and an implementation of std::convert::From for tonic::Status.

These examples are taken from the included examples.

Server Side

async fn div(&self, req: Request<DivRequest>) -> Result<Response<DivResponse>, Status> {
    let req = req.into_inner();
    if req.b == 0 {
        return Err(MathsError::DivByZero(req.a, req.b).into());
    }
    let result = req.a as f64 / req.b as f64;
    Ok(Response::new(DivResponse { result }))
}

Client Side

pub async fn div(&mut self, a: i32, b: i32) -> Result<f64, MathsError> {
    let req = Request::new(DivRequest { a, b });

    let resp = match self.client.div(req).await {
        Ok(r) => r,
        Err(e) => match e.code() {
            Code::Internal => {
                return Err(e.try_into().expect("could not convert status to error"))
            }
            _ => panic!("error making rpc call: {e}"),
        },
    };

    Ok(resp.into_inner().result)
}

Example

See the tonic-error-example subdirectory in this repo for a working client/server example.

License

This is released under the Apache 2.0 license.