How to use question marks in tonic-build async method ? anyhow way or Result<Xxx, Box<dyn Error>>

[xiuno]

anyhow way, I can use question mark:

fn fn1() -> Result<Xxx> {
        let a = "123".parse::<u32>()?;
        let b = "456".parse::<u32>()?;
        ...
}

but in tonic, I have to map_err() any where...

#[tonic::async_trait]
impl Xxx for XxxXxx {
    async fn xxx(&self, request: Request<Empty>) -> Result<Response<Xxx>, Status> {
         let a = "123".parse::<u32>().map_err(|e|Status::new(Code::Xxxx, "xxx"))?;
         let b = "123".parse::<u32>().map_err(|e|Status::new(Code::Xxxx, "xxx"))?;
         ...
    }
}

is there better way ?

if I define MyError and change Status to MyError, will get error Status not match MyError in trait.

[davidpdrsn]

If the error type is local to your crate you can define impl From<MyError> for Status and then ? will work directly.

Doesn't work for anyhow though. That requires using map_err. An anyhow::Error can happen for whatever reason, so tonic couldn't fine a general mapping. Therefore you're required to pick which status is appropriate with map_err.

[xiuno]

I tried that, but Result<Response, Status> and Result<Response, MyError> don't match ! Status is defined in trait, to modify it, may need to modify a lots of codes of tonic build.

[davidpdrsn]

This works:

#[tonic::async_trait]
impl Greeter for MyGreeter {
    async fn say_hello(
        &self,
        request: Request<HelloRequest>,
    ) -> Result<Response<HelloReply>, Status> {
        // try_thing returns Result<_, MyError> but can still use ?
        try_thing()?;

        // ...
    }
}

struct MyError {}

impl From<MyError> for Status {
    fn from(err: MyError) -> Status {
        // ...
    }
}

fn try_thing() -> Result<(), MyError> {
    // ...
}

[xiuno]

In this way, it can really work, wrapping a layer, and it would be better if it could be defined as a macro.

[davidpdrsn]

I don't understand what you mean. Can you clarify what you mean by

[..] wrapping a layer, and it would be better if it could be defined as a macro.

[gcxfd]

@davidpdrsn @xiuno i write a macro https://crates.io/crates/tonic_catch , now can use like this

use tonic_catch::{tonic_catch, Result, Error};

#[tonic_catch]
impl Rmw for RmwSrv {
  async fn head(&self, request: Request<Url>) -> Result<()> {
    let addr = match request.remote_addr() {
      Some(addr) => addr.to_string(),
      None => String::new(),
    };

    let url = request.into_inner();
    println!("{:?} {}/{}", addr, url.addr, url.path);

    self
      .sender
      .send(Evt::Head(url.addr.parse()?, url.path))
      .await?;

    Ok(Response::new(()))
  }
}

[gcxfd]

use this https://crates.io/crates/tonic_catch , everything will be easy

As shown in the figure below, I found that the answer was folded, and I paste it again for convenience