Error handling in async for loop

[phaux]

Wouldn't it be better if the whole async for loop expression evaluated to a possible Err<Stream::Error> if an error occured and Ok(()) otherwise? That way you can do some custom error handling.

Example 1:

let stream = get_stream();
let result = #[async] for message in stream {
    println!("{}", message);
};
if let Err(err) = result {
    println!("An error occured!");
}

Example 2:

let stream = get_stream();
#[async] for message in stream {
    println!("{}", message);
}.unwrap_or_else(|err| {
    println!("An error occured!");
});

To get the current behavior you just put ? after the loop body:

#[async] for message in stream {
    …
}?;

[alexcrichton]

Yeah this is something I'm not entirely sure how to handle. The ability though for a for loop to have a value isn't something I'd though of before, so may have something promising!

[Arnavion]

You can do this right now by wrapping the loop in a catch block since #[async] for uses ? on the result of Stream::poll().

let stream = get_stream();
let result = do catch {
    #[async] for message in stream {
        println!("{}", message);
    }
    Ok(())
};
if let Err(err) = result {
    println!("An error occured!");
}