async_wait.rs

use futures::{future, Future, sync::oneshot};
use tokio::spawn;

/// AsyncWait implements a `.wait()` equivalent that works from any contex.
/// This is required because at some point in the past `.wait()` stopped doing this,
/// and thus calling it in a polling context causes everything to lock up.
/// see: https://github.com/tokio-rs/tokio-core/issues/182 and related issues.
/// ``` norun
/// // This will block forever if run in the main thread context
/// let _client = TcpConnection::<JsonCodec<Request, Response>>::new(&addr, JsonCodec::new()).wait().unwrap();
/// // This will work in the expected manner and return once connection has completed
/// let _client = TcpConnection::<JsonCodec<Request, Response>>::new(&addr, JsonCodec::new()).async_wait().unwrap();
/// ```
pub trait AsyncWait<I, E> {
    fn async_wait(self) -> Result<I, E>;
}

impl <F, I, E> AsyncWait<I, E> for F 
where 
    F: Future<Item=I, Error=E> + Send + 'static,
    I: Send + 'static,
    E: Send + 'static,
{
    fn async_wait(self) -> Result<I, E> {
        let (tx, rx) = oneshot::channel::<Result<I, E>>();

        spawn(self.then(|res| tx.send(res) ).map(|_v| () ).map_err(|_e| () ));

        rx.wait().unwrap()
    }
}