tests/futures_ordered.rs

#[cfg(all(feature = "alloc", feature="executor"))]
#[test]
fn works_1() {
    use futures::channel::oneshot;
    use futures::executor::block_on_stream;
    use futures::stream::{StreamExt, FuturesOrdered};
    use futures_test::task::noop_context;

    let (a_tx, a_rx) = oneshot::channel::<i32>();
    let (b_tx, b_rx) = oneshot::channel::<i32>();
    let (c_tx, c_rx) = oneshot::channel::<i32>();

    let mut stream = vec![a_rx, b_rx, c_rx].into_iter().collect::<FuturesOrdered<_>>();

    b_tx.send(99).unwrap();
    assert!(stream.poll_next_unpin(&mut noop_context()).is_pending());

    a_tx.send(33).unwrap();
    c_tx.send(33).unwrap();

    let mut iter = block_on_stream(stream);
    assert_eq!(Some(Ok(33)), iter.next());
    assert_eq!(Some(Ok(99)), iter.next());
    assert_eq!(Some(Ok(33)), iter.next());
    assert_eq!(None, iter.next());
}

#[cfg(feature = "alloc")]
#[test]
fn works_2() {
    use futures::channel::oneshot;
    use futures::future::{join, FutureExt};
    use futures::stream::{StreamExt, FuturesOrdered};
    use futures_test::task::noop_context;

    let (a_tx, a_rx) = oneshot::channel::<i32>();
    let (b_tx, b_rx) = oneshot::channel::<i32>();
    let (c_tx, c_rx) = oneshot::channel::<i32>();

    let mut stream = vec![
        a_rx.boxed(),
        join(b_rx, c_rx).map(|(a, b)| Ok(a? + b?)).boxed(),
    ].into_iter().collect::<FuturesOrdered<_>>();

    let mut cx = noop_context();
    a_tx.send(33).unwrap();
    b_tx.send(33).unwrap();
    assert!(stream.poll_next_unpin(&mut cx).is_ready());
    assert!(stream.poll_next_unpin(&mut cx).is_pending());
    c_tx.send(33).unwrap();
    assert!(stream.poll_next_unpin(&mut cx).is_ready());
}

#[cfg(feature = "executor")]
#[test]
fn from_iterator() {
    use futures::executor::block_on;
    use futures::future;
    use futures::stream::{StreamExt, FuturesOrdered};

    let stream = vec![
        future::ready::<i32>(1),
        future::ready::<i32>(2),
        future::ready::<i32>(3)
    ].into_iter().collect::<FuturesOrdered<_>>();
    assert_eq!(stream.len(), 3);
    assert_eq!(block_on(stream.collect::<Vec<_>>()), vec![1,2,3]);
}

#[cfg(feature = "alloc")]
#[test]
fn queue_never_unblocked() {
    use futures::channel::oneshot;
    use futures::future::{self, Future, TryFutureExt};
    use futures::stream::{StreamExt, FuturesOrdered};
    use futures_test::task::noop_context;
    use std::any::Any;

    let (_a_tx, a_rx) = oneshot::channel::<Box<dyn Any + Send>>();
    let (b_tx, b_rx) = oneshot::channel::<Box<dyn Any + Send>>();
    let (c_tx, c_rx) = oneshot::channel::<Box<dyn Any + Send>>();

    let mut stream = vec![
        Box::new(a_rx) as Box<dyn Future<Output = _> + Unpin>,
        Box::new(future::try_select(b_rx, c_rx)
            .map_err(|e| e.factor_first().0)
            .and_then(|e| future::ok(Box::new(e) as Box<dyn Any + Send>))) as _,
    ].into_iter().collect::<FuturesOrdered<_>>();

    let cx = &mut noop_context();
    for _ in 0..10 {
        assert!(stream.poll_next_unpin(cx).is_pending());
    }

    b_tx.send(Box::new(())).unwrap();
    assert!(stream.poll_next_unpin(cx).is_pending());
    c_tx.send(Box::new(())).unwrap();
    assert!(stream.poll_next_unpin(cx).is_pending());
    assert!(stream.poll_next_unpin(cx).is_pending());
}