futures 0.3.13

mod countingwaker {
    use futures::task::{self, ArcWake, Waker};
    use std::sync::{Arc, Mutex};

    struct CountingWaker {
        nr_wake: Mutex<i32>,
    }

    impl CountingWaker {
        fn new() -> Self {
            Self {
                nr_wake: Mutex::new(0),
            }
        }

        fn wakes(&self) -> i32 {
            *self.nr_wake.lock().unwrap()
        }
    }

    impl ArcWake for CountingWaker {
        fn wake_by_ref(arc_self: &Arc<Self>) {
            let mut lock = arc_self.nr_wake.lock().unwrap();
            *lock += 1;
        }
    }

    #[test]
    fn create_from_arc() {
        let some_w = Arc::new(CountingWaker::new());

        let w1: Waker = task::waker(some_w.clone());
        assert_eq!(2, Arc::strong_count(&some_w));
        w1.wake_by_ref();
        assert_eq!(1, some_w.wakes());

        let w2 = w1.clone();
        assert_eq!(3, Arc::strong_count(&some_w));

        w2.wake_by_ref();
        assert_eq!(2, some_w.wakes());

        drop(w2);
        assert_eq!(2, Arc::strong_count(&some_w));
        drop(w1);
        assert_eq!(1, Arc::strong_count(&some_w));
    }

    #[test]
    fn ref_wake_same() {
        let some_w = Arc::new(CountingWaker::new());

        let w1: Waker = task::waker(some_w.clone());
        let w2 = task::waker_ref(&some_w);
        let w3 = w2.clone();

        assert!(w1.will_wake(&w2));
        assert!(w2.will_wake(&w3));
    }
}

#[test]
fn proper_refcount_on_wake_panic() {
    use futures::task::{self, ArcWake, Waker};
    use std::sync::Arc;

    struct PanicWaker;

    impl ArcWake for PanicWaker {
        fn wake_by_ref(_arc_self: &Arc<Self>) {
            panic!("WAKE UP");
        }
    }

    let some_w = Arc::new(PanicWaker);

    let w1: Waker = task::waker(some_w.clone());
    assert_eq!("WAKE UP", *std::panic::catch_unwind(|| w1.wake_by_ref()).unwrap_err().downcast::<&str>().unwrap());
    assert_eq!(2, Arc::strong_count(&some_w)); // some_w + w1
    drop(w1);
    assert_eq!(1, Arc::strong_count(&some_w)); // some_w
}