[go: up one dir, main page]

futures 0.3.13

An implementation of futures and streams featuring zero allocations, composability, and iterator-like interfaces.
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137

#[test]
fn map_ok() {
    use futures::future::{self, FutureExt, TryFutureExt};
    use futures_test::future::FutureTestExt;
    use std::sync::mpsc;

    // The closure given to `map_ok` should have been dropped by the time `map`
    // runs.
    let (tx1, rx1) = mpsc::channel::<()>();
    let (tx2, rx2) = mpsc::channel::<()>();

    future::ready::<Result<i32, i32>>(Err(1))
        .map_ok(move |_| { let _tx1 = tx1; panic!("should not run"); })
        .map(move |_| {
            assert!(rx1.recv().is_err());
            tx2.send(()).unwrap()
        })
        .run_in_background();

    rx2.recv().unwrap();
}

#[test]
fn map_err() {
    use futures::future::{self, FutureExt, TryFutureExt};
    use futures_test::future::FutureTestExt;
    use std::sync::mpsc;

    // The closure given to `map_err` should have been dropped by the time `map`
    // runs.
    let (tx1, rx1) = mpsc::channel::<()>();
    let (tx2, rx2) = mpsc::channel::<()>();

    future::ready::<Result<i32, i32>>(Ok(1))
        .map_err(move |_| { let _tx1 = tx1; panic!("should not run"); })
        .map(move |_| {
            assert!(rx1.recv().is_err());
            tx2.send(()).unwrap()
        })
        .run_in_background();

    rx2.recv().unwrap();
}

mod channelled {
    use futures::future::Future;
    use futures::task::{Context,Poll};
    use pin_project::pin_project;
    use std::pin::Pin;

    #[pin_project]
    struct FutureData<F, T> {
        _data: T,
        #[pin]
        future: F,
    }

    impl<F: Future, T: Send + 'static> Future for FutureData<F, T> {
        type Output = F::Output;

        fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<F::Output> {
            self.project().future.poll(cx)
        }
    }

    #[test]
    fn then_drops_eagerly() {
        use futures::channel::oneshot;
        use futures::future::{self, FutureExt, TryFutureExt};
        use futures_test::future::FutureTestExt;
        use std::sync::mpsc;

        let (tx0, rx0) = oneshot::channel::<()>();
        let (tx1, rx1) = mpsc::channel::<()>();
        let (tx2, rx2) = mpsc::channel::<()>();

        FutureData { _data: tx1, future: rx0.unwrap_or_else(|_| { panic!() }) }
            .then(move |_| {
                assert!(rx1.recv().is_err()); // tx1 should have been dropped
                tx2.send(()).unwrap();
                future::ready(())
            })
            .run_in_background();

        assert_eq!(Err(mpsc::TryRecvError::Empty), rx2.try_recv());
        tx0.send(()).unwrap();
        rx2.recv().unwrap();
    }

    #[test]
    fn and_then_drops_eagerly() {
        use futures::channel::oneshot;
        use futures::future::{self, TryFutureExt};
        use futures_test::future::FutureTestExt;
        use std::sync::mpsc;

        let (tx0, rx0) = oneshot::channel::<Result<(), ()>>();
        let (tx1, rx1) = mpsc::channel::<()>();
        let (tx2, rx2) = mpsc::channel::<()>();

        FutureData { _data: tx1, future: rx0.unwrap_or_else(|_| { panic!() }) }
            .and_then(move |_| {
                assert!(rx1.recv().is_err()); // tx1 should have been dropped
                tx2.send(()).unwrap();
                future::ready(Ok(()))
            })
            .run_in_background();

        assert_eq!(Err(mpsc::TryRecvError::Empty), rx2.try_recv());
        tx0.send(Ok(())).unwrap();
        rx2.recv().unwrap();
    }

    #[test]
    fn or_else_drops_eagerly() {
        use futures::channel::oneshot;
        use futures::future::{self, TryFutureExt};
        use futures_test::future::FutureTestExt;
        use std::sync::mpsc;

        let (tx0, rx0) = oneshot::channel::<Result<(), ()>>();
        let (tx1, rx1) = mpsc::channel::<()>();
        let (tx2, rx2) = mpsc::channel::<()>();

        FutureData { _data: tx1, future: rx0.unwrap_or_else(|_| { panic!() }) }
            .or_else(move |_| {
                assert!(rx1.recv().is_err()); // tx1 should have been dropped
                tx2.send(()).unwrap();
                future::ready::<Result<(), ()>>(Ok(()))
            })
            .run_in_background();

        assert_eq!(Err(mpsc::TryRecvError::Empty), rx2.try_recv());
        tx0.send(Err(())).unwrap();
        rx2.recv().unwrap();
    }
}