futures_test/future/
pending_once.rs

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1use futures_core::future::{FusedFuture, Future};
2use futures_core::task::{Context, Poll};
3use pin_project::pin_project;
4use std::pin::Pin;
5
6/// Combinator that guarantees one [`Poll::Pending`] before polling its inner
7/// future.
8///
9/// This is created by the
10/// [`FutureTestExt::pending_once`](super::FutureTestExt::pending_once)
11/// method.
12#[pin_project]
13#[derive(Debug, Clone)]
14#[must_use = "futures do nothing unless you `.await` or poll them"]
15pub struct PendingOnce<Fut> {
16    #[pin]
17    future: Fut,
18    polled_before: bool,
19}
20
21impl<Fut: Future> PendingOnce<Fut> {
22    pub(super) fn new(future: Fut) -> Self {
23        Self { future, polled_before: false }
24    }
25}
26
27impl<Fut: Future> Future for PendingOnce<Fut> {
28    type Output = Fut::Output;
29
30    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
31        let this = self.project();
32        if *this.polled_before {
33            this.future.poll(cx)
34        } else {
35            *this.polled_before = true;
36            cx.waker().wake_by_ref();
37            Poll::Pending
38        }
39    }
40}
41
42impl<Fut: FusedFuture> FusedFuture for PendingOnce<Fut> {
43    fn is_terminated(&self) -> bool {
44        self.polled_before && self.future.is_terminated()
45    }
46}
futures_test/future/pending_once.rs

futures_test/future/
pending_once.rs
