futures_test/future/
pending_once.rs

1use futures_core::future::{Future, FusedFuture};
2use futures_core::task::{Context, Poll};
3use std::pin::Pin;
4use pin_utils::{unsafe_pinned, unsafe_unpinned};
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#[derive(Debug, Clone)]
13#[must_use = "futures do nothing unless you `.await` or poll them"]
14pub struct PendingOnce<Fut: Future> {
15    future: Fut,
16    polled_before: bool,
17}
18
19impl<Fut: Future> PendingOnce<Fut> {
20    unsafe_pinned!(future: Fut);
21    unsafe_unpinned!(polled_before: bool);
22
23    pub(super) fn new(future: Fut) -> Self {
24        Self {
25            future,
26            polled_before: false,
27        }
28    }
29}
30
31impl<Fut: Future> Future for PendingOnce<Fut> {
32    type Output = Fut::Output;
33
34    fn poll(
35        mut self: Pin<&mut Self>,
36        cx: &mut Context<'_>,
37    ) -> Poll<Self::Output> {
38        if self.polled_before {
39            self.as_mut().future().poll(cx)
40        } else {
41            *self.as_mut().polled_before() = true;
42            cx.waker().wake_by_ref();
43            Poll::Pending
44        }
45    }
46}
47
48impl<Fut: FusedFuture> FusedFuture for PendingOnce<Fut> {
49    fn is_terminated(&self) -> bool {
50        self.polled_before && self.future.is_terminated()
51    }
52}
futures_test/future/pending_once.rs

futures_test/future/
pending_once.rs
