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
use futures_core::{Future, Poll, Async};
use futures_core::task;
#[derive(Debug)]
#[must_use = "futures do nothing unless polled"]
pub struct InspectErr<A, F> where A: Future {
future: A,
f: Option<F>,
}
pub fn new<A, F>(future: A, f: F) -> InspectErr<A, F>
where A: Future,
F: FnOnce(&A::Error),
{
InspectErr {
future: future,
f: Some(f),
}
}
impl<A, F> Future for InspectErr<A, F>
where A: Future,
F: FnOnce(&A::Error),
{
type Item = A::Item;
type Error = A::Error;
fn poll(&mut self, cx: &mut task::Context) -> Poll<A::Item, A::Error> {
match self.future.poll(cx) {
Ok(Async::Pending) => Ok(Async::Pending),
Ok(Async::Ready(e)) => Ok(Async::Ready(e)),
Err(e) => {
(self.f.take().expect("cannot poll InspectErr twice"))(&e);
Err(e)
},
}
}
}