1 use futures_core::stream::{FusedStream, Stream};
2 use futures_core::task::{Context, Poll};
3 use pin_project_lite::pin_project;
4 use std::any::Any;
5 use std::boxed::Box;
6 use std::panic::{catch_unwind, AssertUnwindSafe, UnwindSafe};
7 use std::pin::Pin;
8 
9 pin_project! {
10     /// Stream for the [`catch_unwind`](super::StreamExt::catch_unwind) method.
11     #[derive(Debug)]
12     #[must_use = "streams do nothing unless polled"]
13     pub struct CatchUnwind<St> {
14         #[pin]
15         stream: St,
16         caught_unwind: bool,
17     }
18 }
19 
20 impl<St: Stream + UnwindSafe> CatchUnwind<St> {
new(stream: St) -> Self21     pub(super) fn new(stream: St) -> Self {
22         Self { stream, caught_unwind: false }
23     }
24 
25     delegate_access_inner!(stream, St, ());
26 }
27 
28 impl<St: Stream + UnwindSafe> Stream for CatchUnwind<St> {
29     type Item = Result<St::Item, Box<dyn Any + Send>>;
30 
poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>>31     fn poll_next(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
32         let mut this = self.project();
33 
34         if *this.caught_unwind {
35             Poll::Ready(None)
36         } else {
37             let res = catch_unwind(AssertUnwindSafe(|| this.stream.as_mut().poll_next(cx)));
38 
39             match res {
40                 Ok(poll) => poll.map(|opt| opt.map(Ok)),
41                 Err(e) => {
42                     *this.caught_unwind = true;
43                     Poll::Ready(Some(Err(e)))
44                 }
45             }
46         }
47     }
48 
size_hint(&self) -> (usize, Option<usize>)49     fn size_hint(&self) -> (usize, Option<usize>) {
50         if self.caught_unwind {
51             (0, Some(0))
52         } else {
53             self.stream.size_hint()
54         }
55     }
56 }
57 
58 impl<St: FusedStream + UnwindSafe> FusedStream for CatchUnwind<St> {
is_terminated(&self) -> bool59     fn is_terminated(&self) -> bool {
60         self.caught_unwind || self.stream.is_terminated()
61     }
62 }
63