tower/util/
map_err.rs

1use futures_util::{future, TryFutureExt};
2use std::fmt;
3use std::task::{Context, Poll};
4use tower_layer::Layer;
5use tower_service::Service;
6
7/// Service returned by the [`map_err`] combinator.
8///
9/// [`map_err`]: crate::util::ServiceExt::map_err
10#[derive(Clone)]
11pub struct MapErr<S, F> {
12    inner: S,
13    f: F,
14}
15
16impl<S, F> fmt::Debug for MapErr<S, F>
17where
18    S: fmt::Debug,
19{
20    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
21        f.debug_struct("MapErr")
22            .field("inner", &self.inner)
23            .field("f", &format_args!("{}", std::any::type_name::<F>()))
24            .finish()
25    }
26}
27
28/// A [`Layer`] that produces [`MapErr`] services.
29///
30/// [`Layer`]: tower_layer::Layer
31#[derive(Clone, Debug)]
32pub struct MapErrLayer<F> {
33    f: F,
34}
35
36opaque_future! {
37    /// Response future from [`MapErr`] services.
38    ///
39    /// [`MapErr`]: crate::util::MapErr
40    pub type MapErrFuture<F, N> = future::MapErr<F, N>;
41}
42
43impl<S, F> MapErr<S, F> {
44    /// Creates a new [`MapErr`] service.
45    pub const fn new(inner: S, f: F) -> Self {
46        MapErr { f, inner }
47    }
48
49    /// Returns a new [`Layer`] that produces [`MapErr`] services.
50    ///
51    /// This is a convenience function that simply calls [`MapErrLayer::new`].
52    ///
53    /// [`Layer`]: tower_layer::Layer
54    pub fn layer(f: F) -> MapErrLayer<F> {
55        MapErrLayer { f }
56    }
57}
58
59impl<S, F, Request, Error> Service<Request> for MapErr<S, F>
60where
61    S: Service<Request>,
62    F: FnOnce(S::Error) -> Error + Clone,
63{
64    type Response = S::Response;
65    type Error = Error;
66    type Future = MapErrFuture<S::Future, F>;
67
68    #[inline]
69    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
70        self.inner.poll_ready(cx).map_err(self.f.clone())
71    }
72
73    #[inline]
74    fn call(&mut self, request: Request) -> Self::Future {
75        MapErrFuture::new(self.inner.call(request).map_err(self.f.clone()))
76    }
77}
78
79impl<F> MapErrLayer<F> {
80    /// Creates a new [`MapErrLayer`].
81    pub const fn new(f: F) -> Self {
82        MapErrLayer { f }
83    }
84}
85
86impl<S, F> Layer<S> for MapErrLayer<F>
87where
88    F: Clone,
89{
90    type Service = MapErr<S, F>;
91
92    fn layer(&self, inner: S) -> Self::Service {
93        MapErr {
94            f: self.f.clone(),
95            inner,
96        }
97    }
98}
tower/util/map_err.rs

tower/util/
map_err.rs
