tower/util/
map_result.rs

1use futures_util::{future::Map, FutureExt};
2use std::fmt;
3use std::task::{Context, Poll};
4use tower_layer::Layer;
5use tower_service::Service;
6
7/// Service returned by the [`map_result`] combinator.
8///
9/// [`map_result`]: crate::util::ServiceExt::map_result
10#[derive(Clone)]
11pub struct MapResult<S, F> {
12    inner: S,
13    f: F,
14}
15
16impl<S, F> fmt::Debug for MapResult<S, F>
17where
18    S: fmt::Debug,
19{
20    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
21        f.debug_struct("MapResult")
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 a [`MapResult`] service.
29///
30/// [`Layer`]: tower_layer::Layer
31#[derive(Debug, Clone)]
32pub struct MapResultLayer<F> {
33    f: F,
34}
35
36opaque_future! {
37    /// Response future from [`MapResult`] services.
38    ///
39    /// [`MapResult`]: crate::util::MapResult
40    pub type MapResultFuture<F, N> = Map<F, N>;
41}
42
43impl<S, F> MapResult<S, F> {
44    /// Creates a new [`MapResult`] service.
45    pub const fn new(inner: S, f: F) -> Self {
46        MapResult { f, inner }
47    }
48
49    /// Returns a new [`Layer`] that produces [`MapResult`] services.
50    ///
51    /// This is a convenience function that simply calls [`MapResultLayer::new`].
52    ///
53    /// [`Layer`]: tower_layer::Layer
54    pub fn layer(f: F) -> MapResultLayer<F> {
55        MapResultLayer { f }
56    }
57}
58
59impl<S, F, Request, Response, Error> Service<Request> for MapResult<S, F>
60where
61    S: Service<Request>,
62    Error: From<S::Error>,
63    F: FnOnce(Result<S::Response, S::Error>) -> Result<Response, Error> + Clone,
64{
65    type Response = Response;
66    type Error = Error;
67    type Future = MapResultFuture<S::Future, F>;
68
69    #[inline]
70    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
71        self.inner.poll_ready(cx).map_err(Into::into)
72    }
73
74    #[inline]
75    fn call(&mut self, request: Request) -> Self::Future {
76        MapResultFuture::new(self.inner.call(request).map(self.f.clone()))
77    }
78}
79
80impl<F> MapResultLayer<F> {
81    /// Creates a new [`MapResultLayer`] layer.
82    pub const fn new(f: F) -> Self {
83        MapResultLayer { f }
84    }
85}
86
87impl<S, F> Layer<S> for MapResultLayer<F>
88where
89    F: Clone,
90{
91    type Service = MapResult<S, F>;
92
93    fn layer(&self, inner: S) -> Self::Service {
94        MapResult {
95            f: self.f.clone(),
96            inner,
97        }
98    }
99}
tower/util/map_result.rs

tower/util/
map_result.rs
