add .map_err() service combinator

src/service.rs

@@ -15,6 +15,11 @@ pub trait NewServiceExt: NewService {
             Error = Self::Error,
             InitError = Self::InitError,
         >;
+
+    fn map_err<F, E>(self, f: F) -> MapErrNewService<Self, F, E>
+    where
+        Self: Sized,
+        F: Fn(Self::Error) -> E;
 }
 
 impl<T> NewServiceExt for T
@@ -32,6 +37,13 @@ where
     {
         AndThenNewService::new(self, new_service)
     }
+
+    fn map_err<F, E>(self, f: F) -> MapErrNewService<Self, F, E>
+    where
+        F: Fn(Self::Error) -> E
+    {
+        MapErrNewService::new(self, f)
+    }
 }
 
 /// Trait for types that can be converted to a Service
@@ -519,3 +531,163 @@ where
         }
     }
 }
+
+/// `MapErr` service combinator
+pub struct MapErr<A, F, E> {
+    a: A,
+    f: F,
+    e: marker::PhantomData<E>,
+}
+
+impl<A, F, E> MapErr<A, F, E>
+where
+    A: Service,
+    F: Fn(A::Error) -> E,
+{
+    /// Create new `MapErr` combinator
+    pub fn new(a: A, f: F) -> Self {
+        Self { a, f, e: marker::PhantomData }
+    }
+}
+
+impl<A, F, E> Service for MapErr<A, F, E>
+where
+    A: Service,
+    F: Fn(A::Error) -> E + Clone,
+{
+    type Request = A::Request;
+    type Response = A::Response;
+    type Error = E;
+    type Future = MapErrFuture<A, F, E>;
+
+    fn poll_ready(&mut self) -> Poll<(), Self::Error> {
+        self.a.poll_ready().map_err(|e| (self.f)(e))
+    }
+
+    fn call(&mut self, req: Self::Request) -> Self::Future {
+        MapErrFuture::new(self.a.call(req), self.f.clone())
+    }
+}
+
+pub struct MapErrFuture<A, F, E>
+where
+    A: Service,
+    F: Fn(A::Error) -> E,
+{
+    f: F,
+    fut: A::Future,
+}
+
+impl<A, F, E> MapErrFuture<A, F, E>
+where
+    A: Service,
+    F: Fn(A::Error) -> E,
+{
+    fn new(fut: A::Future, f: F) -> Self {
+        MapErrFuture { f, fut }
+    }
+}
+
+impl<A, F, E> Future for MapErrFuture<A, F, E>
+where
+    A: Service,
+    F: Fn(A::Error) -> E,
+{
+    type Item = A::Response;
+    type Error = E;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        self.fut.poll().map_err(|e| (self.f)(e))
+    }
+}
+
+/// `MapErrNewService` new service combinator
+pub struct MapErrNewService<A, F, E> {
+    a: A,
+    f: F,
+    e: marker::PhantomData<E>,
+}
+
+impl<A, F, E> MapErrNewService<A, F, E>
+where
+    A: NewService,
+    F: Fn(A::Error) -> E,
+{
+    /// Create new `MapErr` new service instance
+    pub fn new(a: A, f: F) -> Self {
+        Self { a, f, e: marker::PhantomData }
+    }
+}
+
+impl<A, F, E> NewService for MapErrNewService<A, F, E>
+where
+    A: NewService + Clone,
+    F: Fn(A::Error) -> E + Clone,
+{
+    type Request = A::Request;
+    type Response = A::Response;
+    type Error = E;
+    type Service = MapErr<A::Service, F, E>;
+
+    type InitError = A::InitError;
+    type Future = MapErrNewServiceFuture<A, F, E>;
+
+    fn new_service(&self) -> Self::Future {
+        MapErrNewServiceFuture::new(self.a.new_service(), self.f.clone())
+    }
+}
+
+impl<A, F, E> Clone for MapErrNewService<A, F, E>
+where
+    A: NewService + Clone,
+    F: Fn(A::Error) -> E + Clone,
+{
+    fn clone(&self) -> Self {
+        Self {
+            a: self.a.clone(),
+            f: self.f.clone(),
+            e: marker::PhantomData,
+        }
+    }
+}
+
+pub struct MapErrNewServiceFuture<A, F, E>
+where
+    A: NewService,
+    F: Fn(A::Error) -> E,
+{
+    fut: A::Future,
+    a: Option<A::Service>,
+    f: F,
+}
+
+impl<A, F, E> MapErrNewServiceFuture<A, F, E>
+where
+    A: NewService,
+    F: Fn(A::Error) -> E,
+{
+    fn new(fut: A::Future, f: F) -> Self {
+        MapErrNewServiceFuture {
+            f,
+            fut,
+            a: None,
+        }
+    }
+}
+
+impl<A, F, E> Future for MapErrNewServiceFuture<A, F, E>
+where
+    A: NewService,
+    F: Fn(A::Error) -> E + Clone,
+{
+    type Item = MapErr<A::Service, F, E>;
+    type Error = A::InitError;
+
+    fn poll(&mut self) -> Poll<Self::Item, Self::Error> {
+        if let Async::Ready(service) = self.fut.poll()? {
+            Ok(Async::Ready(MapErr::new(service, self.f.clone())))
+        } else {
+            Ok(Async::NotReady)
+        }
+    }
+}