add optional auth extractor implement. (#205)

actix-web-httpauth/src/extractors/mod.rs

@@ -1,8 +1,15 @@
 //! Type-safe authentication information extractors
 
+use std::{
+    future::Future,
+    pin::Pin,
+    task::{Context, Poll},
+};
+
 use actix_web::dev::ServiceRequest;
 use actix_web::Error;
-use std::future::Future;
+use futures_util::ready;
+use pin_project_lite::pin_project;
 
 pub mod basic;
 pub mod bearer;
@@ -31,3 +38,66 @@ pub trait AuthExtractor: Sized {
     /// Parse the authentication credentials from the actix' `ServiceRequest`.
     fn from_service_request(req: &ServiceRequest) -> Self::Future;
 }
+
+impl<T: AuthExtractor> AuthExtractor for Option<T> {
+    type Error = T::Error;
+
+    type Future = AuthExtractorOptFut<T::Future>;
+
+    fn from_service_request(req: &ServiceRequest) -> Self::Future {
+        let fut = T::from_service_request(req);
+        AuthExtractorOptFut { fut }
+    }
+}
+
+pin_project! {
+    #[doc(hidden)]
+    pub struct AuthExtractorOptFut<F> {
+        #[pin]
+        fut: F
+    }
+}
+
+impl<F, T, E> Future for AuthExtractorOptFut<F>
+where
+    F: Future<Output = Result<T, E>>,
+{
+    type Output = Result<Option<T>, E>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let res = ready!(self.project().fut.poll(cx));
+        Poll::Ready(Ok(res.ok()))
+    }
+}
+
+impl<T: AuthExtractor> AuthExtractor for Result<T, T::Error> {
+    type Error = T::Error;
+
+    type Future = AuthExtractorResFut<T::Future>;
+
+    fn from_service_request(req: &ServiceRequest) -> Self::Future {
+        AuthExtractorResFut {
+            fut: T::from_service_request(req),
+        }
+    }
+}
+
+pin_project! {
+    #[doc(hidden)]
+    pub struct AuthExtractorResFut<F> {
+        #[pin]
+        fut: F
+    }
+}
+
+impl<F, T, E> Future for AuthExtractorResFut<F>
+where
+    F: Future<Output = Result<T, E>>,
+{
+    type Output = Result<F::Output, E>;
+
+    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        let res = ready!(self.project().fut.poll(cx));
+        Poll::Ready(Ok(res))
+    }
+}