perf: eliminate recursive call and unnecessary Option (#814)

actix-service/src/and_then.rs

@@ -57,7 +57,7 @@ where
         AndThenServiceResponse {
             state: State::A {
                 fut: self.0 .0.call(req),
-                b: Some(self.0.clone()),
+                b: self.0.clone(),
             },
         }
     }
@@ -84,7 +84,7 @@ pin_project! {
         A {
             #[pin]
             fut: A::Future,
-            b: Option<Rc<(A, B)>>,
+            b: Rc<(A, B)>,
         },
         B {
             #[pin]
@@ -101,17 +101,17 @@ where
     type Output = Result<B::Response, A::Error>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        loop {
             let mut this = self.as_mut().project();
 
             match this.state.as_mut().project() {
                 StateProj::A { fut, b } => {
                     let res = ready!(fut.poll(cx))?;
-                let b = b.take().unwrap();
                     let fut = b.1.call(res);
                     this.state.set(State::B { fut });
-                self.poll(cx)
                 }
-            StateProj::B { fut } => fut.poll(cx),
+                StateProj::B { fut } => return fut.poll(cx),
+            }
         }
     }
 }

actix-service/src/apply_cfg.rs

@@ -209,24 +209,26 @@ where
     type Output = Result<S, SF::InitError>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        loop {
             let mut this = self.as_mut().project();
 
             match this.state.as_mut().project() {
                 StateProj::A { fut } => {
                     let svc = ready!(fut.poll(cx))?;
                     this.state.set(State::B { svc });
-                self.poll(cx)
                 }
                 StateProj::B { svc } => {
                     ready!(svc.poll_ready(cx))?;
-                {
+
+                    let fut = {
                         let (_, f) = &**this.store;
-                    let fut = f(this.cfg.take().unwrap(), svc);
+                        f(this.cfg.take().unwrap(), svc)
+                    };
+
                     this.state.set(State::C { fut });
                 }
-                self.poll(cx)
+                StateProj::C { fut } => return fut.poll(cx),
             }
-            StateProj::C { fut } => fut.poll(cx),
         }
     }
 }

actix-service/src/then.rs

@@ -57,7 +57,7 @@ where
         ThenServiceResponse {
             state: State::A {
                 fut: self.0 .0.call(req),
-                b: Some(self.0.clone()),
+                b: self.0.clone(),
             },
         }
     }
@@ -81,7 +81,7 @@ pin_project! {
         A: Service<Req>,
         B: Service<Result<A::Response, A::Error>>,
     {
-        A { #[pin] fut: A::Future, b: Option<Rc<(A, B)>> },
+        A { #[pin] fut: A::Future, b: Rc<(A, B)> },
         B { #[pin] fut: B::Future },
     }
 }
@@ -94,17 +94,17 @@ where
     type Output = Result<B::Response, B::Error>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        loop {
             let mut this = self.as_mut().project();
 
             match this.state.as_mut().project() {
                 StateProj::A { fut, b } => {
                     let res = ready!(fut.poll(cx));
-                let b = b.take().unwrap();
                     let fut = b.1.call(res);
                     this.state.set(State::B { fut });
-                self.poll(cx)
                 }
-            StateProj::B { fut } => fut.poll(cx),
+                StateProj::B { fut } => return fut.poll(cx),
+            }
         }
     }
 }

actix-service/src/transform.rs

@@ -205,6 +205,7 @@ where
     type Output = Result<T::Transform, T::InitError>;
 
     fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
+        loop {
             let mut this = self.as_mut().project();
 
             match this.state.as_mut().project() {
@@ -212,9 +213,9 @@ where
                     let srv = ready!(fut.poll(cx))?;
                     let fut = this.store.0.new_transform(srv);
                     this.state.set(ApplyTransformFutureState::B { fut });
-                self.poll(cx)
                 }
-            ApplyTransformFutureStateProj::B { fut } => fut.poll(cx),
+                ApplyTransformFutureStateProj::B { fut } => return fut.poll(cx),
+            }
         }
     }
 }