From af13c539386463b04b82f58155ee04702527212b Mon Sep 17 00:00:00 2001
From: Jonas Platte <jplatte+git@posteo.de>
Date: Tue, 2 Jan 2024 20:18:07 +0100
Subject: [PATCH] Make Router Sync without breaking the API (#2481)

---
 axum/src/boxed.rs         | 18 +++++++++---------
 axum/src/routing/mod.rs   |  1 +
 axum/src/routing/route.rs | 11 ++++++-----
 3 files changed, 16 insertions(+), 14 deletions(-)

diff --git a/axum/src/boxed.rs b/axum/src/boxed.rs
index 5473b2491b..69fda3fd98 100644
--- a/axum/src/boxed.rs
+++ b/axum/src/boxed.rs
@@ -1,4 +1,4 @@
-use std::{convert::Infallible, fmt};
+use std::{convert::Infallible, fmt, sync::Mutex};
 
 use crate::extract::Request;
 use tower::Service;
@@ -9,7 +9,7 @@ use crate::{
     Router,
 };
 
-pub(crate) struct BoxedIntoRoute<S, E>(Box<dyn ErasedIntoRoute<S, E>>);
+pub(crate) struct BoxedIntoRoute<S, E>(Mutex<Box<dyn ErasedIntoRoute<S, E>>>);
 
 impl<S> BoxedIntoRoute<S, Infallible>
 where
@@ -20,10 +20,10 @@ where
         H: Handler<T, S>,
         T: 'static,
     {
-        Self(Box::new(MakeErasedHandler {
+        Self(Mutex::new(Box::new(MakeErasedHandler {
             handler,
             into_route: |handler, state| Route::new(Handler::with_state(handler, state)),
-        }))
+        })))
     }
 }
 
@@ -35,20 +35,20 @@ impl<S, E> BoxedIntoRoute<S, E> {
         F: FnOnce(Route<E>) -> Route<E2> + Clone + Send + 'static,
         E2: 'static,
     {
-        BoxedIntoRoute(Box::new(Map {
-            inner: self.0,
+        BoxedIntoRoute(Mutex::new(Box::new(Map {
+            inner: self.0.into_inner().unwrap(),
             layer: Box::new(f),
-        }))
+        })))
     }
 
     pub(crate) fn into_route(self, state: S) -> Route<E> {
-        self.0.into_route(state)
+        self.0.into_inner().unwrap().into_route(state)
     }
 }
 
 impl<S, E> Clone for BoxedIntoRoute<S, E> {
     fn clone(&self) -> Self {
-        Self(self.0.clone_box())
+        Self(Mutex::new(self.0.lock().unwrap().clone_box()))
     }
 }
 
diff --git a/axum/src/routing/mod.rs b/axum/src/routing/mod.rs
index 13b5725549..49237e4eb8 100644
--- a/axum/src/routing/mod.rs
+++ b/axum/src/routing/mod.rs
@@ -682,4 +682,5 @@ impl<S> fmt::Debug for Endpoint<S> {
 fn traits() {
     use crate::test_helpers::*;
     assert_send::<Router<()>>();
+    assert_sync::<Router<()>>();
 }
diff --git a/axum/src/routing/route.rs b/axum/src/routing/route.rs
index fd63d0e8d0..4f3cffd747 100644
--- a/axum/src/routing/route.rs
+++ b/axum/src/routing/route.rs
@@ -14,6 +14,7 @@ use std::{
     fmt,
     future::Future,
     pin::Pin,
+    sync::Mutex,
     task::{Context, Poll},
 };
 use tower::{
@@ -27,7 +28,7 @@ use tower_service::Service;
 ///
 /// You normally shouldn't need to care about this type. It's used in
 /// [`Router::layer`](super::Router::layer).
-pub struct Route<E = Infallible>(BoxCloneService<Request, Response, E>);
+pub struct Route<E = Infallible>(Mutex<BoxCloneService<Request, Response, E>>);
 
 impl<E> Route<E> {
     pub(crate) fn new<T>(svc: T) -> Self
@@ -36,16 +37,16 @@ impl<E> Route<E> {
         T::Response: IntoResponse + 'static,
         T::Future: Send + 'static,
     {
-        Self(BoxCloneService::new(
+        Self(Mutex::new(BoxCloneService::new(
             svc.map_response(IntoResponse::into_response),
-        ))
+        )))
     }
 
     pub(crate) fn oneshot_inner(
         &mut self,
         req: Request,
     ) -> Oneshot<BoxCloneService<Request, Response, E>, Request> {
-        self.0.clone().oneshot(req)
+        self.0.get_mut().unwrap().clone().oneshot(req)
     }
 
     pub(crate) fn layer<L, NewError>(self, layer: L) -> Route<NewError>
@@ -70,7 +71,7 @@ impl<E> Route<E> {
 
 impl<E> Clone for Route<E> {
     fn clone(&self) -> Self {
-        Self(self.0.clone())
+        Self(Mutex::new(self.0.lock().unwrap().clone()))
     }
 }