Annotate panicking functions with #[track_caller] (#1248)

axum/CHANGELOG.md

@@ -7,7 +7,11 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 # Unreleased
 
-- None.
+- **fixed:** Annotate panicking functions with `#[track_caller]` so the error
+  message points to where the user added the invalid router, rather than
+  somewhere internally in axum ([#1248])
+
+[#1248]: https://github.com/tokio-rs/axum/pull/1248
 
 # 0.5.16 (10. September, 2022)
 

axum/src/routing/method_routing.rs

@@ -207,6 +207,7 @@ macro_rules! chained_service_fn {
         $name:ident, $method:ident
     ) => {
         $(#[$m])+
+        #[track_caller]
         pub fn $name<S, ResBody>(self, svc: S) -> Self
         where
             S: Service<Request<ReqBody>, Response = Response<ResBody>, Error = E>
@@ -271,6 +272,7 @@ macro_rules! chained_handler_fn {
         $name:ident, $method:ident
     ) => {
         $(#[$m])+
+        #[track_caller]
         pub fn $name<H, T>(self, handler: H) -> Self
         where
             H: Handler<T, B>,
@@ -585,6 +587,7 @@ where
     /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
     /// # };
     /// ```
+    #[track_caller]
     pub fn on<H, T>(self, filter: MethodFilter, handler: H) -> Self
     where
         H: Handler<T, B>,
@@ -697,6 +700,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
     /// # axum::Server::bind(&"".parse().unwrap()).serve(app.into_make_service()).await.unwrap();
     /// # };
     /// ```
+    #[track_caller]
     pub fn on_service<S, ResBody>(self, filter: MethodFilter, svc: S) -> Self
     where
         S: Service<Request<ReqBody>, Response = Response<ResBody>, Error = E>
@@ -809,8 +813,10 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
     }
 
     #[doc = include_str!("../docs/method_routing/merge.md")]
+    #[track_caller]
     pub fn merge(mut self, other: MethodRouter<ReqBody, E>) -> Self {
         // written using inner functions to generate less IR
+        #[track_caller]
         fn merge_inner<T>(name: &str, first: Option<T>, second: Option<T>) -> Option<T> {
             match (first, second) {
                 (Some(_), Some(_)) => panic!(
@@ -822,6 +828,7 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
             }
         }
 
+        #[track_caller]
         fn merge_fallback<B, E>(
             fallback: Fallback<B, E>,
             fallback_other: Fallback<B, E>,
@@ -868,12 +875,14 @@ impl<ReqBody, E> MethodRouter<ReqBody, E> {
         self.layer(HandleErrorLayer::new(f))
     }
 
+    #[track_caller]
     fn on_service_boxed_response_body<S>(mut self, filter: MethodFilter, svc: S) -> Self
     where
         S: Service<Request<ReqBody>, Response = Response, Error = E> + Clone + Send + 'static,
         S::Future: Send + 'static,
     {
         // written using an inner function to generate less IR
+        #[track_caller]
         fn set_service<T>(
             method_name: &str,
             out: &mut Option<T>,

axum/src/routing/mod.rs

@@ -121,6 +121,7 @@ where
     }
 
     #[doc = include_str!("../docs/routing/route.md")]
+    #[track_caller]
     pub fn route<T>(mut self, path: &str, service: T) -> Self
     where
         T: Service<Request<B>, Response = Response, Error = Infallible> + Clone + Send + 'static,
@@ -173,6 +174,7 @@ where
         self
     }
 
+    #[track_caller]
     fn set_node(&mut self, path: &str, id: RouteId) {
         let mut node =
             Arc::try_unwrap(Arc::clone(&self.node)).unwrap_or_else(|node| (*node).clone());
@@ -183,6 +185,7 @@ where
     }
 
     #[doc = include_str!("../docs/routing/nest.md")]
+    #[track_caller]
     pub fn nest<T>(mut self, mut path: &str, svc: T) -> Self
     where
         T: Service<Request<B>, Response = Response, Error = Infallible> + Clone + Send + 'static,
@@ -262,6 +265,7 @@ where
     }
 
     #[doc = include_str!("../docs/routing/merge.md")]
+    #[track_caller]
     pub fn merge<R>(mut self, other: R) -> Self
     where
         R: Into<Router<B>>,
@@ -477,6 +481,7 @@ where
         }
     }
 
+    #[track_caller]
     fn panic_on_matchit_error(&self, err: matchit::InsertError) {
         if self.nested_at_root {
             panic!(