Add #[debug_middleware] (#2725)

Co-authored-by: David Pedersen <[email protected]>

axum-macros/tests/debug_middleware/fail/doesnt_take_next.rs

@@ -0,0 +1,13 @@
+use axum::{
+    debug_middleware,
+    extract::Request,
+    response::{IntoResponse, Response},
+};
+
+#[debug_middleware]
+async fn my_middleware(request: Request) -> Response {
+    let _ = request;
+    ().into_response()
+}
+
+fn main() {}

axum-macros/tests/debug_middleware/fail/doesnt_take_next.stderr

@@ -0,0 +1,7 @@
+error: Middleware functions must take `axum::middleware::Next` as the last argument
+ --> tests/debug_middleware/fail/doesnt_take_next.rs:7:1
+  |
+7 | #[debug_middleware]
+  | ^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `debug_middleware` (in Nightly builds, run with -Z macro-backtrace for more info)

axum-macros/tests/debug_middleware/fail/next_not_last.rs

@@ -0,0 +1,13 @@
+use axum::{
+    extract::Request,
+    response::Response,
+    middleware::Next,
+    debug_middleware,
+};
+
+#[debug_middleware]
+async fn my_middleware(next: Next, request: Request) -> Response {
+    next.run(request).await
+}
+
+fn main() {}

axum-macros/tests/debug_middleware/fail/next_not_last.stderr

@@ -0,0 +1,5 @@
+error: `axum::middleware::Next` must the last argument
+ --> tests/debug_middleware/fail/next_not_last.rs:9:24
+  |
+9 | async fn my_middleware(next: Next, request: Request) -> Response {
+  |                        ^^^^^^^^^^

axum-macros/tests/debug_middleware/fail/takes_next_twice.rs

@@ -0,0 +1,9 @@
+use axum::{debug_middleware, extract::Request, middleware::Next, response::Response};
+
+#[debug_middleware]
+async fn my_middleware(request: Request, next: Next, next2: Next) -> Response {
+    let _ = next2;
+    next.run(request).await
+}
+
+fn main() {}

axum-macros/tests/debug_middleware/fail/takes_next_twice.stderr

@@ -0,0 +1,7 @@
+error: Middleware functions can only take one argument of type `axum::middleware::Next`
+ --> tests/debug_middleware/fail/takes_next_twice.rs:3:1
+  |
+3 | #[debug_middleware]
+  | ^^^^^^^^^^^^^^^^^^^
+  |
+  = note: this error originates in the attribute macro `debug_middleware` (in Nightly builds, run with -Z macro-backtrace for more info)