Add test for panic location of overlapping method route panic

Author: jplatte

axum/tests/panic_location.rs

@@ -0,0 +1,41 @@
+//! Separate test binary, because the panic hook is a global resource
+
+use std::{
+    panic::{catch_unwind, set_hook, take_hook},
+    path::Path,
+    sync::OnceLock,
+};
+
+use axum::{routing::get, Router};
+
+#[test]
+fn routes_with_overlapping_method_routes() {
+    static PANIC_LOCATION_FILE: OnceLock<String> = OnceLock::new();
+
+    let default_hook = take_hook();
+    set_hook(Box::new(|panic_info| {
+        if let Some(location) = panic_info.location() {
+            _ = PANIC_LOCATION_FILE.set(location.file().to_owned());
+        }
+    }));
+
+    let result = catch_unwind(|| {
+        async fn handler() {}
+
+        let _: Router = Router::new()
+            .route("/foo/bar", get(handler))
+            .route("/foo/bar", get(handler));
+    });
+    set_hook(default_hook);
+
+    let panic_payload = result.unwrap_err();
+    let panic_msg = panic_payload.downcast_ref::<String>().unwrap();
+
+    assert_eq!(
+        panic_msg,
+        "Overlapping method route. Handler for `GET /foo/bar` already exists"
+    );
+
+    let file = PANIC_LOCATION_FILE.get().unwrap();
+    assert_eq!(Path::new(file).file_name().unwrap(), "panic_location.rs");
+}