Cover clone in fallback with tests

axum/src/routing/tests/fallback.rs

@@ -328,3 +328,21 @@ async fn merge_router_with_fallback_into_empty() {
     assert_eq!(res.status(), StatusCode::NOT_FOUND);
     assert_eq!(res.text().await, "outer");
 }
+
+#[crate::test]
+async fn state_isnt_cloned_too_much_with_fallback() {
+    let state = CountingCloneableState::new();
+
+    let app = Router::new()
+        .fallback(|_: State<CountingCloneableState>| async {})
+        .with_state(state.clone());
+
+    let client = TestClient::new(app);
+
+    // ignore clones made during setup
+    state.setup_done();
+
+    client.get("/does-not-exist").await;
+
+    assert_eq!(state.count(), 4);
+}

axum/src/routing/tests/mod.rs

@@ -16,6 +16,7 @@ use crate::{
     BoxError, Extension, Json, Router, ServiceExt,
 };
 use axum_core::extract::Request;
+use counting_cloneable_state::CountingCloneableState;
 use futures_util::stream::StreamExt;
 use http::{
     header::{ALLOW, CONTENT_LENGTH, HOST},
@@ -27,7 +28,7 @@ use serde_json::json;
 use std::{
     convert::Infallible,
     future::{ready, IntoFuture, Ready},
-    sync::atomic::{AtomicBool, AtomicUsize, Ordering},
+    sync::atomic::{AtomicUsize, Ordering},
     task::{Context, Poll},
     time::Duration,
 };
@@ -905,54 +906,20 @@ fn test_path_for_nested_route() {
 
 #[crate::test]
 async fn state_isnt_cloned_too_much() {
-    static SETUP_DONE: AtomicBool = AtomicBool::new(false);
-    static COUNT: AtomicUsize = AtomicUsize::new(0);
-
-    struct AppState;
-
-    impl Clone for AppState {
-        fn clone(&self) -> Self {
-            #[rustversion::since(1.66)]
-            #[track_caller]
-            fn count() {
-                if SETUP_DONE.load(Ordering::SeqCst) {
-                    let bt = std::backtrace::Backtrace::force_capture();
-                    let bt = bt
-                        .to_string()
-                        .lines()
-                        .filter(|line| line.contains("axum") || line.contains("./src"))
-                        .collect::<Vec<_>>()
-                        .join("\n");
-                    println!("AppState::Clone:\n===============\n{bt}\n");
-                    COUNT.fetch_add(1, Ordering::SeqCst);
-                }
-            }
-
-            #[rustversion::not(since(1.66))]
-            fn count() {
-                if SETUP_DONE.load(Ordering::SeqCst) {
-                    COUNT.fetch_add(1, Ordering::SeqCst);
-                }
-            }
-
-            count();
-
-            Self
-        }
-    }
+    let state = CountingCloneableState::new();
 
     let app = Router::new()
-        .route("/", get(|_: State<AppState>| async {}))
-        .with_state(AppState);
+        .route("/", get(|_: State<CountingCloneableState>| async {}))
+        .with_state(state.clone());
 
     let client = TestClient::new(app);
 
     // ignore clones made during setup
-    SETUP_DONE.store(true, Ordering::SeqCst);
+    state.setup_done();
 
     client.get("/").await;
 
-    assert_eq!(COUNT.load(Ordering::SeqCst), 3);
+    assert_eq!(state.count(), 3);
 }
 
 #[crate::test]

axum/src/test_helpers/counting_cloneable_state.rs

@@ -0,0 +1,52 @@
+use std::sync::{
+    atomic::{AtomicBool, AtomicUsize, Ordering},
+    Arc,
+};
+
+pub(crate) struct CountingCloneableState {
+    state: Arc<InnerState>,
+}
+
+struct InnerState {
+    setup_done: AtomicBool,
+    count: AtomicUsize,
+}
+
+impl CountingCloneableState {
+    pub(crate) fn new() -> Self {
+        let inner_state = InnerState {
+            setup_done: AtomicBool::new(false),
+            count: AtomicUsize::new(0),
+        };
+        CountingCloneableState {
+            state: Arc::new(inner_state),
+        }
+    }
+
+    pub(crate) fn setup_done(&self) {
+        self.state.setup_done.store(true, Ordering::SeqCst);
+    }
+
+    pub(crate) fn count(&self) -> usize {
+        self.state.count.load(Ordering::SeqCst)
+    }
+}
+
+impl Clone for CountingCloneableState {
+    fn clone(&self) -> Self {
+        let state = self.state.clone();
+        if state.setup_done.load(Ordering::SeqCst) {
+            let bt = std::backtrace::Backtrace::force_capture();
+            let bt = bt
+                .to_string()
+                .lines()
+                .filter(|line| line.contains("axum") || line.contains("./src"))
+                .collect::<Vec<_>>()
+                .join("\n");
+            println!("AppState::Clone:\n===============\n{bt}\n");
+            state.count.fetch_add(1, Ordering::SeqCst);
+        }
+
+        CountingCloneableState { state }
+    }
+}

axum/src/test_helpers/mod.rs

@@ -7,6 +7,8 @@ pub(crate) use self::test_client::*;
 
 pub(crate) mod tracing_helpers;
 
+pub(crate) mod counting_cloneable_state;
+
 pub(crate) fn assert_send<T: Send>() {}
 pub(crate) fn assert_sync<T: Sync>() {}