fix: make custom runtime control messages clone-safe

CHANGELOG.md

@@ -55,6 +55,8 @@ and its version numbers follow [Semantic Versioning](https://semver.org/).
 - `RuntimeHandle` now supports forwarding arbitrary control messages, including
   `RuntimeControlMessage::Custom(...)`, via `control(...)` and `custom(...)`
   helpers (`#20`).
+- `RuntimeControlMessage::Custom(...)` is now clone-safe and no longer panics
+  when cloned (`#27`).
 
 ### Removed
 - Unused aliases and imports producing compiler warnings.

src/runtime_guard.rs

@@ -156,7 +156,7 @@ impl RuntimeGuard {
     where
         T: std::any::Any + Send + Sync + 'static,
     {
-        self.control(RuntimeControlMessage::Custom(Box::new(message)))
+        self.control(RuntimeControlMessage::Custom(Arc::new(message)))
     }
 
     /// **Busy-wait** helper for tests and demos.

src/runtime_handle.rs

@@ -44,7 +44,7 @@ impl RuntimeHandle {
     where
         T: std::any::Any + Send + Sync + 'static,
     {
-        self.control(RuntimeControlMessage::Custom(Box::new(message)))
+        self.control(RuntimeControlMessage::Custom(Arc::new(message)))
     }
 }
 

src/runtime_process.rs

@@ -68,28 +68,14 @@ pub enum ProcessOperation<T> {
 /// wildcard arm (`_`) when pattern-matching so that new variants introduced in
 /// future releases do not break compilation.
 #[non_exhaustive]
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub enum RuntimeControlMessage {
     /// Trigger a *hot reload*.
     Reload,
     /// Request a *graceful shutdown*.
     Shutdown,
     /// User-defined message for custom extensions.
-    Custom(Box<dyn std::any::Any + Send + Sync>),
-}
-
-impl Clone for RuntimeControlMessage {
-    /// Manual implementation is required because the enum is
-    /// `#[non_exhaustive]`; remember to update this when adding new variants.
-    fn clone(&self) -> Self {
-        match self {
-            RuntimeControlMessage::Reload => RuntimeControlMessage::Reload,
-            RuntimeControlMessage::Shutdown => RuntimeControlMessage::Shutdown,
-            RuntimeControlMessage::Custom(_) => {
-                panic!("Cloning `Custom` control messages is not supported")
-            }
-        }
-    }
+    Custom(Arc<dyn std::any::Any + Send + Sync>),
 }
 
 impl<R> Runnable for Arc<R>

tests/integration.rs

@@ -313,6 +313,22 @@ async fn test_runtime_handle_custom_control_message_is_delivered() {
     }
 }
 
+#[test]
+fn test_runtime_control_message_custom_clone_is_safe() {
+    let msg = RuntimeControlMessage::Custom(Arc::new(7_u8));
+    let cloned = msg.clone();
+
+    match cloned {
+        RuntimeControlMessage::Custom(payload) => {
+            let value = payload
+                .downcast::<u8>()
+                .expect("expected u8 custom payload");
+            assert_eq!(*value, 7_u8);
+        }
+        _ => panic!("expected custom control message"),
+    }
+}
+
 #[tokio::test]
 async fn test_reload_dispatch_is_parallel() {
     let mut manager = ProcessManager::new();