chore(sdk): Add EventHandlerDropGuard

It isn't used for now, but will be soon.

crates/matrix-sdk/src/client/mod.rs

@@ -2641,7 +2641,7 @@ pub(crate) mod tests {
         Client::builder().homeserver_url(homeserver).server_versions([MatrixVersion::V1_0])
     }
 
-    async fn no_retry_test_client(homeserver_url: Option<String>) -> Client {
+    pub(crate) async fn no_retry_test_client(homeserver_url: Option<String>) -> Client {
         test_client_builder(homeserver_url)
             .request_config(RequestConfig::new().disable_retry())
             .build()

crates/matrix-sdk/src/event_handler.rs

@@ -366,6 +366,14 @@ impl Client {
         EventHandlerHandle { key, handler_id }
     }
 
+    #[allow(dead_code)]
+    pub(crate) fn event_handler_drop_guard(
+        &self,
+        handle: EventHandlerHandle,
+    ) -> EventHandlerDropGuard {
+        EventHandlerDropGuard { client: self.clone(), handle }
+    }
+
     pub(crate) async fn handle_sync_events<T>(
         &self,
         kind: EventKind,
@@ -514,6 +522,18 @@ impl Client {
     }
 }
 
+#[derive(Debug)]
+pub(crate) struct EventHandlerDropGuard {
+    handle: EventHandlerHandle,
+    client: Client,
+}
+
+impl Drop for EventHandlerDropGuard {
+    fn drop(&mut self) {
+        self.client.remove_event_handler(self.handle.clone());
+    }
+}
+
 macro_rules! impl_event_handler {
     ($($ty:ident),* $(,)?) => {
         impl<Ev, Fun, Fut, $($ty),*> EventHandler<Ev, ($($ty,)*)> for Fun
@@ -909,4 +929,20 @@ mod tests {
 
         Ok(())
     }
+
+    #[async_test]
+    async fn event_handler_drop_guard() {
+        let client = crate::client::tests::no_retry_test_client(None).await;
+
+        let handle = client.add_event_handler(|_ev: OriginalSyncRoomMemberEvent| async {});
+        assert_eq!(client.event_handlers().len(), 1);
+
+        {
+            let _guard = client.event_handler_drop_guard(handle);
+            assert_eq!(client.event_handlers().len(), 1);
+            // guard dropped here
+        }
+
+        assert_eq!(client.event_handlers().len(), 0);
+    }
 }