automatically retry returning data in syncv3 (#652)

* automatically retry returning data in syncv3

* reference service

* clippy fixes

src/api/client/sync/v3.rs

@@ -124,6 +124,33 @@ pub(crate) async fn sync_events_route(
 	// Setup watchers, so if there's no response, we can wait for them
 	let watcher = services.sync.watch(sender_user, sender_device);
 
+	let response = build_sync_events(&services, &body).await?;
+	if body.body.full_state
+		|| !(response.rooms.is_empty()
+			&& response.presence.is_empty()
+			&& response.account_data.is_empty()
+			&& response.device_lists.is_empty()
+			&& response.to_device.is_empty())
+	{
+		return Ok(response);
+	}
+
+	// Hang a few seconds so requests are not spammed
+	// Stop hanging if new info arrives
+	let default = Duration::from_secs(30);
+	let duration = cmp::min(body.body.timeout.unwrap_or(default), default);
+	_ = tokio::time::timeout(duration, watcher).await;
+
+	// Retry returning data
+	build_sync_events(&services, &body).await
+}
+
+pub(crate) async fn build_sync_events(
+	services: &Services,
+	body: &Ruma<sync_events::v3::Request>,
+) -> Result<sync_events::v3::Response, RumaResponse<UiaaResponse>> {
+	let (sender_user, sender_device) = body.sender();
+
 	let next_batch = services.globals.current_count()?;
 	let next_batch_string = next_batch.to_string();
 
@@ -163,7 +190,7 @@ pub(crate) async fn sync_events_route(
 		.map(ToOwned::to_owned)
 		.broad_filter_map(|room_id| {
 			load_joined_room(
-				&services,
+				services,
 				sender_user,
 				sender_device,
 				room_id.clone(),
@@ -196,7 +223,7 @@ pub(crate) async fn sync_events_route(
 		.rooms_left(sender_user)
 		.broad_filter_map(|(room_id, _)| {
 			handle_left_room(
-				&services,
+				services,
 				since,
 				room_id.clone(),
 				sender_user,
@@ -242,7 +269,7 @@ pub(crate) async fn sync_events_route(
 	let presence_updates: OptionFuture<_> = services
 		.globals
 		.allow_local_presence()
-		.then(|| process_presence_updates(&services, since, sender_user))
+		.then(|| process_presence_updates(services, since, sender_user))
 		.into();
 
 	let account_data = services
@@ -292,7 +319,7 @@ pub(crate) async fn sync_events_route(
 		.stream()
 		.broad_filter_map(|user_id| async move {
 			let no_shared_encrypted_room =
-				!share_encrypted_room(&services, sender_user, &user_id, None).await;
+				!share_encrypted_room(services, sender_user, &user_id, None).await;
 			no_shared_encrypted_room.then_some(user_id)
 		})
 		.ready_fold(HashSet::new(), |mut device_list_left, user_id| {
@@ -327,21 +354,6 @@ pub(crate) async fn sync_events_route(
 		to_device: ToDevice { events: to_device_events },
 	};
 
-	// TODO: Retry the endpoint instead of returning
-	if !full_state
-		&& response.rooms.is_empty()
-		&& response.presence.is_empty()
-		&& response.account_data.is_empty()
-		&& response.device_lists.is_empty()
-		&& response.to_device.is_empty()
-	{
-		// Hang a few seconds so requests are not spammed
-		// Stop hanging if new info arrives
-		let default = Duration::from_secs(30);
-		let duration = cmp::min(body.body.timeout.unwrap_or(default), default);
-		_ = tokio::time::timeout(duration, watcher).await;
-	}
-
 	Ok(response)
 }