fix: try_recv() channel error : delta may be None

basically if there was no change to report, the oneshot would not get
updated which is bad. so we put back the version we got and send a None
(the channel now has nullable TextChange). so basically its always a
try_recv, but its fine since recv is implemented with try_recv + poll
anyway

src/buffer/controller.rs

@@ -15,6 +15,8 @@ use crate::api::TextChange;
 
 use crate::ext::InternallyMutable;
 
+use super::worker::DeltaRequest;
+
 /// the buffer controller implementation
 ///
 /// for each controller a worker exists, managing outgoing and inbound
@@ -52,7 +54,7 @@ pub(crate) struct BufferControllerInner {
 	pub(crate) poller: mpsc::UnboundedSender<oneshot::Sender<()>>,
 	pub(crate) stopper: mpsc::UnboundedSender<()>, // just exist
 	pub(crate) content_request: mpsc::Sender<oneshot::Sender<String>>,
-	pub(crate) delta_request: mpsc::Sender<(LocalVersion, oneshot::Sender<(LocalVersion, TextChange)>)>,
+	pub(crate) delta_request: mpsc::Sender<DeltaRequest>,
 	pub(crate) callback: watch::Sender<Option<ControllerCallback<BufferController>>>,
 }
 
@@ -85,7 +87,7 @@ impl Controller<TextChange> for BufferController {
 		self.0.delta_request.send((last_update, tx)).await?;
 		let (v, change) = rx.await?;
 		self.0.last_update.set(v);
-		Ok(Some(change))
+		Ok(change)
 	}
 
 	/// enqueue a text change for processing

src/buffer/worker.rs

@@ -14,14 +14,17 @@ use codemp_proto::buffer::{BufferEvent, Operation};
 
 use super::controller::{BufferController, BufferControllerInner};
 
+pub(crate) type DeltaOp = (LocalVersion, Option<TextChange>);
+pub(crate) type DeltaRequest = (LocalVersion, oneshot::Sender<DeltaOp>);
+
 pub(crate) struct BufferWorker {
 	user_id: Uuid,
 	latest_version: watch::Sender<diamond_types::LocalVersion>,
 	ops_in: mpsc::UnboundedReceiver<(TextChange, oneshot::Sender<LocalVersion>)>,
 	poller: mpsc::UnboundedReceiver<oneshot::Sender<()>>,
 	pollers: Vec<oneshot::Sender<()>>,
 	content_checkout: mpsc::Receiver<oneshot::Sender<String>>,
-	delta_req: mpsc::Receiver<(LocalVersion, oneshot::Sender<(LocalVersion, TextChange)>)>,
+	delta_req: mpsc::Receiver<DeltaRequest>,
 	stop: mpsc::UnboundedReceiver<()>,
 	controller: BufferController,
 	callback: watch::Receiver<Option<ControllerCallback<BufferController>>>,
@@ -181,7 +184,9 @@ impl ControllerWorker<TextChange> for BufferWorker {
 									}
 								}
 							};
-							tx.send((new_local_v, tc)).unwrap_or_warn("could not update ops channel -- is controller dead?");
+							tx.send((new_local_v, Some(tc))).unwrap_or_warn("could not update ops channel -- is controller dead?");
+						} else {
+							tx.send((last_ver, None)).unwrap_or_warn("could not update ops channel -- is controller dead?");
 						}
 					},
 				},