feat: handle unknown cursor

...by discarding and logging a warning, instead of displaying an
empty one.

src/cursor/worker.rs

@@ -18,11 +18,36 @@ struct CursorWorker {
 	stream: mpsc::Receiver<oneshot::Sender<Option<Cursor>>>,
 	poll: mpsc::UnboundedReceiver<oneshot::Sender<()>>,
 	pollers: Vec<oneshot::Sender<()>>,
-	store: std::collections::VecDeque<Cursor>,
+	store: std::collections::VecDeque<codemp_proto::cursor::CursorEvent>,
 	controller: std::sync::Weak<CursorControllerInner>,
 	callback: watch::Receiver<Option<ControllerCallback<CursorController>>>,
 }
 
+impl CursorWorker {
+	fn handle_recv(&mut self, tx: oneshot::Sender<Option<Cursor>>) {
+		tx.send(
+			self.store.pop_front().and_then(|event| {
+				let user_id = Uuid::from(event.user);
+				if let Some(user_name) = self.map.get(&user_id).map(|u| u.name.clone()) {
+					Some(Cursor {
+						user: user_name,
+						sel: Selection {
+							buffer: event.position.buffer.path,
+							start_row: event.position.start.row,
+							start_col: event.position.start.col,
+							end_row: event.position.end.row,
+							end_col: event.position.end.col
+						}
+					})
+				} else {
+					tracing::warn!("received cursor for unknown user {user_id}");
+					None
+				}
+			})
+		).unwrap_or_warn("client gave up receiving!");
+	}
+}
+
 impl CursorController {
 	pub(crate) fn spawn(
 		user_map: Arc<dashmap::DashMap<Uuid, User>>,
@@ -88,19 +113,7 @@ impl CursorController {
 					None => break, // clean exit, just weird that we got it here
 					Some(controller) => {
 						tracing::debug!("received cursor from server");
-						let user_id = Uuid::from(cur.user);
-						let cursor = Cursor {
-							user: worker.map.get(&user_id).map(|u| u.name.clone()).unwrap_or_default(),
-							sel: Selection {
-								buffer: cur.position.buffer.path,
-								start_row: cur.position.start.row,
-								start_col: cur.position.start.col,
-								end_row: cur.position.end.row,
-								end_col: cur.position.end.col
-							}
-						};
-
-						worker.store.push_back(cursor);
+						worker.store.push_back(cur);
 						for tx in worker.pollers.drain(..) {
 							tx.send(()).unwrap_or_warn("poller dropped before unblocking");
 						}
@@ -112,8 +125,7 @@ impl CursorController {
 				},
 
 				// client wants to get next cursor event
-				Some(tx) = worker.stream.recv() => tx.send(worker.store.pop_front())
-					.unwrap_or_warn("client gave up receiving"),
+				Some(tx) = worker.stream.recv() => worker.handle_recv(tx),
 
 				else => break,
 			}