fix: ensure websocket is flushed (#6347)

crates/anvil/server/src/pubsub.rs

@@ -170,7 +170,7 @@ where
     fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
         let pin = self.get_mut();
         loop {
-            // drive the sink
+            // drive the websocket
             while let Poll::Ready(Ok(())) = pin.connection.poll_ready_unpin(cx) {
                 // only start sending if socket is ready
                 if let Some(msg) = pin.pending.pop_front() {
@@ -182,6 +182,14 @@ where
                 }
             }
 
+            // Ensure any pending messages are flushed
+            // this needs to be called manually for tungsenite websocket: <https://github.com/foundry-rs/foundry/issues/6345>
+            if let Poll::Ready(Err(err)) = pin.connection.poll_flush_unpin(cx) {
+                trace!(target: "rpc", ?err, "websocket err");
+                // close the connection
+                return Poll::Ready(())
+            }
+
             loop {
                 match pin.connection.poll_next_unpin(cx) {
                     Poll::Ready(Some(req)) => match req {