Abort the "send to client" task when the websocket is closed

src/net/server.rs

@@ -4,6 +4,7 @@ use futures::{channel::mpsc::*, future::try_join, lock::Mutex, prelude::*};
 use serde_json::json;
 use std::sync::Arc;
 use stream::iter;
+use future::abortable;
 
 /// There is a point at which a client falls far enough behind
 /// that it's probably not worth trying to catch them up; for now,
@@ -97,17 +98,25 @@ pub async fn run_client(
     // register player
     let player_id = handle.server.lock().await.add_player(sender).await?;
 
-    let output_task = receiver.map(Ok).forward(sink);
+    let (output_task, output_handle) = abortable(receiver.map(Ok).forward(sink));
 
     let input_task = async {
         loop {
             match source.try_next().await? {
                 Some(msg) => handle.server.lock().await.process_message(player_id, msg),
-                None => break Ok(()),
-            }
+                None => break,
             }
         };
-    let result = try_join(output_task, input_task).await.map(|_| ());
+        // stop the sink so it won't error
+        output_handle.abort();
+        Ok(())
+    };
+
+    // intentional aborting is not a reportable error
+    let output_task = output_task
+        .map(|result| result.unwrap_or(Ok(())));
+
+    let result = try_join(output_task, input_task).await.map(|((),())| ());
 
     // deregister player, whether normally or due to error
     handle.server.lock().await.remove_player(player_id);