cli: fix exec server not reading all stdin with immediate close (#195257)

Fixes https://github.com/microsoft/vscode-remote-tunnels/issues/691

cli/src/rpc.rs

@@ -531,6 +531,7 @@ impl<S: Serialization, C: Send + Sync> RpcDispatcher<S, C> {
 struct StreamRec {
 	write: Option<WriteHalf<DuplexStream>>,
 	q: Vec<Vec<u8>>,
+	ended: bool,
 }
 
 #[derive(Clone, Default)]
@@ -540,13 +541,24 @@ struct Streams {
 
 impl Streams {
 	pub async fn remove(&self, id: u32) {
-		let stream = self.map.lock().unwrap().remove(&id);
-		if let Some(s) = stream {
-			// if there's no 'write' right now, it'll shut down in the write_loop
-			if let Some(mut w) = s.write {
-				let _ = w.shutdown().await;
+		let mut remove = None;
+
+		{
+			let mut map = self.map.lock().unwrap();
+			if let Some(s) = map.get_mut(&id) {
+				if let Some(w) = s.write.take() {
+					map.remove(&id);
+					remove = Some(w);
+				} else {
+					s.ended = true; // will shut down in write loop
+				}
 			}
 		}
+
+		// do this outside of the sync lock:
+		if let Some(mut w) = remove {
+			let _ = w.shutdown().await;
+		}
 	}
 
 	pub fn write(&self, id: u32, buf: Vec<u8>) {
@@ -566,6 +578,7 @@ impl Streams {
 			StreamRec {
 				write: Some(stream),
 				q: Vec::new(),
+				ended: false,
 			},
 		);
 	}
@@ -595,8 +608,13 @@ async fn write_loop(
 			};
 
 			if stream_rec.q.is_empty() {
-				stream_rec.write = Some(w);
-				return;
+				if stream_rec.ended {
+					lock.remove(&id);
+					break;
+				} else {
+					stream_rec.write = Some(w);
+					return;
+				}
 			}
 
 			std::mem::swap(&mut stream_rec.q, &mut items_vec);
@@ -691,3 +709,46 @@ pub enum MaybeSync {
 	Future(BoxFuture<'static, Option<Vec<u8>>>),
 	Sync(Option<Vec<u8>>),
 }
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+
+	#[tokio::test]
+	async fn test_remove() {
+		let streams = Streams::default();
+		let (writer, mut reader) = tokio::io::duplex(1024);
+		streams.insert(1, tokio::io::split(writer).1);
+		streams.remove(1).await;
+
+		assert!(streams.map.lock().unwrap().get(&1).is_none());
+		let mut buffer = Vec::new();
+		assert_eq!(reader.read_to_end(&mut buffer).await.unwrap(), 0);
+	}
+
+	#[tokio::test]
+	async fn test_write() {
+		let streams = Streams::default();
+		let (writer, mut reader) = tokio::io::duplex(1024);
+		streams.insert(1, tokio::io::split(writer).1);
+		streams.write(1, vec![1, 2, 3]);
+
+		let mut buffer = [0; 3];
+		assert_eq!(reader.read_exact(&mut buffer).await.unwrap(), 3);
+		assert_eq!(buffer, [1, 2, 3]);
+	}
+
+	#[tokio::test]
+	async fn test_write_with_immediate_end() {
+		let streams = Streams::default();
+		let (writer, mut reader) = tokio::io::duplex(1);
+		streams.insert(1, tokio::io::split(writer).1);
+		streams.write(1, vec![1, 2, 3]); // spawn write loop
+		streams.write(1, vec![4, 5, 6]); // enqueued while writing
+		streams.remove(1).await; // end stream
+
+		let mut buffer = Vec::new();
+		assert_eq!(reader.read_to_end(&mut buffer).await.unwrap(), 6);
+		assert_eq!(buffer, vec![1, 2, 3, 4, 5, 6]);
+	}
+}