Notify superseded plugin processes and support SDK draining

sdk/src/endpoints.rs

@@ -65,7 +65,7 @@ impl<T: serde::de::DeserializeOwned + 'static> IntoFuture for EndpointCall<T> {
     }
 }
 
-/// Publish a declared interface and keep its listener alive until stdin EOF.
+/// Publish a declared interface and keep its listener alive until stdin EOF or [`drain`].
 #[cfg(target_os = "wasi")]
 pub async fn listen<T: Interface>(path: impl AsRef<Path>, value: Rc<T>) -> Result<()> {
     use wstd::iter::AsyncIterator;
@@ -80,7 +80,7 @@ pub async fn listen<T: Interface>(path: impl AsRef<Path>, value: Rc<T>) -> Resul
         while let Some(Ok(stream)) = incoming.next().await {
             let value = value.clone();
             let name = name.clone();
-            crate::transport::endpoint_task(async move {
+            background(async move {
                 let _ = serve_connection(stream, value, name).await;
             });
         }
@@ -211,7 +211,11 @@ async fn serve_connection<T: Interface>(
     use futures::{FutureExt, StreamExt};
     let (mut reader, mut writer) = stream.split();
     let mut lines = crate::lines::Lines::default();
-    while let Some(request) = lines.rpc(&mut reader).await? {
+    while let Some(request) = crate::transport::until_drained(lines.rpc(&mut reader))
+        .await
+        .transpose()?
+        .flatten()
+    {
         let method = request["method"].as_str().unwrap_or_default();
         let (tx, mut rx) = futures::channel::mpsc::unbounded();
         let ctx = Ctx {