4 files changed, 70 insertions, 1 deletions

diff --git a/cli/ops/dispatch_json.rs b/cli/ops/dispatch_json.rs
index de1f0a752..87cfff51d 100644
--- a/cli/ops/dispatch_json.rs
+++ b/cli/ops/dispatch_json.rs
@@ -14,6 +14,9 @@ pub type AsyncJsonOp =
 pub enum JsonOp {
   Sync(Value),
   Async(AsyncJsonOp),
+  /// AsyncUnref is the variation of Async, which doesn't block the program
+  /// exiting.
+  AsyncUnref(AsyncJsonOp),
 }
 
 fn json_err(err: ErrBox) -> Value {
@@ -77,6 +80,13 @@ where
         });
         CoreOp::Async(fut2.boxed())
       }
+      Ok(JsonOp::AsyncUnref(fut)) => {
+        assert!(promise_id.is_some());
+        let fut2 = fut.then(move |result| {
+          futures::future::ok(serialize_result(promise_id, result))
+        });
+        CoreOp::AsyncUnref(fut2.boxed())
+      }
       Err(sync_err) => {
         let buf = serialize_result(promise_id, Err(sync_err));
         if is_sync {
diff --git a/cli/state.rs b/cli/state.rs
index 02c258280..c07b3d5d0 100644
--- a/cli/state.rs
+++ b/cli/state.rs
@@ -110,6 +110,14 @@ impl ThreadSafeState {
           });
           Op::Async(result_fut.boxed())
         }
+        Op::AsyncUnref(fut) => {
+          let state = state.clone();
+          let result_fut = fut.map_ok(move |buf: Buf| {
+            state.metrics_op_completed(buf.len());
+            buf
+          });
+          Op::AsyncUnref(result_fut.boxed())
+        }
       }
     }
   }
diff --git a/core/isolate.rs b/core/isolate.rs
index f734f687c..e4405b704 100644
--- a/core/isolate.rs
+++ b/core/isolate.rs
@@ -16,6 +16,7 @@ use crate::shared_queue::SharedQueue;
 use crate::shared_queue::RECOMMENDED_SIZE;
 use futures::future::FutureExt;
 use futures::future::TryFutureExt;
+use futures::stream::select;
 use futures::stream::FuturesUnordered;
 use futures::stream::StreamExt;
 use futures::task::AtomicWaker;
@@ -178,6 +179,7 @@ pub struct Isolate {
   needs_init: bool,
   pub(crate) shared: SharedQueue,
   pending_ops: FuturesUnordered<PendingOpFuture>,
+  pending_unref_ops: FuturesUnordered<PendingOpFuture>,
   have_unpolled_ops: bool,
   startup_script: Option<OwnedScript>,
   pub op_registry: Arc<OpRegistry>,
@@ -340,6 +342,7 @@ impl Isolate {
       shared,
       needs_init,
       pending_ops: FuturesUnordered::new(),
+      pending_unref_ops: FuturesUnordered::new(),
       have_unpolled_ops: false,
       startup_script,
       op_registry: Arc::new(OpRegistry::new()),
@@ -519,6 +522,12 @@ impl Isolate {
         self.have_unpolled_ops = true;
         None
       }
+      Op::AsyncUnref(fut) => {
+        let fut2 = fut.map_ok(move |buf| (op_id, buf));
+        self.pending_unref_ops.push(fut2.boxed());
+        self.have_unpolled_ops = true;
+        None
+      }
     }
   }
 
@@ -713,7 +722,9 @@ impl Future for Isolate {
       // Now handle actual ops.
       inner.have_unpolled_ops = false;
       #[allow(clippy::match_wild_err_arm)]
-      match inner.pending_ops.poll_next_unpin(cx) {
+      match select(&mut inner.pending_ops, &mut inner.pending_unref_ops)
+        .poll_next_unpin(cx)
+      {
         Poll::Ready(Some(Err(_))) => panic!("unexpected op error"),
         Poll::Ready(None) => break,
         Poll::Pending => break,
@@ -816,6 +827,7 @@ pub mod tests {
 
   pub enum Mode {
     Async,
+    AsyncUnref,
     OverflowReqSync,
     OverflowResSync,
     OverflowReqAsync,
@@ -838,6 +850,17 @@ pub mod tests {
             let buf = vec![43u8, 0, 0, 0].into_boxed_slice();
             Op::Async(futures::future::ok(buf).boxed())
           }
+          Mode::AsyncUnref => {
+            assert_eq!(control.len(), 1);
+            assert_eq!(control[0], 42);
+            let fut = async {
+              // This future never finish.
+              futures::future::pending::<()>().await;
+              let buf = vec![43u8, 0, 0, 0].into_boxed_slice();
+              Ok(buf)
+            };
+            Op::AsyncUnref(fut.boxed())
+          }
           Mode::OverflowReqSync => {
             assert_eq!(control.len(), 100 * 1024 * 1024);
             let buf = vec![43u8, 0, 0, 0].into_boxed_slice();
@@ -956,6 +979,31 @@ pub mod tests {
   }
 
   #[test]
+  fn test_poll_async_optional_ops() {
+    run_in_task(|cx| {
+      let (mut isolate, dispatch_count) = setup(Mode::AsyncUnref);
+      js_check(isolate.execute(
+        "check1.js",
+        r#"
+          Deno.core.setAsyncHandler(1, (buf) => {
+            // This handler will never be called
+            assert(false);
+          });
+          let control = new Uint8Array([42]);
+          Deno.core.send(1, control);
+        "#,
+      ));
+      assert_eq!(dispatch_count.load(Ordering::Relaxed), 1);
+      // The above op never finish, but isolate can finish
+      // because the op is an unreffed async op.
+      assert!(match isolate.poll_unpin(cx) {
+        Poll::Ready(Ok(_)) => true,
+        _ => false,
+      });
+    })
+  }
+
+  #[test]
   fn terminate_execution() {
     let (tx, rx) = std::sync::mpsc::channel::<bool>();
     let tx_clone = tx.clone();
diff --git a/core/ops.rs b/core/ops.rs
index 7ed142682..e0bdb0184 100644
--- a/core/ops.rs
+++ b/core/ops.rs
@@ -21,6 +21,9 @@ pub type OpResult<E> = Result<Op<E>, E>;
 pub enum Op<E> {
   Sync(Buf),
   Async(OpAsyncFuture<E>),
+  /// AsyncUnref is the variation of Async, which doesn't block the program
+  /// exiting.
+  AsyncUnref(OpAsyncFuture<E>),
 }
 
 pub type CoreError = ();