Fix fut_await cancellation

lib_eio_js/browser/eio_browser.ml

@@ -85,10 +85,11 @@ module Scheduler = struct
 
   let stop t = Brr.Ev.unlisten t.listener
 
-  let wakeup =
+  (* A new message must be created for every call. *)
+  let wakeup t =
     let open Brr_io in
     let args = [| Ev.create Message.Ev.message |> Ev.to_jv |] in
-    fun t -> Jv.call (El.to_jv t.scheduler) "dispatchEvent" args |> ignore
+    Jv.call (El.to_jv t.scheduler) "dispatchEvent" args |> ignore
 
   let enqueue_thread t k v =
     Run_queue.push t.run_q (fun () -> Suspended.continue k v);
@@ -124,7 +125,7 @@ let await fut =
   enter_unchecked @@ fun st k ->
   (* There is no way to cancel a Javascript promise (which Fut wraps) so we
      have to leak this memory unfortunately. *)
-  let cancelled = ref true in
+  let cancelled = ref false in
   Fiber_context.set_cancel_fn k.fiber (fun exn -> cancelled := true; Scheduler.enqueue_failed_thread st k exn);
   Fut.await fut (fun v ->
       if not !cancelled then begin

lib_eio_js/browser/test/test.ml

@@ -56,6 +56,12 @@ module Browser_tests = struct
     in
     Alcotest.(check string) "timeout cancelled" "B" v
 
+  let test_fut_await () =
+    let p, r = Fut.create () in
+    Fiber.both
+      (fun () -> Eio_browser.await p)
+      (fun () -> r ())
+
   let test_fut_cancel () =
     let p, _ = Fut.create () in
     let v =
@@ -76,6 +82,7 @@ module Browser_tests = struct
 
   let tests = [
     Alcotest.test_case "timeout cancelled" `Quick test_timeout_cancel;
+    Alcotest.test_case "fut await" `Quick test_fut_await;
     Alcotest.test_case "fut cancelled" `Quick test_fut_cancel;
     Alcotest.test_case "test timeout" `Quick test_timeout;
     Alcotest.test_case "test multiple timeouts" `Quick test_multiple_timeouts