Remove the hook when the process exits

Before, we only removed the hook if the application awaited the exit
status.

Author: talex5

lib_eio_luv/eio_luv.ml

@@ -556,7 +556,6 @@ module Low_level = struct
     type t = {
       proc : Luv.Process.t;
       status : (int * int64) Promise.t;
-      hook : Switch.hook;
     }
 
     let pid t = Luv.Process.pid t.proc
@@ -565,24 +564,28 @@ module Low_level = struct
       let parent_pipe = Handle.to_luv parent_pipe in
       Luv.Process.to_parent_pipe ?readable_in_child ?writable_in_child ?overlapped ~fd ~parent_pipe ()
 
-    let await_exit t =
-      let res = Promise.await t.status in
-      Switch.remove_hook t.hook;
-      res
+    let await_exit t = Promise.await t.status
 
     let has_exited t = Promise.is_resolved t.status
 
     let send_signal t i = Luv.Process.kill t.proc i |> or_raise
 
     let spawn ?cwd ?env ?uid ?gid ?(redirect=[]) ~sw cmd args =
-      let promise, resolve = Promise.create () in
+      let status, set_status = Promise.create () in
+      let hook = ref None in
       let on_exit _ ~exit_status ~term_signal =
-        let status = (term_signal, exit_status) in
-        Promise.resolve resolve status
+        Option.iter Switch.remove_hook !hook;
+        Promise.resolve set_status (term_signal, exit_status)
       in
       let proc = Luv.Process.spawn ?environment:env ?uid ?gid ~loop:(get_loop ()) ?working_directory:cwd ~redirect ~on_exit cmd args |> or_raise in
-      let hook = Switch.on_release_cancellable sw (fun () -> Luv.Process.kill proc Luv.Signal.sigkill |> or_raise) in
-      { proc; status = promise; hook }
+      if not (Promise.is_resolved status) then (
+        let h = Switch.on_release_cancellable sw (fun () ->
+            Luv.Process.kill proc Luv.Signal.sigkill |> or_raise;
+            ignore (Promise.await status)
+          ) in
+        hook := Some h
+      );
+    { proc; status }
   end
 
   module Poll = Poll