feature(fsevents): multliplex watchers

Allow to create multiple watchers and run them in the same runloop

Signed-off-by: Rudi Grinberg <[email protected]>

src/dune_engine/fs_memo.ml

@@ -31,8 +31,9 @@ let t_ref = ref (Initialization_state.Uninitialized [])
    root is not sufficient to receive events for creation of "root/a/b/c/d".
    (however, subscribing to "root/a/b/c" is sufficient for that) *)
 let watch_path dune_file_watcher path =
-  try Dune_file_watcher.add_watch dune_file_watcher path with
-  | Unix.Unix_error (ENOENT, _, _) -> (
+  match Dune_file_watcher.add_watch dune_file_watcher path with
+  | Ok () -> ()
+  | Error `Does_not_exist -> (
     (* If we're at the root of the workspace (or the unix root) then we can't
        get ENOENT because dune can't start without a workspace and unix root
        always exists, so this [_exn] can't raise (except if the user delets the
@@ -42,9 +43,17 @@ let watch_path dune_file_watcher path =
        the parent. We still try to add a watch for the file itself after that
        succeeds, in case the file was created already before we started watching
        its parent. *)
-    Dune_file_watcher.add_watch dune_file_watcher containing_dir;
-    try Dune_file_watcher.add_watch dune_file_watcher path with
-    | Unix.Unix_error (ENOENT, _, _) -> ())
+    (match Dune_file_watcher.add_watch dune_file_watcher containing_dir with
+    | Ok () -> ()
+    | Error `Does_not_exist ->
+      Log.info
+        [ Pp.textf "attempted to add watch to non-existant directory %s"
+            (Path.to_string containing_dir)
+        ]);
+    match Dune_file_watcher.add_watch dune_file_watcher path with
+    | Error `Does_not_exist
+    | Ok () ->
+      ())
 
 let watch_path_using_ref path =
   match !t_ref with