Revert "Add native polling mode support on Windows (ocaml#7010)"

This reverts commit 73506c2.

boot/libs.ml

@@ -48,7 +48,6 @@ let local_libraries =
   ; ("vendor/ocaml-inotify/src", Some "Ocaml_inotify", false, None)
   ; ("src/async_inotify_for_dune", Some "Async_inotify_for_dune", false,
     None)
-  ; ("src/fswatch_win", Some "Fswatch_win", false, None)
   ; ("src/dune_file_watcher", Some "Dune_file_watcher", false, None)
   ; ("src/dune_engine", Some "Dune_engine", false, None)
   ; ("src/dune_threaded_console", Some "Dune_threaded_console", false, None)

src/dune_file_watcher/dune

@@ -9,8 +9,7 @@
   threads.posix
   ocaml_inotify
   async_inotify_for_dune
-  dune_re
-  fswatch_win)
+  dune_re)
  (synopsis "Internal Dune library, do not use!")
  (instrumentation
   (backend bisect_ppx)))

src/dune_file_watcher/dune_file_watcher.ml

@@ -137,10 +137,6 @@ type kind =
       ; latency : float
       }
   | Inotify of Inotify_lib.t
-  | Fswatch_win of
-      { t : Fswatch_win.t
-      ; scheduler : Scheduler.t
-      }
 
 type t =
   { kind : kind
@@ -160,9 +156,6 @@ let exclude_patterns =
   ; {|/#[^#]*#$|}
   ; {|^4913$|} (* https://github.com/neovim/neovim/issues/3460 *)
   ; {|/4913$|}
-  ; {|/.git|}
-  ; {|/.hg|}
-  ; {|:/windows|}
   ]
 
 module Re = Dune_re
@@ -209,7 +202,6 @@ let shutdown t =
         Fsevents.stop fsevents.sync;
         Watch_trie.to_list fsevents.external_
         |> List.iter ~f:(fun (_, fs) -> Fsevents.stop fs))
-  | Fswatch_win { t; _ } -> `Thunk (fun () -> Fswatch_win.shutdown t)
 
 let buffer_capacity = 65536
 
@@ -361,7 +353,6 @@ let select_watcher_backend () =
     assert (Ocaml_inotify.Inotify.supported_by_the_os ());
     `Inotify_lib)
   else if Fsevents.available () then `Fsevents
-  else if Sys.win32 then `Fswatch_win
   else fswatch_backend ()
 
 let prepare_sync () =
@@ -588,48 +579,6 @@ let create_fsevents ?(latency = 0.2) ~(scheduler : Scheduler.t) () =
   ; sync_table
   }
 
-let fswatch_win_callback ~(scheduler : Scheduler.t) ~sync_table event =
-  let dir = Fswatch_win.Event.directory event in
-  let filename = Filename.concat dir (Fswatch_win.Event.path event) in
-  let localized_path =
-    Path.Expert.try_localize_external (Path.of_string filename)
-  in
-  match localized_path with
-  | In_build_dir _ -> (
-    if Fs_sync.is_special_file_fsevents localized_path then
-      match Fswatch_win.Event.action event with
-      | Added | Modified -> (
-        match Fs_sync.consume_event sync_table filename with
-        | None -> ()
-        | Some id ->
-          scheduler.thread_safe_send_emit_events_job (fun () -> [ Sync id ]))
-      | Removed | Renamed_new | Renamed_old -> ())
-  | path ->
-    let normalized_filename =
-      String.concat ~sep:"/"
-        (String.split_on_char ~sep:'\\' (String.lowercase_ascii filename))
-    in
-    if not (should_exclude normalized_filename) then
-      scheduler.thread_safe_send_emit_events_job (fun () ->
-          let kind =
-            match Fswatch_win.Event.action event with
-            | Added | Renamed_new -> Fs_memo_event.Created
-            | Removed | Renamed_old -> Deleted
-            | Modified -> File_changed
-          in
-          [ Fs_memo_event { kind; path } ])
-
-let create_fswatch_win ~(scheduler : Scheduler.t) ~debounce_interval:sleep =
-  let sync_table = Table.create (module String) 64 in
-  let t = Fswatch_win.create () in
-  Fswatch_win.add t (Path.to_absolute_filename Path.root);
-  scheduler.spawn_thread (fun () ->
-      while true do
-        let events = Fswatch_win.wait t ~sleep in
-        List.iter ~f:(fswatch_win_callback ~scheduler ~sync_table) events
-      done);
-  { kind = Fswatch_win { t; scheduler }; sync_table }
-
 let create_external ~root ~debounce_interval ~scheduler ~backend =
   match debounce_interval with
   | None -> create_no_buffering ~root ~scheduler ~backend
@@ -645,31 +594,15 @@ let create_default ?fsevents_debounce ~scheduler () =
       ~debounce_interval:(Some 0.5 (* seconds *)) ~backend
   | `Fsevents -> create_fsevents ?latency:fsevents_debounce ~scheduler ()
   | `Inotify_lib -> create_inotifylib ~scheduler
-  | `Fswatch_win ->
-    create_fswatch_win ~scheduler ~debounce_interval:500 (* milliseconds *)
 
 let wait_for_initial_watches_established_blocking t =
   match t.kind with
   | Fswatch c -> c.wait_for_watches_established ()
-  | Fsevents _ | Inotify _ | Fswatch_win _ ->
+  | Fsevents _ | Inotify _ ->
     (* no initial watches needed: all watches should be set up at the time just
        before file access *)
     ()
 
-(* Return the parent directory of [ext] if [ext] denotes a file. *)
-let parent_directory ext =
-  let rec loop p =
-    if Path.is_directory (Path.external_ p) then Some ext
-    else
-      match Path.External.parent p with
-      | None ->
-        User_warning.emit
-          [ Pp.textf "Refusing to watch %s" (Path.External.to_string ext) ];
-        None
-      | Some ext -> loop ext
-  in
-  loop ext
-
 let add_watch t path =
   match t.kind with
   | Fsevents f -> (
@@ -678,7 +611,21 @@ let add_watch t path =
     | In_build_dir _ ->
       Code_error.raise "attempted to watch a directory in build" []
     | External ext -> (
-      match parent_directory ext with
+      let ext =
+        let rec loop p =
+          if Path.is_directory (Path.external_ p) then Some ext
+          else
+            match Path.External.parent p with
+            | None ->
+              User_warning.emit
+                [ Pp.textf "Refusing to watch %s" (Path.External.to_string ext)
+                ];
+              None
+            | Some ext -> loop ext
+        in
+        loop ext
+      in
+      match ext with
       | None -> Ok ()
       | Some ext -> (
         let watch =
@@ -702,16 +649,5 @@ let add_watch t path =
   | Inotify inotify -> (
     try Ok (Inotify_lib.add inotify (Path.to_string path))
     with Unix.Unix_error (ENOENT, _, _) -> Error `Does_not_exist)
-  | Fswatch_win fswatch -> (
-    match path with
-    | In_build_dir _ ->
-      Code_error.raise "attempted to watch a directory in build" []
-    | Path.In_source_tree _ -> Ok ()
-    | External ext -> (
-      match parent_directory ext with
-      | None -> Ok ()
-      | Some _ ->
-        Fswatch_win.add fswatch.t (Path.to_absolute_filename path);
-        Ok ()))
 
 let emit_sync = Fs_sync.emit