[utils] `Utils.dir_is_empty` was always returning `false`

Summary:
oops_house

This was introduced when upgrading Core, as `Unix.readdir` became deprecated in
favour of `Unix.readdir_opt` but the exception-based logic was left unchanged.

Reviewed By: mbouaziz

Differential Revision: D5461353

fbshipit-source-id: c0994c3

infer/src/base/Utils.ml

@@ -156,18 +156,7 @@ let directory_iter f path =
   in
   if Sys.is_directory path = `Yes then loop [path] else f path
 
-let dir_is_empty path =
-  let dir_handle = Unix.opendir path in
-  let is_empty = ref true in
-  ( try
-      while !is_empty do
-        if not
-             (Option.value_map (Unix.readdir_opt dir_handle) ~default:false
-                ~f:(List.mem ~equal:String.equal ["."; ".."]))
-        then is_empty := false
-      done
-    with End_of_file -> () ) ;
-  Unix.closedir dir_handle ; !is_empty
+let directory_is_empty path = Sys.readdir path |> Array.is_empty
 
 let string_crc_hex32 s = Digest.to_hex (Digest.string s)
 

infer/src/base/Utils.mli

@@ -53,7 +53,7 @@ val directory_fold : ('a -> string -> 'a) -> 'a -> string -> 'a
 val directory_iter : (string -> unit) -> string -> unit
 (** Functional iter function over all the file of a directory *)
 
-val dir_is_empty : string -> bool
+val directory_is_empty : string -> bool
 (** Returns true if a given directory is empty. The directory is assumed to exist. *)
 
 val read_json_file : string -> (Yojson.Basic.json, string) Result.t

infer/src/integration/Driver.ml

@@ -182,7 +182,7 @@ let check_captured_empty driver_mode =
   let clean_command_opt = clean_compilation_command driver_mode in
   (* if merge is passed, the captured folder will be empty at this point,
      but will be filled later on. *)
-  if Utils.dir_is_empty Config.captured_dir && not Config.merge then (
+  if Utils.directory_is_empty Config.captured_dir && not Config.merge then (
     ( match clean_command_opt with
     | Some clean_command
      -> L.user_warning "@\nNothing to compile. Try running `%s` first.@." clean_command