Ignore special files (BLK, CHR, FIFO, SOCKET)

Fixes ocaml#3124

TODO: we should add some tests but I'm unsure about portability here.

Signed-off-by: Emilio Jesus Gallego Arias <e+git@x80.org>

CHANGES.md

@@ -15,6 +15,8 @@ next
 - Improve error message when invalid package names (such as the empty string)
   are passed to `dune build -p`. (#3561, @emillon)
 
+- Ignore special files (BLK, CHR, FIFO, SOCKET) , fixes #3124 (# ???, @ejgallego)
+
 2.6.0 (05/06/2020)
 ------------------
 

src/dune/file_tree.ml

@@ -160,15 +160,16 @@ end = struct
             if Path.Source.is_in_build_dir path then
               Skip
             else
+              let fstat = Path.stat (Path.source path) in
               let is_directory, file =
-                match Path.stat (Path.source path) with
+                match fstat with
                 | exception _ -> (false, File.dummy)
                 | { st_kind = S_DIR; _ } as st -> (true, File.of_stats st)
                 | _ -> (false, File.dummy)
               in
               if is_directory then
                 Right (fn, path, file)
-              else if is_temp_file fn then
+              else if is_temp_file fn || Path.is_special fstat then
                 Skip
               else
                 Left fn)

src/stdune/path.ml

@@ -1279,6 +1279,15 @@ let local_part = function
 
 let stat t = Unix.stat (to_string t)
 
+let is_special { Unix.st_kind; _ } =
+  match st_kind with
+  | S_CHR
+  | S_BLK
+  | S_FIFO
+  | S_SOCK ->
+    true
+  | _ -> false
+
 include (Comparator.Operators (T) : Comparator.OPS with type t := t)
 
 let path_of_local = of_local

src/stdune/path.mli

@@ -349,6 +349,9 @@ val local_part : t -> Local.t
 
 val stat : t -> Unix.stats
 
+(** special files such as fifos and sockets should be ignored *)
+val is_special : Unix.stats -> bool
+
 (* it would be nice to call this [Set.of_source_paths], but it's annoying to
    change the [Set] signature because then we don't comply with [Path_intf.S] *)
 val set_of_source_paths : Source.Set.t -> Set.t