Port Io to use Path.t

bin/main.ml

@@ -75,7 +75,7 @@ module Main = struct
   let setup ~log ?external_lib_deps_mode common =
     setup
       ~log
-      ?workspace_file:common.workspace_file
+      ?workspace_file:(Option.map ~f:Path.of_string common.workspace_file)
       ?only_packages:common.only_packages
       ?external_lib_deps_mode
       ?x:common.x
@@ -182,7 +182,7 @@ let help_secs =
 type config_file =
   | No_config
   | Default
-  | This of string
+  | This of Path.t
 
 let incompatible a b =
   `Error (true,
@@ -234,7 +234,7 @@ let common =
     let config =
       match config_file with
       | No_config  -> Config.default
-      | This fname -> Config.load_config_file ~fname
+      | This fname -> Config.load_config_file fname
       | Default    ->
         if Config.inside_dune then
           Config.default
@@ -410,7 +410,7 @@ let common =
       let merge config_file no_config =
         match config_file, no_config with
         | None   , false -> `Ok (None                , Default)
-        | Some fn, false -> `Ok (Some "--config-file", This fn)
+        | Some fn, false -> `Ok (Some "--config-file", This (Path.of_string fn))
         | None   , true  -> `Ok (Some "--no-config"  , No_config)
         | Some _ , true  -> incompatible "--no-config" "--config-file"
       in
@@ -455,7 +455,7 @@ let common =
                  else
                    []
                ; (match config_file with
-                  | This fn   -> ["--config-file"; fn]
+                  | This fn   -> ["--config-file"; Path.to_string fn]
                   | No_config -> ["--no-config"]
                   | Default   -> [])
                ]
@@ -859,6 +859,7 @@ let rules =
     ]
   in
   let go common out recursive makefile_syntax targets =
+    let out = Option.map ~f:Path.of_string out in
     set_common common ~targets;
     let log = Log.create common in
     Scheduler.go ~log ~common

src/action.ml

@@ -641,17 +641,15 @@ module Promotion = struct
       Format.eprintf "Promoting %s to %s.@."
         (Path.to_string_maybe_quoted src)
         (Path.to_string_maybe_quoted dst);
-      Io.copy_file
+      Io.copy_file ~src ~dst
-        ~src:(Path.to_string src)
-        ~dst:(Path.to_string dst)
   end
 
-  let db_file = "_build/.to-promote"
+  let db_file = Path.of_string "_build/.to-promote"
 
   let dump_db db =
     if Sys.file_exists "_build" then begin
       match db with
-      | [] -> if Sys.file_exists db_file then Sys.remove db_file
+      | [] -> if Path.is_file db_file then Path.unlink_no_err db_file
       | l ->
         Io.write_file db_file
           (String.concat ~sep:""
@@ -659,8 +657,8 @@ module Promotion = struct
     end
 
   let load_db () =
-    if Sys.file_exists db_file then
+    if Path.is_file db_file then
-      Io.Sexp.load ~fname:db_file ~mode:Many
+      Io.Sexp.load db_file ~mode:Many
       |> List.map ~f:File.t
     else
       []
@@ -765,7 +763,7 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
     exec t ~ectx ~dir ~stdout_to ~stderr_to
       ~env:(Env.add env ~var ~value)
   | Redirect (Stdout, fn, Echo s) ->
-    Io.write_file (Path.to_string fn) s;
+    Io.write_file fn s;
     Fiber.return ()
   | Redirect (outputs, fn, Run (Ok prog, args)) ->
     let out = Process.File (Path.to_string fn) in
@@ -784,7 +782,7 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
     exec_list l ~ectx ~dir ~env ~stdout_to ~stderr_to
   | Echo str -> exec_echo stdout_to str
   | Cat fn ->
-    Io.with_file_in (Path.to_string fn) ~f:(fun ic ->
+    Io.with_file_in fn ~f:(fun ic ->
       let oc =
         match stdout_to with
         | None -> stdout
@@ -793,11 +791,11 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
       Io.copy_channels ic oc);
     Fiber.return ()
   | Copy (src, dst) ->
-    Io.copy_file ~src:(Path.to_string src) ~dst:(Path.to_string dst);
+    Io.copy_file ~src ~dst;
     Fiber.return ()
   | Symlink (src, dst) ->
     if Sys.win32 then
-      Io.copy_file ~src:(Path.to_string src) ~dst:(Path.to_string dst)
+      Io.copy_file ~src ~dst
     else begin
       let src =
         if Path.is_root dst then
@@ -818,8 +816,8 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
     end;
     Fiber.return ()
   | Copy_and_add_line_directive (src, dst) ->
-    Io.with_file_in (Path.to_string src) ~f:(fun ic ->
+    Io.with_file_in src ~f:(fun ic ->
-      Io.with_file_out (Path.to_string dst) ~f:(fun oc ->
+      Io.with_file_out dst ~f:(fun oc ->
         let fn = Path.drop_optional_build_context src in
         let directive =
           if List.mem (Path.extension fn) ~set:[".c"; ".cpp"; ".h"] then
@@ -840,7 +838,7 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
       (Utils.bash_exn ~needed_to:"interpret (bash ...) actions")
       ["-e"; "-u"; "-o"; "pipefail"; "-c"; cmd]
   | Write_file (fn, s) ->
-    Io.write_file (Path.to_string fn) s;
+    Io.write_file fn s;
     Fiber.return ()
   | Rename (src, dst) ->
     Unix.rename (Path.to_string src) (Path.to_string dst);
@@ -870,7 +868,7 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
     exec_echo stdout_to s
   | Diff { optional; file1; file2 } ->
     if (optional && not (Path.exists file1 && Path.exists file2)) ||
-       Io.compare_files (Path.to_string file1) (Path.to_string file2) = Eq then
+       Io.compare_files file1 file2 = Eq then
       Fiber.return ()
     else begin
       let is_copied_from_source_tree file =
@@ -892,21 +890,18 @@ let rec exec t ~ectx ~dir ~env ~stdout_to ~stderr_to =
       List.fold_left
         ~init:(String.Set.of_list extras)
         ~f:(fun set source_path ->
-          Path.to_string source_path
+          Io.lines_of_file source_path
-          |> Io.lines_of_file
           |> String.Set.of_list
           |> String.Set.union set
         )
         sources
     in
-    Io.write_lines
+    Io.write_lines target (String.Set.to_list lines);
-      (Path.to_string target)
-      (String.Set.to_list lines);
     Fiber.return ()
 
 and redirect outputs fn t ~ectx ~dir ~env ~stdout_to ~stderr_to =
-  let fn = Path.to_string fn in
   let oc = Io.open_out fn in
+  let fn = Path.to_string fn in
   let out = Some (fn, oc) in
   let stdout_to, stderr_to =
     match outputs with

src/build_system.ml

@@ -14,13 +14,13 @@ let misc_dir = Path.(relative build_dir) ".misc"
 module Promoted_to_delete = struct
   let db = ref []
 
-  let fn = "_build/.to-delete-in-source-tree"
+  let fn = Path.of_string "_build/.to-delete-in-source-tree"
 
   let add p = db := p :: !db
 
   let load () =
-    if Sys.file_exists fn then
+    if Path.is_file fn then
-      Io.Sexp.load ~fname:fn ~mode:Many
+      Io.Sexp.load fn ~mode:Many
       |> List.map ~f:Path.t
     else
       []
@@ -460,8 +460,8 @@ module Build_exec = struct
       | Paths _ -> x
       | Paths_for_rule _ -> x
       | Paths_glob state -> get_glob_result_exn state
-      | Contents p -> Io.read_file (Path.to_string p)
+      | Contents p -> Io.read_file p
-      | Lines_of p -> Io.lines_of_file (Path.to_string p)
+      | Lines_of p -> Io.lines_of_file p
       | Vpath (Vspec.T (fn, kind)) ->
         let file : b File_spec.t = get_file bs fn (Sexp_file kind) in
         Option.value_exn file.data
@@ -766,9 +766,7 @@ let rec compile_rule t ?(copy_source=false) pre_rule =
            let in_source_tree = Option.value_exn (Path.drop_build_context path) in
            if mode = Promote_but_delete_on_clean then
              Promoted_to_delete.add in_source_tree;
-           Io.copy_file
+           Io.copy_file ~src:path ~dst:in_source_tree));
-             ~src:(Path.to_string path)
-             ~dst:(Path.to_string in_source_tree)));
       t.hook Rule_completed
     end else begin
       t.hook Rule_completed;
@@ -1108,7 +1106,7 @@ let stamp_file_for_files_of t ~dir ~ext =
 module Trace = struct
   type t = (Path.t, Digest.t) Hashtbl.t
 
-  let file = "_build/.db"
+  let file = Path.of_string "_build/.db"
 
   let dump (trace : t) =
     let sexp =
@@ -1125,8 +1123,8 @@ module Trace = struct
 
   let load () =
     let trace = Hashtbl.create 1024 in
-    if Sys.file_exists file then begin
+    if Path.is_file file then begin
-      let sexp = Io.Sexp.load ~fname:file ~mode:Single in
+      let sexp = Io.Sexp.load file ~mode:Single in
       let bindings =
         let open Sexp.Of_sexp in
         list (pair Path.t (fun s -> Digest.from_hex (string s))) sexp
@@ -1204,15 +1202,14 @@ let universe_file = Path.relative Path.build_dir ".universe-state"
 let update_universe t =
   (* To workaround the fact that [mtime] is not precise enough on OSX *)
   Utils.Cached_digest.remove universe_file;
-  let fname = Path.to_string universe_file in
   let n =
-    if Sys.file_exists fname then
+    if Path.is_file universe_file then
-      Sexp.Of_sexp.int (Io.Sexp.load ~mode:Single ~fname) + 1
+      Sexp.Of_sexp.int (Io.Sexp.load ~mode:Single universe_file) + 1
     else
       0
   in
   make_local_dirs t (Pset.singleton Path.build_dir);
-  Io.write_file fname (Sexp.to_string (Sexp.To_sexp.int n))
+  Io.write_file universe_file (Sexp.to_string (Sexp.To_sexp.int n))
 
 let do_build t ~request =
   entry_point t ~f:(fun () ->

src/config.ml

@@ -78,14 +78,15 @@ let t =
             ; concurrency
             })
 
-let user_config_file = Filename.concat Xdg.config_dir "dune/config"
+let user_config_file =
+  Path.relative (Path.of_string Xdg.config_dir) "dune/config"
 
-let load_config_file ~fname =
+let load_config_file p =
-  t (Io.Sexp.load_many_as_one ~fname)
+  t (Io.Sexp.load_many_as_one p)
 
 let load_user_config_file () =
-  if Sys.file_exists user_config_file then
+  if Path.is_file user_config_file then
-    load_config_file ~fname:user_config_file
+    load_config_file user_config_file
   else
     default
 

src/config.mli

@@ -52,9 +52,9 @@ val t : t Sexp.Of_sexp.t
 val merge : t -> Partial.t -> t
 
 val default : t
-val user_config_file : string
+val user_config_file : Path.t
 val load_user_config_file : unit -> t
-val load_config_file : fname:string -> t
+val load_config_file : Path.t -> t
 
 (** Set display mode to [Quiet] if it is [Progress], the output is not
     a tty and we are not running inside emacs. *)

src/configurator/v1.ml

@@ -144,8 +144,8 @@ let run t ~dir cmd =
       (Filename.quote stdout_fn)
       (Filename.quote stderr_fn)
   in
-  let stdout = Io.read_file stdout_fn in
+  let stdout = Io.read_file (Path.of_string stdout_fn) in
-  let stderr = Io.read_file stderr_fn in
+  let stderr = Io.read_file (Path.of_string stderr_fn) in
   logf t "-> process exited with code %d" exit_code;
   logf t "-> stdout:";
   List.iter (String.split_lines stdout) ~f:(logf t " | %s");
@@ -239,7 +239,7 @@ let compile_and_link_c_prog t ?(c_flags=[]) ?(link_flags=[]) code =
   let c_fname = base ^ ".c" in
   let obj_fname = base ^ t.ext_obj in
   let exe_fname = base ^ ".exe" in
-  Io.write_file c_fname code;
+  Io.write_file (Path.of_string c_fname) code;
   logf t "compiling c program:";
   List.iter (String.split_lines code) ~f:(logf t " | %s");
   let run_ok args =
@@ -269,7 +269,7 @@ let compile_c_prog t ?(c_flags=[]) code =
   let base = dir ^/ "test" in
   let c_fname = base ^ ".c" in
   let obj_fname = base ^ t.ext_obj in
-  Io.write_file c_fname code;
+  Io.write_file (Path.of_string c_fname) code;
   logf t "compiling c program:";
   List.iter (String.split_lines code) ~f:(logf t " | %s");
   let run_ok args =
@@ -286,7 +286,7 @@ let compile_c_prog t ?(c_flags=[]) code =
                 ]
               ])
   in
-  if ok then Ok obj_fname else Error ()
+  if ok then Ok (Path.of_string obj_fname) else Error ()
 
 let c_test t ?c_flags ?link_flags code =
   match compile_and_link_c_prog t ?c_flags ?link_flags code with
@@ -415,7 +415,7 @@ const char *s%i = "BEGIN-%i-false-END";
     logf t "writing header file %s" fname;
     List.iter lines ~f:(logf t " | %s");
     let tmp_fname = fname ^ ".tmp" in
-    Io.write_lines tmp_fname lines;
+    Io.write_lines (Path.of_string tmp_fname) lines;
     Sys.rename tmp_fname fname
 end
 
@@ -481,8 +481,9 @@ module Pkg_config = struct
 end
 
 let write_flags fname s =
+  let path = Path.of_string fname in
   let sexp = Usexp.List(List.map ~f:Usexp.atom_or_quoted_string s) in
-  Io.write_file fname (Usexp.to_string sexp)
+  Io.write_file path (Usexp.to_string sexp)
 
 let main ?(args=[]) ~name f =
   let ocamlc  = ref (

src/file_tree.ml

@@ -62,7 +62,7 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
     let files = String.Set.of_list files in
     let ignored_sub_dirs =
       if not ignored && String.Set.mem files "jbuild-ignore" then
-        let ignore_file = Path.to_string (Path.relative path "jbuild-ignore") in
+        let ignore_file = Path.relative path "jbuild-ignore" in
         let files =
           Io.lines_of_file ignore_file
         in
@@ -70,7 +70,8 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
           if Filename.dirname fn = Filename.current_dir_name then
             true
           else begin
-            Loc.(warn (of_pos (ignore_file, index + 1, 0, String.length fn))
+            Loc.(warn (of_pos ( Path.to_string ignore_file
+                              , index + 1, 0, String.length fn))
             "subdirectory expression %s ignored" fn);
             false
           end

src/findlib.ml

@@ -99,7 +99,7 @@ module Config = struct
     if not (Path.exists conf_file) then
       die "@{<error>Error@}: ocamlfind toolchain %s isn't defined in %a \
            (context: %s)" toolchain Path.pp path context;
-    let vars = (Meta.load ~name:"" ~fn:(Path.to_string conf_file)).vars in
+    let vars = (Meta.load ~name:"" conf_file).vars in
     { vars = String.Map.map vars ~f:Rules.of_meta_rules
     ; preds = Ps.make [toolchain]
     }
@@ -266,14 +266,14 @@ let find_and_acknowledge_meta t ~fq_name =
       if Path.exists fn then
         Some (sub_dir,
               fn,
-              Meta.load ~name:root_name ~fn:(Path.to_string fn))
+              Meta.load ~name:root_name fn)
       else
         (* Alternative layout *)
         let fn = Path.relative dir ("META." ^ root_name) in
         if Path.exists fn then
           Some (dir,
                 fn,
-                Meta.load ~fn:(Path.to_string fn) ~name:root_name)
+                Meta.load fn ~name:root_name)
         else
           loop dirs
     | [] ->

src/installed_dune_file.ml

@@ -39,7 +39,7 @@ let of_sexp =
         (fun () l -> parse_sub_systems l)
     ]
 
-let load ~fname = of_sexp (Io.Sexp.load ~mode:Single ~fname)
+let load fname = of_sexp (Io.Sexp.load ~mode:Single fname)
 
 let gen confs =
   let sexps =

src/installed_dune_file.mli

@@ -2,5 +2,5 @@
 
 open Stdune
 
-val load : fname:string -> Jbuild.Sub_system_info.t Sub_system_name.Map.t
+val load : Path.t -> Jbuild.Sub_system_info.t Sub_system_name.Map.t
 val gen : (Syntax.Version.t * Sexp.t) Sub_system_name.Map.t -> Sexp.t

src/jbuild.ml

@@ -1244,7 +1244,7 @@ module Stanzas = struct
               (Path.to_string_maybe_quoted file);
           if List.exists include_stack ~f:(fun (_, f) -> f = file) then
             raise (Include_loop (file, include_stack));
-          let sexps = Io.Sexp.load ~fname:(Path.to_string file) ~mode:Many in
+          let sexps = Io.Sexp.load file ~mode:Many in
           parse pkgs sexps ~default_version:Jbuild_version.V1 ~file ~include_stack)
       ; cstr "documentation" (Documentation.v1 pkgs @> nil)
           (fun d -> [Documentation d])

src/jbuild_load.ml

@@ -33,7 +33,7 @@ module Jbuilds = struct
 
   type requires = No_requires | Unix
 
-  let extract_requires ~fname str =
+  let extract_requires path str =
     let rec loop n lines acc =
       match lines with
       | [] -> acc
@@ -48,7 +48,7 @@ module Jbuilds = struct
             | _ ->
               let start =
                 { Lexing.
-                  pos_fname = fname
+                  pos_fname = Path.to_string path
                 ; pos_lnum  = n
                 ; pos_cnum  = 0
                 ; pos_bol   = 0
@@ -64,9 +64,8 @@ module Jbuilds = struct
     loop 1 (String.split str ~on:'\n') No_requires
 
   let create_plugin_wrapper (context : Context.t) ~exec_dir ~plugin ~wrapper ~target =
-    let plugin = Path.to_string plugin in
     let plugin_contents = Io.read_file plugin in
-    Io.with_file_out (Path.to_string wrapper) ~f:(fun oc ->
+    Io.with_file_out wrapper ~f:(fun oc ->
       let ocamlc_config =
         let vars =
           Ocaml_config.to_list context.ocaml_config
@@ -105,8 +104,8 @@ end
         context.version_string
         ocamlc_config
         (Path.reach ~from:exec_dir target)
-        plugin plugin_contents);
+        (Path.to_string plugin) plugin_contents);
-    extract_requires ~fname:plugin plugin_contents
+    extract_requires plugin plugin_contents
 
   let eval { jbuilds; ignore_promoted_rules } ~(context : Context.t) =
     let open Fiber.O in
@@ -157,7 +156,7 @@ end
         die "@{<error>Error:@} %s failed to produce a valid jbuild file.\n\
              Did you forgot to call [Jbuild_plugin.V*.send]?"
           (Path.to_string file);
-      let sexps = Io.Sexp.load ~fname:(Path.to_string generated_jbuild) ~mode:Many in
+      let sexps = Io.Sexp.load generated_jbuild ~mode:Many in
       Fiber.return (dir, scope, Stanzas.parse scope sexps ~file:generated_jbuild
                                 |> filter_stanzas ~ignore_promoted_rules))
     >>| fun dynamic ->
@@ -183,7 +182,7 @@ module Sexp_io = struct
 
   let load_many_or_ocaml_script fname =
     Io.with_file_in fname ~f:(fun ic ->
-      let state = Parser.create ~fname ~mode:Many in
+      let state = Parser.create ~fname:(Path.to_string fname) ~mode:Many in
       let buf = Bytes.create Io.buf_len in
       let rec loop stack =
         match input ic buf 0 Io.buf_len with
@@ -212,7 +211,7 @@ end
 
 let load ~dir ~scope ~ignore_promoted_rules =
   let file = Path.relative dir "jbuild" in
-  match Sexp_io.load_many_or_ocaml_script (Path.to_string file) with
+  match Sexp_io.load_many_or_ocaml_script file with
   | Sexps sexps ->
     Jbuilds.Literal (dir, scope,
                      Stanzas.parse scope sexps ~file
@@ -230,7 +229,7 @@ let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
         match Filename.split_extension fn with
         | (pkg, ".opam") when pkg <> "" ->
           let version_from_opam_file =
-            let opam = Opam_file.load (Path.relative path fn |> Path.to_string) in
+            let opam = Opam_file.load (Path.relative path fn) in
             match Opam_file.get_field opam "version" with
             | Some (String (_, s)) -> Some s
             | _ -> None

src/lib.ml

@@ -123,8 +123,7 @@ module Info = struct
     let sub_systems =
       match P.dune_file pkg with
       | None -> Sub_system_name.Map.empty
-      | Some fn ->
+      | Some fn -> Installed_dune_file.load fn
-        Installed_dune_file.load ~fname:(Path.to_string fn)
     in
     { loc              = loc
     ; kind             = Normal

src/log.ml

@@ -14,7 +14,7 @@ let no_log = None
 let create ?(display=Config.default.display) () =
   if not (Sys.file_exists "_build") then
     Unix.mkdir "_build" 0o777;
-  let oc = Io.open_out "_build/log" in
+  let oc = Io.open_out (Path.of_string "_build/log") in
   Printf.fprintf oc "# %s\n# OCAMLPARAM: %s\n%!"
     (String.concat (List.map (Array.to_list Sys.argv) ~f:quote_for_shell) ~sep:" ")
     (match Env.get Env.initial "OCAMLPARAM" with

src/main.ml

@@ -30,7 +30,7 @@ let setup_env ~capture_outputs =
 
 let setup ?(log=Log.no_log)
       ?external_lib_deps_mode
-      ?workspace ?(workspace_file="jbuild-workspace")
+      ?workspace ?(workspace_file=Path.of_string "jbuild-workspace")
       ?only_packages
       ?extra_ignored_subtrees
       ?x
@@ -55,7 +55,7 @@ let setup ?(log=Log.no_log)
     match workspace with
     | Some w -> w
     | None ->
-      if Sys.file_exists workspace_file then
+      if Path.is_file workspace_file then
         Workspace.load ?x workspace_file
       else
         { merlin_context = Some "default"

src/main.mli

@@ -20,7 +20,7 @@ val setup
   :  ?log:Log.t
   -> ?external_lib_deps_mode:bool
   -> ?workspace:Workspace.t
-  -> ?workspace_file:string
+  -> ?workspace_file:Path.t
   -> ?only_packages:Package.Name.Set.t
   -> ?x:string
   -> ?ignore_promoted_rules:bool

src/meta.ml

@@ -170,10 +170,10 @@ let rec simplify t =
         in
         { pkg with vars = String.Map.add pkg.vars rule.var rules })
 
-let load ~fn ~name =
+let load p ~name =
   { name
   ; entries =
-      Io.with_lexbuf_from_file fn ~f:(fun lb ->
+      Io.with_lexbuf_from_file p ~f:(fun lb ->
         Parse.entries lb 0 [])
   }
   |> simplify

src/meta.mli

@@ -42,7 +42,7 @@ module Simplified : sig
   val pp : Format.formatter -> t -> unit
 end
 
-val load : fn:string -> name:string -> Simplified.t
+val load : Path.t -> name:string -> Simplified.t
 
 (** Builtin META files for libraries distributed with the compiler. For when ocamlfind is
     not installed. *)

src/opam_file.ml

@@ -6,7 +6,7 @@ type t = opamfile
 let load fn =
   Io.with_lexbuf_from_file fn ~f:(fun lb ->
     try
-      OpamBaseParser.main OpamLexer.token lb fn
+      OpamBaseParser.main OpamLexer.token lb (Path.to_string fn)
     with
     | OpamLexer.Error msg ->
       Loc.fail_lex lb "%s" msg

src/opam_file.mli

@@ -1,12 +1,14 @@
 (** Parsing and interpretation of opam files *)
 
+open Stdune
+
 open OpamParserTypes
 
 (** Type of opam files *)
 type t = opamfile
 
 (** Load a file *)
-val load : string -> t
+val load : Path.t -> t
 
 (** Extracts a field *)
 val get_field : t -> string -> value option

src/process.ml

@@ -255,7 +255,7 @@ let run_internal ?dir ?(stdout_to=Terminal) ?(stderr_to=Terminal) ~env ~purpose
     match output_filename with
     | None -> ""
     | Some fn ->
-      let s = Io.read_file fn in
+      let s = Io.read_file (Path.of_string fn) in
       Temp.destroy fn;
       let len = String.length s in
       if len > 0 && s.[len - 1] <> '\n' then
@@ -329,11 +329,14 @@ let run_capture_gen ?dir ~env ?(purpose=Internal_job) fail_mode prog args ~f =
       Temp.destroy fn;
       x)
 
-let run_capture       = run_capture_gen ~f:Io.read_file
+let run_capture =
-let run_capture_lines = run_capture_gen ~f:Io.lines_of_file
+  run_capture_gen ~f:(fun p -> Io.read_file (Path.of_string p))
+let run_capture_lines =
+  run_capture_gen ~f:(fun p -> Io.lines_of_file (Path.of_string p))
 
 let run_capture_line ?dir ~env ?(purpose=Internal_job) fail_mode prog args =
   run_capture_gen ?dir ~env ~purpose fail_mode prog args ~f:(fun fn ->
+    let fn = Path.of_string fn in
     match Io.lines_of_file fn with
     | [x] -> x
     | l ->

src/stdune/io.ml

@@ -1,9 +1,11 @@
 module P = Pervasives
 
-let open_in ?(binary=true) fn =
+let open_in ?(binary=true) p =
+  let fn = Path.to_string p in
   if binary then P.open_in_bin fn else P.open_in fn
 
-let open_out ?(binary=true) fn =
+let open_out ?(binary=true) p =
+  let fn = Path.to_string p in
   if binary then P.open_out_bin fn else P.open_out fn
 
 let close_in  = close_in
@@ -12,14 +14,14 @@ let close_out = close_out
 let with_file_in ?binary fn ~f =
   Exn.protectx (open_in ?binary fn) ~finally:close_in ~f
 
-let with_file_out ?binary fn ~f =
+let with_file_out ?binary p ~f =
-  Exn.protectx (open_out ?binary fn) ~finally:close_out ~f
+  Exn.protectx (open_out ?binary p) ~finally:close_out ~f
 
 let with_lexbuf_from_file fn ~f =
   with_file_in fn ~f:(fun ic ->
     let lb = Lexing.from_channel ic in
     lb.lex_curr_p <-
-      { pos_fname = fn
+      { pos_fname = Path.to_string fn
       ; pos_lnum  = 1
       ; pos_bol   = 0
       ; pos_cnum  = 0
@@ -69,7 +71,7 @@ let copy_file ~src ~dst =
     Exn.protectx (P.open_out_gen
                     [Open_wronly; Open_creat; Open_trunc; Open_binary]
                     perm
-                    dst)
+                    (Path.to_string dst))
       ~finally:close_out
       ~f:(fun oc ->
         copy_channels ic oc))
@@ -82,9 +84,9 @@ let buf_len = 65_536
 module Sexp = struct
   open Sexp
 
-  let load ~fname ~mode =
+  let load path ~mode =
-    with_file_in fname ~f:(fun ic ->
+    with_file_in path ~f:(fun ic ->
-      let state = Parser.create ~fname ~mode in
+      let state = Parser.create ~fname:(Path.to_string path) ~mode in
       let buf = Bytes.create buf_len in
       let rec loop stack =
         match input ic buf 0 buf_len with
@@ -93,9 +95,9 @@ module Sexp = struct
       in
       loop Parser.Stack.empty)
 
-  let load_many_as_one ~fname =
+  let load_many_as_one path =
-    match load ~fname ~mode:Many with
+    match load path ~mode:Many with
-    | [] -> Ast.List (Loc.in_file fname, [])
+    | [] -> Ast.List (Loc.in_file (Path.to_string path), [])
     | x :: l ->
       let last = Option.value (List.last l) ~default:x in
       let loc = { (Ast.loc x) with stop = (Ast.loc last).stop } in

src/stdune/io.mli

@@ -1,34 +1,34 @@
 (** IO operations *)
 
-val open_in  : ?binary:bool (* default true *) -> string -> in_channel
+val open_in  : ?binary:bool (* default true *) -> Path.t -> in_channel
-val open_out : ?binary:bool (* default true *) -> string -> out_channel
+val open_out : ?binary:bool (* default true *) -> Path.t -> out_channel
 
 val close_in  : in_channel  -> unit
 val close_out : out_channel -> unit
 
-val with_file_in  : ?binary:bool (* default true *) -> string -> f:(in_channel -> 'a) -> 'a
+val with_file_in  : ?binary:bool (* default true *) -> Path.t -> f:(in_channel -> 'a) -> 'a
-val with_file_out : ?binary:bool (* default true *) -> string -> f:(out_channel -> 'a) -> 'a
+val with_file_out : ?binary:bool (* default true *) -> Path.t -> f:(out_channel -> 'a) -> 'a
 
-val with_lexbuf_from_file : string -> f:(Lexing.lexbuf -> 'a) -> 'a
+val with_lexbuf_from_file : Path.t -> f:(Lexing.lexbuf -> 'a) -> 'a
 
-val lines_of_file : string -> string list
+val lines_of_file : Path.t -> string list
 
-val read_file : string -> string
+val read_file : Path.t -> string
-val write_file : string -> string -> unit
+val write_file : Path.t -> string -> unit
 
-val compare_files : string -> string -> Ordering.t
+val compare_files : Path.t -> Path.t -> Ordering.t
 
-val write_lines : string -> string list -> unit
+val write_lines : Path.t -> string list -> unit
 
 val copy_channels : in_channel -> out_channel -> unit
 
-val copy_file : src:string -> dst:string -> unit
+val copy_file : src:Path.t -> dst:Path.t -> unit
 
 val read_all : in_channel -> string
 
 module Sexp : sig
-  val load : fname:string -> mode:'a Sexp.Parser.Mode.t -> 'a
+  val load : Path.t -> mode:'a Sexp.Parser.Mode.t -> 'a
-  val load_many_as_one : fname:string -> Sexp.Ast.t
+  val load_many_as_one : Path.t -> Sexp.Ast.t
 end
 
 (**/**)

src/stdune/path.ml

@@ -431,6 +431,9 @@ let readdir t = Sys.readdir (to_string t) |> Array.to_list
 let is_directory t =
   try Sys.is_directory (to_string t)
   with Sys_error _ -> false
+let is_file t =
+  try Sys.file_exists (to_string t)
+  with Sys_error _ -> false
 let rmdir t = Unix.rmdir (to_string t)
 let win32_unlink fn =
   try

src/stdune/path.mli

@@ -127,6 +127,7 @@ val insert_after_build_dir_exn : t -> string -> t
 val exists : t -> bool
 val readdir : t -> string list
 val is_directory : t -> bool
+val is_file : t -> bool
 val rmdir : t -> unit
 val unlink : t -> unit
 val unlink_no_err : t -> unit

src/utils.ml

@@ -183,7 +183,7 @@ module Cached_digest = struct
 
   let remove fn = Hashtbl.remove cache fn
 
-  let db_file = "_build/.digest-db"
+  let db_file = Path.of_string "_build/.digest-db"
 
   let dump () =
     let module Pmap = Path.Map in
@@ -203,8 +203,8 @@ module Cached_digest = struct
       Io.write_file db_file (Sexp.to_string sexp)
 
   let load () =
-    if Sys.file_exists db_file then begin
+    if Path.is_file db_file then begin
-      let sexp = Io.Sexp.load ~fname:db_file ~mode:Single in
+      let sexp = Io.Sexp.load db_file ~mode:Single in
       let bindings =
         let open Sexp.Of_sexp in
         list

src/vfile_kind.ml

@@ -55,7 +55,7 @@ struct
   let to_string path x = To_sexp.t path x |> Sexp.to_string
 
   let load path =
-    Of_sexp.t path (Io.Sexp.load ~fname:(Path.to_string path) ~mode:Single)
+    Of_sexp.t path (Io.Sexp.load path ~mode:Single)
 end
 
 

src/watermarks.ml

@@ -19,7 +19,7 @@ let is_a_source_file fn =
   | _ -> true
 
 let make_watermark_map ~name ~version ~commit =
-  let opam_file = Opam_file.load (name ^ ".opam") in
+  let opam_file = Opam_file.load (Path.of_string (name ^ ".opam")) in
   let version_num =
     if String.is_prefix version ~prefix:"v" then
       String.sub version ~pos:1 ~len:(String.length version - 1)
@@ -62,7 +62,7 @@ let make_watermark_map ~name ~version ~commit =
     ; "PKG_REPO"       , opam_var "dev-repo"    " "
     ]
 
-let subst_string s ~fname ~map =
+let subst_string s path ~map =
   let len = String.length s in
   let longest_var = String.longest (String.Map.keys map) in
   let loc_of_offset ~ofs ~len =
@@ -70,7 +70,7 @@ let subst_string s ~fname ~map =
       if i = ofs then
         let pos =
           { Lexing.
-            pos_fname = fname
+            pos_fname = Path.to_string path
           ; pos_cnum  = i
           ; pos_lnum  = lnum
           ; pos_bol   = bol
@@ -151,17 +151,18 @@ let subst_string s ~fname ~map =
     Buffer.add_substring buf s pos (len - pos);
     Some (Buffer.contents buf)
 
-let subst_file fn ~map =
+let subst_file path ~map =
-  let s = Io.read_file fn in
+  let s = Io.read_file path in
   let s =
-    if Filename.dirname fn = "." && String.is_suffix fn ~suffix:".opam" then
+    if Path.is_root path
+    && String.is_suffix (Path.to_string path) ~suffix:".opam" then
       "version: \"%%" ^ "VERSION_NUM" ^ "%%\"\n" ^ s
     else
       s
   in
-  match subst_string s ~map ~fname:fn with
+  match subst_string s ~map path with
   | None -> ()
-  | Some s -> Io.write_file fn s
+  | Some s -> Io.write_file path s
 
 let get_name ~files ?name () =
   let package_names =
@@ -223,7 +224,7 @@ let subst_git ?name () =
   let watermarks = make_watermark_map ~name ~version ~commit in
   List.iter files ~f:(fun fn ->
     if is_a_source_file fn then
-      subst_file fn ~map:watermarks);
+      subst_file (Path.of_string fn) ~map:watermarks);
   Fiber.return ()
 
 let subst ?name () =

src/workspace.ml

@@ -135,4 +135,4 @@ let t ?x sexps =
   ; contexts       = List.rev contexts
   }
 
-let load ?x fname = t ?x (Io.Sexp.load ~fname ~mode:Many)
+let load ?x p = t ?x (Io.Sexp.load p ~mode:Many)

src/workspace.mli

@@ -28,4 +28,4 @@ type t =
   ; contexts       : Context.t list
   }
 
-val load : ?x:string -> string -> t
+val load : ?x:string -> Path.t -> t

test/blackbox-tests/cram.mll

@@ -143,7 +143,9 @@ and postprocess tbl b = parse
               | _ -> 255
             in
             let ext_replace = make_ext_replace configurator in
-            List.iter (Io.lines_of_file temp_file) ~f:(fun line ->
+            Path.of_string temp_file
+            |> Io.lines_of_file
+            |> List.iter ~f:(fun line ->
               Printf.bprintf buf "  %s\n"
                 (ext_replace (Ansi_color.strip line)));
             if n <> 0 then Printf.bprintf buf "  [%d]\n" n);

test/unit-tests/tests.mlt

@@ -52,7 +52,8 @@ open Meta
 #install_printer Simplified.pp;;
 
 let meta =
-  Meta.load ~name:"foo" ~fn:"test/unit-tests/findlib-db/foo/META"
+  Path.of_string "test/unit-tests/findlib-db/foo/META"
+  |> Meta.load ~name:"foo"
 
 [%%expect{|
 val meta : Jbuilder.Meta.Simplified.t =