From a2705edeb9745a43cff5360b16bd0bde0256d597 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Tue, 8 May 2018 15:38:28 +0100
Subject: [PATCH 01/11] Add List.rev_filter_map{,i}

---
 src/stdune/list.ml  | 30 ++++++++++++++++++++++++++++++
 src/stdune/list.mli |  3 +++
 2 files changed, 33 insertions(+)

diff --git a/src/stdune/list.ml b/src/stdune/list.ml
index 06c7cb7df66..7566e583568 100644
--- a/src/stdune/list.ml
+++ b/src/stdune/list.ml
@@ -26,6 +26,36 @@ let filteri l ~f =
   in
   filteri l 0
 
+let rev_filter_map =
+  let rec loop acc l ~f =
+    match l with
+    | [] -> acc
+    | x :: l ->
+      let acc =
+        match f x with
+        | None -> acc
+        | Some y -> y :: acc
+      in
+      loop acc l ~f
+  in
+  fun l ~f ->
+    loop [] l ~f
+
+let rev_filter_mapi =
+  let rec loop acc l ~f i =
+    match l with
+    | [] -> acc
+    | x :: l ->
+      let acc =
+        match f i x with
+        | None -> acc
+        | Some y -> y :: acc
+      in
+      loop acc l ~f (i + 1)
+  in
+  fun l ~f ->
+    loop [] l ~f 0
+
 let concat_map l ~f = concat (map l ~f)
 
 let rev_partition_map =
diff --git a/src/stdune/list.mli b/src/stdune/list.mli
index 4cfe2dfdd5c..1f54de22847 100644
--- a/src/stdune/list.mli
+++ b/src/stdune/list.mli
@@ -8,6 +8,9 @@ val filter_map : 'a t -> f:('a -> 'b option) -> 'b t
 
 val filteri : 'a t -> f:(int -> 'a -> bool) -> 'a t
 
+val rev_filter_map  : 'a t -> f:(       'a -> 'b option) -> 'b t
+val rev_filter_mapi : 'a t -> f:(int -> 'a -> 'b option) -> 'b t
+
 val concat_map : 'a t -> f:('a -> 'b t) -> 'b t
 
 val     partition_map : 'a t -> f:('a -> ('b, 'c) Either.t) -> 'b t * 'c t

From 93adef0ea179d272f6ee5eb43be3260ca193d5b8 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Tue, 8 May 2018 16:11:02 +0100
Subject: [PATCH 02/11] Add support for .dune-fs files

---
 CHANGES.md          |   2 +
 src/build_system.ml |   4 +-
 src/file_tree.ml    | 195 +++++++++++++++++++++++++++++++-------------
 src/file_tree.mli   |  15 ++--
 src/jbuild_load.ml  |   6 +-
 5 files changed, 155 insertions(+), 67 deletions(-)

diff --git a/CHANGES.md b/CHANGES.md
index e803d29bea2..c2e977e4949 100644
--- a/CHANGES.md
+++ b/CHANGES.md
@@ -40,6 +40,8 @@ next
 - Fix a crash when using c files from another directory (#758, fixes
   #734, @diml)
 
+- Add support for .dune-fs files (#750, @diml)
+
 1.0+beta20 (10/04/2018)
 -----------------------
 
diff --git a/src/build_system.ml b/src/build_system.ml
index 3cecab2084c..1f434d9ddd6 100644
--- a/src/build_system.ml
+++ b/src/build_system.ml
@@ -263,7 +263,7 @@ module Alias0 = struct
   open Build.O
 
   let dep_rec_internal ~name ~dir ~ctx_dir =
-    File_tree.Dir.fold dir ~traverse_ignored_dirs:false ~init:(Build.return true)
+    File_tree.Dir.fold dir ~traverse_raw_data_dirs:false ~init:(Build.return true)
       ~f:(fun dir acc ->
         let path = Path.append ctx_dir (File_tree.Dir.path dir) in
         let fn = stamp_file (make ~dir:path name) in
@@ -1168,7 +1168,7 @@ end
 
 let all_targets t =
   String.Map.iter t.contexts ~f:(fun ctx ->
-    File_tree.fold t.file_tree ~traverse_ignored_dirs:true ~init:()
+    File_tree.fold t.file_tree ~traverse_raw_data_dirs:true ~init:()
       ~f:(fun dir () ->
         load_dir t
           ~dir:(Path.append ctx.Context.build_dir (File_tree.Dir.path dir))));
diff --git a/src/file_tree.ml b/src/file_tree.ml
index 067f163aa24..4023e1c7b55 100644
--- a/src/file_tree.ml
+++ b/src/file_tree.ml
@@ -1,21 +1,117 @@
 open! Import
 
+module Dune_fs = struct
+  open Sexp.Of_sexp
+
+  type kind =
+    | File
+    | Dir
+    | Any
+
+  type what =
+    | Standard
+    | Raw_data
+    | Ignore
+
+  type entry =
+    { kind : kind
+    ; glob : Re.re
+    ; what : what
+    }
+
+  type t = { rev_entries : entry list } [@@unboxed]
+
+  let find =
+    let rec aux rev_entries fn ~is_directory =
+      match rev_entries with
+      | [] ->
+        if fn = "" || fn = "." ||
+           (is_directory && (fn.[0] = '.' || fn.[0] = '_')) ||
+           (fn.[0] = '.' && fn.[1] = '#')
+        then
+          Ignore
+        else
+          Standard
+      | e :: rest ->
+        if (match e.kind with
+          | File -> not is_directory
+          | Dir  -> is_directory
+          | Any  -> true) &&
+           Re.execp e.glob fn then
+          e.what
+        else
+          aux rest fn ~is_directory
+    in
+    fun t fn ~is_directory ->
+      aux t.rev_entries fn ~is_directory
+
+  let kind =
+    enum
+      [ "file" , File
+      ; "dir"  , Dir
+      ; "_"    , Any
+      ]
+
+  let what =
+    enum
+      [ "standard" , Standard
+      ; "raw_data" , Raw_data
+      ; "ignore"   , Ignore
+      ]
+
+  let glob sexp =
+    let s = string sexp in
+    match Glob_lexer.parse_string s with
+    | Ok re -> Re.compile re
+    | Error (_pos, msg) -> of_sexp_errorf sexp "invalid glob: %s" msg
+
+  let entry sexp =
+    let kind, glob, what = triple kind glob what sexp in
+    { kind; glob; what }
+
+  let t sexps =
+    let rev_entries = List.rev_map sexps ~f:entry in
+    { rev_entries }
+
+  let load path =
+    t (Io.Sexp.load path ~mode:Many)
+
+  let load_jbuild_ignore path =
+    let rev_entries =
+      List.rev_filter_mapi (Io.lines_of_file path) ~f:(fun i fn ->
+        if Filename.dirname fn = Filename.current_dir_name then
+          Some { kind = Dir; glob = Re.compile (Re.str fn); what = Raw_data }
+        else begin
+          Loc.(warn (of_pos ( Path.to_string path
+                            , i + 1, 0
+                            , String.length fn
+                            ))
+                 "subdirectory expression %s ignored" fn);
+          None
+        end)
+    in
+    { rev_entries }
+
+  let default = { rev_entries = [] }
+end
+
 module Dir = struct
   type t =
     { path     : Path.t
-    ; ignored  : bool
+    ; raw_data : bool
     ; contents : contents Lazy.t
     }
 
   and contents =
     { files    : String.Set.t
     ; sub_dirs : t String.Map.t
+    ; dune_fs  : Dune_fs.t
     }
 
   let contents t = Lazy.force t.contents
 
   let path t = t.path
-  let ignored t = t.ignored
+  let raw_data t = t.raw_data
 
   let files    t = (contents t).files
   let sub_dirs t = (contents t).sub_dirs
@@ -31,22 +127,23 @@ module Dir = struct
     String.Map.foldi (sub_dirs t) ~init:Path.Set.empty
       ~f:(fun s _ acc -> Path.Set.add acc (Path.relative t.path s))
 
-  let rec fold t ~traverse_ignored_dirs ~init:acc ~f =
-    if not traverse_ignored_dirs && t.ignored then
+  let rec fold t ~traverse_raw_data_dirs ~init:acc ~f =
+    if not traverse_raw_data_dirs && t.raw_data then
       acc
     else
       let acc = f t acc in
       String.Map.fold (sub_dirs t) ~init:acc ~f:(fun t acc ->
-        fold t ~traverse_ignored_dirs ~init:acc ~f)
+        fold t ~traverse_raw_data_dirs ~init:acc ~f)
 
   let dune_file t =
-    let (lazy { files; _ }) = t.contents in
-    if String.Set.mem files "dune" then
-      Some (Path.relative t.path "dune")
-    else if String.Set.mem files "jbuild" then
-      Some (Path.relative t.path "jbuild")
-    else
-      None
+    let (lazy { files; dune_fs; _ }) = t.contents in
+    List.find_map ["dune"; "jbuild"] ~f:(fun fn ->
+      if String.Set.mem files fn then
+        match Dune_fs.find dune_fs fn ~is_directory:false with
+        | Standard -> Some (Path.relative t.path fn)
+        | _        -> None
+      else
+        None)
 end
 
 type t =
@@ -56,71 +153,59 @@ type t =
 
 let root t = t.root
 
-let ignore_file fn ~is_directory =
-  fn = "" || fn = "." ||
-  (is_directory && (fn.[0] = '.' || fn.[0] = '_')) ||
-  (fn.[0] = '.' && fn.[1] = '#')
-
 let load ?(extra_ignored_subtrees=Path.Set.empty) path =
-  let rec walk path ~ignored : Dir.t =
+  let rec walk path ~raw_data : Dir.t =
     let contents = lazy (
       let files, sub_dirs =
         Path.readdir path
-        |> List.filter_partition_map ~f:(fun fn ->
+        |> List.partition_map ~f:(fun fn ->
           let path = Path.relative path fn in
-          let is_directory = Path.is_directory path in
-          if ignore_file fn ~is_directory then
-            Skip
-          else if is_directory then
+          if Path.is_directory path then
             Right (fn, path)
           else
             Left fn)
       in
       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.relative path "jbuild-ignore" in
-          let files =
-            Io.lines_of_file ignore_file
-          in
-          let remove_subdirs index fn =
-            if Filename.dirname fn = Filename.current_dir_name then
-              true
-            else begin
-              Loc.(warn (of_pos ( Path.to_string ignore_file
-                                , index + 1, 0, String.length fn))
-                     "subdirectory expression %s ignored" fn);
-              false
-            end
-          in
-          String.Set.of_list (List.filteri ~f:remove_subdirs files)
+      let dune_fs =
+        if String.Set.mem files ".dune-fs" then
+          Dune_fs.load (Path.relative path ".dune-fs")
+        else if String.Set.mem files "jbuild-ignore" then
+          Dune_fs.load_jbuild_ignore (Path.relative path "jbuild-ignore")
         else
-          String.Set.empty
+          Dune_fs.default
+      in
+      let files =
+        String.Set.filter files ~f:(fun fn ->
+          match Dune_fs.find dune_fs fn ~is_directory:false with
+          | Ignore              -> false
+          | Standard | Raw_data -> true)
       in
       let sub_dirs =
-        List.map sub_dirs ~f:(fun (fn, path) ->
-          let ignored =
-            ignored
-            || String.Set.mem ignored_sub_dirs fn
-            || Path.Set.mem extra_ignored_subtrees path
-          in
-          (fn, walk path ~ignored))
-        |> String.Map.of_list_exn
+        List.fold_left sub_dirs ~init:String.Map.empty ~f:(fun acc (fn, path) ->
+          match
+            match Dune_fs.find dune_fs fn ~is_directory:true with
+            | Ignore   -> None
+            | Standard -> Some (raw_data ||
+                                Path.Set.mem extra_ignored_subtrees path)
+            | Raw_data -> Some true
+          with
+          | None -> acc
+          | Some raw_data -> String.Map.add acc fn (walk path ~raw_data))
       in
-      { Dir. files; sub_dirs })
+      { Dir. files; sub_dirs; dune_fs })
     in
     { path
     ; contents
-    ; ignored
+    ; raw_data
     }
   in
-  let root = walk path ~ignored:false in
+  let root = walk path ~raw_data:false in
   let dirs = Hashtbl.create 1024      in
   Hashtbl.add dirs Path.root root;
   { root; dirs }
 
-let fold t ~traverse_ignored_dirs ~init ~f =
-  Dir.fold t.root ~traverse_ignored_dirs ~init ~f
+let fold t ~traverse_raw_data_dirs ~init ~f =
+  Dir.fold t.root ~traverse_raw_data_dirs ~init ~f
 
 let rec find_dir t path =
   if not (Path.is_local path) then
@@ -166,7 +251,7 @@ let files_recursively_in t ?(prefix_with=Path.root) path =
   match find_dir t path with
   | None -> Path.Set.empty
   | Some dir ->
-    Dir.fold dir ~init:Path.Set.empty ~traverse_ignored_dirs:true
+    Dir.fold dir ~init:Path.Set.empty ~traverse_raw_data_dirs:true
       ~f:(fun dir acc ->
         let path = Path.append prefix_with (Dir.path dir) in
         String.Set.fold (Dir.files dir) ~init:acc ~f:(fun fn acc ->
diff --git a/src/file_tree.mli b/src/file_tree.mli
index be098fa9ea0..8405e434520 100644
--- a/src/file_tree.mli
+++ b/src/file_tree.mli
@@ -12,13 +12,14 @@ module Dir : sig
   val sub_dir_paths : t -> Path.Set.t
   val sub_dir_names : t -> String.Set.t
 
-  (** Whether this directory is ignored by a [jbuild-ignore] file in
-      one of its ancestor directories. *)
-  val ignored : t -> bool
+  (** Whether this directory contains raw data, as configured by a
+      [.dune-fs] or [jbuild-ignore] file in one of its ancestor
+      directories. *)
+  val raw_data : t -> bool
 
   val fold
     :  t
-    -> traverse_ignored_dirs:bool
+    -> traverse_raw_data_dirs:bool
     -> init:'a
     -> f:(t -> 'a -> 'a)
     -> 'a
@@ -35,12 +36,12 @@ type t
 
 val load : ?extra_ignored_subtrees:Path.Set.t -> Path.t -> t
 
-(** Passing [~traverse_ignored_dirs:true] to this functions causes the
-    whole source tree to be deeply scanned, including ignored
+(** Passing [~traverse_raw_data_dirs:true] to this functions causes the
+    whole source tree to be deeply scanned, including raw_data
     directories. *)
 val fold
   :  t
-  -> traverse_ignored_dirs:bool
+  -> traverse_raw_data_dirs:bool
   -> init:'a
   -> f:(Dir.t -> 'a -> 'a)
   -> 'a
diff --git a/src/jbuild_load.ml b/src/jbuild_load.ml
index a387816ed16..3f18889a2dd 100644
--- a/src/jbuild_load.ml
+++ b/src/jbuild_load.ml
@@ -219,7 +219,7 @@ let load ~dir ~scope ~ignore_promoted_rules ~file =
 let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
   let ftree = File_tree.load Path.root ?extra_ignored_subtrees in
   let packages =
-    File_tree.fold ftree ~traverse_ignored_dirs:false ~init:[] ~f:(fun dir pkgs ->
+    File_tree.fold ftree ~traverse_raw_data_dirs:false ~init:[] ~f:(fun dir pkgs ->
       let path = File_tree.Dir.path dir in
       let files = File_tree.Dir.files dir in
       String.Set.fold files ~init:pkgs ~f:(fun fn acc ->
@@ -259,7 +259,7 @@ let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
   in
 
   let projects =
-    File_tree.fold ftree ~traverse_ignored_dirs:false ~init:[]
+    File_tree.fold ftree ~traverse_raw_data_dirs:false ~init:[]
       ~f:(fun dir acc ->
         let path = File_tree.Dir.path dir in
         let files = File_tree.Dir.files dir in
@@ -294,7 +294,7 @@ let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
       Path.Map.add scopes Path.root Scope_info.anonymous
   in
   let rec walk dir jbuilds scope =
-    if File_tree.Dir.ignored dir then
+    if File_tree.Dir.raw_data dir then
       jbuilds
     else begin
       let path = File_tree.Dir.path dir in

From 5bee48fc5059c2546200fb4f2e0058d42670c446 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Tue, 8 May 2018 16:13:03 +0100
Subject: [PATCH 03/11] Rename jbuild-ignore files

---
 example/.dune-fs                  | 1 +
 example/jbuild-ignore             | 1 -
 test/blackbox-tests/.dune-fs      | 1 +
 test/blackbox-tests/jbuild-ignore | 1 -
 4 files changed, 2 insertions(+), 2 deletions(-)
 create mode 100644 example/.dune-fs
 delete mode 100644 example/jbuild-ignore
 create mode 100644 test/blackbox-tests/.dune-fs
 delete mode 100644 test/blackbox-tests/jbuild-ignore

diff --git a/example/.dune-fs b/example/.dune-fs
new file mode 100644
index 00000000000..1bd01dfe0d7
--- /dev/null
+++ b/example/.dune-fs
@@ -0,0 +1 @@
+(dir sample-projects raw_data)
diff --git a/example/jbuild-ignore b/example/jbuild-ignore
deleted file mode 100644
index 9741c984949..00000000000
--- a/example/jbuild-ignore
+++ /dev/null
@@ -1 +0,0 @@
-sample-projects
diff --git a/test/blackbox-tests/.dune-fs b/test/blackbox-tests/.dune-fs
new file mode 100644
index 00000000000..20f09d37a4b
--- /dev/null
+++ b/test/blackbox-tests/.dune-fs
@@ -0,0 +1 @@
+(dir test-cases raw_data)
diff --git a/test/blackbox-tests/jbuild-ignore b/test/blackbox-tests/jbuild-ignore
deleted file mode 100644
index 1007655629a..00000000000
--- a/test/blackbox-tests/jbuild-ignore
+++ /dev/null
@@ -1 +0,0 @@
-test-cases

From 2823525c6fae02dcccb885772e1883c6e288fab3 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Tue, 8 May 2018 16:15:59 +0100
Subject: [PATCH 04/11] Fix bootstrap

---
 src/glob_lexer.boot.ml | 3 +++
 vendor/boot/re.ml      | 1 +
 2 files changed, 4 insertions(+)

diff --git a/src/glob_lexer.boot.ml b/src/glob_lexer.boot.ml
index d7d30df7ef0..e88b931e67d 100644
--- a/src/glob_lexer.boot.ml
+++ b/src/glob_lexer.boot.ml
@@ -2,3 +2,6 @@
    ocaml-re. This speeds up the bootstrap. *)
 
 let parse_string _ = failwith "globs are not available during bootstrap"
+
+(* To force the ordering during bootstrap *)
+let _ = Re.compile
diff --git a/vendor/boot/re.ml b/vendor/boot/re.ml
index 34fce92c04a..898b89823d9 100644
--- a/vendor/boot/re.ml
+++ b/vendor/boot/re.ml
@@ -2,3 +2,4 @@ type t = unit
 type re = unit
 let compile () = ()
 let execp _ _ = false
+let str _ = ()

From 6fdb265a57bcfd327ac06bdd50136b898968f0a3 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Tue, 8 May 2018 16:28:20 +0100
Subject: [PATCH 05/11] Document .dune-fs files

---
 doc/project-layout-specification.rst | 57 ++++++++++++++++++++++------
 1 file changed, 45 insertions(+), 12 deletions(-)

diff --git a/doc/project-layout-specification.rst b/doc/project-layout-specification.rst
index b89ee580e21..1367eabc86d 100644
--- a/doc/project-layout-specification.rst
+++ b/doc/project-layout-specification.rst
@@ -221,20 +221,53 @@ Note that this includes files present in the source tree as well as
 generated files. So for instance a changelog generated by a user rule
 will be automatically installed as well.
 
-jbuild-ignore
-=============
+.dune-fs
+========
 
-By default Jbuilder traverses the whole source tree, ignoring the
-following files and directories:
+``.dune-fs`` files allows to control how Dune interprets the file
+system. They can be used to make Dune completely ignore certain files
+or directories or to make a sub-tree appear as plain raw data.
 
-- any file that start with ``.#``
-- any directory that start with either ``.`` or ``_``
+They consist of a list of entries of the form:
 
-To ignore a subtree, simply write a ``jbuild-ignore`` file in the
-parent directory containing the name of the sub-directories to ignore.
+.. code:: scheme
+
+          (<kind> <glob> <status>)
+
+Where ``<kind>`` is one of ``file``, ``directory`` or ``_`` and
+indicate whether the entry matches files, directories or both. See
+:ref:`glob <glob>` ford details about what globs are
+available. ``<status>`` gives the status of files and/or directories
+matched by this entry and can be one of:
+
+- ``standard``
+- ``raw_data`` meaning that Dune will not try to interpret ``Dune``
+  or other special files for this file or sub-tree. This also prevents
+  Dune from eagerly scanning a sub-tree
+- ``ignore`` meaning that Dune will completely ignore this file or
+  sub-tree. It is the same as removing it before running Dune
+
+The status of a given file or sub-directory is given by the last entry
+that matches. The following default is assumed in any directory that
+doesn't have a ``.dune-fs`` file:
+
+.. code:: scheme
+
+          (dir  [._]* ignore)
+          (_    .#*   ignore)
+
+So for instance ``.git`` directories are completely ignored. If you
+wanted to write an action that would read files inside the ``.git``
+directory, you could override this default by adding the following
+``.dune-fs`` file:
+
+.. code:: scheme
+
+          (dir .git raw_data)
 
-So for instance, if you write ``foo`` in ``src/jbuild-ignore``, then
-``src/foo`` won't be traversed and any ``jbuild`` file it contains will
-be ignored.
+jbuild-ignore (deprecated)
+==========================
 
-``jbuild-ignore`` files contain a list of directory names, one per line.
+``jbuild-ignore`` files are deprecated. Each line of a
+``jbuild-ignore`` file is interpreted in the same way as a ``(dir
+<dirname> raw_data)`` entry in a ``.dune-fs`` file.

From 1af3bc9aa6965a078b9f98b4fca1fb458fb1d877 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Thu, 10 May 2018 12:29:10 +0100
Subject: [PATCH 06/11] Replace .dune-fs by fs stanza

---
 src/build_system.ml |   2 +-
 src/file_tree.ml    | 111 ++++++++++++++++++++++++++++++++++----------
 src/file_tree.mli   |  12 ++++-
 src/jbuild_load.ml  |  52 +++------------------
 4 files changed, 105 insertions(+), 72 deletions(-)

diff --git a/src/build_system.ml b/src/build_system.ml
index 1f434d9ddd6..d05549c9765 100644
--- a/src/build_system.ml
+++ b/src/build_system.ml
@@ -134,7 +134,7 @@ let rule_loc ~file_tree ~loc ~dir =
         Option.bind (File_tree.find_dir file_tree dir)
           ~f:File_tree.Dir.dune_file
       with
-      | Some file -> file
+      | Some file -> File_tree.Dune_file.path file
       | None      -> Path.relative dir "_unknown_"
     in
     Loc.in_file (Path.to_string file)
diff --git a/src/file_tree.ml b/src/file_tree.ml
index 4023e1c7b55..3a2602a603d 100644
--- a/src/file_tree.ml
+++ b/src/file_tree.ml
@@ -1,5 +1,47 @@
 open! Import
 
+module Dune_file = struct
+  type t =
+    | Sexps        of Path.t * Sexp.Ast.t list
+    | Ocaml_script of Path.t
+
+  let path = function
+    | Sexps        (p, _) -> p
+    | Ocaml_script  p     -> p
+  
+  let ocaml_script_prefix = "(* -*- tuareg -*- *)"
+  let ocaml_script_prefix_len = String.length ocaml_script_prefix
+
+  let load file =
+    Io.with_file_in file ~f:(fun ic ->
+      let open Sexp in
+      let state = Parser.create ~fname:(Path.to_string file) ~mode:Many in
+      let buf = Bytes.create Io.buf_len in
+      let rec loop stack =
+        match input ic buf 0 Io.buf_len with
+        | 0 -> Parser.feed_eoi state stack
+        | n -> loop (Parser.feed_subbytes state buf ~pos:0 ~len:n stack)
+      in
+      let rec loop0 stack i =
+        match input ic buf i (Io.buf_len - i) with
+        | 0 ->
+          let stack = Parser.feed_subbytes state buf ~pos:0 ~len:i stack in
+          Sexps (file, Parser.feed_eoi state stack)
+        | n ->
+          let i = i + n in
+          if i < ocaml_script_prefix_len then
+            loop0 stack i
+          else if Bytes.sub_string buf 0 ocaml_script_prefix_len
+                    [@warning "-6"]
+                  = ocaml_script_prefix then
+            Ocaml_script file
+          else
+            let stack = Parser.feed_subbytes state buf ~pos:0 ~len:i stack in
+            Sexps (file, loop stack)
+      in
+      loop0 Parser.Stack.empty 0)
+end
+
 module Dune_fs = struct
   open Sexp.Of_sexp
 
@@ -73,9 +115,6 @@ module Dune_fs = struct
     let rev_entries = List.rev_map sexps ~f:entry in
     { rev_entries }
 
-  let load path =
-    t (Io.Sexp.load path ~mode:Many)
-
   let load_jbuild_ignore path =
     let rev_entries =
       List.rev_filter_mapi (Io.lines_of_file path) ~f:(fun i fn ->
@@ -103,9 +142,10 @@ module Dir = struct
     }
 
   and contents =
-    { files    : String.Set.t
-    ; sub_dirs : t String.Map.t
-    ; dune_fs  : Dune_fs.t
+    { files     : String.Set.t
+    ; sub_dirs  : t String.Map.t
+    ; dune_fs   : Dune_fs.t
+    ; dune_file : Dune_file.t option
     }
 
   let contents t = Lazy.force t.contents
@@ -113,8 +153,9 @@ module Dir = struct
   let path t = t.path
   let raw_data t = t.raw_data
 
-  let files    t = (contents t).files
-  let sub_dirs t = (contents t).sub_dirs
+  let files     t = (contents t).files
+  let sub_dirs  t = (contents t).sub_dirs
+  let dune_file t = (contents t).dune_file
 
   let file_paths t =
     Path.Set.of_string_set (files t) ~f:(Path.relative t.path)
@@ -134,16 +175,6 @@ module Dir = struct
       let acc = f t acc in
       String.Map.fold (sub_dirs t) ~init:acc ~f:(fun t acc ->
         fold t ~traverse_raw_data_dirs ~init:acc ~f)
-
-  let dune_file t =
-    let (lazy { files; dune_fs; _ }) = t.contents in
-    List.find_map ["dune"; "jbuild"] ~f:(fun fn ->
-      if String.Set.mem files fn then
-        match Dune_fs.find dune_fs fn ~is_directory:false with
-        | Standard -> Some (Path.relative t.path fn)
-        | _        -> None
-      else
-        None)
 end
 
 type t =
@@ -166,13 +197,45 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
             Left fn)
       in
       let files = String.Set.of_list files in
+      let dune_file =
+        match List.filter ["dune"; "jbuild"] ~f:(String.Set.mem files) with
+        | [] -> None
+        | [fn] -> Some (Dune_file.load (Path.relative path fn))
+        | _ ->
+          die "Directory %s has both a 'dune' and 'jbuild' file.\n\
+               This is not allowed"
+            (Path.to_string_maybe_quoted path)
+      in
+      let dune_file, dune_fs =
+        match dune_file with
+        | None | Some (Ocaml_script _) -> (dune_file, None)
+        | Some (Sexps (file, l)) ->
+          let fs_stanzas, other =
+            List.partition_map l ~f:(function
+              | List (loc, Atom (_, A "fs") :: sexps) -> Left (loc, sexps)
+              | x -> Right x)
+          in
+          match fs_stanzas with
+          | [] -> (dune_file, None)
+          | _ :: (loc, _) :: _ ->
+            Loc.fail loc "Too many fs stanzas."
+          | [(loc, sexps)] ->
+            (Some (Sexps (file, other)), Some (loc, Dune_fs.t sexps))
+      in
       let dune_fs =
-        if String.Set.mem files ".dune-fs" then
-          Dune_fs.load (Path.relative path ".dune-fs")
-        else if String.Set.mem files "jbuild-ignore" then
-          Dune_fs.load_jbuild_ignore (Path.relative path "jbuild-ignore")
+        if String.Set.mem files "jbuild-ignore" then
+          let file = Path.relative path "jbuild-ignore" in
+          match dune_fs with
+          | None ->
+            Dune_fs.load_jbuild_ignore file
+          | Some (loc, _) ->
+            Loc.fail loc
+              "It is not allowed to have both a fs stanza and a \
+               jbuild-ignore file in the same directory."
         else
-          Dune_fs.default
+          match dune_fs with
+          | None -> Dune_fs.default
+          | Some (_, x) -> x
       in
       let files =
         String.Set.filter files ~f:(fun fn ->
@@ -192,7 +255,7 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
           | None -> acc
           | Some raw_data -> String.Map.add acc fn (walk path ~raw_data))
       in
-      { Dir. files; sub_dirs; dune_fs })
+      { Dir. files; sub_dirs; dune_fs; dune_file })
     in
     { path
     ; contents
diff --git a/src/file_tree.mli b/src/file_tree.mli
index 8405e434520..4206d1590e8 100644
--- a/src/file_tree.mli
+++ b/src/file_tree.mli
@@ -2,6 +2,14 @@
 
 open! Import
 
+module Dune_file : sig
+  type t =
+    | Sexps        of Path.t * Sexp.Ast.t list
+    | Ocaml_script of Path.t
+
+  val path : t -> Path.t
+end
+
 module Dir : sig
   type t
 
@@ -24,8 +32,8 @@ module Dir : sig
     -> f:(t -> 'a -> 'a)
     -> 'a
 
-  (** Return the dune (or jbuild) file in this directory *)
-  val dune_file : t -> Path.t option
+  (** Return the contents of the dune (or jbuild) file in this directory *)
+  val dune_file : t -> Dune_file.t option
 end
 
 (** A [t] value represent a view of the source tree. It is lazily
diff --git a/src/jbuild_load.ml b/src/jbuild_load.ml
index 3f18889a2dd..24035cfa0c3 100644
--- a/src/jbuild_load.ml
+++ b/src/jbuild_load.ml
@@ -168,52 +168,14 @@ type conf =
   ; scopes    : Scope_info.t list
   }
 
-module Sexp_io = struct
-  open Sexp
-
-  let ocaml_script_prefix = "(* -*- tuareg -*- *)"
-  let ocaml_script_prefix_len = String.length ocaml_script_prefix
-
-  type sexps_or_ocaml_script =
-    | Sexps of Ast.t list
-    | Ocaml_script
-
-  let load_many_or_ocaml_script fname =
-    Io.with_file_in fname ~f:(fun ic ->
-      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
-        | 0 -> Parser.feed_eoi state stack
-        | n -> loop (Parser.feed_subbytes state buf ~pos:0 ~len:n stack)
-      in
-      let rec loop0 stack i =
-        match input ic buf i (Io.buf_len - i) with
-        | 0 ->
-          let stack = Parser.feed_subbytes state buf ~pos:0 ~len:i stack in
-          Sexps (Parser.feed_eoi state stack)
-        | n ->
-          let i = i + n in
-          if i < ocaml_script_prefix_len then
-            loop0 stack i
-          else if Bytes.sub_string buf 0 ocaml_script_prefix_len
-                    [@warning "-6"]
-                  = ocaml_script_prefix then
-            Ocaml_script
-          else
-            let stack = Parser.feed_subbytes state buf ~pos:0 ~len:i stack in
-            Sexps (loop stack)
-      in
-      loop0 Parser.Stack.empty 0)
-end
-
-let load ~dir ~scope ~ignore_promoted_rules ~file =
-  match Sexp_io.load_many_or_ocaml_script file with
-  | Sexps sexps ->
+let interpret ~dir ~scope ~ignore_promoted_rules
+      ~(dune_file:File_tree.Dune_file.t) =
+  match dune_file with
+  | Sexps (file, sexps) ->
     Jbuilds.Literal (dir, scope,
                      Stanzas.parse scope sexps ~file
                      |> filter_stanzas ~ignore_promoted_rules)
-  | Ocaml_script ->
+  | Ocaml_script file ->
     Script { dir; scope; file }
 
 let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
@@ -303,9 +265,9 @@ let load ?extra_ignored_subtrees ?(ignore_promoted_rules=false) () =
       let jbuilds =
         match File_tree.Dir.dune_file dir with
         | None -> jbuilds
-        | Some file ->
+        | Some dune_file ->
           let jbuild =
-            load ~dir:path ~scope ~ignore_promoted_rules ~file
+            interpret ~dir:path ~scope ~ignore_promoted_rules ~dune_file
           in
           jbuild :: jbuilds
       in

From 0d299d941149c0f6fd7131a3033b49422e0f2752 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Thu, 10 May 2018 12:30:10 +0100
Subject: [PATCH 07/11] Use fs stanzas

---
 example/.dune-fs             | 1 -
 example/dune                 | 3 +++
 test/blackbox-tests/.dune-fs | 1 -
 test/blackbox-tests/dune     | 3 +++
 4 files changed, 6 insertions(+), 2 deletions(-)
 delete mode 100644 example/.dune-fs
 delete mode 100644 test/blackbox-tests/.dune-fs

diff --git a/example/.dune-fs b/example/.dune-fs
deleted file mode 100644
index 1bd01dfe0d7..00000000000
--- a/example/.dune-fs
+++ /dev/null
@@ -1 +0,0 @@
-(dir sample-projects raw_data)
diff --git a/example/dune b/example/dune
index a96fdcae683..51ef72196e8 100644
--- a/example/dune
+++ b/example/dune
@@ -1,5 +1,8 @@
 (jbuild_version 1)
 
+(fs
+ (dir sample-projects raw_data))
+
 (alias
  ((name runtest)
   (deps ((package dune)
diff --git a/test/blackbox-tests/.dune-fs b/test/blackbox-tests/.dune-fs
deleted file mode 100644
index 20f09d37a4b..00000000000
--- a/test/blackbox-tests/.dune-fs
+++ /dev/null
@@ -1 +0,0 @@
-(dir test-cases raw_data)
diff --git a/test/blackbox-tests/dune b/test/blackbox-tests/dune
index a8254a66069..b519e7465d8 100644
--- a/test/blackbox-tests/dune
+++ b/test/blackbox-tests/dune
@@ -1,5 +1,8 @@
 (jbuild_version 1)
 
+(fs
+ (dir test-cases raw_data))
+
 (library
  ((name platform)
   (modules (platform))

From bf7243854526bdb0dcee1f3358a1a2e80168a50b Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jdimino@janestreet.com>
Date: Thu, 10 May 2018 12:35:26 +0100
Subject: [PATCH 08/11] optim

---
 src/file_tree.ml   | 25 ++++++++++++++++---------
 src/file_tree.mli  | 12 +++++++++++-
 src/jbuild_load.ml | 12 ++++++++----
 3 files changed, 35 insertions(+), 14 deletions(-)

diff --git a/src/file_tree.ml b/src/file_tree.ml
index 3a2602a603d..41c19dfb649 100644
--- a/src/file_tree.ml
+++ b/src/file_tree.ml
@@ -1,14 +1,21 @@
 open! Import
 
 module Dune_file = struct
+  module Plain = struct
+    type t =
+      { path          : Path.t
+      ; mutable sexps : Sexp.Ast.t list
+      }
+  end
+
   type t =
-    | Sexps        of Path.t * Sexp.Ast.t list
+    | Plain of Plain.t
     | Ocaml_script of Path.t
 
   let path = function
-    | Sexps        (p, _) -> p
-    | Ocaml_script  p     -> p
-  
+    | Plain x -> x.path
+    | Ocaml_script  p -> p
+
   let ocaml_script_prefix = "(* -*- tuareg -*- *)"
   let ocaml_script_prefix_len = String.length ocaml_script_prefix
 
@@ -26,7 +33,7 @@ module Dune_file = struct
         match input ic buf i (Io.buf_len - i) with
         | 0 ->
           let stack = Parser.feed_subbytes state buf ~pos:0 ~len:i stack in
-          Sexps (file, Parser.feed_eoi state stack)
+          Plain { path = file; sexps = Parser.feed_eoi state stack }
         | n ->
           let i = i + n in
           if i < ocaml_script_prefix_len then
@@ -37,7 +44,7 @@ module Dune_file = struct
             Ocaml_script file
           else
             let stack = Parser.feed_subbytes state buf ~pos:0 ~len:i stack in
-            Sexps (file, loop stack)
+            Plain { path = file; sexps = loop stack }
       in
       loop0 Parser.Stack.empty 0)
 end
@@ -209,9 +216,9 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
       let dune_file, dune_fs =
         match dune_file with
         | None | Some (Ocaml_script _) -> (dune_file, None)
-        | Some (Sexps (file, l)) ->
+        | Some (Plain { path; sexps }) ->
           let fs_stanzas, other =
-            List.partition_map l ~f:(function
+            List.partition_map sexps ~f:(function
               | List (loc, Atom (_, A "fs") :: sexps) -> Left (loc, sexps)
               | x -> Right x)
           in
@@ -220,7 +227,7 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
           | _ :: (loc, _) :: _ ->
             Loc.fail loc "Too many fs stanzas."
           | [(loc, sexps)] ->
-            (Some (Sexps (file, other)), Some (loc, Dune_fs.t sexps))
+            (Some (Plain { path; sexps = other }), Some (loc, Dune_fs.t sexps))
       in
       let dune_fs =
         if String.Set.mem files "jbuild-ignore" then
diff --git a/src/file_tree.mli b/src/file_tree.mli
index 4206d1590e8..07266e6f596 100644
--- a/src/file_tree.mli
+++ b/src/file_tree.mli
@@ -3,8 +3,18 @@
 open! Import
 
 module Dune_file : sig
+  module Plain : sig
+    (** [sexps] is mutable as we get of the S-expressions once they
+        have been parsed, in order to release the memory as soon as we
+        don't need them. *)
+    type t =
+      { path          : Path.t
+      ; mutable sexps : Sexp.Ast.t list
+      }
+  end
+
   type t =
-    | Sexps        of Path.t * Sexp.Ast.t list
+    | Plain of Plain.t
     | Ocaml_script of Path.t
 
   val path : t -> Path.t
diff --git a/src/jbuild_load.ml b/src/jbuild_load.ml
index 24035cfa0c3..92846e12938 100644
--- a/src/jbuild_load.ml
+++ b/src/jbuild_load.ml
@@ -171,10 +171,14 @@ type conf =
 let interpret ~dir ~scope ~ignore_promoted_rules
       ~(dune_file:File_tree.Dune_file.t) =
   match dune_file with
-  | Sexps (file, sexps) ->
-    Jbuilds.Literal (dir, scope,
-                     Stanzas.parse scope sexps ~file
-                     |> filter_stanzas ~ignore_promoted_rules)
+  | Plain p ->
+    let jbuild =
+      Jbuilds.Literal (dir, scope,
+                       Stanzas.parse scope p.sexps ~file:p.path
+                       |> filter_stanzas ~ignore_promoted_rules)
+    in
+    p.sexps <- [];
+    jbuild
   | Ocaml_script file ->
     Script { dir; scope; file }
 

From 304e981ce50bc17ca3e6b188003597c07213aa78 Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jeremie@dimino.org>
Date: Thu, 10 May 2018 15:13:27 +0100
Subject: [PATCH 09/11] typo

---
 src/file_tree.mli | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/file_tree.mli b/src/file_tree.mli
index 07266e6f596..09dc663e8e3 100644
--- a/src/file_tree.mli
+++ b/src/file_tree.mli
@@ -4,9 +4,9 @@ open! Import
 
 module Dune_file : sig
   module Plain : sig
-    (** [sexps] is mutable as we get of the S-expressions once they
-        have been parsed, in order to release the memory as soon as we
-        don't need them. *)
+    (** [sexps] is mutable as we get rid of the S-expressions once
+        they have been parsed, in order to release the memory as soon
+        as we don't need them. *)
     type t =
       { path          : Path.t
       ; mutable sexps : Sexp.Ast.t list

From 2787c95aca5ad649c5ee840ed3bee419e441508c Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jeremie@dimino.org>
Date: Thu, 10 May 2018 15:25:20 +0100
Subject: [PATCH 10/11] Add a test for fs stanza

---
 test/blackbox-tests/dune.inc                          | 10 ++++++++++
 test/blackbox-tests/test-cases/fs-stanza/data/dune    |  1 +
 test/blackbox-tests/test-cases/fs-stanza/dune         |  3 +++
 .../blackbox-tests/test-cases/fs-stanza/ignored-dir/x |  0
 test/blackbox-tests/test-cases/fs-stanza/ignored-file |  0
 .../test-cases/fs-stanza/old-style/data/dune          |  1 +
 .../test-cases/fs-stanza/old-style/data/jbuild        |  1 +
 .../test-cases/fs-stanza/old-style/jbuild-ignore      |  1 +
 test/blackbox-tests/test-cases/fs-stanza/run.t        | 11 +++++++++++
 9 files changed, 28 insertions(+)
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/data/dune
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/dune
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/ignored-dir/x
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/ignored-file
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/old-style/data/dune
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/old-style/data/jbuild
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/old-style/jbuild-ignore
 create mode 100644 test/blackbox-tests/test-cases/fs-stanza/run.t

diff --git a/test/blackbox-tests/dune.inc b/test/blackbox-tests/dune.inc
index e9eeb6cb82d..089870dd242 100644
--- a/test/blackbox-tests/dune.inc
+++ b/test/blackbox-tests/dune.inc
@@ -106,6 +106,14 @@
     test-cases/force-test
     (progn (run ${exe:cram.exe} -test run.t) (diff? run.t run.t.corrected))))))
 
+(alias
+ ((name fs-stanza)
+  (deps ((package dune) (files_recursively_in test-cases/fs-stanza)))
+  (action
+   (chdir
+    test-cases/fs-stanza
+    (progn (run ${exe:cram.exe} -test run.t) (diff? run.t run.t.corrected))))))
+
 (alias
  ((name gen-opam-install-file)
   (deps
@@ -490,6 +498,7 @@
     (alias exec-cmd)
     (alias findlib)
     (alias force-test)
+    (alias fs-stanza)
     (alias gen-opam-install-file)
     (alias github20)
     (alias github24)
@@ -547,6 +556,7 @@
     (alias exec-cmd)
     (alias findlib)
     (alias force-test)
+    (alias fs-stanza)
     (alias gen-opam-install-file)
     (alias github20)
     (alias github24)
diff --git a/test/blackbox-tests/test-cases/fs-stanza/data/dune b/test/blackbox-tests/test-cases/fs-stanza/data/dune
new file mode 100644
index 00000000000..9ce7649da02
--- /dev/null
+++ b/test/blackbox-tests/test-cases/fs-stanza/data/dune
@@ -0,0 +1 @@
+garbage
diff --git a/test/blackbox-tests/test-cases/fs-stanza/dune b/test/blackbox-tests/test-cases/fs-stanza/dune
new file mode 100644
index 00000000000..11feb541e60
--- /dev/null
+++ b/test/blackbox-tests/test-cases/fs-stanza/dune
@@ -0,0 +1,3 @@
+(fs
+ (dir data      raw_data)
+ (_   ignored-* ignore))
diff --git a/test/blackbox-tests/test-cases/fs-stanza/ignored-dir/x b/test/blackbox-tests/test-cases/fs-stanza/ignored-dir/x
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/test/blackbox-tests/test-cases/fs-stanza/ignored-file b/test/blackbox-tests/test-cases/fs-stanza/ignored-file
new file mode 100644
index 00000000000..e69de29bb2d
diff --git a/test/blackbox-tests/test-cases/fs-stanza/old-style/data/dune b/test/blackbox-tests/test-cases/fs-stanza/old-style/data/dune
new file mode 100644
index 00000000000..d58adb0f78a
--- /dev/null
+++ b/test/blackbox-tests/test-cases/fs-stanza/old-style/data/dune
@@ -0,0 +1 @@
+garbage
\ No newline at end of file
diff --git a/test/blackbox-tests/test-cases/fs-stanza/old-style/data/jbuild b/test/blackbox-tests/test-cases/fs-stanza/old-style/data/jbuild
new file mode 100644
index 00000000000..9ce7649da02
--- /dev/null
+++ b/test/blackbox-tests/test-cases/fs-stanza/old-style/data/jbuild
@@ -0,0 +1 @@
+garbage
diff --git a/test/blackbox-tests/test-cases/fs-stanza/old-style/jbuild-ignore b/test/blackbox-tests/test-cases/fs-stanza/old-style/jbuild-ignore
new file mode 100644
index 00000000000..6320cd248dd
--- /dev/null
+++ b/test/blackbox-tests/test-cases/fs-stanza/old-style/jbuild-ignore
@@ -0,0 +1 @@
+data
\ No newline at end of file
diff --git a/test/blackbox-tests/test-cases/fs-stanza/run.t b/test/blackbox-tests/test-cases/fs-stanza/run.t
new file mode 100644
index 00000000000..0418657717f
--- /dev/null
+++ b/test/blackbox-tests/test-cases/fs-stanza/run.t
@@ -0,0 +1,11 @@
+  $ jbuilder build data/dune
+  $ jbuilder build old-style/data/dune
+
+The follow command must fail due to the fs settings:
+
+  $ jbuilder build ignored-file
+  Don't know how to build ignored-file
+  [1]
+  $ jbuilder build ignored-dir/x
+  Don't know how to build ignored-dir/x
+  [1]

From a907a1a6b9710d829d108437a84a0d35faba65fd Mon Sep 17 00:00:00 2001
From: Jeremie Dimino <jeremie@dimino.org>
Date: Thu, 10 May 2018 16:34:05 +0100
Subject: [PATCH 11/11] Fix: don't read dune files in raw data sub-trees

---
 src/file_tree.ml | 81 ++++++++++++++++++++++++++----------------------
 1 file changed, 44 insertions(+), 37 deletions(-)

diff --git a/src/file_tree.ml b/src/file_tree.ml
index 41c19dfb649..1bb624bcea5 100644
--- a/src/file_tree.ml
+++ b/src/file_tree.ml
@@ -204,45 +204,52 @@ let load ?(extra_ignored_subtrees=Path.Set.empty) path =
             Left fn)
       in
       let files = String.Set.of_list files in
-      let dune_file =
-        match List.filter ["dune"; "jbuild"] ~f:(String.Set.mem files) with
-        | [] -> None
-        | [fn] -> Some (Dune_file.load (Path.relative path fn))
-        | _ ->
-          die "Directory %s has both a 'dune' and 'jbuild' file.\n\
-               This is not allowed"
-            (Path.to_string_maybe_quoted path)
-      in
       let dune_file, dune_fs =
-        match dune_file with
-        | None | Some (Ocaml_script _) -> (dune_file, None)
-        | Some (Plain { path; sexps }) ->
-          let fs_stanzas, other =
-            List.partition_map sexps ~f:(function
-              | List (loc, Atom (_, A "fs") :: sexps) -> Left (loc, sexps)
-              | x -> Right x)
-          in
-          match fs_stanzas with
-          | [] -> (dune_file, None)
-          | _ :: (loc, _) :: _ ->
-            Loc.fail loc "Too many fs stanzas."
-          | [(loc, sexps)] ->
-            (Some (Plain { path; sexps = other }), Some (loc, Dune_fs.t sexps))
-      in
-      let dune_fs =
-        if String.Set.mem files "jbuild-ignore" then
-          let file = Path.relative path "jbuild-ignore" in
-          match dune_fs with
-          | None ->
-            Dune_fs.load_jbuild_ignore file
-          | Some (loc, _) ->
-            Loc.fail loc
-              "It is not allowed to have both a fs stanza and a \
-               jbuild-ignore file in the same directory."
+        if raw_data then
+          (None, Dune_fs.default)
         else
-          match dune_fs with
-          | None -> Dune_fs.default
-          | Some (_, x) -> x
+          let dune_file =
+            match List.filter ["dune"; "jbuild"] ~f:(String.Set.mem files) with
+            | [] -> None
+            | [fn] -> Some (Dune_file.load (Path.relative path fn))
+            | _ ->
+              die "Directory %s has both a 'dune' and 'jbuild' file.\n\
+                   This is not allowed"
+                (Path.to_string_maybe_quoted path)
+          in
+          let dune_file, dune_fs =
+            match dune_file with
+            | None | Some (Ocaml_script _) -> (dune_file, None)
+            | Some (Plain { path; sexps }) ->
+              let fs_stanzas, other =
+                List.partition_map sexps ~f:(function
+                  | List (loc, Atom (_, A "fs") :: sexps) -> Left (loc, sexps)
+                  | x -> Right x)
+              in
+              match fs_stanzas with
+              | [] -> (dune_file, None)
+              | _ :: (loc, _) :: _ ->
+                Loc.fail loc "Too many fs stanzas."
+              | [(loc, sexps)] ->
+                (Some (Plain { path; sexps = other }),
+                 Some (loc, Dune_fs.t sexps))
+          in
+          let dune_fs =
+            if String.Set.mem files "jbuild-ignore" then
+              let file = Path.relative path "jbuild-ignore" in
+              match dune_fs with
+              | None ->
+                Dune_fs.load_jbuild_ignore file
+              | Some (loc, _) ->
+                Loc.fail loc
+                  "It is not allowed to have both a fs stanza and a \
+                   jbuild-ignore file in the same directory."
+            else
+              match dune_fs with
+              | None -> Dune_fs.default
+              | Some (_, x) -> x
+          in
+          (dune_file, dune_fs)
       in
       let files =
         String.Set.filter files ~f:(fun fn ->