Introduce a Dir primitive to Value

This is like Path but users will know not to infer dependencies from it

Signed-off-by: Rudi Grinberg <rudi.grinberg@gmail.com>

src/action.ml

@@ -337,6 +337,9 @@ end
 let prog_and_args_of_values p ~dir =
   match p with
   | [] -> (Unresolved.Program.Search "", [])
+  | Value.Dir p :: _ ->
+    die "%s is a directory and cannot be used as an executable"
+      (Path.to_string_maybe_quoted p)
   | Value.Path p :: xs -> (This p, Value.L.to_strings ~dir xs)
   | String s :: xs ->
     (Unresolved.Program.of_string ~dir s, Value.L.to_strings ~dir xs)

src/super_context.ml

@@ -817,7 +817,7 @@ module Action = struct
             let exp = expand var syntax_version in
             Option.iter exp ~f:(fun vs ->
               acc.sdeps <- Path.Set.union (Path.Set.of_list
-                                             (Value.L.paths_only vs)) acc.sdeps;
+                                             (Value.L.deps_only vs)) acc.sdeps;
             );
             exp)
     in

src/value.ml

@@ -2,6 +2,7 @@ open Stdune
 
 type t =
   | String of string
+  | Dir of Path.t
   | Path of Path.t
 
 let string_of_path ~dir p = Path.reach ~from:dir p
@@ -9,11 +10,13 @@ let string_of_path ~dir p = Path.reach ~from:dir p
 let to_string t ~dir =
   match t with
   | String s -> s
+  | Dir p
   | Path p -> string_of_path ~dir p
 
 let to_path ?error_loc t ~dir =
   match t with
   | String s -> Path.relative ?error_loc dir s
+  | Dir p
   | Path p -> p
 
 module L = struct
@@ -23,8 +26,9 @@ module L = struct
     List.map ~f:(to_string ~dir) ts
     |> String.concat ~sep:" "
 
-  let paths_only =
+  let deps_only =
     List.filter_map ~f:(function
+      | Dir _
       | String _ -> None
       | Path p -> Some p)
 

src/value.mli

@@ -2,6 +2,7 @@ open Stdune
 
 type t =
   | String of string
+  | Dir of Path.t
   | Path of Path.t
 
 val to_string : t -> dir:Path.t -> string
@@ -13,7 +14,7 @@ module L : sig
 
   val paths : Path.t list -> t list
 
-  val paths_only : t list -> Path.t list
+  val deps_only : t list -> Path.t list
 
   val concat : t list -> dir:Path.t -> string