All IO must go through Build

src/build.ml

@@ -29,6 +29,8 @@ module Repr = struct
     | Fanout : ('a, 'b) t * ('a, 'c) t -> ('a, 'b * 'c) t
     | Paths : Pset.t -> ('a, 'a) t
     | Paths_glob : Path.t * Re.re -> ('a, 'a) t
+    | Contents : Path.t -> ('a, string) t
+    | Lines_of : Path.t -> ('a, string list) t
     | Vpath : 'a Vspec.t -> (unit, 'a) t
     | Dyn_paths : ('a, Path.t list) t -> ('a, 'a) t
     | Record_lib_deps : Path.t * lib_deps -> ('a, 'a) t
@@ -99,6 +101,9 @@ let paths_glob ~dir re = Paths_glob (dir, re)
 let vpath vp = Vpath vp
 let dyn_paths t = Dyn_paths t
 
+let contents p = Contents p
+let lines_of p = Lines_of p
+
 let fail x = Fail x
 
 let files_recursively_in ~dir =

src/build.mli

@@ -42,6 +42,9 @@ val vpath : 'a Vspec.t  -> (unit, 'a) t
 
 val dyn_paths : ('a, Path.t list) t -> ('a, 'a) t
 
+val contents : Path.t -> ('a, string) t
+val lines_of : Path.t -> ('a, string list) t
+
 (** Always fail when executed. We pass a function rather than an exception to get a proper
     backtrace *)
 val fail : fail -> ('a, 'a) t
@@ -107,6 +110,8 @@ module Repr : sig
     | Fanout : ('a, 'b) t * ('a, 'c) t -> ('a, 'b * 'c) t
     | Paths : Path.Set.t -> ('a, 'a) t
     | Paths_glob : Path.t * Re.re -> ('a, 'a) t
+    | Contents : Path.t -> ('a, string) t
+    | Lines_of : Path.t -> ('a, string list) t
     | Vpath : 'a Vspec.t -> (unit, 'a) t
     | Dyn_paths : ('a, Path.t list) t -> ('a, 'a) t
     | Record_lib_deps : Path.t * lib_deps -> ('a, 'a) t

src/build_interpret.ml

@@ -40,6 +40,8 @@ let deps t ~all_targets_by_dir =
             Re.execp re (Path.basename path))
       end
     | Dyn_paths t -> loop t acc
+    | Contents p -> Pset.add p acc
+    | Lines_of p -> Pset.add p acc
     | Record_lib_deps _ -> acc
     | Fail _ -> acc
   in
@@ -61,6 +63,8 @@ let lib_deps =
       | Vpath _ -> acc
       | Paths_glob _ -> acc
       | Dyn_paths t -> loop t acc
+      | Contents _ -> acc
+      | Lines_of _ -> acc
       | Record_lib_deps (dir, deps) ->
         let data =
           match Pmap.find dir acc with
@@ -88,6 +92,8 @@ let targets =
     | Vpath _ -> acc
     | Paths_glob _ -> acc
     | Dyn_paths t -> loop t acc
+    | Contents _ -> acc
+    | Lines_of _ -> acc
     | Record_lib_deps _ -> acc
     | Fail _ -> acc
   in

src/build_system.ml

@@ -209,6 +209,8 @@ module Build_exec = struct
         both (exec a x) (exec b x)
       | Paths _ -> return x
       | Paths_glob _ -> return x
+      | Contents p -> return (read_file (Path.to_string p))
+      | Lines_of p -> return (lines_of_file (Path.to_string p))
       | Vpath (Vspec.T (fn, kind)) ->
         let file : b File_spec.t = get_file bs fn (Sexp_file kind) in
         return (Option.value_exn file.data)

src/gen_rules.ml

@@ -511,10 +511,8 @@ module Gen(P : Params) = struct
     add_rule
       (Build.run (Dep ctx.ocamldep) [A "-modules"; S files] ~stdout_to:ocamldep_output);
     add_rule
-      (Build.path ocamldep_output
-       >>^ (fun () ->
-         parse_deps ~dir ~modules ~alias_module
-           (lines_of_file (Path.to_string ocamldep_output)))
+      (Build.lines_of ocamldep_output
+       >>^ parse_deps ~dir ~modules ~alias_module
        >>> Build.store_vfile vdepends);
     Build.vpath vdepends
 
@@ -1652,9 +1650,7 @@ end of your list of preprocessors. Consult the manual for more details."
       let template =
         if has_meta_tmpl then
           let meta_templ_path = Path.relative pkg.path meta_templ_fn in
-          Build.path meta_templ_path
-          >>^ fun () ->
-          lines_of_file (Path.to_string meta_templ_path)
+          Build.lines_of meta_templ_path
         else
           Build.return ["# JBUILDER_GEN"]
       in