Prepare sourcemap interface to input index maps (unsupported for now)

compiler/lib/link_js.ml

@@ -173,14 +173,19 @@ let prefix_kind line =
       | true -> `Json_base64 (String.length sourceMappingURL_base64)
       | false -> `Url (String.length sourceMappingURL))
 
+let rule_out_index_map = function
+      | `Standard sm -> sm
+      | `Index _ -> failwith "unexpected index map at this stage"
+
 let action ~resolve_sourcemap_url ~drop_source_map file line =
   match prefix_kind line, drop_source_map with
   | `Other, (true | false) -> Keep
   | `Unit, (true | false) -> Unit
   | `Build_info bi, _ -> Build_info bi
   | (`Json_base64 _ | `Url _), true -> Drop
   | `Json_base64 offset, false ->
-      Source_map (Source_map_io.of_string (Base64.decode_exn ~off:offset line))
+      Source_map (
+        rule_out_index_map (Source_map_io.of_string (Base64.decode_exn ~off:offset line)))
   | `Url _, false when not resolve_sourcemap_url -> Drop
   | `Url offset, false ->
       let url = String.sub line ~pos:offset ~len:(String.length line - offset) in
@@ -189,7 +194,7 @@ let action ~resolve_sourcemap_url ~drop_source_map file line =
       let l = in_channel_length ic in
       let content = really_input_string ic l in
       close_in ic;
-      Source_map (Source_map_io.of_string content)
+      Source_map (rule_out_index_map (Source_map_io.of_string content))
 
 module Units : sig
   val read : Line_reader.t -> Unit_info.t -> Unit_info.t
@@ -471,12 +476,12 @@ let link ~output ~linkall ~mklib ~toplevel ~files ~resolve_sourcemap_url ~source
           | _ -> false);
         { version = init_sm.version
         ; file = init_sm.file
-        ; Composite.sections =
+        ; Index.sections =
             (let _, sections =
                List.fold_right
                  sourcemaps_and_line_counts
                  ~f:(fun (sm, generated_line_count) (cur_ofs, sections) ->
-                   let offset = Composite.{ gen_line = cur_ofs; gen_column = 0 } in
+                   let offset = Index.{ gen_line = cur_ofs; gen_column = 0 } in
                    cur_ofs + generated_line_count, (offset, `Map sm) :: sections)
                  ~init:(0, [])
              in
@@ -493,11 +498,11 @@ let link ~output ~linkall ~mklib ~toplevel ~files ~resolve_sourcemap_url ~source
       in
       (match file with
       | None ->
-          let data = Source_map_io.Composite.to_string merged_sourcemap in
+          let data = Source_map_io.Index.to_string merged_sourcemap in
           let s = sourceMappingURL_base64 ^ Base64.encode_exn data in
           Line_writer.write oc s |> ignore
       | Some file ->
-          Source_map_io.Composite.to_file merged_sourcemap file;
+          Source_map_io.Index.to_file merged_sourcemap file;
           let s = sourceMappingURL ^ Filename.basename file in
           Line_writer.write oc s |> ignore);
       if times () then Format.eprintf "  sourcemap: %a@." Timer.print t

compiler/lib/source_map.ml

@@ -675,7 +675,7 @@ let concat ~file ~sourceroot s1 s2 =
         s2.mappings
   }
 
-module Composite = struct
+module Index = struct
   type offset =
     { gen_line : int
     ; gen_column : int

compiler/lib/source_map.mli

@@ -118,7 +118,7 @@ val concat : file:string -> sourceroot:string option -> t -> t -> t
     codebases, as it decodes the whole source text. This may be fixed in the
     future. *)
 
-module Composite : sig
+module Index : sig
   type offset =
     { gen_line : int
     ; gen_column : int

compiler/lib/source_map_io.mli

@@ -25,10 +25,10 @@ val to_string : t -> string
 
 val to_file : t -> string -> unit
 
-val of_string : string -> t
+module Index : sig
+  val to_string : Index.t -> string
 
-module Composite : sig
-  val to_string : Composite.t -> string
-
-  val to_file : Composite.t -> string -> unit
+  val to_file : Index.t -> string -> unit
 end
+
+val of_string : string -> [ `Standard of Source_map.t | `Index of Source_map.Index.t ]

compiler/lib/source_map_io.yojson.ml

@@ -97,6 +97,10 @@ let of_json json =
       | `Intlit version when Int.equal (int_of_string version) 3 -> ()
       | `Floatlit _ | `Intlit _ -> invalid_arg "Source_map_io.of_json: version != 3"
       | _ -> invalid_arg "Source_map_io.of_json: version field is not a number");
+      (match List.assoc "sections" rest with
+      | _ ->
+          invalid_arg "Source_map_io.of_json: this seems to be an index map. Reading index maps is currently not supported."
+      | exception Not_found -> ());
       let file = string "file" rest in
       let sourceroot = string "sourceRoot" rest in
       let names = list_string "names" rest in
@@ -124,23 +128,23 @@ let of_json json =
       }
   | _ -> invalid ()
 
-let of_string s = of_json (Yojson.Raw.from_string s)
+let of_string s = `Standard (of_json (Yojson.Raw.from_string s))
 
 let to_string m = Yojson.Raw.to_string (json m)
 
 let to_file m file = Yojson.Raw.to_file file (json m)
 
 let enabled = true
 
-module Composite = struct
+module Index = struct
   let json t =
     `Assoc
-      [ "version", `Intlit (Int.to_string t.Composite.version)
+      [ "version", `Intlit (Int.to_string t.Index.version)
       ; "file", stringlit_of_string (rewrite_path t.file)
       ; ( "sections"
         , `List
             (List.map
-               (fun ({ Composite.gen_line; gen_column }, `Map sm) ->
+               (fun ({ Index.gen_line; gen_column }, `Map sm) ->
                  `Assoc
                    [ ( "offset"
                      , `Assoc

compiler/tests-compiler/build_path_prefix_map.ml

@@ -29,12 +29,13 @@ let%expect_test _ =
       |> compile_cmo_to_javascript ~sourcemap:true ~pretty:false
       |> extract_sourcemap
       |> function
-      | Some (sm : Js_of_ocaml_compiler.Source_map.t) ->
+      | Some (`Standard (sm : Js_of_ocaml_compiler.Source_map.t)) ->
           Printf.printf "file: %s\n" sm.file;
           Printf.printf "sourceRoot: %s\n" (Option.value ~default:"<none>" sm.sourceroot);
           Printf.printf "sources:\n";
           List.iter sm.sources ~f:(fun source ->
               Printf.printf "- %s\n" (normalize_path source))
+      | Some (`Index _) -> failwith "unexpected index map"
       | None -> failwith "no sourcemap generated!");
   [%expect
     {|

compiler/tests-compiler/sourcemap.ml

@@ -55,7 +55,8 @@ let%expect_test _ =
       print_file (Filetype.path_of_js_file js_file);
       match extract_sourcemap js_file with
       | None -> Printf.printf "No sourcemap found\n"
-      | Some sm -> print_mapping sm);
+      | Some (`Standard sm) -> print_mapping sm
+      | Some (`Index _) -> failwith "unexpected index map");
   [%expect
     {|
       $ cat "test.ml"

compiler/tests-compiler/util/util.mli

@@ -53,7 +53,7 @@ val compile_bc_to_javascript :
 val jsoo_minify :
   ?flags:string list -> pretty:bool -> Filetype.js_file -> Filetype.js_file
 
-val extract_sourcemap : Filetype.js_file -> Js_of_ocaml_compiler.Source_map.t option
+val extract_sourcemap : Filetype.js_file -> [ `Standard of Js_of_ocaml_compiler.Source_map.t | `Index of Js_of_ocaml_compiler.Source_map.Index.t ] option
 
 val run_javascript : Filetype.js_file -> string