Source map: only specify the names of bindings

The Chrome debugger uses this information to get the original names of
variables. It does not look at all the identifier occurences but only at
where they are bound.

Also, we provide the original name, not the shortened name, which is not
very useful.

Author: vouillon

compiler/lib/js_output.ml

@@ -200,25 +200,24 @@ struct
                ; ori_name = get_name_index nm
                })
 
-  let ident f = function
+  let ident f ~kind = function
     | S { name = Utf8 name; var = Some v; _ } ->
-        output_debug_info_ident f name (Code.Var.get_loc v);
+        (match kind, Code.Var.get_name v with
+        | `Binding, Some nm -> output_debug_info_ident f nm (Code.Var.get_loc v)
+        | `Reference, _ | `Binding, None -> ());
         if false then PP.string f (Printf.sprintf "/* %d */" (Code.Var.idx v));
         PP.string f name
-    | S { name = Utf8 name; var = None; loc = Pi pi } ->
-        output_debug_info_ident f name (Some pi);
-        PP.string f name
-    | S { name = Utf8 name; var = None; loc = U | N } -> PP.string f name
+    | S { name = Utf8 name; var = None; _ } -> PP.string f name
     | V v ->
         assert accept_unnamed_var;
         PP.string f ("<" ^ Code.Var.to_string v ^ ">")
 
-  let opt_identifier f i =
+  let opt_identifier f ~kind i =
     match i with
     | None -> ()
     | Some i ->
         PP.space f;
-        ident f i
+        ident f ~kind i
 
   let early_error _ = assert false
 
@@ -578,7 +577,7 @@ struct
 
   let rec expression (l : prec) f e =
     match e with
-    | EVar v -> ident f v
+    | EVar v -> ident f ~kind:`Reference v
     | ESeq (e1, e2) ->
         if Prec.(l > Expression)
         then (
@@ -853,9 +852,9 @@ struct
     | EAssignTarget t -> (
         let property f p =
           match p with
-          | TargetPropertyId (Prop_and_ident id, None) -> ident f id
+          | TargetPropertyId (Prop_and_ident id, None) -> ident f ~kind:`Reference id
           | TargetPropertyId (Prop_and_ident id, Some (e, _)) ->
-              ident f id;
+              ident f ~kind:`Reference id;
               PP.space f;
               PP.string f "=";
               PP.space f;
@@ -886,9 +885,9 @@ struct
         let element f p =
           match p with
           | TargetElementHole -> ()
-          | TargetElementId (id, None) -> ident f id
+          | TargetElementId (id, None) -> ident f ~kind:`Reference id
           | TargetElementId (id, Some (e, _)) ->
-              ident f id;
+              ident f ~kind:`Reference id;
               PP.space f;
               PP.string f "=";
               PP.space f;
@@ -1185,11 +1184,11 @@ struct
 
   and variable_declaration f ?(in_ = true) x =
     match x with
-    | DeclIdent (i, None) -> ident f i
+    | DeclIdent (i, None) -> ident f ~kind:`Binding i
     | DeclIdent (i, Some (e, loc)) ->
         PP.start_group f 1;
         PP.start_group f 0;
-        ident f i;
+        ident f ~kind:`Binding i;
         PP.space f;
         PP.string f "=";
         PP.end_group f;
@@ -1238,9 +1237,9 @@ struct
         PP.string f ":";
         PP.space f;
         binding_element f e
-    | Prop_ident (Prop_and_ident i, None) -> ident f i
+    | Prop_ident (Prop_and_ident i, None) -> ident f ~kind:`Binding i
     | Prop_ident (Prop_and_ident i, Some (e, loc)) ->
-        ident f i;
+        ident f ~kind:`Binding i;
         PP.space f;
         PP.string f "=";
         PP.space f;
@@ -1260,7 +1259,7 @@ struct
 
   and binding f x =
     match x with
-    | BindingIdent id -> ident f id
+    | BindingIdent id -> ident f ~kind:`Binding id
     | BindingPattern p -> pattern f p
 
   and binding_array_elt f x =
@@ -1278,7 +1277,7 @@ struct
           ~force_last_comma:(fun _ -> false)
           binding_property
           list
-          ident
+          (ident ~kind:`Binding)
           rest;
         PP.string f "}";
         PP.end_group f
@@ -1591,7 +1590,7 @@ struct
             PP.start_group f 0;
             PP.start_group f 0;
             PP.string f "return function";
-            opt_identifier f i;
+            opt_identifier f ~kind:`Binding i;
             PP.end_group f;
             PP.break f;
             PP.start_group f 1;
@@ -1732,19 +1731,19 @@ struct
         | SideEffect -> ()
         | Default i ->
             PP.space f;
-            ident f i
+            ident f ~kind:`Binding i
         | Namespace (def, i) ->
             Option.iter def ~f:(fun def ->
                 PP.space f;
-                ident f def;
+                ident f ~kind:`Binding def;
                 PP.string f ",");
             PP.space f;
             PP.string f "* as ";
-            ident f i
+            ident f ~kind:`Binding i
         | Named (def, l) ->
             Option.iter def ~f:(fun def ->
                 PP.space f;
-                ident f def;
+                ident f ~kind:`Binding def;
                 PP.string f ",");
             PP.space f;
             PP.string f "{";
@@ -1756,11 +1755,11 @@ struct
                 if match i with
                    | S { name; _ } when Stdlib.Utf8_string.equal name s -> true
                    | _ -> false
-                then ident f i
+                then ident f ~kind:`Binding i
                 else (
                   pp_ident_or_string_lit f s;
                   PP.string f " as ";
-                  ident f i))
+                  ident f ~kind:`Binding i))
               l;
             PP.space f;
             PP.string f "}");
@@ -1788,9 +1787,9 @@ struct
                 if match i with
                    | S { name; _ } when Stdlib.Utf8_string.equal name s -> true
                    | _ -> false
-                then ident f i
+                then ident f ~kind:`Reference i
                 else (
-                  ident f i;
+                  ident f ~kind:`Reference i;
                   PP.string f " as ";
                   pp_ident_or_string_lit f s))
               l;
@@ -1917,7 +1916,7 @@ struct
       | { async = true; generator = true } -> "async function*"
       | { async = false; generator = true } -> "function*"
     in
-    function_declaration f prefix ident name l b loc'
+    function_declaration f prefix (ident ~kind:`Binding) name l b loc'
 
   and class_declaration f i x =
     PP.start_group f 1;
@@ -1928,7 +1927,7 @@ struct
     | None -> ()
     | Some i ->
         PP.space f;
-        ident f i);
+        ident f ~kind:`Binding i);
     PP.end_group f;
     Option.iter x.extends ~f:(fun e ->
         PP.space f;

compiler/tests-compiler/sourcemap.ml

@@ -87,10 +87,8 @@ let%expect_test _ =
       /dune-root/test.ml:1:4 -> 6:12
       /dune-root/test.ml:1:7 -> 6:15
       /dune-root/test.ml:1:11 -> 6:18
-      /dune-root/test.ml:1:7 -> 6:25
       /dune-root/test.ml:1:11 -> 6:26
       /dune-root/test.ml:1:12 -> 6:28
-      /dune-root/test.ml:1:4 -> 7:18
       null -> 10:2
     |}]
 

compiler/tests-sourcemap/dump.reference

@@ -2,7 +2,5 @@ sourcemap for test.bc.js
 /my/sourceRoot#b.ml:1:4 -> 12:   function <>f(x){return x - 1 | 0; }
 /my/sourceRoot#b.ml:1:6 -> 14:   function f(<>x){return x - 1 | 0; }
 /my/sourceRoot#b.ml:1:10 -> 17:   function f(x){<>return x - 1 | 0; }
-/my/sourceRoot#b.ml:1:6 -> 24:   function f(x){return <>x - 1 | 0; }
 /my/sourceRoot#b.ml:1:10 -> 33:   function f(x){return x - 1 | 0<>; }
 /my/sourceRoot#b.ml:1:15 -> 35:   function f(x){return x - 1 | 0; <>}
-/my/sourceRoot#b.ml:1:4 -> 23:   var Testlib_B = [0, <>f];