CR: add CONFIG macro

compiler/lib/macro.ml

@@ -23,6 +23,11 @@ type m =
   | Replace
   | Count of int ref
 
+let string_of_effects_backend = function
+  | None -> "none"
+  | Some Config.Cps -> "cps"
+  | Some Config.Double_translation -> "double-translation"
+
 class macro_mapper ~flags =
   object (m)
     inherit Js_traverse.map as super
@@ -40,6 +45,16 @@ class macro_mapper ~flags =
               | Count count ->
                   incr count;
                   super#expression x)
+          | "CONFIG", [ J.Arg (J.EStr (Utf8 "effects")) ] -> (
+              match flags with
+              | Replace ->
+                  let s = string_of_effects_backend (Config.effects ()) in
+                  J.EStr (Utf8_string.of_string_exn s)
+              | Count count ->
+                  incr count;
+                  super#expression x)
+          | "CONFIG", [ J.Arg (J.EStr (Utf8 s)) ] ->
+              failwith ("unsupported CONFIG parameter " ^ s)
           | "BLOCK", J.Arg (J.ENum tag) :: (_ :: _ as args)
             when List.for_all args ~f:(function
                    | J.Arg _ -> true

runtime/js/jslib.js

@@ -139,23 +139,8 @@ function caml_jsoo_flags_use_js_string(unit) {
 }
 
 //Provides: caml_jsoo_flags_effects
-//If: !effects
-function caml_jsoo_flags_effects(unit) {
-  return "none";
-}
-
-//Provides: caml_jsoo_flags_effects
-//If: effects
-//If: !doubletranslate
-function caml_jsoo_flags_effects(unit) {
-  return "cps";
-}
-
-//Provides: caml_jsoo_flags_effects
-//If: effects
-//If: doubletranslate
 function caml_jsoo_flags_effects(unit) {
-  return "double-translation";
+  return CONFIG("effects");
 }
 
 //Provides: caml_wrap_exception const (mutable)