Poor man feature flag

Author: nojaf

compiler/bsc/rescript_compiler_main.ml

@@ -237,7 +237,7 @@ let buckle_script_flags : (string * Bsc_args.spec * string) array =
       "*internal* <module>  Opens the module <module> before typing" );
     ( "-bs-jsx",
       string_call (fun i ->
-          if i <> "3" && i <> "4" then
+          if i <> "3" && i <> "4" && i <> "5" then
             Bsc_args.bad_arg (" Not supported jsx version : " ^ i);
           Js_config.jsx_version :=
             Js_config.jsx_version_of_int @@ int_of_string i),

compiler/common/js_config.ml

@@ -24,7 +24,7 @@
 
 (** Browser is not set via command line only for internal use *)
 
-type jsx_version = Jsx_v4
+type jsx_version = Jsx_v4 | Jsx_preserve
 type jsx_module = React | Generic of {module_name: string}
 
 let no_version_header = ref false
@@ -56,13 +56,14 @@ let no_stdlib = ref false
 let no_export = ref false
 let int_of_jsx_version = function
   | Jsx_v4 -> 4
-
+  | Jsx_preserve -> 5
 let string_of_jsx_module = function
   | React -> "react"
   | Generic {module_name} -> module_name
 
 let jsx_version_of_int = function
   | 4 -> Some Jsx_v4
+  | 5 -> Some Jsx_preserve
   | _ -> None
 
 let jsx_module_of_string = function

compiler/common/js_config.mli

@@ -22,7 +22,7 @@
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. *)
 
-type jsx_version = Jsx_v4
+type jsx_version = Jsx_v4 | Jsx_preserve
 type jsx_module = React | Generic of {module_name: string}
 
 (* val get_packages_info :

compiler/syntax/src/jsx_ppx.ml

@@ -77,12 +77,12 @@ let get_mapper ~config =
 
   let expr mapper e =
     match config.version with
-    | 4 -> expr4 mapper e
+    | 4 | 5 -> expr4 mapper e
     | _ -> default_mapper.expr mapper e
   in
   let module_binding mapper mb =
     match config.version with
-    | 4 -> module_binding4 mapper mb
+    | 4 | 5 -> module_binding4 mapper mb
     | _ -> default_mapper.module_binding mapper mb
   in
   let save_config () =

compiler/syntax/src/jsx_v4.ml

@@ -1277,7 +1277,7 @@ let mk_react_jsx (config : Jsx_common.jsx_config) mapper loc attrs
         [key_prop; (nolabel, unit_expr ~loc:Location.none)] )
   in
   let args = [(nolabel, elementTag); (nolabel, props_record)] @ key_and_unit in
-  Exp.apply ~loc ~attrs ~transformed_jsx:true jsx_expr args
+  Exp.apply ~loc ~attrs ~transformed_jsx:(config.version = 5) jsx_expr args
 
 (* In most situations, the component name is the make function from a module. 
     However, if the name contains a lowercase letter, it means it probably an external component.