WIP: parse the keywords item from OCAMLPARAM

TODO:
 - Should be 5.3+
 - Command line option as well?
 - Duplicates the splitting logic slightly with Compenv

Signed-off-by: David Allsopp <[email protected]>

src/driver.ml

@@ -1414,9 +1414,30 @@ let standalone_args =
 let get_args ?(standalone_args = standalone_args) () =
   standalone_args @ List.rev !args
 
+let apply_keyword_edition () =
+  match Sys.getenv_opt "OCAMLPARAM" with
+  | None -> ()
+  | Some s ->
+      let items =
+        if String.equal s "" then []
+        else
+          (* cf. Compenv.parse_args *)
+          match s.[0] with
+          | (':' | '|' | ';' | ' ' | ',') as sep ->
+              List.tl (String.split_on_char s ~sep)
+          | _ -> String.split_on_char s ~sep:','
+      in
+      let apply_if_keyword item =
+        if String.starts_with ~prefix:"keywords=" item then
+          Clflags.keyword_edition :=
+            Some (String.sub item ~pos:9 ~len:(String.length item - 9))
+      in
+      List.iter items ~f:apply_if_keyword
+
 let standalone_main () =
   let usage = Printf.sprintf "%s [extra_args] [<files>]" exe_name in
   let args = get_args () in
+  apply_keyword_edition ();
   Arg.parse (Arg.align args) set_input usage;
   interpret_mask ();
   if !request_print_transformations then (

src/dune

@@ -3,6 +3,7 @@
  (public_name ppxlib)
  (libraries
   (re_export ppxlib_ast)
+  compiler-libs.common
   ocaml-compiler-libs.shadow
   astlib
   ppxlib_print_diff