Fix implementation of directives.

The compiler's ppx is only run when parsing the source file.
For config settings such as directives, this is OK when `bsc` is invoked directly, but not when part of building a project. In the latter case, the ast is compiled separately, and the builtin ppx is not run again before emitting code.

Author: cristianoc

CHANGELOG.md

@@ -51,6 +51,7 @@ These are only breaking changes for unformatted code.
 - Parser: fix location of variable when function definition `{v => ...}` is enclosed in braces https://github.com/rescript-lang/rescript-compiler/pull/5949
 - Fix issue with error messages for uncurried functions where expected and given type were swapped https://github.com/rescript-lang/rescript-compiler/pull/5973
 - Fix issue with integer overflow check https://github.com/rescript-lang/rescript-compiler/pull/6028
+- Fix implementation of directives https://github.com/rescript-lang/rescript-compiler/pull/6052
 
 #### :nail_care: Polish
 

jscomp/core/js_implementation.ml

@@ -127,7 +127,15 @@ let no_export (rest : Parsetree.structure) : Parsetree.structure =
         ]
   | _ -> rest
 
+let process_attributes items =
+  items |> List.iter(fun (item : Parsetree.structure_item) -> match item.pstr_desc with
+  | Pstr_attribute ({ txt = "directive" },
+     PStr [ { pstr_desc = Pstr_eval ({ pexp_desc = Pexp_constant (Pconst_string (d, _)) }, _) } ]) ->
+      Js_config.directives := !Js_config.directives @ [d]
+  | _ -> ())
+
 let after_parsing_impl ppf outputprefix (ast : Parsetree.structure) =
+  process_attributes ast;
   if !Clflags.only_parse = false then (
     Js_config.all_module_aliases :=
       !Clflags.assume_no_mli = Mli_non_exists && all_module_alias ast;

jscomp/frontend/bs_builtin_ppx.ml

@@ -431,10 +431,6 @@ let structure_item_mapper (self : mapper) (str : Parsetree.structure_item) :
                   [ { pvb_pat; pvb_expr; pvb_attributes; pvb_loc } ] );
           })
   | Pstr_attribute ({ txt = "bs.config" | "config" }, _) -> str
-  | Pstr_attribute ({ txt = "directive" },
-     PStr [ { pstr_desc = Pstr_eval ({ pexp_desc = Pexp_constant (Pconst_string (d, _)) }, _) } ]) ->
-      Js_config.directives := d :: !Js_config.directives;
-      str
   | _ -> default_mapper.structure_item self str
 
 let local_module_name =