await for dynamic import without async context

Author: mununki

jscomp/frontend/bs_builtin_ppx.ml

@@ -227,9 +227,15 @@ let expr_mapper ~async_context ~in_function_def (self : mapper)
   match Ast_attributes.has_await_payload e.pexp_attributes with
   | None -> result
   | Some _ ->
-      (* if !async_context = false then
+      (if !async_context = false then
+        let isJsImport (e : Parsetree.expression) =
+          match e with
+          | { pexp_desc = Pexp_apply ({ pexp_desc = Pexp_ident { txt = Ldot ( Lident "Js", "import") } }, _) } -> true
+          | _ -> false
+        in
+        if not (isJsImport e) then
          Location.raise_errorf ~loc:e.pexp_loc
-           "Await on expression not in an async context"; *)
+           "Await on expression not in an async context");
       Ast_await.create_await_expression result
 
 let typ_mapper (self : mapper) (typ : Parsetree.core_type) =

jscomp/test/Import.js

@@ -44,7 +44,7 @@ eachIntAsync({
         console.log("async", n);
       }));
 
-var beltAsModule = import("../../lib/js/belt_List.js");
+var beltAsModule = await import("../../lib/js/belt_List.js");
 
 var M = await import("../../lib/js/belt_List.js");
 

jscomp/test/Import.res

@@ -9,7 +9,7 @@ let _ = list{1, 2, 3}->eachIntLazy(n => Js.log2("lazy", n))
 let _ = list{1, 2, 3}->eachIntAsync(n => Js.log2("async", n))
 
 module type BeltList = module type of Belt.List
-let beltAsModule = Js.import(module(Belt.List: BeltList))
+let beltAsModule = await Js.import(module(Belt.List: BeltList))
 
 // module type BeltList0 = module type of Belt.List
 // module M = unpack(@res.await Js.import(module(Belt.List: BeltList0)))