support async in JSX ppx

Author: mununki

CHANGELOG.md

@@ -24,6 +24,7 @@
 - Add builtin abstract types for File and Blob APIs. https://github.com/rescript-lang/rescript-compiler/pull/6383
 - Untagged variants: Support `promise`, RegExes, Dates, File and Blob. https://github.com/rescript-lang/rescript-compiler/pull/6383
 - Support aliased types as payloads to untagged variants. https://github.com/rescript-lang/rescript-compiler/pull/6394
+- Support the async component for React Server Component in JSX ppx
 
 #### :nail_care: Polish
 

jscomp/syntax/src/react_jsx_common.ml

@@ -63,3 +63,16 @@ let removeArity binding =
     | _ -> expr
   in
   {binding with pvb_expr = removeArityRecord binding.pvb_expr}
+
+let add_async_attribute ~async (body : Parsetree.expression) =
+  if async then
+    {
+      body with
+      pexp_attributes =
+        ({txt = "res.async"; loc = Location.none}, PStr [])
+        :: body.pexp_attributes;
+    }
+  else body
+
+let is_async : Parsetree.attribute -> bool =
+ fun ({txt}, _) -> txt = "async" || txt = "res.async"

jscomp/syntax/src/reactjs_jsx_v4.ml

@@ -909,6 +909,11 @@ let mapBinding ~config ~emptyLoc ~pstr_loc ~fileName ~recFlag binding =
     let bindingWrapper, hasForwardRef, expression =
       modifiedBinding ~bindingLoc ~bindingPatLoc ~fnName binding
     in
+    let isAsync =
+      Ext_list.find_first binding.pvb_expr.pexp_attributes
+        React_jsx_common.is_async
+      |> Option.is_some
+    in
     (* do stuff here! *)
     let namedArgList, newtypes, _typeConstraints =
       recursivelyTransformNamedArgsForMake
@@ -1083,6 +1088,9 @@ let mapBinding ~config ~emptyLoc ~pstr_loc ~fileName ~recFlag binding =
                 | _ -> [Typ.any ()]))))
         expression
     in
+    let expression =
+      React_jsx_common.add_async_attribute ~async:isAsync expression
+    in
     let expression =
       (* Add new tupes (type a,b,c) to make's definition *)
       newtypes

jscomp/syntax/tests/ppx/react/expected/asyncAwait.res.txt

@@ -1,7 +1,7 @@
 let f = a => Js.Promise.resolve(a + a)
 type props<'a> = {a: 'a}
 
-let make = ({a, _}: props<_>) => {
+let make = async ({a, _}: props<_>) => {
   let a = await f(a)
   ReactDOM.jsx("div", {children: ?ReactDOM.someElement({React.int(a)})})
 }