Support async component for React Server component in JSX v4 (#6399)

* add tests

* support async in JSX ppx

* update changelog

* convert async component type

* eof

* use asyncComponent func

* fix polymorphic type inference

* remove duplicated function

* relocate ast_await into ml

* remove duplicated is_async function

CHANGELOG.md

@@ -25,6 +25,7 @@
 - Untagged variants: Support `promise`, RegExes, Dates, File and Blob. https://github.com/rescript-lang/rescript-compiler/pull/6383
 - Untagged variants: Support `bool`. https://github.com/rescript-lang/rescript-compiler/pull/6368
 - 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 V4. https://github.com/rescript-lang/rescript-compiler/pull/6399
 
 #### :boom: Breaking Change
 - Add smart printer for pipe-chains.  https://github.com/rescript-lang/rescript-compiler/pull/6411 (the formatter will reformat existing code in certain cases)

jscomp/frontend/ast_attributes.ml

@@ -166,14 +166,8 @@ let is_inline : attr -> bool =
 
 let has_inline_payload (attrs : t) = Ext_list.find_first attrs is_inline
 
-let is_await : attr -> bool =
- fun ({txt}, _) -> txt = "await" || txt = "res.await"
-
-let is_async : attr -> bool =
- fun ({txt}, _) -> txt = "async" || txt = "res.async"
-
-let has_await_payload (attrs : t) = Ext_list.find_first attrs is_await
-let has_async_payload (attrs : t) = Ext_list.find_first attrs is_async
+let has_await_payload (attrs : t) = Ext_list.find_first attrs Ast_await.is_await
+let has_async_payload (attrs : t) = Ext_list.find_first attrs Ast_async.is_async
 
 type derive_attr = {bs_deriving: Ast_payload.action list option} [@@unboxed]
 

jscomp/frontend/ast_async.ml → jscomp/ml/ast_async.ml

@@ -1,3 +1,6 @@
+let is_async : Parsetree.attribute -> bool =
+  fun ({txt}, _) -> txt = "async" || txt = "res.async"
+
 let add_promise_type ?(loc = Location.none) ~async
     (result : Parsetree.expression) =
   if async then

jscomp/frontend/ast_await.ml → jscomp/ml/ast_await.ml

@@ -1,3 +1,6 @@
+let is_await : Parsetree.attribute -> bool =
+  fun ({txt}, _) -> txt = "await" || txt = "res.await"
+
 let create_await_expression (e : Parsetree.expression) =
   let loc = e.pexp_loc in
   let unsafe_await =

jscomp/others/jsxPPXReactSupportC.res

@@ -48,3 +48,5 @@ let createElementWithKey = (~key=?, component, props) =>
 
 let createElementVariadicWithKey = (~key=?, component, props, elements) =>
   createElementVariadic(component, addKeyProp(~key?, props), elements)
+
+external asyncComponent: promise<Jsx.element> => Jsx.element = "%identity"

jscomp/others/jsxPPXReactSupportU.res

@@ -50,3 +50,5 @@ let createElementWithKey = (~key=?, component, props) =>
 
 let createElementVariadicWithKey = (~key=?, component, props, elements) =>
   createElementVariadic(component, addKeyProp(~key?, props), elements)
+
+external asyncComponent: promise<Jsx.element> => Jsx.element = "%identity"

jscomp/syntax/src/react_jsx_common.ml

@@ -63,3 +63,15 @@ let removeArity binding =
     | _ -> expr
   in
   {binding with pvb_expr = removeArityRecord binding.pvb_expr}
+
+let async_component ~async expr =
+  if async then
+    let open Ast_helper in
+    Exp.apply
+      (Exp.ident
+         {
+           loc = Location.none;
+           txt = Ldot (Lident "JsxPPXReactSupport", "asyncComponent");
+         })
+      [(Nolabel, expr)]
+  else expr

jscomp/syntax/src/reactjs_jsx_v4.ml

@@ -909,6 +909,10 @@ 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 Ast_async.is_async
+      |> Option.is_some
+    in
     (* do stuff here! *)
     let namedArgList, newtypes, _typeConstraints =
       recursivelyTransformNamedArgsForMake
@@ -942,6 +946,9 @@ let mapBinding ~config ~emptyLoc ~pstr_loc ~fileName ~recFlag binding =
           (Pat.var @@ Location.mknoloc "props")
           (Typ.constr (Location.mknoloc @@ Lident "props") [Typ.any ()])
     in
+    let innerExpression =
+      React_jsx_common.async_component ~async:isAsync innerExpression
+    in
     let fullExpression =
       (* React component name should start with uppercase letter *)
       (* let make = { let \"App" = props => make(props); \"App" } *)
@@ -1083,6 +1090,7 @@ let mapBinding ~config ~emptyLoc ~pstr_loc ~fileName ~recFlag binding =
                 | _ -> [Typ.any ()]))))
         expression
     in
+    let expression = Ast_async.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/asyncAwait.res

@@ -0,0 +1,19 @@
+let f = a => Js.Promise.resolve(a + a)
+
+module C0 = {
+  @react.component
+  let make = async (~a) => {
+    let a = await f(a)
+    <div> {React.int(a)} </div>
+  }
+}
+
+module C1 = {
+  @react.component
+  let make = async (~status) => {
+    switch status {
+    | #on => React.string("on")
+    | #off => React.string("off")
+    }
+  }
+}

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

@@ -0,0 +1,31 @@
+let f = a => Js.Promise.resolve(a + a)
+
+module C0 = {
+  type props<'a> = {a: 'a}
+
+  let make = async ({a, _}: props<_>) => {
+    let a = await f(a)
+    ReactDOM.jsx("div", {children: ?ReactDOM.someElement({React.int(a)})})
+  }
+  let make = {
+    let \"AsyncAwait$C0" = (props: props<_>) => JsxPPXReactSupport.asyncComponent(make(props))
+
+    \"AsyncAwait$C0"
+  }
+}
+
+module C1 = {
+  type props<'status> = {status: 'status}
+
+  let make = async ({status, _}: props<_>) => {
+    switch status {
+    | #on => React.string("on")
+    | #off => React.string("off")
+    }
+  }
+  let make = {
+    let \"AsyncAwait$C1" = (props: props<_>) => JsxPPXReactSupport.asyncComponent(make(props))
+
+    \"AsyncAwait$C1"
+  }
+}