fix: flushSync support (#13755)

fix: clone request if we have to read the body

Author: jacob-ebey

packages/react-router/lib/rsc/browser.tsx

@@ -1,4 +1,5 @@
 import * as React from "react";
+import * as ReactDOM from "react-dom";
 
 import { RouterProvider } from "../components";
 import type { DataRouteMatch, DataRouteObject } from "../context";
@@ -80,7 +81,7 @@ export function createCallServer({
       const promise = new Promise<void>((resolve, rejectFn) => {
         reject = rejectFn;
       });
-      
+
       const unsubscribe = window.__router.subscribe(({ navigation }) => {
         if (navigation.state === "idle") {
           unsubscribe();
@@ -530,7 +531,7 @@ export function RSCHydratedRouter({
 
   return (
     <FrameworkContext.Provider value={frameworkContext}>
-      <RouterProvider router={router} />
+      <RouterProvider router={router} flushSync={ReactDOM.flushSync} />
     </FrameworkContext.Provider>
   );
 }

packages/react-router/lib/rsc/server.rsc.ts

@@ -276,6 +276,7 @@ async function processServerAction(
   }
 
   if (request.method === "POST") {
+    const clone = request.clone();
     const formData = await request.formData();
     if (Array.from(formData.keys()).some((k) => k.startsWith("$ACTION_"))) {
       if (!decodeFormAction) {
@@ -296,6 +297,9 @@ async function processServerAction(
         revalidationRequest: getRevalidationRequest(),
       };
     }
+    return {
+      revalidationRequest: clone,
+    };
   }
 }