fix(rsc): reject inline "use server" inside "use client" module

[hi-ogawa]

Description

• Closes Reject inline "use server" inside client boundary #883

todo

• test with react-router client routes

example

• client.tsx

'use client'

import React from 'react'

export function ClientCounter() {
  const [count, setCount] = React.useState(0)

  function someFn() {
    "use server";
    console.log("foo");
  }

  return (
    <button onClick={() => setCount((count) => count + 1)}>
      Client Counter: {count}
    </button>
  )
}

This code will cause a build error:

error during build:
[rsc:use-client] [plugin rsc:use-client] src/client.tsx (7:4): 'use server' directive is not allowed within 'use client'
file: /home/hiroshi/code/others/vite-plugin-react/packages/plugin-rsc/examples/starter/src/client.tsx:7:4

5:   const [count, setCount] = React.useState(0);
6:   function someFn() {
7:     "use server";
       ^
8:     console.log("foo");
9:   }

example (react router client module)

• route.tsx

function serverFnInsideClienRoute() {
  "use server";
  console.log("nooo");
}

export default function Index() {
  return (
    <div>
      <form action={serverFnInsideClienRoute}>foo</form>
    </div>
  );
}

• build error

vite v7.1.6 building SSR bundle for production...
🧪 Using React Router's RSC Framework Mode (experimental)
✓ 33 modules transformed.
✗ Build failed in 221ms
[rsc:use-client] [plugin rsc:use-client] app/routes/_index/route.tsx?client-route-module (3:2): 'use server' directive is not allowed inside 'use client'
file: /home/hiroshi/Downloads/github-mu2rn18z-rvf27n9w/app/routes/_index/route.tsx?client-route-module:3:2

1: "use client";import { jsx } from "react/jsx-runtime";
2: function serverFnInsideClienRoute() {
3:   "use server";
     ^
4: 
5:   console.log("nooo");

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@vitejs/plugin-react@884

npm i https://pkg.pr.new/@vitejs/plugin-react-oxc@884

npm i https://pkg.pr.new/@vitejs/plugin-rsc@884

npm i https://pkg.pr.new/@vitejs/plugin-react-swc@884

commit: c48caaa