fix(next): correctly parse headers with RSC (#5753)

* fix(next): correctly parse headers with RSC

* chore(dev): simplify/fix dev app

* make authOptions optional for RSC case

Author: balazsorban44

apps/dev/app/server-component/page.tsx

@@ -1,7 +1,6 @@
 import { unstable_getServerSession } from "next-auth/next"
-import { authOptions } from "pages/api/auth/[...nextauth]"
 
 export default async function Page() {
-  const session = await unstable_getServerSession(authOptions)
+  const session = await unstable_getServerSession()
   return <pre>{JSON.stringify(session, null, 2)}</pre>
 }

apps/dev/pages/api/examples/session.js

@@ -3,6 +3,6 @@ import { unstable_getServerSession } from "next-auth/next"
 import { authOptions } from "../auth/[...nextauth]"
 
 export default async (req, res) => {
-  const session = await unstable_getServerSession(authOptions)
+  const session = await unstable_getServerSession(req, res, authOptions)
   res.json(session)
 }

packages/next-auth/src/next/index.ts

@@ -94,6 +94,7 @@ export async function unstable_getServerSession(
       ]
     | [NextApiRequest, NextApiResponse, NextAuthOptions]
     | [NextAuthOptions]
+    | []
 ): Promise<Session | null> {
   if (!experimentalWarningShown && process.env.NODE_ENV !== "production") {
     console.warn(
@@ -105,7 +106,7 @@ export async function unstable_getServerSession(
     experimentalWarningShown = true
   }
 
-  const isRSC = args.length === 1
+  const isRSC = args.length === 0 || args.length === 1
   if (
     !experimentalRSCWarningShown &&
     isRSC &&
@@ -122,11 +123,11 @@ export async function unstable_getServerSession(
 
   let req, res, options: NextAuthOptions
   if (isRSC) {
-    options = args[0]
+    options = args[0] ?? { providers: [] }
     // eslint-disable-next-line @typescript-eslint/no-var-requires
     const { headers, cookies } = require("next/headers")
     req = {
-      headers,
+      headers: Object.fromEntries(headers() as Headers),
       cookies: Object.fromEntries(
         cookies()
           .getAll()