fix(nextjs): Include protect types in auth (#4398)

.changeset/selfish-pianos-push.md

@@ -0,0 +1,5 @@
+---
+"@clerk/nextjs": patch
+---
+
+Bug fix: Include protect types in `auth`

packages/nextjs/src/app-router/server/auth.ts

@@ -5,13 +5,19 @@ import { notFound, redirect } from 'next/navigation';
 import { PUBLISHABLE_KEY, SIGN_IN_URL, SIGN_UP_URL } from '../../server/constants';
 import { createGetAuth } from '../../server/createGetAuth';
 import { authAuthHeaderMissing } from '../../server/errors';
+import type { AuthProtect } from '../../server/protect';
 import { createProtect } from '../../server/protect';
 import { decryptClerkRequestData, getAuthKeyFromRequest, getHeader } from '../../server/utils';
 import { buildRequestLike } from './utils';
 
 type Auth = AuthObject & { redirectToSignIn: RedirectFun<ReturnType<typeof redirect>> };
 
-export async function auth(): Promise<Auth> {
+export interface AuthFn {
+  (): Promise<Auth>;
+  protect: AuthProtect;
+}
+
+export const auth: AuthFn = async () => {
   require('server-only');
 
   const request = await buildRequestLike();
@@ -44,9 +50,9 @@ export async function auth(): Promise<Auth> {
   };
 
   return Object.assign(authObject, { redirectToSignIn });
-}
+};
 
-auth.protect = async (...args: any[]) => {
+auth.protect = async (...args) => {
   require('server-only');
 
   const request = await buildRequestLike();
@@ -59,5 +65,7 @@ auth.protect = async (...args: any[]) => {
     notFound,
     redirect,
   });
+
+  // @ts-expect-error TS flattens all possible combinations of the for AuthProtect signatures in a union.
   return protect(...args);
 };