chore(nextjs): Introduce build-time error for server-only helpers on client-side

.changeset/perfect-chairs-work.md

@@ -0,0 +1,5 @@
+---
+"@clerk/nextjs": patch
+---
+
+Return build-time error if `auth` and `currentUser` server-side helpers are imported into Client Components.

packages/nextjs/package.json

@@ -73,6 +73,7 @@
     "@clerk/types": "4.8.0",
     "crypto-js": "4.2.0",
     "path-to-regexp": "6.2.2",
+    "server-only": "0.0.1",
     "tslib": "2.4.1"
   },
   "devDependencies": {

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

@@ -1,3 +1,5 @@
+import 'server-only';
+
 import type { AuthObject, RedirectFun } from '@clerk/backend/internal';
 import { constants, createClerkRequest, createRedirect } from '@clerk/backend/internal';
 import { notFound, redirect } from 'next/navigation';

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

@@ -1,3 +1,5 @@
+import 'server-only';
+
 import type { User } from '@clerk/backend';
 
 import { clerkClient } from '../../server/clerkClient';

packages/nextjs/src/server/__tests__/exports.test.ts

@@ -1,3 +1,5 @@
+jest.mock('server-only', () => null);
+
 import * as publicExports from '../index';
 
 describe('/server public exports', () => {