fix(nextjs): Improve page detection for Next 15 (#4383)

.changeset/fluffy-eyes-arrive.md

@@ -0,0 +1,5 @@
+---
+"@clerk/nextjs": minor
+---
+
+Bug fix: Correctly redirect to sign in page in Next 15.

packages/nextjs/src/server/nextFetcher.ts

@@ -12,7 +12,14 @@ type NextFetcher = Fetcher & {
  * Full type can be found https://github.com/vercel/next.js/blob/6185444e0a944a82e7719ac37dad8becfed86acd/packages/next/src/client/components/static-generation-async-storage.external.ts#L4
  */
 interface StaticGenerationAsyncStorage {
+  /**
+   * Available for Next 14
+   */
   readonly pagePath?: string;
+  /**
+   * Available for Next 15
+   */
+  readonly page?: string;
 }
 
 function isNextFetcher(fetch: Fetcher | NextFetcher): fetch is NextFetcher {

packages/nextjs/src/server/protect.ts

@@ -134,7 +134,19 @@ const isAppRouterInternalNavigation = (req: Request) =>
 
 const isPagePathAvailable = () => {
   const __fetch = globalThis.fetch;
-  return Boolean(isNextFetcher(__fetch) ? __fetch.__nextGetStaticStore().getStore()?.pagePath : false);
+
+  if (!isNextFetcher(__fetch)) {
+    return false;
+  }
+
+  const { page, pagePath } = __fetch.__nextGetStaticStore().getStore() || {};
+
+  return Boolean(
+    // available on next@14
+    pagePath ||
+      // available on next@15
+      page,
+  );
 };
 
 const isPagesRouterInternalNavigation = (req: Request) => !!req.headers.get(nextConstants.Headers.NextjsData);