Fix failure

Author: timneutkens

packages/next/src/build/webpack/loaders/next-app-loader/index.ts

@@ -835,7 +835,7 @@ const nextAppLoader: AppLoader = async function nextAppLoader() {
       const [createdRootLayout, rootLayoutPath] = await verifyRootLayout({
         appDir: appDir,
         dir: rootDir!,
-        tsconfigPath: tsconfigPath!,
+        tsconfigPath: tsconfigPath,
         pagePath,
         pageExtensions,
       })

packages/next/src/lib/verify-root-layout.ts

@@ -63,7 +63,7 @@ export async function verifyRootLayout({
 }: {
   dir: string
   appDir: string
-  tsconfigPath: string
+  tsconfigPath: string | undefined
   pagePath: string
   pageExtensions: PageExtensions
 }): Promise<[boolean, string | undefined]> {
@@ -112,7 +112,8 @@ export async function verifyRootLayout({
     }
 
     if (typeof availableDir === 'string') {
-      const resolvedTsConfigPath = path.join(dir, tsconfigPath)
+      const tsConfigFileName = tsconfigPath || 'tsconfig.json'
+      const resolvedTsConfigPath = path.join(dir, tsConfigFileName)
       const hasTsConfig = await fs.access(resolvedTsConfigPath).then(
         () => true,
         () => false