fix: normalize path with nextjs normalizeAppPath utility function

.changeset/friendly-windows-count.md

@@ -0,0 +1,5 @@
+---
+"nextra": patch
+---
+
+fix route group within `app/` dir crash the `convertToPageMap`

docs/app/_components/i18n-demo.tsx

@@ -34,7 +34,6 @@ export const I18n: FC = () => {
           <div
             key={lang}
             onPointerOver={() => setActive(lang)}
-            // eslint-disable-next-line tailwindcss/no-custom-classname -- TODO: configure eslint-plugin-tailwindcss to import nextra-theme-docs styles so below classes could be removed
             className={cn(
               'relative cursor-default px-4 py-1.5 whitespace-nowrap select-none',
               active === lang

examples/docs/src/app/showcase/(overview)/page.jsx

@@ -0,0 +1,20 @@
+/**
+ * @see https://github.com/shuding/nextra/issues/4148
+ */
+
+export const metadata = {}
+
+export default function Page() {
+  return (
+    <h1
+      style={{
+        textAlign: 'center',
+        fontSize: 64,
+        margin: '25vh 0',
+        fontWeight: 'bold'
+      }}
+    >
+      Showcase
+    </h1>
+  )
+}

packages/eslint-config/src/index.ts

@@ -3,7 +3,7 @@ import { includeIgnoreFile } from '@eslint/compat'
 import js from '@eslint/js'
 // @ts-expect-error -- no types
 import eslintPluginNext from '@next/eslint-plugin-next'
-import type { Linter } from 'eslint'
+// import type { Linter } from 'eslint'
 // @ts-expect-error -- no types
 import eslintConfigPrettier from 'eslint-config-prettier'
 import eslintPluginImport from 'eslint-plugin-import-x'
@@ -13,24 +13,24 @@ import * as eslintPluginReactCompiler from 'eslint-plugin-react-compiler'
 // @ts-expect-error -- no types
 import eslintPluginReactHooks from 'eslint-plugin-react-hooks'
 import eslintPluginSonarJs from 'eslint-plugin-sonarjs'
-// @ts-expect-error -- no types
-import eslintPluginTailwindCss from 'eslint-plugin-tailwindcss'
+// import eslintPluginTailwindCss from 'eslint-plugin-tailwindcss'
 // @ts-expect-error -- no types
 import eslintPluginTsSortKeys from 'eslint-plugin-typescript-sort-keys'
 import eslintPluginUnicorn from 'eslint-plugin-unicorn'
 import tseslint from 'typescript-eslint'
 import type { Config } from 'typescript-eslint'
 
-const TAILWIND_CONFIG = {
-  extends: [eslintPluginTailwindCss.configs['flat/recommended']],
-  rules: {
-    'tailwindcss/classnames-order': 'off', // conflicts with prettier-plugin-tailwindcss
-    'tailwindcss/enforces-negative-arbitrary-values': 'error',
-    'tailwindcss/enforces-shorthand': 'error',
-    'tailwindcss/migration-from-tailwind-2': 'error',
-    'tailwindcss/no-custom-classname': 'error'
-  } satisfies Linter.RulesRecord
-}
+// TODO: Enable once `eslint-plugin-tailwindcss` will support Tailwind CSS v4
+// const TAILWIND_CONFIG = {
+//   extends: [eslintPluginTailwindCss.configs['flat/recommended']],
+//   rules: {
+//     'tailwindcss/classnames-order': 'off', // conflicts with prettier-plugin-tailwindcss
+//     'tailwindcss/enforces-negative-arbitrary-values': 'error',
+//     'tailwindcss/enforces-shorthand': 'error',
+//     'tailwindcss/migration-from-tailwind-2': 'error',
+//     'tailwindcss/no-custom-classname': 'error'
+//   } satisfies Linter.RulesRecord
+// }
 
 const REACT_COMPILER_RESTRICT = {
   name: 'react',
@@ -201,7 +201,7 @@ const config: Config = tseslint.config(
   },
   // ⚙️ nextra-theme-docs
   {
-    ...TAILWIND_CONFIG,
+    // ...TAILWIND_CONFIG,
     files: ['packages/nextra-theme-docs/**'],
     settings: {
       tailwindcss: {
@@ -217,7 +217,7 @@ const config: Config = tseslint.config(
       }
     },
     rules: {
-      ...TAILWIND_CONFIG.rules,
+      // ...TAILWIND_CONFIG.rules,
       'no-restricted-imports': [
         'error',
         { name: 'next/link', message: 'Use `<Anchor>` instead' },
@@ -229,10 +229,10 @@ const config: Config = tseslint.config(
   },
   // ⚙️ nextra-theme-blog
   {
-    ...TAILWIND_CONFIG,
+    // ...TAILWIND_CONFIG,
     files: ['packages/nextra-theme-blog/**'],
     rules: {
-      ...TAILWIND_CONFIG.rules,
+      // ...TAILWIND_CONFIG.rules,
       'no-restricted-imports': [
         'error',
         {
@@ -252,7 +252,7 @@ const config: Config = tseslint.config(
   },
   // ⚙️ nextra
   {
-    ...TAILWIND_CONFIG,
+    // ...TAILWIND_CONFIG,
     files: ['packages/nextra/**'],
     settings: {
       tailwindcss: {
@@ -267,15 +267,15 @@ const config: Config = tseslint.config(
       }
     },
     rules: {
-      ...TAILWIND_CONFIG.rules,
+      // ...TAILWIND_CONFIG.rules,
       'import/extensions': ['error', 'ignorePackages'],
       // False positive due Tailwind CSS v4
       'tailwindcss/no-custom-classname': 'off'
     }
   },
   // ⚙️ Docs
   {
-    ...TAILWIND_CONFIG,
+    // ...TAILWIND_CONFIG,
     files: ['docs/**'],
     settings: {
       tailwindcss: {
@@ -307,7 +307,7 @@ const config: Config = tseslint.config(
   },
   // ⚙️ SWR-site example
   {
-    ...TAILWIND_CONFIG,
+    // ...TAILWIND_CONFIG,
     files: ['examples/swr-site/**'],
     settings: {
       tailwindcss: {

packages/nextra/src/server/__tests__/to-page-map.test.ts

@@ -873,6 +873,7 @@ describe('generatePageMap()', () => {
           "src/app/_meta.js",
           "src/app/blog/page.jsx",
           "src/app/page.jsx",
+          "src/app/showcase/(overview)/page.jsx",
           "src/content/_meta.js",
           "src/content/advanced/code-highlighting.mdx",
           "src/content/features/_meta.js",
@@ -1011,6 +1012,11 @@ describe('generatePageMap()', () => {
             "name": "index",
             "route": "/",
           },
+          {
+            "__pagePath": "src/app/showcase/(overview)/page.jsx",
+            "name": "showcase",
+            "route": "/showcase",
+          },
           {
             "children": [
               {
@@ -1220,6 +1226,11 @@ describe('generatePageMap()', () => {
             "name": "index",
             "route": "/",
           },
+          {
+            "__pagePath": "src/app/showcase/(overview)/page.jsx",
+            "name": "showcase",
+            "route": "/showcase",
+          },
         ]
       `)
     })

packages/nextra/src/server/page-map/to-page-map.ts

@@ -1,4 +1,5 @@
 import path from 'node:path'
+import { normalizeAppPath } from 'next/dist/shared/lib/router/utils/app-paths.js'
 import type { TItem } from '../../types.js'
 
 interface NestedMap {
@@ -54,7 +55,9 @@ export function convertToPageMap({
           //
           // will be normalized to:
           // app/posts/aaron-swartz-a-programmable-web/page.mdx
-          dir.replaceAll(/\(.*?\)(\/|$)/g, '')
+          //
+          // The `normalizeAppPath` function ensures a leading slash is present, so we slice it off.
+          normalizeAppPath(dir).slice(1)
         : [dir, name !== 'index' && name].filter(Boolean).join('/')
       pages[key] = filePath
     }