Fix dynamic routes with pages under index folder

packages/next/export/worker.ts

@@ -215,8 +215,8 @@ export default async function exportPage({
         subFolders ? `${_path}${sep}index.html` : `${_path}.html`
       let htmlFilename = getHtmlFilename(filePath)
 
-      const pageExt = extname(page)
-      const pathExt = extname(path)
+      const pageExt = isDynamic ? '' : extname(page)
+      const pathExt = isDynamic ? '' : extname(path)
       // Make sure page isn't a folder with a dot in the name e.g. `v1.2`
       if (pageExt !== pathExt && pathExt !== '') {
         const isBuiltinPaths = ['/500', '/404'].some(

packages/next/server/denormalize-page-path.ts

@@ -1,10 +1,12 @@
+import { isDynamicRoute } from '../shared/lib/router/utils'
+
 export function normalizePathSep(path: string): string {
   return path.replace(/\\/g, '/')
 }
 
 export function denormalizePagePath(page: string) {
   page = normalizePathSep(page)
-  if (page.startsWith('/index/')) {
+  if (page.startsWith('/index/') && !isDynamicRoute(page)) {
     page = page.slice(6)
   } else if (page === '/index') {
     page = '/'

packages/next/server/normalize-page-path.ts

@@ -1,12 +1,13 @@
 import { posix } from 'path'
+import { isDynamicRoute } from '../shared/lib/router/utils'
 
 export { normalizePathSep, denormalizePagePath } from './denormalize-page-path'
 
 export function normalizePagePath(page: string): string {
   // If the page is `/` we need to append `/index`, otherwise the returned directory root will be bundles instead of pages
   if (page === '/') {
     page = '/index'
-  } else if (/^\/index(\/|$)/.test(page)) {
+  } else if (/^\/index(\/|$)/.test(page) && !isDynamicRoute(page)) {
     page = `/index${page}`
   }
   // Resolve on anything that doesn't start with `/`

packages/next/shared/lib/router/utils/get-route-from-asset-path.ts

@@ -1,4 +1,7 @@
 // Translate a pages asset path (relative from a common prefix) back into its logical route
+
+import { isDynamicRoute } from './is-dynamic'
+
 // "asset path" being its javascript file, data file, prerendered html,...
 export default function getRouteFromAssetPath(
   assetPath: string,
@@ -7,7 +10,7 @@ export default function getRouteFromAssetPath(
   assetPath = assetPath.replace(/\\/g, '/')
   assetPath =
     ext && assetPath.endsWith(ext) ? assetPath.slice(0, -ext.length) : assetPath
-  if (assetPath.startsWith('/index/')) {
+  if (assetPath.startsWith('/index/') && !isDynamicRoute(assetPath)) {
     assetPath = assetPath.slice(6)
   } else if (assetPath === '/index') {
     assetPath = '/'

test/integration/dynamic-routing/pages/index/[...slug].js

@@ -0,0 +1,3 @@
+export default function page() {
+  return 'index/[...slug]'
+}

test/integration/dynamic-routing/test/index.test.js

@@ -27,7 +27,7 @@ let buildId
 const appDir = join(__dirname, '../')
 const buildIdPath = join(appDir, '.next/BUILD_ID')
 
-function runTests(dev) {
+function runTests({ dev, serverless }) {
   if (dev) {
     it('should not have error after pinging WebSocket', async () => {
       const browser = await webdriver(appPort, '/')
@@ -1256,6 +1256,14 @@ function runTests(dev) {
               helloworld: 'hello-world',
             },
           },
+          {
+            namedRegex: '^/index/(?<slug>.+?)(?:/)?$',
+            page: '/index/[...slug]',
+            regex: normalizeRegEx('^/index/(.+?)(?:/)?$'),
+            routeKeys: {
+              slug: 'slug',
+            },
+          },
           {
             namedRegex: `^/on\\-mount/(?<post>[^/]+?)(?:/)?$`,
             page: '/on-mount/[post]',
@@ -1338,6 +1346,43 @@ function runTests(dev) {
         ],
       })
     })
+
+    if (!serverless) {
+      it('should output a pages-manifest correctly', async () => {
+        const manifest = await fs.readJson(
+          join(appDir, '.next/server/pages-manifest.json')
+        )
+
+        expect(manifest).toEqual({
+          '/[name]/[comment]': 'pages/[name]/[comment].js',
+          '/[name]/comments': 'pages/[name]/comments.js',
+          '/[name]': 'pages/[name].js',
+          '/[name]/on-mount-redir': 'pages/[name]/on-mount-redir.html',
+          '/another': 'pages/another.html',
+          '/b/[123]': 'pages/b/[123].js',
+          '/blog/[name]/comment/[id]': 'pages/blog/[name]/comment/[id].js',
+          '/c/[alongparamnameshouldbeallowedeventhoughweird]':
+            'pages/c/[alongparamnameshouldbeallowedeventhoughweird].js',
+          '/catchall-dash/[...hello-world]':
+            'pages/catchall-dash/[...hello-world].html',
+          '/d/[id]': 'pages/d/[id].html',
+          '/dash/[hello-world]': 'pages/dash/[hello-world].html',
+          '/': 'pages/index.html',
+          '/index/[...slug]': 'pages/index/[...slug].html',
+          '/on-mount/[post]': 'pages/on-mount/[post].html',
+          '/p1/p2/all-ssg/[...rest]': 'pages/p1/p2/all-ssg/[...rest].js',
+          '/p1/p2/all-ssr/[...rest]': 'pages/p1/p2/all-ssr/[...rest].js',
+          '/p1/p2/nested-all-ssg/[...rest]':
+            'pages/p1/p2/nested-all-ssg/[...rest].js',
+          '/p1/p2/predefined-ssg/[...rest]':
+            'pages/p1/p2/predefined-ssg/[...rest].js',
+          '/_app': 'pages/_app.js',
+          '/_error': 'pages/_error.js',
+          '/_document': 'pages/_document.js',
+          '/404': 'pages/404.html',
+        })
+      })
+    }
   }
 }
 
@@ -1354,7 +1399,7 @@ describe('Dynamic Routing', () => {
     })
     afterAll(() => killApp(app))
 
-    runTests(true)
+    runTests({ dev: true, serverless: false })
   })
 
   describe('production mode', () => {
@@ -1369,7 +1414,7 @@ describe('Dynamic Routing', () => {
     })
     afterAll(() => killApp(app))
 
-    runTests()
+    runTests({ dev: false, serverless: false })
   })
 
   describe('serverless mode', () => {
@@ -1389,6 +1434,6 @@ describe('Dynamic Routing', () => {
       await killApp(app)
       await fs.remove(nextConfig)
     })
-    runTests()
+    runTests({ dev: false, serverless: true })
   })
 })