From 83fb9ebc07317a1953d5daec7d6940c8aa6b89f4 Mon Sep 17 00:00:00 2001
From: Zack Tanner <zacktanner@gmail.com>
Date: Thu, 4 Jan 2024 13:03:25 -0800
Subject: [PATCH] ensure more specific `default` segments match parallel routes
 before greedier catch-all segments

---
 packages/next/src/build/index.ts              |  4 +-
 .../build/normalize-catchall-routes.test.ts   | 23 ++++++++++
 .../src/build/normalize-catchall-routes.ts    |  7 ++-
 packages/next/src/export/index.ts             |  9 +++-
 packages/next/src/lib/is-default-route.ts     |  3 ++
 .../dev-app-page-route-matcher-provider.ts    |  6 ++-
 .../next/src/server/lib/find-page-file.ts     |  5 +++
 .../app/[locale]/[[...catchAll]]/page.tsx     |  3 ++
 .../[foo]/[bar]/@slot/[baz]/default.tsx       |  3 ++
 .../nested/[foo]/[bar]/@slot/[baz]/page.tsx   |  3 ++
 .../nested/[foo]/[bar]/@slot/default.tsx      |  3 ++
 .../nested/[foo]/[bar]/@slot/page.tsx         |  3 ++
 .../[locale]/nested/[foo]/[bar]/default.tsx   |  3 ++
 .../[locale]/nested/[foo]/[bar]/layout.tsx    |  8 ++++
 .../app/layout.tsx                            | 11 +++++
 .../app/page.tsx                              |  3 ++
 .../next.config.js                            |  6 +++
 .../parallel-routes-catchall-default.test.ts  | 44 +++++++++++++++++++
 .../app/@slot/default.tsx                     |  7 ---
 19 files changed, 140 insertions(+), 14 deletions(-)
 create mode 100644 packages/next/src/lib/is-default-route.ts
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/[[...catchAll]]/page.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/default.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/page.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/default.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/page.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/default.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/layout.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/layout.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/app/page.tsx
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/next.config.js
 create mode 100644 test/e2e/app-dir/parallel-routes-catchall-default/parallel-routes-catchall-default.test.ts
 delete mode 100644 test/e2e/app-dir/parallel-routes-catchall/app/@slot/default.tsx

diff --git a/packages/next/src/build/index.ts b/packages/next/src/build/index.ts
index f19fde79196f5..442d0b664fb5e 100644
--- a/packages/next/src/build/index.ts
+++ b/packages/next/src/build/index.ts
@@ -902,7 +902,9 @@ export default async function build(
                 validFileMatcher.isAppRouterPage(absolutePath) ||
                 // For now we only collect the root /not-found page in the app
                 // directory as the 404 fallback
-                validFileMatcher.isRootNotFound(absolutePath),
+                validFileMatcher.isRootNotFound(absolutePath) ||
+                // Default slots are also valid pages, and need to be considered during path normalization
+                validFileMatcher.isDefaultSlot(absolutePath),
               ignorePartFilter: (part) => part.startsWith('_'),
             })
           )
diff --git a/packages/next/src/build/normalize-catchall-routes.test.ts b/packages/next/src/build/normalize-catchall-routes.test.ts
index 1ae0c771d883a..636da8b6966fb 100644
--- a/packages/next/src/build/normalize-catchall-routes.test.ts
+++ b/packages/next/src/build/normalize-catchall-routes.test.ts
@@ -96,4 +96,27 @@ describe('normalizeCatchallRoutes', () => {
       ],
     })
   })
+
+  it('should not add the catch-all route to segments that have a more specific default', () => {
+    const appPaths = {
+      '/': ['/page'],
+      '/[[...catchAll]]': ['/[[...catchAll]]/page'],
+      '/nested/[foo]/[bar]/default': [
+        '/nested/[foo]/[bar]/default',
+        '/nested/[foo]/[bar]/@slot/default',
+      ],
+      '/nested/[foo]/[bar]': ['/nested/[foo]/[bar]/@slot/page'],
+      '/nested/[foo]/[bar]/[baz]/default': [
+        '/nested/[foo]/[bar]/@slot/[baz]/default',
+        '/[[...catchAll]]/page',
+      ],
+      '/nested/[foo]/[bar]/[baz]': ['/nested/[foo]/[bar]/@slot/[baz]/page'],
+    }
+
+    const initialAppPaths = JSON.parse(JSON.stringify(appPaths))
+
+    normalizeCatchAllRoutes(appPaths)
+
+    expect(appPaths).toMatchObject(initialAppPaths)
+  })
 })
diff --git a/packages/next/src/build/normalize-catchall-routes.ts b/packages/next/src/build/normalize-catchall-routes.ts
index f24f95897e77b..f84c62db21694 100644
--- a/packages/next/src/build/normalize-catchall-routes.ts
+++ b/packages/next/src/build/normalize-catchall-routes.ts
@@ -36,12 +36,15 @@ export function normalizeCatchAllRoutes(
         0,
         normalizedCatchAllRoute.search(catchAllRouteRegex)
       )
-
       if (
         // check if the appPath could match the catch-all
         appPath.startsWith(normalizedCatchAllRouteBasePath) &&
         // check if there's not already a slot value that could match the catch-all
-        !appPaths[appPath].some((path) => hasMatchedSlots(path, catchAllRoute))
+        !appPaths[appPath].some((path) =>
+          hasMatchedSlots(path, catchAllRoute)
+        ) &&
+        // check if the catch-all is not already matched by a default route
+        !appPaths[`${appPath}/default`]
       ) {
         appPaths[appPath].push(catchAllRoute)
       }
diff --git a/packages/next/src/export/index.ts b/packages/next/src/export/index.ts
index eb949220ffb19..d99993f196faa 100644
--- a/packages/next/src/export/index.ts
+++ b/packages/next/src/export/index.ts
@@ -55,6 +55,7 @@ import isError from '../lib/is-error'
 import { needsExperimentalReact } from '../lib/needs-experimental-react'
 import { formatManifest } from '../build/manifests/formatter/format-manifest'
 import { validateRevalidate } from '../server/lib/patch-fetch'
+import { isDefaultRoute } from '../lib/is-default-route'
 
 function divideSegments(number: number, segments: number): number[] {
   const result = []
@@ -559,9 +560,13 @@ export async function exportAppImpl(
   ]
 
   const filteredPaths = exportPaths.filter(
-    // Remove API routes
     (route) =>
-      exportPathMap[route]._isAppDir || !isAPIRoute(exportPathMap[route].page)
+      // Remove default routes -- they don't need to be exported
+      // and are only used for parallel route normalization
+      !isDefaultRoute(exportPathMap[route].page) &&
+      (exportPathMap[route]._isAppDir ||
+        // Remove API routes
+        !isAPIRoute(exportPathMap[route].page))
   )
 
   if (filteredPaths.length !== exportPaths.length) {
diff --git a/packages/next/src/lib/is-default-route.ts b/packages/next/src/lib/is-default-route.ts
new file mode 100644
index 0000000000000..adbd42d508f7f
--- /dev/null
+++ b/packages/next/src/lib/is-default-route.ts
@@ -0,0 +1,3 @@
+export function isDefaultRoute(value?: string) {
+  return value?.endsWith('/default')
+}
diff --git a/packages/next/src/server/future/route-matcher-providers/dev/dev-app-page-route-matcher-provider.ts b/packages/next/src/server/future/route-matcher-providers/dev/dev-app-page-route-matcher-provider.ts
index 2a5b0f05be2fc..bb7ef7cc97587 100644
--- a/packages/next/src/server/future/route-matcher-providers/dev/dev-app-page-route-matcher-provider.ts
+++ b/packages/next/src/server/future/route-matcher-providers/dev/dev-app-page-route-matcher-provider.ts
@@ -19,9 +19,11 @@ export class DevAppPageRouteMatcherProvider extends FileCacheRouteMatcherProvide
 
     this.normalizers = new DevAppNormalizers(appDir, extensions)
 
-    // Match any page file that ends with `/page.${extension}` under the app
+    // Match any page file that ends with `/page.${extension}` or `/default.${extension}` under the app
     // directory.
-    this.expression = new RegExp(`[/\\\\]page\\.(?:${extensions.join('|')})$`)
+    this.expression = new RegExp(
+      `[/\\\\](page|default)\\.(?:${extensions.join('|')})$`
+    )
   }
 
   protected async transform(
diff --git a/packages/next/src/server/lib/find-page-file.ts b/packages/next/src/server/lib/find-page-file.ts
index d51935a761d17..42b046e8efc54 100644
--- a/packages/next/src/server/lib/find-page-file.ts
+++ b/packages/next/src/server/lib/find-page-file.ts
@@ -127,6 +127,10 @@ export function createValidFileMatcher(
     return validExtensionFileRegex.test(filePath) || isMetadataFile(filePath)
   }
 
+  function isDefaultSlot(filePath: string) {
+    return filePath.endsWith(`default.${pageExtensions[0]}`)
+  }
+
   function isRootNotFound(filePath: string) {
     if (!appDirPath) {
       return false
@@ -143,5 +147,6 @@ export function createValidFileMatcher(
     isAppRouterPage,
     isMetadataFile,
     isRootNotFound,
+    isDefaultSlot,
   }
 }
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/[[...catchAll]]/page.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/[[...catchAll]]/page.tsx
new file mode 100644
index 0000000000000..32aad01038734
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/[[...catchAll]]/page.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <div>/[locale]/[[...catchAll]]/page.tsx</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/default.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/default.tsx
new file mode 100644
index 0000000000000..335a52a0d00de
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/default.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <div>/[locale]/nested/[foo]/[bar]/@slot/[baz]/default.tsx</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/page.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/page.tsx
new file mode 100644
index 0000000000000..6078f8edee1d1
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/[baz]/page.tsx
@@ -0,0 +1,3 @@
+export default function Page({ params }) {
+  return <div>/[locale]/nested/[foo]/[bar]/@slot/[baz]/page.tsx</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/default.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/default.tsx
new file mode 100644
index 0000000000000..5a33f15b80591
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/default.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <div>/[locale]/nested/[foo]/[bar]/@slot/default.tsx</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/page.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/page.tsx
new file mode 100644
index 0000000000000..32afde0e4032a
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/@slot/page.tsx
@@ -0,0 +1,3 @@
+export default function Foo() {
+  return <div>/[locale]/nested/[foo]/[bar]/@slot/page.tsx</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/default.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/default.tsx
new file mode 100644
index 0000000000000..b99ced4ae3d61
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/default.tsx
@@ -0,0 +1,3 @@
+export default function Page() {
+  return <div>/[locale]/nested/[foo]/[bar]/default.tsx</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/layout.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/layout.tsx
new file mode 100644
index 0000000000000..f2619e0b884b9
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/[locale]/nested/[foo]/[bar]/layout.tsx
@@ -0,0 +1,8 @@
+export default function Layout({ children, slot }) {
+  return (
+    <>
+      Children: <div id="nested-children">{children}</div>
+      Slot: <div id="slot">{slot}</div>
+    </>
+  )
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/layout.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/layout.tsx
new file mode 100644
index 0000000000000..98b2ba6e286e8
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/layout.tsx
@@ -0,0 +1,11 @@
+import React from 'react'
+
+export default function Root({ children }: { children: React.ReactNode }) {
+  return (
+    <html>
+      <body>
+        Children: <div id="children">{children}</div>
+      </body>
+    </html>
+  )
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/app/page.tsx b/test/e2e/app-dir/parallel-routes-catchall-default/app/page.tsx
new file mode 100644
index 0000000000000..0e3edd2c011b1
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/app/page.tsx
@@ -0,0 +1,3 @@
+export default async function Home() {
+  return <div>Root Page</div>
+}
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/next.config.js b/test/e2e/app-dir/parallel-routes-catchall-default/next.config.js
new file mode 100644
index 0000000000000..807126e4cf0bf
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/next.config.js
@@ -0,0 +1,6 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {}
+
+module.exports = nextConfig
diff --git a/test/e2e/app-dir/parallel-routes-catchall-default/parallel-routes-catchall-default.test.ts b/test/e2e/app-dir/parallel-routes-catchall-default/parallel-routes-catchall-default.test.ts
new file mode 100644
index 0000000000000..7c4fd86b93aad
--- /dev/null
+++ b/test/e2e/app-dir/parallel-routes-catchall-default/parallel-routes-catchall-default.test.ts
@@ -0,0 +1,44 @@
+import { createNextDescribe } from 'e2e-utils'
+
+createNextDescribe(
+  'parallel-routes-catchall-default',
+  {
+    files: __dirname,
+  },
+  ({ next }) => {
+    it('should match default paths before catch-all', async () => {
+      let browser = await next.browser('/en/nested')
+
+      // we have a top-level catch-all but the /nested dir doesn't have a default/page until the /[foo]/[bar] segment
+      // so we expect the top-level catch-all to render
+      expect(await browser.elementById('children').text()).toBe(
+        '/[locale]/[[...catchAll]]/page.tsx'
+      )
+
+      browser = await next.browser('/en/nested/foo/bar')
+
+      // we're now at the /[foo]/[bar] segment, so we expect the matched page to be the default (since there's no page defined)
+      expect(await browser.elementById('nested-children').text()).toBe(
+        '/[locale]/nested/[foo]/[bar]/default.tsx'
+      )
+
+      // we expect the slot to match since there's a page defined at this segment
+      expect(await browser.elementById('slot').text()).toBe(
+        '/[locale]/nested/[foo]/[bar]/@slot/page.tsx'
+      )
+
+      browser = await next.browser('/en/nested/foo/bar/baz')
+
+      // the page slot should still be the one matched at the /[foo]/[bar] segment because it's the default and we
+      // didn't define a page at the /[foo]/[bar]/[baz] segment
+      expect(await browser.elementById('nested-children').text()).toBe(
+        '/[locale]/nested/[foo]/[bar]/default.tsx'
+      )
+
+      // however we do have a slot for the `[baz]` segment and so we expect that to no match
+      expect(await browser.elementById('slot').text()).toBe(
+        '/[locale]/nested/[foo]/[bar]/@slot/[baz]/page.tsx'
+      )
+    })
+  }
+)
diff --git a/test/e2e/app-dir/parallel-routes-catchall/app/@slot/default.tsx b/test/e2e/app-dir/parallel-routes-catchall/app/@slot/default.tsx
deleted file mode 100644
index 129f875a30b3a..0000000000000
--- a/test/e2e/app-dir/parallel-routes-catchall/app/@slot/default.tsx
+++ /dev/null
@@ -1,7 +0,0 @@
-export default function Default() {
-  return (
-    <div>
-      <div>Default</div>
-    </div>
-  )
-}