fix: use the match result after matching using the matched path header (vercel#77994)

When rendering the page on Vercel, we send the `x-matched-path` header
to indicate which route should be rendered. Sometimes, like in the case
of a middleware rewrite, we will rewrite a path to a statically
generated one. This results in a `x-matched-path` header being equal to
the generated page and not the route with the dynamic path params in it.

This ensures that if we get such a path that we match against that we do
save the result of the path matching as they are valid parameters.

This also fixes a related bug associated with route denormalization
which must occur before the routes i18n is parsed.

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Fixes vercel#77789

---------

Co-authored-by: Jiwon Choi <devjiwonchoi@gmail.com>

Author: wyattjoh

packages/next/src/server/base-server.ts

@@ -1131,6 +1131,8 @@ export default abstract class Server<
           matchedPath = this.normalize(matchedPath)
           const normalizedUrlPath = this.stripNextDataPath(urlPathname)
 
+          matchedPath = denormalizePagePath(matchedPath)
+
           // Perform locale detection and normalization.
           const localeAnalysisResult = this.i18nProvider?.analyze(matchedPath, {
             defaultLocale,
@@ -1151,11 +1153,15 @@ export default abstract class Server<
             }
           }
 
-          // TODO: check if this is needed any more?
-          matchedPath = denormalizePagePath(matchedPath)
-
           let srcPathname = matchedPath
           let pageIsDynamic = isDynamicRoute(srcPathname)
+          let paramsResult: {
+            params: ParsedUrlQuery | false
+            hasValidParams: boolean
+          } = {
+            params: false,
+            hasValidParams: false,
+          }
 
           if (!pageIsDynamic) {
             const match = await this.matchers.match(srcPathname, {
@@ -1165,8 +1171,15 @@ export default abstract class Server<
             // Update the source pathname to the matched page's pathname.
             if (match) {
               srcPathname = match.definition.pathname
-              // The page is dynamic if the params are defined.
-              pageIsDynamic = typeof match.params !== 'undefined'
+
+              // The page is dynamic if the params are defined. We know at this
+              // stage that the matched path is not a static page if the params
+              // were parsed from the matched path header.
+              if (typeof match.params !== 'undefined') {
+                pageIsDynamic = true
+                paramsResult.params = match.params
+                paramsResult.hasValidParams = true
+              }
             }
           }
 
@@ -1236,10 +1249,14 @@ export default abstract class Server<
           if (pageIsDynamic) {
             let params: ParsedUrlQuery | false = {}
 
-            let paramsResult = utils.normalizeDynamicRouteParams(
-              queryParams,
-              false
-            )
+            // If we don't already have valid params, try to parse them from
+            // the query params.
+            if (!paramsResult.hasValidParams) {
+              paramsResult = utils.normalizeDynamicRouteParams(
+                queryParams,
+                false
+              )
+            }
 
             // for prerendered ISR paths we attempt parsing the route
             // params from the URL directly as route-matches may not

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/app/[locale]/[...rest]/page.tsx

@@ -0,0 +1,17 @@
+import { type Params, expectedParams } from '../../../expected'
+
+export default async function CatchAll({
+  params,
+}: {
+  params: Promise<Params>
+}) {
+  const received = await params
+
+  return <p>{JSON.stringify(received)}</p>
+}
+
+export async function generateStaticParams(): Promise<Params[]> {
+  return [expectedParams]
+}
+
+export const dynamic = 'force-dynamic'

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/app/[locale]/page.tsx

@@ -0,0 +1,5 @@
+import Link from 'next/link'
+
+export default function Home() {
+  return <Link href="/1/2">Go to /1/2</Link>
+}

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/app/layout.tsx

@@ -0,0 +1,8 @@
+import { ReactNode } from 'react'
+export default function Root({ children }: { children: ReactNode }) {
+  return (
+    <html>
+      <body>{children}</body>
+    </html>
+  )
+}

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/expected.ts

@@ -0,0 +1,9 @@
+export type Params = {
+  locale: string
+  rest: string[]
+}
+
+export const expectedParams: Params = {
+  locale: 'en',
+  rest: ['1', '2'],
+}

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/middleware.ts

@@ -0,0 +1,21 @@
+import type { NextRequest } from 'next/server'
+import { NextResponse } from 'next/server'
+
+export function middleware(request: NextRequest) {
+  return NextResponse.rewrite(
+    new URL('/en' + request.nextUrl.pathname, request.url)
+  )
+}
+
+export const config = {
+  matcher: [
+    /*
+     * Match all request paths except for the ones starting with:
+     * - api (API routes)
+     * - _next/static (static files)
+     * - _next/image (image optimization files)
+     * - favicon.ico, sitemap.xml, robots.txt (metadata files)
+     */
+    '/((?!api|_next/static|_next/image|favicon.ico|sitemap.xml|robots.txt).*)',
+  ],
+}

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/next.config.js

@@ -0,0 +1,10 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+const nextConfig = {
+  experimental: {
+    ppr: true,
+  },
+}
+
+module.exports = nextConfig

test/e2e/app-dir/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params/ppr-middleware-rewrite-force-dynamic-ssg-dynamic-params.test.ts

@@ -0,0 +1,26 @@
+import { nextTestSetup } from 'e2e-utils'
+import { expectedParams as expected } from './expected'
+
+describe('ppr-middleware-rewrite-force-dynamic-generate-static-params', () => {
+  const { next } = nextTestSetup({
+    files: __dirname,
+  })
+
+  const expectedParams = JSON.stringify(expected)
+
+  it('should have correct dynamic params', async () => {
+    // should be rewritten with /en
+    const browser = await next.browser('/')
+    expect(await browser.elementByCss('a').text()).toBe('Go to /1/2')
+
+    // navigate to /1/2
+    await browser.elementByCss('a').click()
+
+    // should be rewritten with /en/1/2 with correct params
+    expect(await browser.elementByCss('p').text()).toBe(expectedParams)
+
+    // reloading the page should have the same params
+    await browser.refresh()
+    expect(await browser.elementByCss('p').text()).toBe(expectedParams)
+  })
+})