Fix parsing params for i18n optional route in minimal mode (vercel#33896

)

This fixes our parsing of params with i18n for optional catch-all routes and ensures a regression test catches this case.

## Bug

- [x] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

Fixes: vercel#30631

packages/next/build/webpack/loaders/next-serverless-loader/utils.ts

@@ -179,10 +179,11 @@ export function getUtils({
             // Simulate a RegExp match from the \`req.url\` input
             exec: (str: string) => {
               const obj = parseQs(str)
+              const matchesHasLocale =
+                i18n && detectedLocale && obj['1'] === detectedLocale
 
               // favor named matches if available
               const routeKeyNames = Object.keys(routeKeys || {})
-
               const filterLocaleItem = (val: string | string[]) => {
                 if (i18n) {
                   // locale items can be included in route-matches
@@ -228,8 +229,13 @@ export function getUtils({
 
               return Object.keys(obj).reduce((prev, key) => {
                 if (!filterLocaleItem(obj[key])) {
+                  let normalizedKey = key
+
+                  if (matchesHasLocale) {
+                    normalizedKey = parseInt(key, 10) - 1 + ''
+                  }
                   return Object.assign(prev, {
-                    [key]: obj[key],
+                    [normalizedKey]: obj[key],
                   })
                 }
                 return prev

test/production/required-server-files-i18n.test.ts

@@ -601,11 +601,12 @@ describe('should set-up next', () => {
   it('should normalize optional values correctly for SSG page', async () => {
     const res = await fetchViaHTTP(
       appPort,
-      '/optional-ssg',
-      { rest: '', another: 'value' },
+      '/en/optional-ssg/[[...rest]]',
+      undefined,
       {
         headers: {
-          'x-matched-path': '/optional-ssg/[[...rest]]',
+          'x-matched-path': '/en/optional-ssg/[[...rest]]',
+          'x-now-route-matches': 'nextLocale=en&1=en',
         },
       }
     )
@@ -616,6 +617,28 @@ describe('should set-up next', () => {
     expect(props.params).toEqual({})
   })
 
+  it('should normalize optional values correctly for nested optional SSG page', async () => {
+    const res = await fetchViaHTTP(
+      appPort,
+      '/en/[slug]/social/[[...rest]]',
+      undefined,
+      {
+        headers: {
+          'x-matched-path': '/en/[slug]/social/[[...rest]]',
+          'x-now-route-matches': 'nextLocale=en&1=en&2=user-123&slug=user-123',
+        },
+      }
+    )
+
+    const html = await res.text()
+    const $ = cheerio.load(html)
+    const props = JSON.parse($('#props').text())
+    expect(props.params).toEqual({
+      slug: 'user-123',
+    })
+    expect($('#page').text()).toBe('/[slug]/social/[[...rest]]')
+  })
+
   it('should normalize optional values correctly for SSG page with encoded slash', async () => {
     const res = await fetchViaHTTP(
       appPort,

test/production/required-server-files/pages/[slug]/social/[[...rest]].js

@@ -0,0 +1,25 @@
+export const getStaticProps = ({ params }) => {
+  return {
+    props: {
+      random: Math.random(),
+      params: params || null,
+    },
+    revalidate: 1,
+  }
+}
+
+export const getStaticPaths = () => {
+  return {
+    paths: [],
+    fallback: true,
+  }
+}
+
+export default function Page(props) {
+  return (
+    <>
+      <p id="page">/[slug]/social/[[...rest]]</p>
+      <p id="props">{JSON.stringify(props)}</p>
+    </>
+  )
+}