fix i18n data pathname resolving

packages/next/src/server/lib/router-utils/resolve-routes.ts

@@ -395,6 +395,17 @@ export function getResolveRoutes(
               normalized = normalizers.postponed.normalize(normalized, true)
             }
 
+            if (config.i18n) {
+              const curLocaleResult = normalizeLocalePath(
+                normalized,
+                config.i18n.locales
+              )
+
+              if (curLocaleResult.detectedLocale) {
+                parsedUrl.query.__nextLocale = curLocaleResult.detectedLocale
+              }
+            }
+
             // If we updated the pathname, and it had a base path, re-add the
             // base path.
             if (updated) {

test/e2e/i18n-navigations-middleware/i18n-navigations-middleware.test.ts

@@ -0,0 +1,43 @@
+import { nextTestSetup } from 'e2e-utils'
+
+describe('i18n-navigations-middleware', () => {
+  const { next } = nextTestSetup({
+    files: __dirname,
+  })
+
+  it('should respect selected locale when navigating to a dynamic route', async () => {
+    const browser = await next.browser('/')
+    // change to "de" locale
+    await browser.elementByCss("[href='/de']").click()
+    const dynamicLink = await browser.waitForElementByCss(
+      "[href='/de/dynamic/1']"
+    )
+    expect(await browser.elementById('current-locale').text()).toBe(
+      'Current locale: de'
+    )
+
+    // navigate to dynamic route
+    await dynamicLink.click()
+
+    // the locale should still be "de"
+    expect(await browser.elementById('dynamic-locale').text()).toBe(
+      'Locale: de'
+    )
+  })
+
+  it('should respect selected locale when navigating to a static route', async () => {
+    const browser = await next.browser('/')
+    // change to "de" locale
+    await browser.elementByCss("[href='/de']").click()
+    const staticLink = await browser.waitForElementByCss("[href='/de/static']")
+    expect(await browser.elementById('current-locale').text()).toBe(
+      'Current locale: de'
+    )
+
+    // navigate to static route
+    await staticLink.click()
+
+    // the locale should still be "de"
+    expect(await browser.elementById('static-locale').text()).toBe('Locale: de')
+  })
+})

test/e2e/i18n-navigations-middleware/middleware.js

@@ -0,0 +1,6 @@
+import { NextResponse } from 'next/server'
+
+export const config = { matcher: ['/foo'] }
+export async function middleware(req) {
+  return NextResponse.next()
+}

test/e2e/i18n-navigations-middleware/next.config.js

@@ -0,0 +1,9 @@
+/**
+ * @type {import('next').NextConfig}
+ */
+module.exports = {
+  i18n: {
+    defaultLocale: 'default',
+    locales: ['default', 'en', 'de'],
+  },
+}

test/e2e/i18n-navigations-middleware/pages/dynamic/[id].js

@@ -0,0 +1,11 @@
+export const getServerSideProps = async ({ locale }) => {
+  return {
+    props: {
+      locale,
+    },
+  }
+}
+
+export default function Dynamic({ locale }) {
+  return <div id="dynamic-locale">Locale: {locale}</div>
+}

test/e2e/i18n-navigations-middleware/pages/index.js

@@ -0,0 +1,37 @@
+import Link from 'next/link'
+
+export const getServerSideProps = async ({ locale }) => {
+  return {
+    props: {
+      locale,
+    },
+  }
+}
+
+export default function Home({ locale }) {
+  return (
+    <main
+      style={{
+        display: 'flex',
+        flexDirection: 'column',
+        gap: '20px',
+      }}
+    >
+      <p id="current-locale">Current locale: {locale}</p>
+      Locale switch:
+      <Link href="/" locale="default">
+        Default
+      </Link>
+      <Link href="/" locale="en">
+        English
+      </Link>
+      <Link href="/" locale="de">
+        German
+      </Link>
+      <br />
+      Test links:
+      <Link href="/dynamic/1">Dynamic 1</Link>
+      <Link href="/static">Static</Link>
+    </main>
+  )
+}

test/e2e/i18n-navigations-middleware/pages/static.js

@@ -0,0 +1,11 @@
+export const getServerSideProps = async ({ locale }) => {
+  return {
+    props: {
+      locale,
+    },
+  }
+}
+
+export default function Static({ locale }) {
+  return <div id="static-locale">Locale: {locale}</div>
+}