fix: preserve locale in redirects (#276)

Author: ascorbic

edge-runtime/lib/response.ts

@@ -195,7 +195,7 @@ export const buildResponse = async ({
 
   // If we are redirecting a request that had a locale in the URL, we need to add it back in
   if (redirect && requestLocale) {
-    redirect = normalizeLocalizedTarget({ target: redirect, request, nextConfig })
+    redirect = normalizeLocalizedTarget({ target: redirect, request, nextConfig, requestLocale })
     if (redirect === request.url) {
       logger.withFields({ rewrite_url: rewrite }).debug('Rewrite url is same as original url')
       return

tests/fixtures/middleware-i18n/middleware.js

@@ -0,0 +1,83 @@
+import { NextResponse } from 'next/server'
+
+export async function middleware(request) {
+  const url = request.nextUrl
+
+  // this is needed for tests to get the BUILD_ID
+  if (url.pathname.startsWith('/_next/static/__BUILD_ID')) {
+    return NextResponse.next()
+  }
+
+  if (url.pathname === '/old-home') {
+    if (url.searchParams.get('override') === 'external') {
+      return Response.redirect('https://example.vercel.sh')
+    } else {
+      url.pathname = '/new-home'
+      return Response.redirect(url)
+    }
+  }
+
+  if (url.searchParams.get('foo') === 'bar') {
+    url.pathname = '/new-home'
+    url.searchParams.delete('foo')
+    return Response.redirect(url)
+  }
+
+  // Chained redirects
+  if (url.pathname === '/redirect-me-alot') {
+    url.pathname = '/redirect-me-alot-2'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/redirect-me-alot-2') {
+    url.pathname = '/redirect-me-alot-3'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/redirect-me-alot-3') {
+    url.pathname = '/redirect-me-alot-4'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/redirect-me-alot-4') {
+    url.pathname = '/redirect-me-alot-5'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/redirect-me-alot-5') {
+    url.pathname = '/redirect-me-alot-6'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/redirect-me-alot-6') {
+    url.pathname = '/redirect-me-alot-7'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/redirect-me-alot-7') {
+    url.pathname = '/new-home'
+    return Response.redirect(url)
+  }
+
+  // Infinite loop
+  if (url.pathname === '/infinite-loop') {
+    url.pathname = '/infinite-loop-1'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/infinite-loop-1') {
+    url.pathname = '/infinite-loop'
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/to') {
+    url.pathname = url.searchParams.get('pathname')
+    url.searchParams.delete('pathname')
+    return Response.redirect(url)
+  }
+
+  if (url.pathname === '/with-fragment') {
+    console.log(String(new URL('/new-home#fragment', url)))
+    return Response.redirect(new URL('/new-home#fragment', url))
+  }
+}

tests/fixtures/middleware-i18n/next.config.js

@@ -0,0 +1,23 @@
+module.exports = {
+  output: 'standalone',
+  eslint: {
+    ignoreDuringBuilds: true,
+  },
+  i18n: {
+    locales: ['en', 'fr', 'nl', 'es'],
+    defaultLocale: 'en',
+  },
+  experimental: {
+    clientRouterFilter: true,
+    clientRouterFilterRedirects: true,
+  },
+  redirects() {
+    return [
+      {
+        source: '/to-new',
+        destination: '/dynamic/new',
+        permanent: false,
+      },
+    ]
+  },
+}