Ensure default locale is redirected to without accept-language

Author: ijjk

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

@@ -229,7 +229,7 @@ const nextServerlessLoader: loader.Loader = function () {
         detectedLocale = accept.language(
           req.headers['accept-language'],
           i18n.locales
-        )
+        ) || i18n.defaultLocale
       }
 
       if (

packages/next/next-server/server/next-server.ts

@@ -308,10 +308,9 @@ export default class Server {
       let detectedLocale = detectLocaleCookie(req, i18n.locales)
 
       if (!detectedLocale) {
-        detectedLocale = accept.language(
-          req.headers['accept-language'],
-          i18n.locales
-        )
+        detectedLocale =
+          accept.language(req.headers['accept-language'], i18n.locales) ||
+          i18n.defaultLocale
       }
 
       if (

test/integration/i18n-support/test/index.test.js

@@ -58,6 +58,31 @@ function runTests() {
     expect(parsedUrl2.query).toEqual({ hello: 'world' })
   })
 
+  it('should redirect to default locale route for / without accept-language', async () => {
+    const res = await fetchViaHTTP(appPort, '/', undefined, {
+      redirect: 'manual',
+    })
+    expect(res.status).toBe(307)
+
+    const parsedUrl = url.parse(res.headers.get('location'), true)
+    expect(parsedUrl.pathname).toBe('/en')
+    expect(parsedUrl.query).toEqual({})
+
+    const res2 = await fetchViaHTTP(
+      appPort,
+      '/',
+      { hello: 'world' },
+      {
+        redirect: 'manual',
+      }
+    )
+    expect(res2.status).toBe(307)
+
+    const parsedUrl2 = url.parse(res2.headers.get('location'), true)
+    expect(parsedUrl2.pathname).toBe('/en')
+    expect(parsedUrl2.query).toEqual({ hello: 'world' })
+  })
+
   it('should load getStaticProps page correctly SSR', async () => {
     const html = await renderViaHTTP(appPort, '/en-US/gsp')
     const $ = cheerio.load(html)