Add more feature flagging, lang setting, and serverless handling

packages/next/build/entries.ts

@@ -97,6 +97,9 @@ export function createEntrypoints(
     loadedEnvFiles: Buffer.from(JSON.stringify(loadedEnvFiles)).toString(
       'base64'
     ),
+    i18n: config.experimental.i18n
+      ? JSON.stringify(config.experimental.i18n)
+      : '',
   }
 
   Object.keys(pages).forEach((page) => {

packages/next/build/webpack-config.ts

@@ -986,6 +986,9 @@ export default async function getBaseWebpackConfig(
         ),
         'process.env.__NEXT_ROUTER_BASEPATH': JSON.stringify(config.basePath),
         'process.env.__NEXT_HAS_REWRITES': JSON.stringify(hasRewrites),
+        'process.env.__NEXT_i18n_SUPPORT': JSON.stringify(
+          !!config.experimental.i18n
+        ),
         ...(isServer
           ? {
               // Fix bad-actors in the npm ecosystem (e.g. `node-formidable`)

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

@@ -28,6 +28,7 @@ export type ServerlessLoaderQuery = {
   runtimeConfig: string
   previewProps: string
   loadedEnvFiles: string
+  i18n: string
 }
 
 const vercelHeader = 'x-vercel-id'
@@ -49,6 +50,7 @@ const nextServerlessLoader: loader.Loader = function () {
     runtimeConfig,
     previewProps,
     loadedEnvFiles,
+    i18n,
   }: ServerlessLoaderQuery =
     typeof this.query === 'string' ? parse(this.query.substr(1)) : this.query
 
@@ -66,6 +68,8 @@ const nextServerlessLoader: loader.Loader = function () {
     JSON.parse(previewProps) as __ApiPreviewProps
   )
 
+  const i18nEnabled = !!i18n
+
   const defaultRouteRegex = pageIsDynamicRoute
     ? `
       const defaultRouteRegex = getRouteRegex("${page}")
@@ -207,6 +211,58 @@ const nextServerlessLoader: loader.Loader = function () {
   `
     : ''
 
+  const handleLocale = i18nEnabled
+    ? `
+      // get pathname from URL with basePath stripped for locale detection
+      const i18n = ${i18n}
+      const accept = require('@hapi/accept')
+      const { detectLocaleCookie } = require('next/dist/next-server/lib/i18n/detect-locale-cookie')
+      const { normalizeLocalePath } = require('next/dist/next-server/lib/i18n/normalize-locale-path')
+      let detectedLocale = detectLocaleCookie(req, i18n.locales)
+
+      if (!detectedLocale) {
+        detectedLocale = accept.language(
+          req.headers['accept-language'],
+          i18n.locales
+        )
+      }
+
+      if (
+        !nextStartMode &&
+        i18n.localeDetection !== false &&
+        denormalizePagePath(parsedUrl.pathname || '/') === '/'
+      ) {
+        res.setHeader(
+          'Location',
+          formatUrl({
+            // make sure to include any query values when redirecting
+            ...parsedUrl,
+            pathname: \`/\${detectedLocale}\`,
+          })
+        )
+        res.statusCode = 307
+        res.end()
+      }
+
+      // TODO: domain based locales (domain to locale mapping needs to be provided in next.config.js)
+      const localePathResult = normalizeLocalePath(parsedUrl.pathname, i18n.locales)
+
+      if (localePathResult.detectedLocale) {
+        detectedLocale = localePathResult.detectedLocale
+        req.url = formatUrl({
+          ...parsedUrl,
+          pathname: localePathResult.pathname,
+        })
+        parsedUrl.pathname = localePathResult.pathname
+      }
+
+      detectedLocale = detectedLocale || i18n.defaultLocale
+    `
+    : `
+      const i18n = {}
+      const detectedLocale = undefined
+    `
+
   if (page.match(API_ROUTE)) {
     return `
       import initServer from 'next-plugin-loader?middleware=on-init-server!'
@@ -300,6 +356,7 @@ const nextServerlessLoader: loader.Loader = function () {
     const { renderToHTML } = require('next/dist/next-server/server/render');
     const { tryGetPreviewData } = require('next/dist/next-server/server/api-utils');
     const { denormalizePagePath } = require('next/dist/next-server/server/denormalize-page-path')
+    const { setLazyProp, getCookieParser } = require('next/dist/next-server/server/api-utils')
     const {sendPayload} = require('next/dist/next-server/server/send-payload');
     const buildManifest = require('${buildManifest}');
     const reactLoadableManifest = require('${reactLoadableManifest}');
@@ -333,6 +390,9 @@ const nextServerlessLoader: loader.Loader = function () {
     export const _app = App
     export async function renderReqToHTML(req, res, renderMode, _renderOpts, _params) {
       const fromExport = renderMode === 'export' || renderMode === true;
+      const nextStartMode = renderMode === 'passthrough'
+
+      setLazyProp({ req }, 'cookies', getCookieParser(req))
 
       const options = {
         App,
@@ -383,12 +443,16 @@ const nextServerlessLoader: loader.Loader = function () {
           routeNoAssetPath = parsedUrl.pathname
         }
 
+        ${handleLocale}
+
         const renderOpts = Object.assign(
           {
             Component,
             pageConfig: config,
             nextExport: fromExport,
             isDataReq: _nextData,
+            locale: detectedLocale,
+            locales: i18n.locales,
           },
           options,
         )

packages/next/client/index.tsx

@@ -3,7 +3,6 @@ import '@next/polyfill-module'
 import React from 'react'
 import ReactDOM from 'react-dom'
 import { HeadManagerContext } from '../next-server/lib/head-manager-context'
-import { normalizeLocalePath } from '../next-server/lib/i18n/normalize-locale-path'
 import mitt from '../next-server/lib/mitt'
 import { RouterContext } from '../next-server/lib/router-context'
 import type Router from '../next-server/lib/router/router'
@@ -90,12 +89,18 @@ if (hasBasePath(asPath)) {
 
 asPath = delLocale(asPath, locale)
 
-if (isFallback && locales) {
-  const localePathResult = normalizeLocalePath(asPath, locales)
+if (process.env.__NEXT_i18n_SUPPORT) {
+  const {
+    normalizeLocalePath,
+  } = require('../next-server/lib/i18n/normalize-locale-path')
 
-  if (localePathResult.detectedLocale) {
-    asPath = asPath.substr(localePathResult.detectedLocale.length + 1)
-    locale = localePathResult.detectedLocale
+  if (isFallback && locales) {
+    const localePathResult = normalizeLocalePath(asPath, locales)
+
+    if (localePathResult.detectedLocale) {
+      asPath = asPath.substr(localePathResult.detectedLocale.length + 1)
+      locale = localePathResult.detectedLocale
+    }
   }
 }
 

packages/next/export/worker.ts

@@ -239,6 +239,8 @@ export default async function exportPage({
             fontManifest: optimizeFonts
               ? requireFontManifest(distDir, serverless)
               : null,
+            locale: renderOpts.locale!,
+            locales: renderOpts.locales!,
           },
           // @ts-ignore
           params

packages/next/next-server/lib/router/router.ts

@@ -56,15 +56,21 @@ function addPathPrefix(path: string, prefix?: string) {
 }
 
 export function addLocale(path: string, locale?: string) {
-  return locale && !path.startsWith('/' + locale)
-    ? addPathPrefix(path, '/' + locale)
-    : path
+  if (process.env.__NEXT_i18n_SUPPORT) {
+    return locale && !path.startsWith('/' + locale)
+      ? addPathPrefix(path, '/' + locale)
+      : path
+  }
+  return path
 }
 
 export function delLocale(path: string, locale?: string) {
-  return locale && path.startsWith('/' + locale)
-    ? path.substr(locale.length + 1) || '/'
-    : path
+  if (process.env.__NEXT_i18n_SUPPORT) {
+    return locale && path.startsWith('/' + locale)
+      ? path.substr(locale.length + 1) || '/'
+      : path
+  }
+  return path
 }
 
 export function hasBasePath(path: string): boolean {
@@ -430,8 +436,11 @@ export default class Router implements BaseRouter {
     this.isSsr = true
 
     this.isFallback = isFallback
-    this.locale = locale
-    this.locales = locales
+
+    if (process.env.__NEXT_i18n_SUPPORT) {
+      this.locale = locale
+      this.locales = locales
+    }
 
     if (typeof window !== 'undefined') {
       // make sure "as" doesn't start with double slashes or else it can

packages/next/next-server/lib/utils.ts

@@ -188,6 +188,7 @@ export type DocumentProps = DocumentInitialProps & {
   headTags: any[]
   unstable_runtimeJS?: false
   devOnlyCacheBusterQueryString: string
+  locale?: string
 }
 
 /**

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

@@ -1207,6 +1207,7 @@ export default class Server {
             {
               fontManifest: this.renderOpts.fontManifest,
               locale: (req as any)._nextLocale,
+              locales: this.renderOpts.locales,
             }
           )
 

packages/next/next-server/server/render.tsx

@@ -281,6 +281,7 @@ function renderDocument(
           headTags,
           unstable_runtimeJS,
           devOnlyCacheBusterQueryString,
+          locale,
           ...docProps,
         })}
       </AmpStateContext.Provider>

packages/next/pages/_document.tsx

@@ -123,7 +123,7 @@ export function Html(
     HTMLHtmlElement
   >
 ) {
-  const { inAmpMode, docComponentsRendered } = useContext(
+  const { inAmpMode, docComponentsRendered, locale } = useContext(
     DocumentComponentContext
   )
 
@@ -132,6 +132,7 @@ export function Html(
   return (
     <html
       {...props}
+      lang={props.lang || locale || undefined}
       amp={inAmpMode ? '' : undefined}
       data-ampdevmode={
         inAmpMode && process.env.NODE_ENV !== 'production' ? '' : undefined

test/integration/i18n-support/next.config.js

@@ -1,4 +1,5 @@
 module.exports = {
+  // target: 'experimental-serverless-trace',
   experimental: {
     i18n: {
       locales: ['nl-NL', 'nl-BE', 'nl', 'en-US', 'en'],