Update to generate auto static pages with all locales (#17730)

Follow-up PR to #17370 this adds generating auto-export, non-dynamic SSG, and fallback pages with all locales. Dynamic SSG pages still control which locales the pages are generated with using `getStaticPaths`. To further control which locales non-dynamic SSG pages will be prerendered with a follow-up PR adding handling for 404 behavior from `getStaticProps` will be needed. 

x-ref: #17110

packages/next/build/index.ts

@@ -725,6 +725,8 @@ export default async function build(
       // n.b. we cannot handle this above in combinedPages because the dynamic
       // page must be in the `pages` array, but not in the mapping.
       exportPathMap: (defaultMap: any) => {
+        const { i18n } = config.experimental
+
         // Dynamically routed pages should be prerendered to be used as
         // a client-side skeleton (fallback) while data is being fetched.
         // This ensures the end-user never sees a 500 or slow response from the
@@ -738,7 +740,14 @@ export default async function build(
             if (ssgStaticFallbackPages.has(page)) {
               // Override the rendering for the dynamic page to be treated as a
               // fallback render.
-              defaultMap[page] = { page, query: { __nextFallback: true } }
+              if (i18n) {
+                defaultMap[`/${i18n.defaultLocale}${page}`] = {
+                  page,
+                  query: { __nextFallback: true },
+                }
+              } else {
+                defaultMap[page] = { page, query: { __nextFallback: true } }
+              }
             } else {
               // Remove dynamically routed pages from the default path map when
               // fallback behavior is disabled.
@@ -760,6 +769,39 @@ export default async function build(
           }
         }
 
+        if (i18n) {
+          for (const page of [
+            ...staticPages,
+            ...ssgPages,
+            ...(useStatic404 ? ['/404'] : []),
+          ]) {
+            const isSsg = ssgPages.has(page)
+            const isDynamic = isDynamicRoute(page)
+            const isFallback = isSsg && ssgStaticFallbackPages.has(page)
+
+            for (const locale of i18n.locales) {
+              if (!isSsg && locale === i18n.defaultLocale) continue
+              // skip fallback generation for SSG pages without fallback mode
+              if (isSsg && isDynamic && !isFallback) continue
+              const outputPath = `/${locale}${page === '/' ? '' : page}`
+
+              defaultMap[outputPath] = {
+                page: defaultMap[page].page,
+                query: { __nextLocale: locale },
+              }
+
+              if (isFallback) {
+                defaultMap[outputPath].query.__nextFallback = true
+              }
+            }
+
+            if (isSsg && !isFallback) {
+              // remove non-locale prefixed variant from defaultMap
+              delete defaultMap[page]
+            }
+          }
+        }
+
         return defaultMap
       },
       trailingSlash: false,
@@ -786,7 +828,8 @@ export default async function build(
       page: string,
       file: string,
       isSsg: boolean,
-      ext: 'html' | 'json'
+      ext: 'html' | 'json',
+      additionalSsgFile = false
     ) => {
       file = `${file}.${ext}`
       const orig = path.join(exportOptions.outdir, file)
@@ -820,8 +863,58 @@ export default async function build(
       if (!isSsg) {
         pagesManifest[page] = relativeDest
       }
-      await promises.mkdir(path.dirname(dest), { recursive: true })
-      await promises.rename(orig, dest)
+
+      const { i18n } = config.experimental
+
+      // for SSG files with i18n the non-prerendered variants are
+      // output with the locale prefixed so don't attempt moving
+      // without the prefix
+      if (!i18n || !isSsg || additionalSsgFile) {
+        await promises.mkdir(path.dirname(dest), { recursive: true })
+        await promises.rename(orig, dest)
+      }
+
+      if (i18n) {
+        if (additionalSsgFile) return
+
+        for (const locale of i18n.locales) {
+          // auto-export default locale files exist at root
+          // TODO: should these always be prefixed with locale
+          // similar to SSG prerender/fallback files?
+          if (!isSsg && locale === i18n.defaultLocale) {
+            continue
+          }
+
+          const localeExt = page === '/' ? path.extname(file) : ''
+          const relativeDestNoPages = relativeDest.substr('pages/'.length)
+
+          const updatedRelativeDest = path.join(
+            'pages',
+            locale + localeExt,
+            // if it's the top-most index page we want it to be locale.EXT
+            // instead of locale/index.html
+            page === '/' ? '' : relativeDestNoPages
+          )
+          const updatedOrig = path.join(
+            exportOptions.outdir,
+            locale + localeExt,
+            page === '/' ? '' : file
+          )
+          const updatedDest = path.join(
+            distDir,
+            isLikeServerless ? SERVERLESS_DIRECTORY : SERVER_DIRECTORY,
+            updatedRelativeDest
+          )
+
+          if (!isSsg) {
+            pagesManifest[
+              `/${locale}${page === '/' ? '' : page}`
+            ] = updatedRelativeDest
+          }
+          await promises.mkdir(path.dirname(updatedDest), { recursive: true })
+          await promises.rename(updatedOrig, updatedDest)
+        }
+      }
     }
 
     // Only move /404 to /404 when there is no custom 404 as in that case we don't know about the 404 page
@@ -877,13 +970,13 @@ export default async function build(
           const extraRoutes = additionalSsgPaths.get(page) || []
           for (const route of extraRoutes) {
             const pageFile = normalizePagePath(route)
-            await moveExportedPage(page, route, pageFile, true, 'html')
-            await moveExportedPage(page, route, pageFile, true, 'json')
+            await moveExportedPage(page, route, pageFile, true, 'html', true)
+            await moveExportedPage(page, route, pageFile, true, 'json', true)
 
             if (hasAmp) {
               const ampPage = `${pageFile}.amp`
-              await moveExportedPage(page, ampPage, ampPage, true, 'html')
-              await moveExportedPage(page, ampPage, ampPage, true, 'json')
+              await moveExportedPage(page, ampPage, ampPage, true, 'html', true)
+              await moveExportedPage(page, ampPage, ampPage, true, 'json', true)
             }
 
             finalPrerenderRoutes[route] = {

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

@@ -242,6 +242,7 @@ const nextServerlessLoader: loader.Loader = function () {
       detectedLocale = detectedLocale || i18n.defaultLocale
 
       if (
+        !fromExport &&
         !nextStartMode &&
         i18n.localeDetection !== false &&
         (shouldAddLocalePrefix || shouldStripDefaultLocale)

packages/next/export/worker.ts

@@ -100,14 +100,21 @@ export default async function exportPage({
     const { page } = pathMap
     const filePath = normalizePagePath(path)
     const ampPath = `${filePath}.amp`
+    const isDynamic = isDynamicRoute(page)
     let query = { ...originalQuery }
     let params: { [key: string]: string | string[] } | undefined
 
-    const localePathResult = normalizeLocalePath(path, renderOpts.locales)
+    let updatedPath = path
+    let locale = query.__nextLocale || renderOpts.locale
+    delete query.__nextLocale
 
-    if (localePathResult.detectedLocale) {
-      path = localePathResult.pathname
-      renderOpts.locale = localePathResult.detectedLocale
+    if (renderOpts.locale) {
+      const localePathResult = normalizeLocalePath(path, renderOpts.locales)
+
+      if (localePathResult.detectedLocale) {
+        updatedPath = localePathResult.pathname
+        locale = localePathResult.detectedLocale
+      }
     }
 
     // We need to show a warning if they try to provide query values
@@ -122,8 +129,8 @@ export default async function exportPage({
     }
 
     // Check if the page is a specified dynamic route
-    if (isDynamicRoute(page) && page !== path) {
-      params = getRouteMatcher(getRouteRegex(page))(path) || undefined
+    if (isDynamic && page !== path) {
+      params = getRouteMatcher(getRouteRegex(page))(updatedPath) || undefined
       if (params) {
         // we have to pass these separately for serverless
         if (!serverless) {
@@ -134,7 +141,7 @@ export default async function exportPage({
         }
       } else {
         throw new Error(
-          `The provided export path '${path}' doesn't match the '${page}' page.\nRead more: https://err.sh/vercel/next.js/export-path-mismatch`
+          `The provided export path '${updatedPath}' doesn't match the '${page}' page.\nRead more: https://err.sh/vercel/next.js/export-path-mismatch`
         )
       }
     }
@@ -149,7 +156,7 @@ export default async function exportPage({
     }
 
     const req = ({
-      url: path,
+      url: updatedPath,
       ...headerMocks,
     } as unknown) as IncomingMessage
     const res = ({
@@ -239,7 +246,7 @@ export default async function exportPage({
             fontManifest: optimizeFonts
               ? requireFontManifest(distDir, serverless)
               : null,
-            locale: renderOpts.locale!,
+            locale: locale!,
             locales: renderOpts.locales!,
           },
           // @ts-ignore
@@ -298,6 +305,7 @@ export default async function exportPage({
           fontManifest: optimizeFonts
             ? requireFontManifest(distDir, serverless)
             : null,
+          locale: locale as string,
         }
         // @ts-ignore
         html = await renderMethod(req, res, page, query, curRenderOpts)

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

@@ -354,7 +354,7 @@ export default class Server {
         parsedUrl.pathname = localePathResult.pathname
       }
 
-      ;(req as any)._nextLocale = detectedLocale || i18n.defaultLocale
+      parsedUrl.query.__nextLocale = detectedLocale || i18n.defaultLocale
     }
 
     res.statusCode = 200
@@ -510,7 +510,7 @@ export default class Server {
               pathname = localePathResult.pathname
               detectedLocale = localePathResult.detectedLocale
             }
-            ;(req as any)._nextLocale = detectedLocale || i18n.defaultLocale
+            _parsedUrl.query.__nextLocale = detectedLocale || i18n.defaultLocale
           }
           pathname = getRouteFromAssetPath(pathname, '.json')
 
@@ -1015,11 +1015,21 @@ export default class Server {
     query: ParsedUrlQuery = {},
     params: Params | null = null
   ): Promise<FindComponentsResult | null> {
-    const paths = [
+    let paths = [
       // try serving a static AMP version first
       query.amp ? normalizePagePath(pathname) + '.amp' : null,
       pathname,
     ].filter(Boolean)
+
+    if (query.__nextLocale) {
+      paths = [
+        ...paths.map(
+          (path) => `/${query.__nextLocale}${path === '/' ? '' : path}`
+        ),
+        ...paths,
+      ]
+    }
+
     for (const pagePath of paths) {
       try {
         const components = await loadComponents(
@@ -1031,7 +1041,11 @@ export default class Server {
           components,
           query: {
             ...(components.getStaticProps
-              ? { _nextDataReq: query._nextDataReq, amp: query.amp }
+              ? {
+                  amp: query.amp,
+                  _nextDataReq: query._nextDataReq,
+                  __nextLocale: query.__nextLocale,
+                }
               : query),
             ...(params || {}),
           },
@@ -1141,7 +1155,8 @@ export default class Server {
       urlPathname = stripNextDataPath(urlPathname)
     }
 
-    const locale = (req as any)._nextLocale
+    const locale = query.__nextLocale as string
+    delete query.__nextLocale
 
     const ssgCacheKey =
       isPreviewMode || !isSSG
@@ -1214,7 +1229,7 @@ export default class Server {
             'passthrough',
             {
               fontManifest: this.renderOpts.fontManifest,
-              locale: (req as any)._nextLocale,
+              locale,
               locales: this.renderOpts.locales,
             }
           )
@@ -1235,7 +1250,7 @@ export default class Server {
             ...opts,
             isDataReq,
             resolvedUrl,
-            locale: (req as any)._nextLocale,
+            locale,
             // For getServerSideProps we need to ensure we use the original URL
             // and not the resolved URL to prevent a hydration mismatch on
             // asPath
@@ -1321,7 +1336,9 @@ export default class Server {
 
         // Production already emitted the fallback as static HTML.
         if (isProduction) {
-          html = await this.incrementalCache.getFallback(pathname)
+          html = await this.incrementalCache.getFallback(
+            locale ? `/${locale}${pathname}` : pathname
+          )
         }
         // We need to generate the fallback on-demand for development.
         else {
@@ -1442,7 +1459,6 @@ export default class Server {
       res.statusCode = 500
       return await this.renderErrorToHTML(err, req, res, pathname, query)
     }
-
     res.statusCode = 404
     return await this.renderErrorToHTML(null, req, res, pathname, query)
   }
@@ -1488,7 +1504,7 @@ export default class Server {
 
     // use static 404 page if available and is 404 response
     if (is404) {
-      result = await this.findPageComponents('/404')
+      result = await this.findPageComponents('/404', query)
       using404Page = result !== null
     }
 

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

@@ -413,6 +413,7 @@ export async function renderToHTML(
 
   const isFallback = !!query.__nextFallback
   delete query.__nextFallback
+  delete query.__nextLocale
 
   const isSSG = !!getStaticProps
   const isBuildTimeSSG = isSSG && renderOpts.nextExport
@@ -506,9 +507,6 @@ export async function renderToHTML(
   }
   if (isAutoExport) renderOpts.autoExport = true
   if (isSSG) renderOpts.nextExport = false
-  // don't set default locale for fallback pages since this needs to be
-  // handled at request time
-  if (isFallback) renderOpts.locale = undefined
 
   await Loadable.preloadAll() // Make sure all dynamic imports are loaded
 

test/integration/i18n-support/pages/auto-export/index.js

@@ -0,0 +1,21 @@
+import Link from 'next/link'
+import { useRouter } from 'next/router'
+
+export default function Page(props) {
+  const router = useRouter()
+
+  return (
+    <>
+      <p id="auto-export">auto-export page</p>
+      <p id="props">{JSON.stringify(props)}</p>
+      <p id="router-locale">{router.locale}</p>
+      <p id="router-locales">{JSON.stringify(router.locales)}</p>
+      <p id="router-query">{JSON.stringify(router.query)}</p>
+      <p id="router-pathname">{router.pathname}</p>
+      <p id="router-as-path">{router.asPath}</p>
+      <Link href="/">
+        <a id="to-index">to /</a>
+      </Link>
+    </>
+  )
+}

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

@@ -44,12 +44,3 @@ export default function Page(props) {
     </>
   )
 }
-
-export const getServerSideProps = ({ locale, locales }) => {
-  return {
-    props: {
-      locale,
-      locales,
-    },
-  }
-}