Update i18n locales limit to warning (#28429)

* Update i18n locales limit to warning * update version -> versions * bump * Use Log.warn instead * Apply suggestions from code review Co-authored-by: Lee Robinson <me@leerob.io> Co-authored-by: Lee Robinson <me@leerob.io>
vercel · Aug 25, 2021 · f216855 · f216855
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diff --git a/docs/advanced-features/i18n-routing.md b/docs/advanced-features/i18n-routing.md
@@ -234,6 +234,30 @@ Next.js doesn't know about variants of a page so it's up to you to add the `href
 
 > Note that Internationalized Routing does not integrate with [`next export`](/docs/advanced-features/static-html-export.md) as `next export` does not leverage the Next.js routing layer. Hybrid Next.js applications that do not use `next export` are fully supported.
 
+### Dynamic Routes and `getStaticProps` Pages
+
+For pages using `getStaticProps` with [Dynamic Routes](/docs/routing/dynamic-routes.md), all locale variants of the page desired to be prerendered need to be returned from [`getStaticPaths`](/docs/basic-features/data-fetching.md#getstaticpaths-static-generation). Along with the `params` object returned for `paths`, you can also return a `locale` field specifying which locale you want to render. For example:
+
+```js
+// pages/blog/[slug].js
+export const getStaticPaths = ({ locales }) => {
+  return {
+    paths: [
+      // if no `locale` is provided only the defaultLocale will be generated
+      { params: { slug: 'post-1' }, locale: 'en-US' },
+      { params: { slug: 'post-1' }, locale: 'fr' },
+    ],
+    fallback: true,
+  }
+}
+```
+
+For [Automatically Statically Optimized](/docs/advanced-features/automatic-static-optimization.md) and non-dynamic `getStaticProps` pages, **a version of the page will be generated for each locale**. This is important to consider because it can increase build times depending on how many locales are configured inside `getStaticProps`.
+
+For example, if you have 50 locales configured with 10 non-dynamic pages using `getStaticProps`, this means `getStaticProps` will be called 500 times. 50 versions of the 10 pages will be generated during each build.
+
+To decrease the build time of dynamic pages with `getStaticProps`, use a [`fallback` mode](https://nextjs.org/docs/basic-features/data-fetching#fallback-true). This allows you to return only the most popular paths and locales from `getStaticPaths` for prerendering during the build. Then, Next.js will build the remaining pages at runtime as they are requested.
+
 ### Automatically Statically Optimized Pages
 
 For pages that are [automatically statically optimized](/docs/advanced-features/automatic-static-optimization.md), a version of the page will be generated for each locale.
@@ -265,24 +289,9 @@ export async function getStaticProps({ locale }) {
 }
 ```
 
-### Dynamic getStaticProps Pages
-
-For dynamic `getStaticProps` pages, any locale variants of the page that is desired to be prerendered needs to be returned from [`getStaticPaths`](/docs/basic-features/data-fetching.md#getstaticpaths-static-generation). Along with the `params` object that can be returned for the `paths`, you can also return a `locale` field specifying which locale you want to render. For example:
-
-```js
-// pages/blog/[slug].js
-export const getStaticPaths = ({ locales }) => {
-  return {
-    paths: [
-      { params: { slug: 'post-1' }, locale: 'en-US' },
-      { params: { slug: 'post-1' }, locale: 'fr' },
-    ],
-    fallback: true,
-  }
-}
-```
-
 ## Limits for the i18n config
 
 - `locales`: 100 total locales
 - `domains`: 100 total locale domain items
+
+> **Note:** These limits have been added initially to prevent potential [performance issues at build time](#dynamic-routes-and-getStaticProps-pages). We are continuing to evaluate if these limits are sufficient.
diff --git a/packages/next/server/config.ts b/packages/next/server/config.ts
@@ -329,8 +329,8 @@ function assignDefaults(userConfig: { [key: string]: any }) {
     }
 
     if (i18n.locales.length > 100) {
-      throw new Error(
-        `Received ${i18n.locales.length} i18n.locales items which exceeds the max of 100, please reduce the number of items to continue.\nSee more info here: https://nextjs.org/docs/messages/invalid-i18n-config`
+      Log.warn(
+        `Received ${i18n.locales.length} i18n.locales items which exceeds the recommended max of 100.\nSee more info here: https://nextjs.org/docs/advanced-features/i18n-routing#how-does-this-work-with-static-generation`
       )
     }