Update i18n locales limit to warning

Author: ijjk

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 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: [
+      // 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 and non-dynamic `getStaticProps` pages a version of the page will be generated for each locale. This is important to consider since it can increase build times depending on how many locales are configured and what data fetching is being done inside of `getStaticProps`.
+
+If you have 50 locales configured with 10 non-dynamic pages with `getStaticProps` this means `getStaticProps` will be called 500 times and 50 version of these 10 pages will be generated during each build.
+
+To improve the performance of generating these pages during build time dynamic pages with `getStaticProps` and [a `fallback` mode](https://nextjs.org/docs/basic-features/data-fetching#fallback-true) can be leveraged instead. This allows you to return only the most popular paths and locales from `getStaticPaths` to prerender during the build and then lazily build the rest during runtime when 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
+
+> These limits are initial to provide a upper bound on how many locales should be configured to prevent performance impacts, we will re-visit these if they appear to be too low for valid use cases.

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`
+      console.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`
       )
     }