fix: custom headers for root route when using i18n (#1893)

* fix: escape locale strings when matching from routes-manifest

* chore: amend i18n headers test to cover regex special characters

Author: orinokai

packages/runtime/src/helpers/config.ts

@@ -9,6 +9,7 @@ import slash from 'slash'
 import { HANDLER_FUNCTION_NAME, ODB_FUNCTION_NAME } from '../constants'
 
 import type { RoutesManifest } from './types'
+import { escapeStringRegexp } from './utils'
 
 const ROUTES_MANIFEST_FILE = 'routes-manifest.json'
 
@@ -214,7 +215,9 @@ export const generateCustomHeaders = (nextConfig: NextConfig, netlifyHeaders: Ne
 
     if (useLocale) {
       const { locales } = i18n
-      const joinedLocales = locales.join('|')
+
+      // escape the locale strings to match the way Next writes the routes-manifest.json file
+      const joinedLocales = locales.map((locale: string) => escapeStringRegexp(locale)).join('|')
 
       /**
        *  converts e.g.

packages/runtime/src/helpers/utils.ts

@@ -313,3 +313,8 @@ export const getRemotePatterns = (experimental: ExperimentalConfigWithLegacy, im
   }
   return []
 }
+
+// Taken from next/src/shared/lib/escape-regexp.ts
+const reHasRegExp = /[|\\{}()[\]^$+*?.-]/
+const reReplaceRegExp = /[|\\{}()[\]^$+*?.-]/g
+export const escapeStringRegexp = (str: string) => (reHasRegExp.test(str) ? str.replace(reReplaceRegExp, '\\$&') : str)

test/index.spec.js

@@ -1606,13 +1606,13 @@ describe('function helpers', () => {
         // Next.js has modified the routesManifest to have the locales in the source.
         const nextConfig = {
           i18n: {
-            locales: ['en', 'fr'],
+            locales: ['en-US', 'fr'],
             defaultLocale: 'en',
           },
           routesManifest: {
             headers: [
               {
-                source: '/:nextInternalLocale(en|fr)/with-locale/:path*',
+                source: '/:nextInternalLocale(en\\-US|fr)/with-locale/:path*',
                 headers: [
                   {
                     key: 'X-Unit-Test',
@@ -1635,7 +1635,7 @@ describe('function helpers', () => {
             },
           },
           {
-            for: '/en/with-locale/*',
+            for: '/en-US/with-locale/*',
             values: {
               'X-Unit-Test': 'true',
             },