feat: Support usage of rootParams in i18n/request.ts

Author: amannn

packages/next-intl/src/server/react-server/getConfig.tsx

@@ -38,6 +38,8 @@ See also: https://next-intl.dev/docs/usage/configuration#i18n-request
   }
 
   const params: GetRequestConfigParams = {
+    locale: localeOverride,
+
     // In case the consumer doesn't read `params.locale` and instead provides the
     // `locale` (either in a single-language workflow or because the locale is
     // read from the user settings), don't attempt to read the request locale.

packages/next-intl/src/server/react-server/getRequestConfig.tsx

@@ -1,4 +1,4 @@
-import type {IntlConfig} from 'use-intl/core';
+import type {IntlConfig, Locale} from 'use-intl/core';
 
 export type RequestConfig = Omit<IntlConfig, 'locale'> & {
   /**
@@ -8,6 +8,13 @@ export type RequestConfig = Omit<IntlConfig, 'locale'> & {
 };
 
 export type GetRequestConfigParams = {
+  /**
+   * If you provide an explicit locale to an async server-side function like
+   * `getTranslations({locale: 'en'})`, it will be passed via `locale` to
+   * `getRequestConfig` so you can use it instead of the segment value.
+   */
+  locale?: Locale;
+
   /**
    * Typically corresponds to the `[locale]` segment that was matched by the middleware.
    *

packages/use-intl/src/core/hasLocale.test.tsx

@@ -1,4 +1,4 @@
-import {it} from 'vitest';
+import {expect, it} from 'vitest';
 import hasLocale from './hasLocale.tsx';
 
 it('narrows down the type', () => {
@@ -24,3 +24,11 @@ it('can be called with a non-matching narrow candidate', () => {
     candidate satisfies never;
   }
 });
+
+it('can be called with any candidate', () => {
+  const locales = ['en-US', 'en-GB'] as const;
+  expect(hasLocale(locales, 'unknown')).toBe(false);
+
+  // Relevant since `ParamValue` in Next.js includes `string[]`
+  expect(hasLocale(locales, ['de'])).toBe(false);
+});

packages/use-intl/src/core/hasLocale.tsx

@@ -7,7 +7,7 @@ import type {Locale} from './AppConfig.tsx';
  */
 export default function hasLocale<LocaleType extends Locale>(
   locales: ReadonlyArray<LocaleType>,
-  candidate?: string | null
+  candidate?: unknown
 ): candidate is LocaleType {
   return locales.includes(candidate as LocaleType);
 }