implementation

Author: amannn

Diff for: docs/src/pages/docs/routing/middleware.mdx

@@ -93,14 +93,13 @@ Since the middleware is aware of all your domains, if a domain receives a reques
 4. The middleware recognizes that the user wants to switch to another domain and responds with a redirect to `ca.example.com/fr`.
 
 <Details id="domain-matching">
-<summary>How is the best matching domain for a given locale detected?</summary>
+<summary>How is the best-matching domain for a given locale detected?</summary>
 
-The bestmatching domain is detected based on these priorities:
+The best-matching domain is detected based on these priorities:
 
 1. Stay on the current domain if the locale is supported here
 2. Use an alternative domain where the locale is configured as the `defaultLocale`
-3. Use an alternative domain where the available `locales` are restricted and the locale is supported
-4. Use an alternative domain that supports all locales
+3. Use an alternative domain that supports the locale
 
 </Details>
 

Diff for: examples/example-app-router-playground/src/i18n/routing.ts

@@ -18,11 +18,13 @@ export const routing = defineRouting({
       ? [
           {
             domain: 'example.com',
-            defaultLocale: 'en'
+            defaultLocale: 'en',
+            locales: ['en', 'de', 'es', 'ja']
           },
           {
             domain: 'example.de',
-            defaultLocale: 'de'
+            defaultLocale: 'de',
+            locales: ['en', 'de', 'es', 'ja']
           }
         ]
       : undefined,

Diff for: packages/next-intl/.size-limit.ts

@@ -21,13 +21,13 @@ const config: SizeLimitConfig = [
     name: "import {createNavigation} from 'next-intl/navigation' (react-client)",
     path: 'dist/esm/production/navigation.react-client.js',
     import: '{createNavigation}',
-    limit: '2.485 KB'
+    limit: '2.285 KB'
   },
   {
     name: "import {createNavigation} from 'next-intl/navigation' (react-server)",
     path: 'dist/esm/production/navigation.react-server.js',
     import: '{createNavigation}',
-    limit: '3.275 KB'
+    limit: '3.055 KB'
   },
   {
     name: "import * from 'next-intl/server' (react-client)",
@@ -42,7 +42,7 @@ const config: SizeLimitConfig = [
   {
     name: "import * from 'next-intl/middleware'",
     path: 'dist/esm/production/middleware.js',
-    limit: '9.315 KB'
+    limit: '9.285 KB'
   },
   {
     name: "import * from 'next-intl/routing'",

Diff for: packages/next-intl/src/middleware/getAlternateLinksHeaderValue.test.tsx

@@ -197,8 +197,8 @@ describe.each([{basePath: undefined}, {basePath: '/base'}])(
         domains: [
           {
             domain: 'example.com',
-            defaultLocale: 'en'
-            // (supports all locales)
+            defaultLocale: 'en',
+            locales: ['en', 'es', 'fr']
           },
           {
             domain: 'example.es',
@@ -264,8 +264,8 @@ describe.each([{basePath: undefined}, {basePath: '/base'}])(
         domains: [
           {
             domain: 'example.com',
-            defaultLocale: 'en'
-            // (supports all locales)
+            defaultLocale: 'en',
+            locales: ['en', 'es', 'fr']
           },
           {
             domain: 'example.es',

Diff for: packages/next-intl/src/middleware/middleware.test.tsx

@@ -2480,7 +2480,8 @@ describe('domain-based routing', () => {
         domains: [
           {
             defaultLocale: 'fr',
-            domain: 'ca.example.com'
+            domain: 'ca.example.com',
+            locales: ['en', 'fr']
           }
         ]
       });

Diff for: packages/next-intl/src/middleware/resolveLocale.tsx

@@ -197,7 +197,7 @@ function resolveLocaleFromDomain<
   if (!locale && routing.localeDetection) {
     const headerLocale = getAcceptLanguageLocale(
       requestHeaders,
-      domain.locales || routing.locales,
+      domain.locales,
       domain.defaultLocale
     );
 

Diff for: packages/next-intl/src/middleware/utils.tsx

@@ -258,11 +258,7 @@ export function isLocaleSupportedOnDomain<AppLocales extends Locales>(
   locale: Locale,
   domain: DomainConfig<AppLocales>
 ) {
-  return (
-    domain.defaultLocale === locale ||
-    !domain.locales ||
-    domain.locales.includes(locale)
-  );
+  return domain.defaultLocale === locale || domain.locales.includes(locale);
 }
 
 export function getBestMatchingDomain<AppLocales extends Locales>(
@@ -282,19 +278,9 @@ export function getBestMatchingDomain<AppLocales extends Locales>(
     domainConfig = domainsConfig.find((cur) => cur.defaultLocale === locale);
   }
 
-  // Prio 3: Use alternative domain with restricted matching locale
-  if (!domainConfig) {
-    domainConfig = domainsConfig.find((cur) => cur.locales?.includes(locale));
-  }
-
-  // Prio 4: Stay on the current domain if it supports all locales
-  if (!domainConfig && curHostDomain?.locales == null) {
-    domainConfig = curHostDomain;
-  }
-
-  // Prio 5: Use alternative domain that supports all locales
+  // Prio 3: Use alternative domain that supports the locale
   if (!domainConfig) {
-    domainConfig = domainsConfig.find((cur) => !cur.locales);
+    domainConfig = domainsConfig.find((cur) => cur.locales.includes(locale));
   }
 
   return domainConfig;

Diff for: packages/next-intl/src/navigation/createNavigation.test.tsx

@@ -53,12 +53,13 @@ const defaultLocale = 'en' as const;
 const domains = [
   {
     defaultLocale: 'en',
-    domain: 'example.com'
+    domain: 'example.com',
+    locales: ['en']
   },
   {
     defaultLocale: 'de',
     domain: 'example.de',
-    locales: ['de', 'en']
+    locales: ['de', 'ja']
   }
 ] satisfies DomainsConfig<typeof locales>;
 
@@ -907,10 +908,9 @@ describe.each([
     });
 
     describe('Link', () => {
-      it('renders a prefix during SSR even for the default locale', () => {
-        // (see comment in source for reasoning)
+      it('renders no prefix during SSR for the default locale', () => {
         const markup = renderToString(<Link href="/about">About</Link>);
-        expect(markup).toContain('href="/en/about"');
+        expect(markup).toContain('href="/about"');
       });
 
       it('does not render a prefix eventually on the client side for the default locale of the given domain', () => {
@@ -935,11 +935,11 @@ describe.each([
 
       it('renders a prefix when currently on a secondary locale', () => {
         mockLocation({host: 'example.de'});
-        mockCurrentLocale('en');
+        mockCurrentLocale('ja');
         render(<Link href="/about">About</Link>);
         expect(
           screen.getByRole('link', {name: 'About'}).getAttribute('href')
-        ).toBe('/en/about');
+        ).toBe('/ja/about');
       });
 
       it('does not render a prefix when currently on a domain with a different default locale', () => {
@@ -973,30 +973,9 @@ describe.each([
     });
 
     describe('getPathname', () => {
-      it('does not add a prefix for the default locale', () => {
-        expect(
-          getPathname({locale: 'en', href: '/about', domain: 'example.com'})
-        ).toBe('/about');
-        expect(
-          getPathname({locale: 'de', href: '/about', domain: 'example.de'})
-        ).toBe('/about');
-      });
-
-      it('adds a prefix for a secondary locale', () => {
-        expect(
-          getPathname({locale: 'de', href: '/about', domain: 'example.com'})
-        ).toBe('/de/about');
-        expect(
-          getPathname({locale: 'en', href: '/about', domain: 'example.de'})
-        ).toBe('/en/about');
-      });
-
-      it('prints a warning when no domain is provided', () => {
-        const consoleSpy = vi.spyOn(console, 'error');
-        // @ts-expect-error -- Domain is not provided
-        getPathname({locale: 'de', href: '/about'});
-        expect(consoleSpy).toHaveBeenCalled();
-        consoleSpy.mockRestore();
+      it('does not add a prefix for a default locale', () => {
+        expect(getPathname({locale: 'en', href: '/about'})).toBe('/about');
+        expect(getPathname({locale: 'de', href: '/about'})).toBe('/about');
       });
     });
 
@@ -1005,21 +984,19 @@ describe.each([
       ['permanentRedirect', permanentRedirect, nextPermanentRedirect]
     ])('%s', (_, redirectFn, nextRedirectFn) => {
       it('adds a prefix even for the default locale', () => {
-        // (see comment in source for reasoning)
+        // There's one edge case that is not handled here: If `localePrefix:
+        // 'as-needed'` is used and the user redirects from a non-default locale
+        // to the default locale, no cookie will be updated and therefore the user
+        // redirected back to the original locale. Typically, redirect is not used
+        // for language switching though and uses the current locale of the user,
+        // therefore this is currently neglected.
         runInRender(() => redirectFn({href: '/', locale: 'en'}));
-        expect(nextRedirectFn).toHaveBeenLastCalledWith('/en');
-      });
-
-      it('does not add a prefix when domain is provided for the default locale', () => {
-        runInRender(() =>
-          redirectFn({href: '/', locale: 'en', domain: 'example.com'})
-        );
         expect(nextRedirectFn).toHaveBeenLastCalledWith('/');
       });
 
       it('adds a prefix for a secondary locale', () => {
-        runInRender(() => redirectFn({href: '/', locale: 'de'}));
-        expect(nextRedirectFn).toHaveBeenLastCalledWith('/de');
+        runInRender(() => redirectFn({href: '/', locale: 'ja'}));
+        expect(nextRedirectFn).toHaveBeenLastCalledWith('/ja');
       });
     });
   });
@@ -1052,7 +1029,7 @@ describe.each([
         runInRender(() =>
           redirectFn({href: {pathname: '/', query: {foo: 'bar'}}, locale: 'en'})
         );
-        expect(nextRedirectFn).toHaveBeenLastCalledWith('/en?foo=bar');
+        expect(nextRedirectFn).toHaveBeenLastCalledWith('/?foo=bar');
       });
     });
   });

Diff for: packages/next-intl/src/navigation/react-client/createNavigation.test.tsx

@@ -55,12 +55,13 @@ const defaultLocale = 'en' as const;
 const domains: DomainsConfig<typeof locales> = [
   {
     defaultLocale: 'en',
-    domain: 'example.com'
+    domain: 'example.com',
+    locales: ['en']
   },
   {
     defaultLocale: 'de',
     domain: 'example.de',
-    locales: ['de', 'en']
+    locales: ['de', 'ja']
   }
 ];
 
@@ -563,43 +564,20 @@ describe("localePrefix: 'as-needed', with `basePath` and `domains`", () => {
   describe('useRouter', () => {
     const invokeRouter = getInvokeRouter(useRouter);
 
-    describe('example.com, defaultLocale: "en"', () => {
-      beforeEach(() => {
-        mockLocation(
-          {pathname: '/base/path/about', host: 'example.com'},
-          '/base/path'
-        );
-      });
-
-      it('can compute the correct pathname when the default locale on the current domain matches the current locale', () => {
-        invokeRouter((router) => router.push('/test'));
-        expect(useNextRouter().push).toHaveBeenCalledWith('/test');
-      });
-
-      it('can compute the correct pathname when the default locale on the current domain does not match the current locale', () => {
-        invokeRouter((router) => router.push('/test', {locale: 'de'}));
-        expect(useNextRouter().push).toHaveBeenCalledWith('/de/test');
-      });
+    it('can compute the correct pathname when on the default locale and not supplying a locale', () => {
+      invokeRouter((router) => router.push('/test'));
+      expect(useNextRouter().push).toHaveBeenCalledWith('/test');
     });
 
-    describe('example.de, defaultLocale: "de"', () => {
-      beforeEach(() => {
-        mockCurrentLocale('de');
-        mockLocation(
-          {pathname: '/base/path/about', host: 'example.de'},
-          '/base/path'
-        );
-      });
-
-      it('can compute the correct pathname when the default locale on the current domain matches the current locale', () => {
-        invokeRouter((router) => router.push('/test'));
-        expect(useNextRouter().push).toHaveBeenCalledWith('/test');
-      });
+    it('can compute the correct pathname when on the default locale and supplying a secondary locale', () => {
+      invokeRouter((router) => router.push('/test', {locale: 'ja'}));
+      expect(useNextRouter().push).toHaveBeenCalledWith('/ja/test');
+    });
 
-      it('can compute the correct pathname when the default locale on the current domain does not match the current locale', () => {
-        invokeRouter((router) => router.push('/test', {locale: 'en'}));
-        expect(useNextRouter().push).toHaveBeenCalledWith('/en/test');
-      });
+    it('can compute the correct pathname when on a secondary locale and navigating to the default locale', () => {
+      mockCurrentLocale('ja');
+      invokeRouter((router) => router.push('/test', {locale: 'en'}));
+      expect(useNextRouter().push).toHaveBeenCalledWith('/test');
     });
   });
 });
@@ -639,13 +617,6 @@ describe("localePrefix: 'as-needed', with `domains`", () => {
         expect(consoleSpy).not.toHaveBeenCalled();
         consoleSpy.mockRestore();
       });
-
-      it('prefixes the default locale when on a domain with a different defaultLocale', () => {
-        mockCurrentLocale('de');
-        mockLocation({pathname: '/about', host: 'example.de'});
-        invokeRouter((router) => router[method]('/about', {locale: 'en'}));
-        expect(useNextRouter()[method]).toHaveBeenCalledWith('/en/about');
-      });
     });
   });
 

Diff for: packages/next-intl/src/navigation/react-client/createNavigation.tsx

@@ -85,11 +85,9 @@ export default function createNavigation<
         ): void {
           const {locale: nextLocale, ...rest} = options || {};
 
-          // @ts-expect-error -- We're passing a domain here just in case
           const pathname = getPathname({
             href,
-            locale: nextLocale || curLocale,
-            domain: window.location.host
+            locale: nextLocale || curLocale
           });
 
           const args: [href: string, options?: Options] = [pathname];