fix(i18n): ensure the redirect pathname is non-empty (#13730)

Co-authored-by: Emanuele Stoppa <[email protected]>
Co-authored-by: Florian Lefebvre <[email protected]>

Author: 3 people

.changeset/olive-papers-hide.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes a bug in i18n, where Astro caused an infinite loop when a locale that doesn't have an index, and Astro falls back to the index of the default locale.

packages/astro/src/i18n/index.ts

@@ -399,6 +399,11 @@ export function redirectToFallback({
 				if (pathFallbackLocale === defaultLocale && strategy === 'pathname-prefix-other-locales') {
 					if (context.url.pathname.includes(`${base}`)) {
 						newPathname = context.url.pathname.replace(`/${urlLocale}`, ``);
+						// Ensure the pathname are non-empty. Redirects like "/fr" => "" may create infinite loops,
+						// as the "Location" response header is empty.
+						if (newPathname === '') {
+							newPathname = '/';
+						}
 					} else {
 						newPathname = context.url.pathname.replace(`/${urlLocale}`, `/`);
 					}

packages/astro/test/i18n-routing.test.js

@@ -774,6 +774,50 @@ describe('[SSG] i18n routing', () => {
 		});
 	});
 
+	describe('i18n routing with routing strategy [prefix-other-locales] with root base', () => {
+		/** @type {import('./test-utils').Fixture} */
+		let fixture;
+		/** @type {import('./test-utils').DevServer} */
+		let devServer;
+
+		before(async () => {
+			fixture = await loadFixture({
+				root: './fixtures/i18n-routing-prefix-other-locales/',
+				output: 'server',
+				adapter: testAdapter(),
+				base: '/',
+				i18n: {
+					defaultLocale: 'en',
+					locales: ['en', 'pt', 'fr'],
+					fallback: {
+						fr: 'en',
+					},
+					routing: {
+						prefixDefaultLocale: false,
+						redirectToDefaultLocale: true,
+						fallbackType: 'redirect',
+					},
+				},
+			});
+			await fixture.build();
+			devServer = await fixture.startDevServer();
+		});
+
+		afterEach(async () => {
+			devServer.stop();
+		});
+
+		it('should redirect to English page', async () => {
+			const response = await fixture.fetch('/fr', { redirect: 'manual' });
+			assert.equal(response.headers.get('Location'), '/');
+			assert.equal(response.status, 302);
+
+			const followRedirectResponse = await fixture.fetch('/fr');
+			assert.equal(followRedirectResponse.status, 200);
+			assert.equal((await followRedirectResponse.text()).includes('Hello'), true);
+		});
+	});
+
 	describe('i18n routing with routing strategy [pathname-prefix-always-no-redirect]', () => {
 		/** @type {import('./test-utils').Fixture} */
 		let fixture;