fix(i18n): default locale in server islands (#12341)

.changeset/gorgeous-foxes-divide.md

@@ -0,0 +1,5 @@
+---
+'astro': patch
+---
+
+Fixes and issue where `Astro.currentLocale` always returned the default locale when consumed inside a server island.

packages/astro/e2e/fixtures/i18n/astro.config.mjs

@@ -1,5 +1,5 @@
 import { defineConfig } from 'astro/config';
-
+import nodejs from "@astrojs/node"
 // https://astro.build/config
 export default defineConfig({
 	i18n: {
@@ -17,4 +17,6 @@ export default defineConfig({
 				],
 		}],
 	},
+	output: 'static',
+	adapter: nodejs({ mode: 'standalone' }),
 });

packages/astro/e2e/fixtures/i18n/components/Greeting.astro

@@ -0,0 +1,4 @@
+---
+const locale = Astro.currentLocale
+---
+<p data-testid="greeting">Greeting {locale}!</p>

packages/astro/e2e/fixtures/i18n/package.json

@@ -3,6 +3,7 @@
   "version": "0.0.0",
   "private": true,
   "dependencies": {
-    "astro": "workspace:*"
+    "astro": "workspace:*",
+    "@astrojs/node": "^8.3.4"
   }
 }

packages/astro/e2e/fixtures/i18n/src/pages/fr/island.astro

@@ -0,0 +1,5 @@
+---
+import Greeting from "../../../components/Greeting.astro"
+---
+<p>This is a test</p>
+<Greeting server:defer />

packages/astro/e2e/fixtures/i18n/src/pages/island.astro

@@ -0,0 +1,6 @@
+---
+import Greeting from "../../components/Greeting.astro"
+---
+
+<p>This is a test</p>
+<Greeting server:defer />

packages/astro/e2e/i18n.test.js

@@ -32,3 +32,21 @@ test.describe('i18n', () => {
 		await expect(p3).toHaveText('Locale: pt-AO');
 	});
 });
+
+test.describe('i18n default locale', () => {
+	test('is "en" when navigating the default locale page', async ({ page, astro }) => {
+		await page.goto(astro.resolveUrl('/island'));
+		let el = page.getByTestId('greeting');
+
+		await expect(el, 'element rendered').toBeVisible();
+		await expect(el).toHaveText('Greeting en!');
+	});
+
+	test('is "fr" when navigating the french page', async ({ page, astro }) => {
+		await page.goto(astro.resolveUrl('/fr/island'));
+		let el = page.getByTestId('greeting');
+
+		await expect(el, 'element rendered').toBeVisible();
+		await expect(el).toHaveText('Greeting fr!');
+	});
+});

packages/astro/src/core/render-context.ts

@@ -29,6 +29,7 @@ import { sequence } from './middleware/index.js';
 import { renderRedirect } from './redirects/render.js';
 import { type Pipeline, Slots, getParams, getProps } from './render/index.js';
 import { copyRequest, setOriginPathname } from './routing/rewrite.js';
+import { SERVER_ISLAND_COMPONENT } from './server-islands/endpoint.js';
 
 export const apiContextRoutesSymbol = Symbol.for('context.routes');
 
@@ -526,11 +527,22 @@ export class RenderContext {
 		}
 
 		let computedLocale;
-		if (routeData.pathname) {
-			computedLocale = computeCurrentLocale(routeData.pathname, locales, defaultLocale);
+		if (routeData.component === SERVER_ISLAND_COMPONENT) {
+			let referer = this.request.headers.get('referer');
+			if (referer) {
+				if (URL.canParse(referer)) {
+					referer = new URL(referer).pathname;
+				}
+				computedLocale = computeCurrentLocale(referer, locales, defaultLocale);
+			}
 		} else {
-			computedLocale = computeCurrentLocale(url.pathname, locales, defaultLocale);
+			if (routeData.pathname) {
+				computedLocale = computeCurrentLocale(routeData.pathname, locales, defaultLocale);
+			} else {
+				computedLocale = computeCurrentLocale(url.pathname, locales, defaultLocale);
+			}
 		}
+
 		this.#currentLocale = computedLocale ?? fallbackTo;
 
 		return this.#currentLocale;