Update i18next (#3858)

Co-authored-by: HiDeoo <494699+HiDeoo@users.noreply.github.com>
Co-authored-by: Felix Schneider <99918022+trueberryless@users.noreply.github.com>

Author: 3 people

.changeset/proud-schools-peel.md

@@ -0,0 +1,7 @@
+---
+'@astrojs/starlight': minor
+---
+
+Updates `i18next`, used for Starlight’s localization APIs, from v23 to v26
+
+There should not be any user-facing changes from this update

packages/starlight/package.json

@@ -73,7 +73,7 @@
     "hast-util-select": "^6.0.4",
     "hast-util-to-string": "^3.0.1",
     "hastscript": "^9.0.1",
-    "i18next": "^23.11.5",
+    "i18next": "^26.0.7",
     "js-yaml": "^4.1.1",
     "klona": "^2.0.6",
     "magic-string": "^0.30.21",

packages/starlight/utils/createTranslationSystem.ts

@@ -72,7 +72,11 @@ export async function createTranslationSystem<T extends i18nSchemaOutput>(
 
 		const t = i18n.getFixedT(lang, I18nextNamespace) as I18nT;
 		t.all = () => i18n.getResourceBundle(lang, I18nextNamespace) as ReturnType<I18nT['all']>;
-		t.exists = (key, options) => i18n.exists(key, { lng: lang, ns: I18nextNamespace, ...options });
+		// Since i18next 25.10.4 the `ExistsFunction` type has a signature including a predicate that
+		// TS cannot preserve when composing a new function to add default options.
+		// See: https://github.com/i18next/i18next/issues/2425
+		t.exists = ((key, options) =>
+			i18n.exists(key, { lng: lang, ns: I18nextNamespace, ...options })) as ExistsFunction;
 		t.dir = (dirLang = lang) => i18n.dir(dirLang);
 
 		return t;