fix(i18n): properly share i18n instance across JS modules

javascript-create-module/templates/hello-world/src/components/Hello/World/Celebrate.client.tsx

@@ -1,7 +1,7 @@
 import clsx from "clsx";
-import { t } from "i18next";
 import { useEffect, useState } from "react";
 import classes from "./styles.module.css";
+import { useTranslation } from "react-i18next";
 
 export default function () {
   const [confetti, setConfetti] = useState<typeof import("canvas-confetti")>();
@@ -13,6 +13,11 @@ export default function () {
     });
   });
 
+  // IMPORTANT: Always use useTranslation() (not { t } from "i18next") in React components.
+  // This ensures translations are context-aware, update on language/namespace changes,
+  // and avoid hydration mismatches between server and client.
+  const { t } = useTranslation();
+
   return (
     <button
       className={clsx(classes.button, confetti && classes.hydrated)}

javascript-modules-engine/src/client/hydrate.tsx

@@ -1,7 +1,8 @@
 import * as devalue from "devalue";
-import i18next from "i18next";
+import i18n from "i18next";
 import type { ComponentType } from "react";
 import { createRoot, hydrateRoot } from "react-dom/client";
+import { I18nextProvider } from "react-i18next";
 
 /** Ensures the component is hydrated with the right i18next context */
 const ComponentWrapper = ({
@@ -19,14 +20,16 @@ const ComponentWrapper = ({
   /** Props object for the app component */
   props: Record<string, unknown>;
 }) => {
-  i18next.setDefaultNamespace(ns);
-  i18next.changeLanguage(lang);
-
+  // Not thread-safe if multiple hydrated components use different languages on the same page.
+  // But assumes a single language per page, so i18n.changeLanguage(lang) is safe in this context.
+  i18n.changeLanguage(lang);
   return (
-    <Component {...props}>
-      {/* @ts-expect-error This is an hydration border: hydration will stop here */}
-      <jsm-children dangerouslySetInnerHTML={{ __html: "" }} suppressHydrationWarning />
-    </Component>
+    <I18nextProvider i18n={i18n} defaultNS={ns}>
+      <Component {...props}>
+        {/* @ts-expect-error This is an hydration border: hydration will stop here */}
+        <jsm-children dangerouslySetInnerHTML={{ __html: "" }} suppressHydrationWarning />
+      </Component>
+    </I18nextProvider>
   );
 };
 

javascript-modules-engine/src/client/i18next.ts

@@ -4,18 +4,14 @@ import * as devalue from "devalue";
 
 i18n.use(initReactI18next).init({
   fallbackLng: "en",
-  ns: "javascript-modules-engine",
-  defaultNS: "javascript-modules-engine",
   initImmediate: false,
   react: { useSuspense: false },
 });
 
 const initialI18nStore: Record<string, Record<string, unknown>> = {};
-const namespaces: string[] = [];
 
 for (const store of document.querySelectorAll<HTMLScriptElement>("script[data-i18n-store]")) {
   const namespace = store.dataset.i18nStore;
-  namespaces.push(namespace);
 
   const allTranslations = devalue.parse(store.textContent);
   for (const [lang, translations] of Object.entries(allTranslations)) {
@@ -26,4 +22,3 @@ for (const store of document.querySelectorAll<HTMLScriptElement>("script[data-i1
 
 // Init i18n internal store
 i18n.services.resourceStore.data = initialI18nStore;
-i18n.options.ns = namespaces;

samples/hydrogen/settings/locales/en.json

@@ -6,6 +6,7 @@
   "89D3xFLMZmCAencaqw68C": "Click this button to add a new content node",
   "hBBhbeE0-a4KS9HVFPsOz": "Hydrated client-side",
   "AI95bg1EJsr48SR-4f_pl": "Rendered server-side",
+  "0yvhe06c8uhrPuqm15zq6": "Rendered client-side only",
   "OfBsezopuIko8aJ6X3kpw": "Despite being written with React, this page is fully rendered server-side. No JavaScript is sent to the client by default! This does not mean you cannot use client-side code:",
   "nr31fYHB-RqO06BCl4rYO": "This pattern is named <a>Islands Architecture.</a>",
   "JI87mYV8J5pAEST4RIUcb": "This page is available in:"

samples/hydrogen/settings/locales/fr.json

@@ -5,6 +5,7 @@
   "8S0DVCRSnmQRKF9lZnNGj": "Illustrations par <a>Katerina Limpitsouni</a>",
   "89D3xFLMZmCAencaqw68C": "Cliquez ce bouton pour ajouter un nouveau contenu",
   "AI95bg1EJsr48SR-4f_pl": "Rendu par le serveur",
+  "0yvhe06c8uhrPuqm15zq6": "Rendu côté client uniquement",
   "OfBsezopuIko8aJ6X3kpw": "Bien que cette page soit codée avec React, elle est entièrement rendue par le serveur. Le JavaScript côté client n'est pas nécessaire par défaut ! Vous pouvez tout de même vous en servir quand vous le souhaitez :",
   "hBBhbeE0-a4KS9HVFPsOz": "Hydraté côté client",
   "nr31fYHB-RqO06BCl4rYO": "Cela s'appelle la <a>Conception en archipel (en)</a>.",

samples/hydrogen/src/components/HelloWorld/Celebrate.client.tsx

@@ -1,17 +1,31 @@
 import clsx from "clsx";
-import { t } from "i18next";
 import { useEffect, useState } from "react";
 import classes from "./component.module.css";
+import { useTranslation } from "react-i18next";
 
 export default function () {
   const [confetti, setConfetti] = useState<typeof import("canvas-confetti")>();
+  const [isClient, setIsClient] = useState(false);
 
   useEffect(() => {
+    let mounted = true;
     // This library only works client-side, import it dynamically in an effect
     import("canvas-confetti").then(({ default: confetti }) => {
-      setConfetti(() => confetti);
+      if (mounted) setConfetti(() => confetti);
     });
-  });
+    // Use a microtask to avoid direct setState in useEffect
+    Promise.resolve().then(() => {
+      if (mounted) setIsClient(true);
+    });
+    return () => {
+      mounted = false;
+    };
+  }, []);
+
+  // IMPORTANT: Always use useTranslation() (not { t } from "i18next") in React components.
+  // This ensures translations are context-aware, update on language/namespace changes,
+  // and avoid hydration mismatches between server and client.
+  const { t } = useTranslation();
 
   return (
     <button
@@ -25,6 +39,10 @@ export default function () {
     >
       <span className={classes.before}>{t("AI95bg1EJsr48SR-4f_pl")}</span>
       <span className={classes.after}>{t("hBBhbeE0-a4KS9HVFPsOz")}</span>
+      {/*add a client-side-only text for testing and demo purposes*/}
+      <span hidden data-testid="i18n-client-only">
+        {isClient ? t("0yvhe06c8uhrPuqm15zq6") : ""}
+      </span>
     </button>
   );
 }

tests/cypress/e2e/ui/testI18n.cy.ts

@@ -1,4 +1,10 @@
-import { addNode, createSite, deleteSite, publishAndWaitJobEnding } from "@jahia/cypress";
+import {
+  addNode,
+  createSite,
+  deleteSite,
+  enableModule,
+  publishAndWaitJobEnding,
+} from "@jahia/cypress";
 import { addSimplePage } from "../../utils/helpers";
 
 const testData = {
@@ -23,30 +29,24 @@ const testData = {
 };
 
 describe("Test i18n", () => {
-  before("Create test site/contents", () => {
-    createSite("javascriptI18NTestSite", {
+  const createSiteWithContent = (siteKey: string) => {
+    deleteSite(siteKey); // cleanup from previous test runs
+    createSite(siteKey, {
       languages: "en,fr_LU,fr,de",
       templateSet: "javascript-modules-engine-test-module",
       locale: "en",
       serverName: "localhost",
     });
 
-    addSimplePage(
-      "/sites/javascriptI18NTestSite/home",
-      "testPageI18N",
-      "Test i18n en",
-      "en",
-      "simple",
-      [
-        {
-          name: "pagecontent",
-          primaryNodeType: "jnt:contentList",
-        },
-      ],
-    ).then(() => {
+    addSimplePage(`/sites/${siteKey}/home`, "testPageI18N", "Test i18n en", "en", "simple", [
+      {
+        name: "pagecontent",
+        primaryNodeType: "jnt:contentList",
+      },
+    ]).then(() => {
       cy.apollo({
         variables: {
-          pathOrId: "/sites/javascriptI18NTestSite/home/testPageI18N",
+          pathOrId: `/sites/${siteKey}/home/testPageI18N`,
           properties: [
             { name: "jcr:title", value: "Test i18n fr_LU", language: "fr_LU" },
             { name: "jcr:title", value: "Test i18n fr", language: "fr" },
@@ -57,57 +57,45 @@ describe("Test i18n", () => {
       });
 
       addNode({
-        parentPathOrId: "/sites/javascriptI18NTestSite/home/testPageI18N/pagecontent",
+        parentPathOrId: `/sites/${siteKey}/home/testPageI18N/pagecontent`,
         name: "test",
         primaryNodeType: "javascriptExample:testI18n",
       });
     });
 
-    publishAndWaitJobEnding("/sites/javascriptI18NTestSite/home/testPageI18N", [
-      "en",
-      "fr_LU",
-      "fr",
-      "de",
-    ]);
-  });
+    publishAndWaitJobEnding(`/sites/${siteKey}/home/testPageI18N`, ["en", "fr_LU", "fr", "de"]);
+  };
 
   it("Test I18n values in various workspace/locales and various type of usage SSR/hydrate/rendered client side", () => {
+    const siteKey = "javascriptI18NTestSite";
+    createSiteWithContent(siteKey);
+
     cy.login();
     ["live", "default"].forEach((workspace) => {
       ["en", "fr_LU", "fr", "de"].forEach((locale) => {
-        cy.visit(
-          `/cms/render/${workspace}/${locale}/sites/javascriptI18NTestSite/home/testPageI18N.html`,
-        );
-        testI18n(
-          workspace,
-          locale,
-          'div[data-testid="i18n-server-side"]',
-          "We are server side !",
-          false,
-        );
+        cy.visit(`/cms/render/${workspace}/${locale}/sites/${siteKey}/home/testPageI18N.html`);
+        testI18n(locale, 'div[data-testid="i18n-server-side"]', "We are server side !", false);
         testI18n(
-          workspace,
           locale,
           'div[data-testid="i18n-hydrated-client-side"]',
           "We are hydrated client side !",
           true,
         );
         testI18n(
-          workspace,
           locale,
           'div[data-testid="i18n-rendered-client-side"]',
           "We are rendered client side !",
           true,
         );
       });
-
       cy.get('[data-testid="getSiteLocales"]').should("contain", "de,en,fr,fr_LU");
     });
     cy.logout();
+
+    deleteSite(siteKey);
   });
 
   const testI18n = (
-    workspace: string,
     locale: string,
     mainSelector: string,
     placeholderIntialValue: string,
@@ -141,8 +129,46 @@ describe("Test i18n", () => {
     }
   };
 
-  after("Cleanup", () => {
-    cy.visit("/start", { failOnStatusCode: false });
-    deleteSite("javascriptI18NTestSite");
+  it("Support client-side i18n with components from multiple JS modules on the same page", () => {
+    const siteKey = "javascriptI18NMultiModuleTestSite";
+    createSiteWithContent(siteKey);
+    // add a component from another JS module
+    enableModule("hydrogen", siteKey);
+    addNode({
+      parentPathOrId: `/sites/${siteKey}/home/testPageI18N/pagecontent`,
+      name: "testOtherModule",
+      primaryNodeType: "hydrogen:helloWorld",
+      properties: [{ name: "name", value: "John Doe", language: "en" }],
+    });
+    publishAndWaitJobEnding(`/sites/${siteKey}/home/testPageI18N`, ["en"]);
+
+    cy.login();
+    ["live", "default"].forEach((workspace) => {
+      cy.visit(`/cms/render/${workspace}/en/sites/${siteKey}/home/testPageI18N.html`);
+
+      // make sure the 2 modules are present on the page with their i18n store
+      cy.get('script[data-i18n-store="javascript-modules-engine-test-module"]').should("exist");
+      cy.get('script[data-i18n-store="hydrogen"]').should("exist");
+      cy.get("jsm-island").then(($islands) => {
+        // get unique "data-bundle" values from all islands elements
+        const bundles = new Set($islands.get().map((el) => el.getAttribute("data-bundle")));
+        expect(bundles.size).to.eq(2);
+        expect(bundles).to.contain("javascript-modules-engine-test-module");
+        expect(bundles).to.contain("hydrogen");
+      });
+
+      // make sure the translations are rendered client-side
+      cy.get(
+        'jsm-island[data-bundle="javascript-modules-engine-test-module"] [data-testid="i18n-simple"]',
+      ).should("contain", testData.translations.en.simple);
+      cy.get('jsm-island[data-bundle="hydrogen"] [data-testid="i18n-client-only"]').should(
+        "contain",
+        "Rendered client-side only", // the translated content
+      );
+    });
+
+    cy.logout();
+
+    deleteSite(siteKey);
   });
 });