Trans ignores the secondary namespaces of useTranslation for a selector i18nKey #1933

🐛 Bug Report

With useTranslation(['ns1', 'ns2']), t($ => $.ns2.message) resolves since 17.0.7. <Trans t={t} i18nKey={$ => $.ns2.message} /> with the same t renders the raw key ns2.message.

17.0.7 fixed i18next/i18next#2429 "for useTranslation-based callers": the hook passes its namespace list to getFixedT as scopeNs. Trans does not get that fix:

• Trans passes ns: ns || t?.ns || … to TransWithoutContext (src/Trans.js), which calls t(key, { …, ns: namespaces }) (src/TransWithoutContext.js). t.ns holds the primary namespace only ('ns1').
• In i18next's getFixedT, an explicit ns sets explicitCallNs, so selectorOpts.ns = scopeNs is skipped. keysFromSelector then sees ['ns1'], does not treat ns2 as a namespace, and looks up ns2.message in ns1.

To Reproduce

import i18next from 'i18next'
import { renderToStaticMarkup } from 'react-dom/server'
import { I18nextProvider, initReactI18next, Trans, useTranslation } from 'react-i18next'

const i18n = i18next.createInstance()
await i18n.use(initReactI18next).init({
  lng: 'en',
  resources: { en: { ns1: { title: 'Title' }, ns2: { message: 'Hello <b>world</b>' } } },
})

const App = () => {
  const { t } = useTranslation(['ns1', 'ns2'])
  return (
    <>
      <p>{t($ => $.ns2.message)}</p>
      <p><Trans t={t} i18nKey={$ => $.ns2.message} components={{ b: <b /> }} /></p>
    </>
  )
}

console.log(renderToStaticMarkup(<I18nextProvider i18n={i18n}><App /></I18nextProvider>))

Output:

<p>Hello &lt;b&gt;world&lt;/b&gt;</p><p>ns2.message</p>

Expected behavior

Trans resolves the selector as t() does:

<p>Hello &lt;b&gt;world&lt;/b&gt;</p><p>Hello <b>world</b></p>

Each of these renders the translation today, so only the selector form without an ns prop fails:

• a string key: i18nKey="ns2:message"
• the same selector with ns={['ns1', 'ns2']}
• ns="ns2" with i18nKey={$ => $.message}

Possible fix

When Trans receives a t and no ns prop, leave ns out of the options it passes to that t, so that the fixed t applies its own ns and scopeNs. Both Trans.js (which fills ns from t.ns) and TransWithoutContext.js would need the change.

Related: i18next-cli

i18next-cli 1.74.4 follows the current Trans behavior, not t(). In the same component, it files the Trans key as ns1:ns2.message and the t() key as ns2:message. A fix here would need the extractor to follow.

Environment

• react-i18next 17.0.15
• i18next 26.4.2
• i18next-cli 1.74.4
• react / react-dom 19.3.0
• The reproduction needs no TypeScript setup. Our project uses TypeScript 7.0.2 with enableSelector: 'optimize'.