Not existing context not detected as type error if covered by string union

Author: stefan-schweigerCreated Apr 12, 2024Updated Mar 27, 2026

Labelshelp wantedtypescript

Bug Report

I was told to move this issue here from the https://github.com/i18next/react-i18next/issues/1743 repo.

When you use a string union as the context parameter it's possible to supply values for which a context does not exist and it does not result in an error. If you just use the plain string value or a const it works.

To Reproduce

A minimal reproducible example.

json

{
  "translation": {
    "testContext1_Test1": "EN: Context1 Test1",
    "testContext1_Test2": "EN: Context1 Test2",
  },
}

javascript

const App = () => {
  const { t } = useTranslation('translation');

  return (
    <div>
      <p>
        {t('testContext1', { context: 'Test1' as 'Test1' | 'Test2' | 'Test3' })}
      </p>
      <p>{t('testContext1', { context: 'Test2' })}</p>
      <p>{t('testContext1', { context: 'Test2' as const })}</p>
      <p>
        {t('testContext1', { context: 'Test3' as 'Test1' | 'Test2' | 'Test3' })}
      </p>
      {/* Error: Type '{ context: "Test3"; }' is not assignable to type 'string' */}
      <p>{t('testContext1', { context: 'Test3' })}</p>
      {/* Error: Type '{ context: "Test3"; }' is not assignable to type 'string' */}
      <p>{t('testContext1', { context: 'Test3' as const })}</p>
    </div>
  );
};

Expected behavior

String unions should be correctly detected as errors if they have cases which are not covered by the context.

Your Environment

i18next version: 23.11.1

Source: i18next/i18next

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