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Typescript: error when using multiple fallback key and at least one key is valid #2183

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lpproulx opened this issue May 10, 2024 · 2 comments
Closed

Typescript: error when using multiple fallback key and at least one key is valid #2183

lpproulx opened this issue May 10, 2024 · 2 comments
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@marcalexiei
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typescript working as expected/designed

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@lpproulx
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lpproulx commented May 10, 2024 •
edited
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🐛 Bug Report

Maybe there is something i'm doing wrong or i don't understand correctly but i was expecting typescript to not give an error when there is at least one valid key that it can fallback to.

To Reproduce

import i18n from 'i18next';
import { initReactI18next } from 'react-i18next';

export const defaultNS = 'common';
export const resources = {
  en: {
    common: {
      error: {
        unspecific: 'Unknown error',
        existingError: 'Something went wrong',
      },
    },
  },
} as const;

i18n.use(initReactI18next).init({
  defaultNS,
  resources,
  lng: 'en',
});

const existingError = 'existingError';
const nonExistingError = 'otherError';

i18n.t([`common:error.${existingError}`, 'common:error.unspecific']);
// Typescript error here
i18n.t([`common:error.${nonExistingError}`, 'common:error.unspecific']);
import 'react-i18next';
import { defaultNS, resources } from '../locales';

declare module 'i18next' {
  interface CustomTypeOptions {
    defaultNS: typeof defaultNS;
    resources: (typeof resources)['en'];
  }
}
Argument of type '[("common:error.unspecific" | "common:error.otherError")[]]' is not assignable to parameter of type '[key: string | string[], options: TOptionsBase & $Dictionary & { defaultValue: string; }] | [key: string | string[], defaultValue: string, options?: (TOptionsBase & $Dictionary) | undefined] | [key: ...]'.
  Type '[("common:error.unspecific" | "common:error.otherError")[]]' is not assignable to type '[key: TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific" | (TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific")[], options?: (TOptionsBase & $Dictionary) | undefined]'.
    Type at position 0 in source is not compatible with type at position 0 in target.
      Type '("common:error.unspecific" | "common:error.otherError")[]' is not assignable to type 'TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific" | (TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific")[]'.
        Type '("common:error.unspecific" | "common:error.otherError")[]' is not assignable to type '(TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific")[]'.
          Type '"common:error.unspecific" | "common:error.otherError"' is not assignable to type 'TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific"'.
            Type '"common:error.otherError"' is not assignable to type 'TemplateStringsArray | "error.existingError" | "error.unspecific" | "common:error.existingError" | "common:error.unspecific"'.ts(2345)

Expected behavior

There is no typescript error when there is at least 1 valid key

Your Environment

  • runtime version: node 20.11.1
  • i18next version: 23.11.2
  • os: Windows
  • typescript: 5.4.5
@marcalexiei
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This is the expected behaviour: all keys are type checked. If you need to provide a fallback use defaultValue option: https://www.i18next.com/translation-function/essentials#overview-options

@lpproulx
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lpproulx commented May 13, 2024 •
edited
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Thanks. I tried this way early on but i was using the key as a defaultValue and it was not working, but you made me realize that i can do

i18n.t([`common:error.${nonExistingError}`, 'anyOtherPossiblyWrongKey'], { defaultValue: i18n.t( 'common:error.unspecific') });
or this way in my case
i18n.t(`common:error.${nonExistingError}`, { defaultValue: i18n.t( 'common:error.unspecific') });

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@adrai @lpproulx @marcalexiei