How to customize validation messages globally?

[chanlito]

Instead of passing custom message to each decorator.

[kanatkubash]

Maybe you could write your own function that is similar to Validator Functions definition . Then in that custom function set message and call corresponding validation function from class-validator.
Something like

var CustomMatches = (pattern: RegExp, validationOptions?: ValidationOptions) => {
    validationOptions = {};
    validationOptions.message = "Message";
    return Matches(pattern, validationOptions);
}

[NoNameProvided]

Hey, this is on my list, I will add it.

[MichalLytek]

It would be really nice and allow for i18n of the error messages. Really useful while reusing validation classes on backend (english) and on frontend (multilanguage) 😉

[mendrik]

@chanlito as work around I do it by delegating new decorators to existing ones:
export const IsRequired: Function = () => IsNotEmpty({ message: () => translate('validation.required') });

[bruno-lombardi]

@mendrik how would you create that translate decorator? Which library do you use? I see that there is nestjs-i18n, but it does not provide you that kind of validator decorator.

[josephbuchma]

@bruno-lombardi translate is not a decorator in example above, it's just a regular function that returns translated string by given key.

[adamscybot]

Trouvble is I want all the constraints back not just key code. You cant get the contraints in the error for rendering later.

[borjadev]

Any planning on the road map to add this feature? I would like to integrate i18next (i18next-express-middleware) with class-validator, but I don't know how to do this

[tmtron]

NOTE: this only works in versions < 0.12!

As a workaround, we monkey patch ValidationTypes.getMessage():

export function patchClassValidatorI18n() {
  const orig = ValidationTypes.getMessage.bind(ValidationTypes);
  ValidationTypes.getMessage = (type: string, isEach: boolean): string | ((args: ValidationArguments) => string) => {
    switch (type) {
      case ValidationTypes.IS_NOT_EMPTY:
        return i18next.t('msg.inputRequired');
      case ValidationTypes.MAX_LENGTH:
        return i18next.t('validation.inputLength.tooLong', {
          threshold: '$constraint1'
        });

      // return the original (English) message from class-validator when a type is not handled
      default:
        return orig(type, isEach);
    }
  };
}

Then call patchClassValidatorI18n at the start of your entry-point (e.g. in main.ts, test-setup.ts, ..).
We use i18next for translations, but you can simple replace i18next.t with your own custom translation function.