Custom Decorator Message

[jerradpatch]

Do custom validators not support a default message?

[pleerock]

there is an option called dismissDefaultMessages you can specify into your validate method:

validator.validate(model, { dismissDefaultMessages: true })

[jerradpatch]

gottcha. but what I was looking for was how to specify a default message in a custom validator. for example

export function IsLongerThan(property: string, validationOptions?: ValidationOptions) {
   return function (object: Object, propertyName: string) {
        registerDecorator({
            name: "isLongerThan",
            target: object.constructor,
            propertyName: propertyName,
            options: validationOptions,
            message: "here is the defualt message when 'message is not defined on the annotation itself'"
            validator: {
                validate(value: any, args: ValidationArguments) {
                   const [relatedPropertyName] = args.constraints;
                    const relatedValue = (args.object as any)[relatedPropertyName];
                    return  typeof value === "string" &&
                           typeof relatedValue === "string" &&
                           value.length > relatedValue.length; // you can return a Promise<boolean> here as well, if you want to make async validation
                }
            }
        });
   };
}

The use case would be if I have an annotation for validating 1 < X < 10, I can say in the custom annotation definition "value must be between 1 and 10" instead of having to repeat the text in the annotation decorator.

ie

@IsLongerThan("title", {
       message: "Text must be longer than the title"
    })

[patrickhousley]

@jerradpatch I just ran into this and was able to solve it by using a class validator as described here. Below is an example. If you would like to use just a decorator, then I assume the object you pass to validator just needs the defaultMessage(args: ValidationArguments) method implemented.

import { registerDecorator, ValidatorConstraint, ValidatorConstraintInterface, ValidationOptions, ValidationArguments } from 'class-validator';

@ValidatorConstraint({ name: 'matchesProperty', async: false })
export class MatchesPropertyConstraint implements ValidatorConstraintInterface {

    public validate(value: string, args: ValidationArguments) {
      const [relatedPropertyName] = args.constraints;
      const relatedValue = (args.object as any)[relatedPropertyName];
      return typeof value === typeof relatedValue &&
        value === relatedValue;
    }

    public defaultMessage(args: ValidationArguments) { // Set the default error message here
      const [relatedPropertyName] = args.constraints;
      return `$property must match ${relatedPropertyName} exactly`;
    }

}

export function MatchesProperty(property: string, validationOptions?: ValidationOptions) {
  return (object: Object, propertyName: string) => {
    registerDecorator({
      name: 'matchesProperty',
      target: object.constructor,
      propertyName,
      constraints: [property],
      options: validationOptions,
      validator: MatchesPropertyConstraint
    });
  };
}

[NoNameProvided]

I am going to close this as @patrickhousley already showed the correct solution.