Feature Request: @Default Annotation

Currently it is very unhandy to set a default value for properties in case of a validation failure. You have to evaluate the ValidationError and set the default value on your own. It would be nice to have a new annotation, something like @Default(‘en-GB’), which allows the user to set a default value.

Instead of

@IsNotEmpty()
locale: string;

const localeErrors = validationErrors.find(error => error.property === 'locale');
if (localeErrors) {
    initialQueryParameters.locale = 'en-GB';
}

you could simply write

@Default('en-GB')
@IsNotEmpty()
locale: string;

which sets a default value in case of an ocuring error.

[driescroons]

For those interested; this is the decorator I quickly threw together using the Transform function.

import { Transform } from 'class-transformer';

const defaultValueDecorator = (defaultValue: any) => {
  return Transform((target: any) => target || defaultValue);
};

export default defaultValueDecorator;

Example form my paginationQueryValidator (for lists)

@Exclude()
class PaginationQueryValidator {
  @Expose()
  @numeric()
  @defaultValueDecorator(0)
  public offset: number;

  @Expose()
  @numeric()
  @defaultValueDecorator(20)
  public limit: number;
}

export default PaginationQueryValidator;

[lock[bot]]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a new issue for related bugs.