Async validators & model passing

Currently the signature for validator interface is

export interface ValidatorInterface {
    validate(value: any): boolean;
}

This is fine for trivial validation, but more complex validation needs to be able to access the whole object, and also return promised booleans for async.

Proposed signature

export interface ValidatorInterface {
    validate(value: any, meta:ValidationMetadata): boolean | Promise<boolean>;
}

This will allow for

• context-aware validators like @IsLongerThan('propertyName'), @RequiredIf('propertyName', 'value')
• async validators like @UsernameAvailable

Notes:

• If skipMissingProperties == true then a context aware validator will fail. The passed ValidationMetadata should pass the skipMissingProperties value through so that the validator can act appropriately.
• Allowing promised validation will require a significant refactor to the Validator.validate method
  • It’s probably best to refactor everything to be promise based - wrapping all calls with Promise.resolve() will allow both promised and basic validators to run
  • validateOrThrow would need a timeout(() => throw new ValidationError()) in the promise chain so the thrown errors escape. (for backwards compatibility).
  • validate would need a call signature of validate(object: any, validatorOptions?: ValidatorOptions): Promise<ValidationErrorInterface[]>. This would have to be a breaking change.

[pleerock]

I like this idea, and think it should be here in class validator. However I need to change validator interface - all methods will be async then. It will be a breaking change. I was planning to completely refactor class validator a while ago, but didn’t had time for this. Now its look like time has come. There is one big issue in class validator right now - since it uses validator.js and mostly usable in string validations. This is annoying and not usable, and I’m planning to either switch validation framework, either add another one. I’ll plan to refactor it on the next week, and will notify what other changes Im going to do. Until that provide as much proposals as you think I should include in the library.

[pleerock]

added in 0.4.0