New features to improve support for instance-level validation

[dkent600]

I'm submitting a feature request

• Library Version:
  0.12.5
• Browser:
  any
• Language:
  Typescript 2.0

Current behavior:
Aurelia-Validation has some great features for validating both properties and whole instances. The property-level features seem to be more fleshed-out than the instance-level features. I am developing an application that uses instance-level validation, and would like to propose some new features that will facilitate the use of instance-level validation, and provide more flexibility to the aurelia-validation framework in general.

Feature Requests:

1. Add the ability to detect when validation state has changed on a specific instance (and specific properties, for that matter). I am currently observing controller.validator.validationMessages.length, but that feels like a hack and doesn't provide any easy information about what changed (property or instance).

Possible solutions: Add callback methods in the ValidationController or its Validator? Publish an event?

2. Add the ability to associate multiple propertyNames with a Rule.

Possible solutions: Add a parameter propertyNames to satisfies(instance, propertyNames?: string[]) and change ValidationError.propertyName:string to ValidationError.propertyName: string | Array<string> (or have it always be an array). (Also change the name of the property to be plural?)

3. Add the ability to facilitate instance-level validation through bindings.

Possible solutions: Create a new binding like validation-errors called validation-object-errors for instance-level (rather than property-level) validation. This new binding would change behavior of the inner validate binding by causing whole object to be validated on each property change (rather than a single property). In the ValidationRenderer, RenderInstruction.object.elements would be filled-in with elements corresponding to all of the propertyNames on all the rules that fail. (Change # 2, above, comes in handy here).

[jdanyow]

@dkent600 nice writeup. Thank you for the feedback. I'd like to split this issue up because we have a couple issues open for some of these items.

For item 1, could you review #318 and add any thoughts you have there.

For item 2, could you review #279 and add your scenario and thoughts.

Finally, please open a new issue for the third item, it's not being tracked anywhere yet and sounds like a good idea.

thanks!

[dkent600]

@jdanyow Phew, done. See #351