feat(ngModelOptions): add validateOn option

[shahata]

Add option to set different triggers for validation than the triggers that actually update the model. A new method $$validateViewValue was extracted from $commitViewValue which can be called when a validateOn trigger occurs. This method sets the control as dirty and runs all $parsers, but doesn't actually change the model. The idea is that many times people want to pend or debounce the updates to the model in order to prevent a lot of invocations of watchers or just simply to update their model only when a form is submitted, but they would still like their users to get feedback immediately when the view is dirty or invalid.

BREAKING CHANGE:

This commit introduces the option to run $parsers without setting the $modelValue with the result.

Closes #7016

[mary-poppins]

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[IgorMinar]

The idea is that many times people want to pend or debounce the updates to the model in order to prevent a lot of invocations of watchers or just simply to update their model only when a form is submitted, but they would still like their users to get feedback immediately when the view is dirty or invalid.

You can't render anything if you are not triggering a digest. So in this case, the system would know that the field is invalid but it couldn't do anything about it.

This is why I think this PR is flawed.

[shahata]

@IgorMinar - I must be completely missing what you meant to say. A digest always occurs after validation in the current implementation.

Here is a working example of my current implementation: http://plnkr.co/edit/iQzU78XgWP42cfGnGAtq?p=preview As you can see, this behaves as I intended - the validation errors are displayed, but the model is not updated.

Here is how it works without validateOn: http://plnkr.co/edit/cve42XuNC0ykuw8hz81S?p=preview As you can see this is not so comfortable for the user since he can see the validation error only when the model is updated (on blur/submit)

[IgorMinar]

@shahata I see what you mean. ignore my comment :-)

let me take a better look

[petebacondarwin]

This is not a high priority feature so we are going to pop it in the icebox for a bit and revisit it if people start to show an interest.

[sryzycki]

+1