Add option to write invalid $modelValues to scope

[Narretz]

Since the validation refactoring, theoretically all invalid models appear in the input even if invalid. It's however not possible to write an invalid $modelValue to the scope. The $validators now actively set $modelValue to undefined when it is invalid, meaning that users cannot use the previous workarounds for this behavior. They now only have $$invalidModelValue to get the raw value, but that is undocumented and quasi-private. Additionally, with $validators, it is not possible anymore to use a $parser to set the model even if invalid (another common workaround)

I propose we use ng-model-options to make it possible to write the parsed $modelValue to scope even if invalid.

Why is this needed?

1. Server-side validation with using $setValidity manually is broken (see $setValidity somehow breaks model binding in 1.3.0 Beta 12 and after #8080 (comment))
2. Keeping input regardless of validity (see input not showing invalid model values #1412 (comment))
3. Displaying invalid models (from DB etc.): It currently displays the invalid model in the input, but at the same time resets the model to undefined (see http://plnkr.co/edit/Fapn7ePUhajjGNsjwIlg?p=preview)
4. All common workarounds for this are broken in 1.3

/cc @matsko @shahata @petebacondarwin @caitp

[shahata]

I'll take a stab at this

[leefernandes]

+1

logic using invalidated $modelValues is broken: http://codepen.io/ItsLeeOwen/pen/BcjDI

[pocesar]

just happened, I'm validating stuff server side, and when the user resubmit the form, it's gone, then the input becomes marked with required (since no data was sent to the server), even if I reset the validity state

• I'm using required, minlength and "name" (custom validation state).
• I set name manually using $setValidity from the server.
• The field becomes $error = {required: false, minlength:false, name: true}
• On model update on $watch, I reset name to false
• $modelValue is now undefined on form submission
• Server returns required: true, name: true, becomes an "endless client-server" loop

[leefernandes]

Why can't or won't angular 1.3.x return to the days when invalid $modelValues were not undefined?

http://codepen.io/ItsLeeOwen/pen/DuJhg

[petebacondarwin]

@itsleeowen - this was never the case with builtin validators: http://codepen.io/anon/pen/jykGi

[leefernandes]

@petebacondarwin I don't know whether the change in behavior has anything to do with validators, I suspect a change to ngModel.$setValidity because in this comparison between 1.2.x - 1.3.x I'm not using $validators, and only end up with undefined $modelValues in the 1.3.x branch.

1.2.21: http://codepen.io/ItsLeeOwen/pen/EfwKC

1.3.x http://codepen.io/ItsLeeOwen/pen/CwALx