Angularjs: Set form to dirty on model change [Advanced]

Angularjs: Set form to dirty on model change [Advanced]

I'm having a peculiar case on my hands. I'm using the number-polyfill for
input[type="number"] in my Angular app. Now, the problem with that is that
it's doesn't take into accound Angularjs's way of handling things.
Like, if I increment/decrement the input value programatically, the
ngModel associated with the input does not get the updated value.
I've resolved that by writing a custom directive, and passing the model
into the pollyfill
angular.module('appModule').
directive('type', ['$parse', '$timeout', function($parse, $timeout) {
restrict: 'A',
require: '?ngModel',
link: function($scope, iElement, iAttrs, ngModel) {
...
if iAttrs.type is 'number'
iElement.inputNumber(ngModel) // <-- THIS LINE
...
}
}
In the polyfill code, I've modified this:
increment = function(elem) {
...
if (model != null) {
model.$setViewValue(newVal);
}
...
}
which works perfectly. Now, the problem is that even after updating the
model's value, the associated form does not become dirty. In my code, it's
not possible to pass the form as an argument into this polyfill.
I tried using model.$dirty = true, but that's not working.
Any other way?