An Angular directive for nested forms that prevents $invalid from propagating, allowing a nested form to be invalid without affecting its parent's validity.
Code originally written by 91K00, as seen here and here.
Usage:
<form name="parent">
<input type="text" ng-model="outside"/>
<ng-form name="subform" isolate-form>
<input type="text" ng-model="inside"/>
</ng-form>
</form>
Example: http://jsfiddle.net/gikoo/qNrFX/