How to add validation attributes in an angularjs directive

Question

I am trying to write an angular directive that adds validation attributes to the tag, but it doesn't seem to be working. Here is my demo. You will notice that "Is Valid" remains true if you delete the text in the second input box, but goes to false if you delete the text in the first input box.

http://plnkr.co/edit/Rr81dGOd2Zvio1cLYW8D?p=preview

Here is my directive:

angular.module('demo', [])
.directive('metaValidate', function () {
    return {
        restrict: 'A',
        link: function (scope, element, attrs) {
            element.attr("required", true);
        }
    };
});

I'm guessing I am just missing something simple.

Answer 1

All rules for validation of the form are being read in compilation phase of the form, so after making changes in a child node, you need to recompile form directive (form it's a custom directive in AngularJS). But do it only once, avoid infinite loops (your directive's 'link' function will be called again after form's compilation).

angular.module('demo', [])
.directive('metaValidate', function ($compile) {
    return {
        restrict: 'A',
        link: function (scope,element, attrs) {
          if (!element.attr('required')){
            element.attr("required", true);
            $compile(element[0].form)(scope);
          }
        }
    };
});

Working plunker: http://plnkr.co/edit/AB6extu46W4gFIHk0hIl?p=preview