fix(ngRequired): always evaluate ngRequired at least once

when ngRequired is initially false the required attribute will now be
updated properly.

Fixes: #angular#16814

src/ng/directive/validators.js

@@ -69,6 +69,7 @@ var requiredDirective = ['$parse', function($parse) {
     link: function(scope, elm, attr, ctrl) {
       if (!ctrl) return;
       var oldVal = attr.required || $parse(attr.ngRequired)(scope);
+      var evaluated = false;
 
       attr.required = true; // force truthy in case we are on non input element
 
@@ -77,9 +78,10 @@ var requiredDirective = ['$parse', function($parse) {
       };
 
       attr.$observe('required', function(val) {
-        if (oldVal !== val) {
+        if (oldVal !== val || !evaluated) {
           oldVal = val;
           ctrl.$validate();
+          evaluated = true;
         }
       });
     }

test/ng/directive/validatorsSpec.js

@@ -707,6 +707,15 @@ describe('validators', function() {
       expect(helper.validationCounter.required).toBe(1);
     });
 
+    it('should validate once when inside ngRepeat and ngRequired is false as ngRequired sets a default required flag of true', function() {
+      $rootScope.isRequired = false;
+      helper.compileInput(
+        '<div ng-repeat="input in [0]">' +
+        '<input type="text" ng-model="value" ng-required="isRequired" validation-spy="required" />' +
+        '</div>');
+
+      expect(helper.validationCounter.required).toBe(1);
+    });
 
     it('should validate only once after compilation when inside ngRepeat and ngRequired is true', function() {
       $rootScope.isRequired = true;