fix(form): fix submit prevention

Do not prevent submit when action
attribute equals to an empty string.

Closes #3370
Closes #3776

src/ng/directive/form.js

@@ -454,7 +454,8 @@ var formDirectiveFactory = function(isNgForm) {
 
         return {
           pre: function ngFormPreLink(scope, formElement, attr, controller) {
-            if (!attr.action) {
+            // if `action` attr is not present on the form, prevent the default action (submission)
+            if (!('action' in attr)) {
               // we can't use jq events because if a form is destroyed during submission the default
               // action is not prevented. see #1238
               //

test/ng/directive/ngEventDirsSpec.js

@@ -12,10 +12,14 @@ describe('event directives', function() {
   describe('ngSubmit', function() {
 
     it('should get called on form submit', inject(function($rootScope, $compile) {
-      element = $compile('<form action="" ng-submit="submitted = true">' +
+      element = $compile('<form action="/foo" ng-submit="submitted = true">' +
         '<input type="submit"/>' +
         '</form>')($rootScope);
       $rootScope.$digest();
+
+      // prevent submit within the test harness
+      element.on('submit', function(e) { e.preventDefault(); });
+
       expect($rootScope.submitted).not.toBeDefined();
 
       browserTrigger(element.children()[0]);
@@ -29,10 +33,14 @@ describe('event directives', function() {
         }
       };
 
-      element = $compile('<form action="" ng-submit="formSubmission($event)">' +
+      element = $compile('<form action="/foo" ng-submit="formSubmission($event)">' +
         '<input type="submit"/>' +
         '</form>')($rootScope);
       $rootScope.$digest();
+
+      // prevent submit within the test harness
+      element.on('submit', function(e) { e.preventDefault(); });
+
       expect($rootScope.formSubmitted).not.toBeDefined();
 
       browserTrigger(element.children()[0]);