feat(input): support dynamic element validation

Interpolates the form controll attribute name, so that dynamic form controls (such as those rendered
in an ngRepeat) will always have their expected interpolated name.

Closes #4791

Author: caitp

src/ng/directive/input.js

@@ -1657,8 +1657,8 @@ var VALID_CLASS = 'ng-valid',
  *
  *
  */
-var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$parse', '$animate', '$timeout', '$rootScope', '$q',
-    function($scope, $exceptionHandler, $attr, $element, $parse, $animate, $timeout, $rootScope, $q) {
+var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$parse', '$animate', '$timeout', '$rootScope', '$q', '$interpolate',
+    function($scope, $exceptionHandler, $attr, $element, $parse, $animate, $timeout, $rootScope, $q, $interpolate) {
   this.$viewValue = Number.NaN;
   this.$modelValue = Number.NaN;
   this.$validators = {};
@@ -1675,7 +1675,7 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
   this.$error = {}; // keep invalid keys here
   this.$$success = {}; // keep valid keys here
   this.$pending = undefined; // keep pending keys here
-  this.$name = $attr.name;
+  this.$name = $interpolate($attr.name || '', false)($scope);
 
 
   var parsedNgModel = $parse($attr.ngModel),

test/ng/directive/inputSpec.js

@@ -1289,6 +1289,34 @@ describe('input', function() {
     }
   }));
 
+
+  it('should interpolate input names (string)', function() {
+    scope.nameID = '47';
+    compileInput('<input type="text" ng-model="name" name="name{{nameID}}" />');
+    expect(scope.form.name47.$pristine).toBeTruthy();
+    changeInputValueTo('caitp');
+    expect(scope.form.name47.$dirty).toBeTruthy();
+  });
+
+
+  it('should interpolate input names (number)', function() {
+    scope.nameID = 47;
+    compileInput('<input type="text" ng-model="name" name="name{{nameID}}" />');
+    expect(scope.form.name47.$pristine).toBeTruthy();
+    changeInputValueTo('caitp');
+    expect(scope.form.name47.$dirty).toBeTruthy();
+  });
+
+
+  it('should interpolate input names (undefined)', function() {
+    scope.nameID = undefined;
+    compileInput('<input type="text" ng-model="name" name="name{{nameID}}" />');
+    expect(scope.form.name.$pristine).toBeTruthy();
+    changeInputValueTo('caitp');
+    expect(scope.form.name.$dirty).toBeTruthy();
+  });
+
+
   describe('"change" event', function() {
     function assertBrowserSupportsChangeEvent(inputEventSupported) {
       // Force browser to report a lack of an 'input' event