feat(ngModel) Allow running the formatters without a change to the modelValue

Fixes #3407

Author: realityking

src/ng/directive/ngModel.js

@@ -799,6 +799,36 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
     }
   };
 
+  function formatValue(modelValue) {
+    var formatters = ctrl.$formatters,
+        idx = formatters.length;
+
+    var viewValue = modelValue;
+    while (idx--) {
+      viewValue = formatters[idx](viewValue);
+    }
+
+    return viewValue;
+  }
+
+  /**
+   * @ngdoc method
+   * @name ngModel.NgModelController#$setModelValue
+   *
+   */
+  this.$setModelValue = function(modelValue) {
+    ctrl.$modelValue = ctrl.$$rawModelValue = modelValue;
+
+    var viewValue = formatValue(this.$modelValue);
+
+    if (this.$viewValue !== viewValue) {
+      this.$viewValue = ctrl.$$lastCommittedViewValue = viewValue;
+      this.$render();
+
+      ctrl.$$runValidators(undefined, modelValue, ctrl.$viewValue, noop);
+    }
+  };
+
   // model -> value
   // Note: we cannot use a normal scope.$watch as we want to detect the following:
   // 1. scope value is 'a'
@@ -813,21 +843,7 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
     // if scope model value and ngModel value are out of sync
     // TODO(perf): why not move this to the action fn?
     if (modelValue !== ctrl.$modelValue) {
-      ctrl.$modelValue = ctrl.$$rawModelValue = modelValue;
-
-      var formatters = ctrl.$formatters,
-          idx = formatters.length;
-
-      var viewValue = modelValue;
-      while (idx--) {
-        viewValue = formatters[idx](viewValue);
-      }
-      if (ctrl.$viewValue !== viewValue) {
-        ctrl.$viewValue = ctrl.$$lastCommittedViewValue = viewValue;
-        ctrl.$render();
-
-        ctrl.$$runValidators(undefined, modelValue, viewValue, noop);
-      }
+      ctrl.$setModelValue(modelValue);
     }
 
     return modelValue;

test/ng/directive/ngModelSpec.js

@@ -455,6 +455,28 @@ describe('ngModel', function() {
     });
 
 
+    describe('$setModelValue', function() {
+
+      it('should set the value to $modelValue', function() {
+        ctrl.$setModelValue(10);
+        expect(ctrl.$modelValue).toBe(10);
+      });
+
+      it('should $render only if value changed', function() {
+        spyOn(ctrl, '$render');
+
+        ctrl.$setModelValue(3);
+        expect(ctrl.$render).toHaveBeenCalledOnce();
+        ctrl.$render.reset();
+
+        ctrl.$formatters.push(function() {return 3;});
+        ctrl.$setModelValue(5);
+        expect(ctrl.$render).not.toHaveBeenCalled();
+      });
+
+    });
+
+
     describe('model -> view', function() {
 
       it('should set the value to $modelValue', function() {