revert: fix(input): always pass in the model value to ctrl.$isEmpty

This commit tried to create consistency by ensuring that `$isEmpty` is not
called on both model and view values but it chose to only use `$modelValue`,
which is not actually correct.

`$isEmpty` is designed to compute whether the `$viewValue` is empty. In
practice this is the only part of the parse/format system that the
directive has control over. We can't rely on the `$modelValue` being in
any particular format since other directives can add in their own formatters
and parsers to completely change this.

(reverted from commit 3e51b84)

Author: petebacondarwin

src/ng/directive/input.js

@@ -1039,7 +1039,7 @@ function baseInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   element.on('change', listener);
 
   ctrl.$render = function() {
-    element.val(ctrl.$isEmpty(ctrl.$modelValue) ? '' : ctrl.$viewValue);
+    element.val(ctrl.$isEmpty(ctrl.$viewValue) ? '' : ctrl.$viewValue);
   };
 }
 
@@ -1274,7 +1274,8 @@ function urlInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   stringBasedInputType(ctrl);
 
   ctrl.$$parserName = 'url';
-  ctrl.$validators.url = function(value) {
+  ctrl.$validators.url = function(modelValue, viewValue) {
+    var value = modelValue || viewValue;
     return ctrl.$isEmpty(value) || URL_REGEXP.test(value);
   };
 }
@@ -1286,7 +1287,8 @@ function emailInputType(scope, element, attr, ctrl, $sniffer, $browser) {
   stringBasedInputType(ctrl);
 
   ctrl.$$parserName = 'email';
-  ctrl.$validators.email = function(value) {
+  ctrl.$validators.email = function(modelValue, viewValue) {
+    var value = modelValue || viewValue;
     return ctrl.$isEmpty(value) || EMAIL_REGEXP.test(value);
   };
 }
@@ -1340,7 +1342,7 @@ function checkboxInputType(scope, element, attr, ctrl, $sniffer, $browser, $filt
     element[0].checked = ctrl.$viewValue;
   };
 
-  // Override the standard `$isEmpty` because an empty checkbox is never equal to the trueValue
+  // Override the standard `$isEmpty` because a value of `false` means empty in a checkbox.
   ctrl.$isEmpty = function(value) {
     return value !== trueValue;
   };
@@ -1819,7 +1821,7 @@ var NgModelController = ['$scope', '$exceptionHandler', '$attrs', '$element', '$
    * default. The `checkboxInputType` directive does this because in its case a value of `false`
    * implies empty.
    *
-   * @param {*} value Model value to check.
+   * @param {*} value Reference to check.
    * @returns {boolean} True if `value` is empty.
    */
   this.$isEmpty = function(value) {
@@ -2647,8 +2649,8 @@ var requiredDirective = function() {
       if (!ctrl) return;
       attr.required = true; // force truthy in case we are on non input element
 
-      ctrl.$validators.required = function(value) {
-        return !attr.required || !ctrl.$isEmpty(value);
+      ctrl.$validators.required = function(modelValue, viewValue) {
+        return !attr.required || !ctrl.$isEmpty(viewValue);
       };
 
       attr.$observe('required', function() {
@@ -2723,7 +2725,7 @@ var minlengthDirective = function() {
         ctrl.$validate();
       });
       ctrl.$validators.minlength = function(modelValue, viewValue) {
-        return ctrl.$isEmpty(modelValue) || viewValue.length >= minlength;
+        return ctrl.$isEmpty(viewValue) || viewValue.length >= minlength;
       };
     }
   };