fix(ngModel): ensure that string-based inputs always provide string values to parsers

lib/directive/ng_model.dart

@@ -40,6 +40,8 @@ class NgModel extends NgControl implements AttachAware {
   Watch _watch;
   bool _watchCollection;
 
+  bool stringBasedInput = false;
+
   NgModel(this._scope, NgElement element, DirectiveInjector injector, NodeAttrs attrs,
           Animate animate, ElementProbe probe)
       : super(element, injector, animate)
@@ -196,13 +198,22 @@ class NgModel extends NgControl implements AttachAware {
 
   get viewValue => _viewValue;
   void set viewValue(value) {
+    if (stringBasedInput && value != null) {
+      // string-based input types will always deal with string-based values.
+      // Therefore there is no reason to allow other types to be set
+      // as the view value
+      value = value.toString();
+    }
     _viewValue = value;
     modelValue = value;
   }
 
   get modelValue => _modelValue;
   void set modelValue(value) {
     try {
+      if (stringBasedInput && value != null) {
+        value = value.toString();
+      }
       value = converter.parse(value);
     } catch(e) {
       value = null;
@@ -364,6 +375,7 @@ class InputTextLike {
   }
 
   InputTextLike(this.inputElement, this.ngModel, this.scope, this.ngModelOptions) {
+    ngModel.stringBasedInput = true;
     ngModel.render = (value) {
       scope.rootScope.domWrite(() {
         if (value == null) value = '';
@@ -824,7 +836,9 @@ class InputRadio {
 @Decorator(selector: '[contenteditable][ng-model]')
 class ContentEditable extends InputTextLike {
   ContentEditable(dom.Element inputElement, NgModel ngModel, Scope scope, NgModelOptions modelOptions)
-      : super(inputElement, ngModel, scope, modelOptions);
+      : super(inputElement, ngModel, scope, modelOptions) {
+    ngModel.stringBasedInput = true;
+  }
 
   // The implementation is identical to InputTextLike but use innerHtml instead of value
   String get typedValue => (inputElement as dynamic).innerHtml;

test/directive/ng_model_spec.dart

@@ -1583,6 +1583,39 @@ void main() {
         expect(model.viewValue).toEqual('iee');
         expect(model.modelValue).toEqual('hi there');
       });
+
+      it('should always provide the parser input as a string for string-based inputs', (Scope scope) {
+        _.compile('<input type="text" ng-model="model" probe="i">');
+        scope.apply();
+
+        var probe = scope.context['i'];
+        var input = probe.element;
+        var model = probe.directive(NgModel);
+
+        model.converter = new StringAssertConverter();
+        model.viewValue = new Date();
+        _.rootScope.apply();
+
+        expect(model.converter.isParsedString).toBe(true);
+      });
+
+      it('should always render the initial value as a string for string-based inputs', (Scope scope) {
+        scope.context['model'] = new Date();
+
+        _.compile('<input type="text" ng-model="model" probe="i">');
+        scope.apply();
+
+        var probe = scope.context['i'];
+        var input = probe.element;
+        var model = probe.directive(NgModel);
+
+        model.converter = new StringAssertConverter();
+        _.rootScope.apply();
+
+        model.reset();
+        _.rootScope.apply();
+        expect(model.converter.isParsedString).toBe(true);
+      });
     });
   });
 }
@@ -1593,6 +1626,17 @@ void main() {
 class ComponentWithNoLove {
 }
 
+class StringAssertConverter implements NgModelConverter {
+  final name = 'stringAssert';
+  bool isParsedString = false;
+
+  format(value) => value;
+  parse(value) {
+    isParsedString = !!(value is String);
+    return value;
+  }
+}
+
 class LowercaseValueParser implements NgModelConverter {
   final name = 'lowercase';
   format(value) => value;