feat(forms): introduce the control.hasError helper method

Author: matsko

lib/directive/ng_control.dart

@@ -49,6 +49,8 @@ abstract class NgControl implements NgDetachAware {
     untouched = true;
   }
 
+  bool hasError(String key) => errors.containsKey(key);
+
   _onSubmit(bool valid) {
     if (valid) {
       _submit_valid = true;
@@ -241,5 +243,6 @@ class NgNullControl implements NgControl {
 
   reset() => null;
   detach() => null;
+  bool hasError(String key) => false;
 
 }

test/directive/ng_form_spec.dart

@@ -342,6 +342,32 @@ void main() {
       }));
     });
 
+    describe('error handling', () {
+      it('should return true or false depending on if an error exists on a form',
+        inject((Scope scope, TestBed _) {
+
+        var element = $('<form name="myForm">'
+                        '  <input type="text" ng-model="input" name="input" />' +
+                        '</form>');
+
+        _.compile(element);
+        scope.apply();
+
+        var form = scope.context['myForm'];
+        NgModel input = form['input'];
+
+        expect(form.hasError('big-failure')).toBe(false);
+
+        form.updateControlValidity(input, "big-failure", false);
+
+        expect(form.hasError('big-failure')).toBe(true);
+
+        form.updateControlValidity(input, "big-failure", true);
+
+        expect(form.hasError('big-failure')).toBe(false);
+      }));
+    });
+
     describe('reset()', () {
       it('should reset the model value to its original state', inject((TestBed _) {
         _.compile('<form name="superForm">' +

test/directive/ng_model_spec.dart

@@ -981,6 +981,30 @@ void main() {
       }));
     });
 
+    describe('error handling', () {
+      it('should return true or false depending on if an error exists on a form',
+        inject((Scope scope, TestBed _) {
+
+        var element = $('<input type="text" ng-model="input" name="input" probe="i" />');
+
+        _.compile(element);
+        scope.apply();
+
+        Probe p = scope.context['i'];
+        NgModel model = p.directive(NgModel);
+
+        expect(model.hasError('big-failure')).toBe(false);
+
+        model.setValidity("big-failure", false);
+
+        expect(model.hasError('big-failure')).toBe(true);
+
+        model.setValidity("big-failure", true);
+
+        expect(model.hasError('big-failure')).toBe(false);
+      }));
+    });
+
     describe('text-like events', () {
       it('should update the binding on the "input" event', inject(() {
         _.compile('<input type="text" ng-model="model" probe="p">');