fix(forms): handle control change in NgFormControl

when a new Control instance is bound to the directive, use the new instance, not the old one

modules/angular2/src/core/forms/directives/ng_form_control.ts

@@ -8,7 +8,7 @@ import {NgControl} from './ng_control';
 import {Control} from '../model';
 import {Validators, NG_VALIDATORS} from '../validators';
 import {ControlValueAccessor, NG_VALUE_ACCESSOR} from './control_value_accessor';
-import {setUpControl, isPropertyUpdated, selectValueAccessor} from './shared';
+import {setUpControl, isPropertyUpdated, isControlChanged, selectValueAccessor} from './shared';
 
 const formControlBinding =
     CONST_EXPR(new Provider(NgControl, {useExisting: forwardRef(() => NgFormControl)}));
@@ -70,8 +70,6 @@ const formControlBinding =
 export class NgFormControl extends NgControl implements OnChanges {
   form: Control;
   update = new EventEmitter();
-  /** @internal */
-  _added = false;
   model: any;
   viewModel: any;
   validators: Function[];
@@ -84,10 +82,9 @@ export class NgFormControl extends NgControl implements OnChanges {
   }
 
   onChanges(changes: {[key: string]: SimpleChange}): void {
-    if (!this._added) {
+    if (isControlChanged(changes)) {
       setUpControl(this.form, this);
       this.form.updateValidity();
-      this._added = true;
     }
     if (isPropertyUpdated(changes, this.viewModel)) {
       this.form.updateValue(this.model);

modules/angular2/src/core/forms/directives/shared.ts

@@ -60,6 +60,12 @@ export function isPropertyUpdated(changes: {[key: string]: any}, viewModel: any)
   return !looseIdentical(viewModel, change.currentValue);
 }
 
+export function isControlChanged(changes: {[key: string]: any}): boolean {
+  if (!StringMapWrapper.contains(changes, "form")) return false;
+  var change = changes["form"];
+  return change.previousValue !== change.currentValue;
+}
+
 // TODO: vsavkin remove it once https://github.com/angular/angular/issues/3011 is implemented
 export function selectValueAccessor(dir: NgControl, valueAccessors: ControlValueAccessor[]):
     ControlValueAccessor {

modules/angular2/test/core/forms/directives_spec.ts

@@ -38,6 +38,7 @@ import {
 
 import {selectValueAccessor} from 'angular2/src/core/forms/directives/shared';
 
+import {SimpleChange} from 'angular2/src/core/change_detection';
 
 class DummyControlValueAccessor implements ControlValueAccessor {
   writtenValue;
@@ -275,6 +276,16 @@ export function main() {
     describe("NgFormControl", () => {
       var controlDir;
       var control;
+      var checkProperties = function(control) {
+        expect(controlDir.control).toBe(control);
+        expect(controlDir.value).toBe(control.value);
+        expect(controlDir.valid).toBe(control.valid);
+        expect(controlDir.errors).toBe(control.errors);
+        expect(controlDir.pristine).toBe(control.pristine);
+        expect(controlDir.dirty).toBe(control.dirty);
+        expect(controlDir.touched).toBe(control.touched);
+        expect(controlDir.untouched).toBe(control.untouched);
+      };
 
       beforeEach(() => {
         controlDir = new NgFormControl([], [defaultAccessor]);
@@ -284,15 +295,14 @@ export function main() {
         controlDir.form = control;
       });
 
-      it("should reexport control properties", () => {
-        expect(controlDir.control).toBe(control);
-        expect(controlDir.value).toBe(control.value);
-        expect(controlDir.valid).toBe(control.valid);
-        expect(controlDir.errors).toBe(control.errors);
-        expect(controlDir.pristine).toBe(control.pristine);
-        expect(controlDir.dirty).toBe(control.dirty);
-        expect(controlDir.touched).toBe(control.touched);
-        expect(controlDir.untouched).toBe(control.untouched);
+      it("should reexport control properties", () => { checkProperties(control); });
+
+      it("should reexport new control properties", () => {
+        var newControl = new Control(null);
+        controlDir.form = newControl;
+        controlDir.onChanges({"form": new SimpleChange(control, newControl)});
+
+        checkProperties(newControl);
       });
 
       it("should set up validator", () => {
@@ -301,7 +311,7 @@ export function main() {
         expect(control.valid).toBe(true);
 
         // this will add the required validator and recalculate the validity
-        controlDir.onChanges({});
+        controlDir.onChanges({"form": new SimpleChange(null, control)});
 
         expect(control.valid).toBe(false);
       });