fix(datepicker): input not picking up changes if datepicker is assigned after init (#12546)

src/lib/datepicker/datepicker-input.ts

@@ -9,7 +9,6 @@
 import {coerceBooleanProperty} from '@angular/cdk/coercion';
 import {DOWN_ARROW} from '@angular/cdk/keycodes';
 import {
-  AfterContentInit,
   Directive,
   ElementRef,
   EventEmitter,
@@ -92,22 +91,28 @@ export class MatDatepickerInputEvent<D> {
   },
   exportAs: 'matDatepickerInput',
 })
-export class MatDatepickerInput<D> implements AfterContentInit, ControlValueAccessor, OnDestroy,
-    Validator {
+export class MatDatepickerInput<D> implements ControlValueAccessor, OnDestroy, Validator {
   /** The datepicker that this input is associated with. */
   @Input()
   set matDatepicker(value: MatDatepicker<D>) {
-    this.registerDatepicker(value);
+    if (!value) {
+      return;
+    }
+
+    this._datepicker = value;
+    this._datepicker._registerInput(this);
+    this._datepickerSubscription.unsubscribe();
+
+    this._datepickerSubscription = this._datepicker._selectedChanged.subscribe((selected: D) => {
+      this.value = selected;
+      this._cvaOnChange(selected);
+      this._onTouched();
+      this.dateInput.emit(new MatDatepickerInputEvent(this, this._elementRef.nativeElement));
+      this.dateChange.emit(new MatDatepickerInputEvent(this, this._elementRef.nativeElement));
+    });
   }
   _datepicker: MatDatepicker<D>;
 
-  private registerDatepicker(value: MatDatepicker<D>) {
-    if (value) {
-      this._datepicker = value;
-      this._datepicker._registerInput(this);
-    }
-  }
-
   /** Function that can be used to filter out dates within the datepicker. */
   @Input()
   set matDatepickerFilter(value: (date: D | null) => boolean) {
@@ -252,18 +257,6 @@ export class MatDatepickerInput<D> implements AfterContentInit, ControlValueAcce
     });
   }
 
-  ngAfterContentInit() {
-    if (this._datepicker) {
-      this._datepickerSubscription = this._datepicker._selectedChanged.subscribe((selected: D) => {
-        this.value = selected;
-        this._cvaOnChange(selected);
-        this._onTouched();
-        this.dateInput.emit(new MatDatepickerInputEvent(this, this._elementRef.nativeElement));
-        this.dateChange.emit(new MatDatepickerInputEvent(this, this._elementRef.nativeElement));
-      });
-    }
-  }
-
   ngOnDestroy() {
     this._datepickerSubscription.unsubscribe();
     this._localeSubscription.unsubscribe();
@@ -318,7 +311,7 @@ export class MatDatepickerInput<D> implements AfterContentInit, ControlValueAcce
   }
 
   _onKeydown(event: KeyboardEvent) {
-    if (event.altKey && event.keyCode === DOWN_ARROW) {
+    if (this._datepicker && event.altKey && event.keyCode === DOWN_ARROW) {
       this._datepicker.open();
       event.preventDefault();
     }

src/lib/datepicker/datepicker.spec.ts

@@ -1,4 +1,4 @@
-import {ENTER, ESCAPE, RIGHT_ARROW, UP_ARROW} from '@angular/cdk/keycodes';
+import {ENTER, ESCAPE, RIGHT_ARROW, UP_ARROW, DOWN_ARROW} from '@angular/cdk/keycodes';
 import {Overlay, OverlayContainer, ScrollDispatcher} from '@angular/cdk/overlay';
 import {
   createKeyboardEvent,
@@ -432,15 +432,66 @@ describe('MatDatepicker', () => {
         expect(testComponent.datepicker.opened).toBe(false);
       }));
 
+      it('should open the datpeicker using ALT + DOWN_ARROW', fakeAsync(() => {
+        expect(testComponent.datepicker.opened).toBe(false);
+
+        const event = createKeyboardEvent('keydown', DOWN_ARROW);
+        Object.defineProperty(event, 'altKey', {get: () => true});
+
+        dispatchEvent(fixture.nativeElement.querySelector('input'), event);
+        fixture.detectChanges();
+        flush();
+
+        expect(testComponent.datepicker.opened).toBe(true);
+        expect(event.defaultPrevented).toBe(true);
+      }));
+
     });
 
     describe('datepicker with too many inputs', () => {
       it('should throw when multiple inputs registered', fakeAsync(() => {
-        let fixture = createComponent(MultiInputDatepicker, [MatNativeDateModule]);
+        const fixture = createComponent(MultiInputDatepicker, [MatNativeDateModule]);
         expect(() => fixture.detectChanges()).toThrow();
       }));
     });
 
+    describe('datepicker that is assigned to input at a later point', () => {
+      it('should not throw on ALT + DOWN_ARROW for input without datepicker', fakeAsync(() => {
+        const fixture = createComponent(DelayedDatepicker, [MatNativeDateModule]);
+        fixture.detectChanges();
+
+        expect(() => {
+          const event = createKeyboardEvent('keydown', DOWN_ARROW);
+          Object.defineProperty(event, 'altKey', {get: () => true});
+          dispatchEvent(fixture.nativeElement.querySelector('input'), event);
+          fixture.detectChanges();
+          flush();
+        }).not.toThrow();
+      }));
+
+      it('should handle value changes when a datepicker is assigned after init', fakeAsync(() => {
+        const fixture = createComponent(DelayedDatepicker, [MatNativeDateModule]);
+        const testComponent: DelayedDatepicker = fixture.componentInstance;
+        const toSelect = new Date(2017, JAN, 1);
+
+        fixture.detectChanges();
+
+        expect(testComponent.datepickerInput.value).toBeNull();
+        expect(testComponent.datepicker._selected).toBeNull();
+
+        testComponent.assignedDatepicker = testComponent.datepicker;
+        fixture.detectChanges();
+
+        testComponent.assignedDatepicker.select(toSelect);
+        fixture.detectChanges();
+        flush();
+        fixture.detectChanges();
+
+        expect(testComponent.datepickerInput.value).toEqual(toSelect);
+        expect(testComponent.datepicker._selected).toEqual(toSelect);
+      }));
+    });
+
     describe('datepicker with no inputs', () => {
       let fixture: ComponentFixture<NoInputDatepicker>;
       let testComponent: NoInputDatepicker;
@@ -1787,3 +1838,18 @@ class DatepickerWithCustomHeader {
   `,
 })
 class CustomHeaderForDatepicker {}
+
+
+
+@Component({
+  template: `
+    <input [matDatepicker]="assignedDatepicker" [value]="date">
+    <mat-datepicker #d [touchUi]="touch"></mat-datepicker>
+  `,
+})
+class DelayedDatepicker {
+  @ViewChild('d') datepicker: MatDatepicker<Date>;
+  @ViewChild(MatDatepickerInput) datepickerInput: MatDatepickerInput<Date>;
+  date: Date | null;
+  assignedDatepicker: MatDatepicker<Date>;
+}