fix(datepicker): not revalidating after value is changed through the calendar

src/material/datepicker/datepicker-input-base.ts

@@ -71,7 +71,7 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
   }
   set value(value: D | null) {
     value = this._dateAdapter.deserialize(value);
-    this._lastValueValid = !value || this._dateAdapter.isValid(value);
+    this._lastValueValid = this._isValidValue(value);
     value = this._getValidDateOrNull(value);
     const oldDate = this.value;
     this._assignValue(value);
@@ -194,6 +194,7 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
     this._valueChangesSubscription = this._model.selectionChanged.subscribe(event => {
       if (event.source !== this) {
         const value = this._getValueFromModel(event.selection);
+        this._lastValueValid = this._isValidValue(value);
         this._cvaOnChange(value);
         this._onTouched();
         this._formatValue(value);
@@ -298,7 +299,7 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
   _onInput(value: string) {
     const lastValueWasValid = this._lastValueValid;
     let date = this._dateAdapter.parse(value, this._dateFormats.parse.dateInput);
-    this._lastValueValid = !date || this._dateAdapter.isValid(date);
+    this._lastValueValid = this._isValidValue(date);
     date = this._getValidDateOrNull(date);
 
     if (!this._dateAdapter.sameDate(date, this.value)) {
@@ -351,6 +352,11 @@ export abstract class MatDatepickerInputBase<S, D = ExtractDateTypeFromSelection
     }
   }
 
+  /** Whether a value is considered valid. */
+  private _isValidValue(value: D | null): boolean {
+    return !value || this._dateAdapter.isValid(value);
+  }
+
   /**
    * Checks whether a parent control is disabled. This is in place so that it can be overridden
    * by inputs extending this one which can be placed inside of a group that can be disabled.

src/material/datepicker/datepicker.spec.ts

@@ -1241,6 +1241,12 @@ describe('MatDatepicker', () => {
         testComponent = fixture.componentInstance;
       }));
 
+      function revalidate() {
+        fixture.detectChanges();
+        flush();
+        fixture.detectChanges();
+      }
+
       afterEach(fakeAsync(() => {
         testComponent.datepicker.close();
         fixture.detectChanges();
@@ -1253,50 +1259,39 @@ describe('MatDatepicker', () => {
 
       it('should mark invalid when value is before min', fakeAsync(() => {
         testComponent.date = new Date(2009, DEC, 31);
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        revalidate();
 
         expect(fixture.debugElement.query(By.css('input'))!.nativeElement.classList)
             .toContain('ng-invalid');
       }));
 
       it('should mark invalid when value is after max', fakeAsync(() => {
         testComponent.date = new Date(2020, JAN, 2);
-        fixture.detectChanges();
-        flush();
-
-        fixture.detectChanges();
+        revalidate();
 
         expect(fixture.debugElement.query(By.css('input'))!.nativeElement.classList)
             .toContain('ng-invalid');
       }));
 
       it('should not mark invalid when value equals min', fakeAsync(() => {
         testComponent.date = testComponent.datepicker._minDate;
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        revalidate();
 
         expect(fixture.debugElement.query(By.css('input'))!.nativeElement.classList)
             .not.toContain('ng-invalid');
       }));
 
       it('should not mark invalid when value equals max', fakeAsync(() => {
         testComponent.date = testComponent.datepicker._maxDate;
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        revalidate();
 
         expect(fixture.debugElement.query(By.css('input'))!.nativeElement.classList)
             .not.toContain('ng-invalid');
       }));
 
       it('should not mark invalid when value is between min and max', fakeAsync(() => {
         testComponent.date = new Date(2010, JAN, 2);
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        revalidate();
 
         expect(fixture.debugElement.query(By.css('input'))!.nativeElement.classList)
             .not.toContain('ng-invalid');
@@ -1306,31 +1301,49 @@ describe('MatDatepicker', () => {
         const inputEl = fixture.debugElement.query(By.css('input'))!.nativeElement;
         inputEl.value = '';
         dispatchFakeEvent(inputEl, 'input');
-
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        revalidate();
 
         expect(testComponent.model.valid).toBe(true);
 
         inputEl.value = 'abcdefg';
         dispatchFakeEvent(inputEl, 'input');
-
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        revalidate();
 
         expect(testComponent.model.valid).toBe(false);
 
         inputEl.value = '';
         dispatchFakeEvent(inputEl, 'input');
+        revalidate();
 
-        fixture.detectChanges();
-        flush();
-        fixture.detectChanges();
+        expect(testComponent.model.valid).toBe(true);
+      }));
+
+      it('should update validity when a value is assigned', fakeAsync(() => {
+        const inputEl = fixture.debugElement.query(By.css('input'))!.nativeElement;
+        inputEl.value = '';
+        dispatchFakeEvent(inputEl, 'input');
+        revalidate();
+
+        expect(testComponent.model.valid).toBe(true);
+
+        inputEl.value = 'abcdefg';
+        dispatchFakeEvent(inputEl, 'input');
+        revalidate();
+
+        expect(testComponent.model.valid).toBe(false);
+
+        const validDate = new Date(2010, JAN, 2);
+
+        // Assigning through the selection model simulates the user doing it via the calendar.
+        const model = fixture.debugElement.query(By.directive(MatDatepicker))
+            .injector.get<MatDateSelectionModel<Date>>(MatDateSelectionModel);
+        model.updateSelection(validDate, null);
+        revalidate();
 
         expect(testComponent.model.valid).toBe(true);
+        expect(testComponent.date).toBe(validDate);
       }));
+
     });
 
     describe('datepicker with filter and validation', () => {