fix(datepicker): multiple dialog open if the user holds down enter key

src/lib/datepicker/datepicker.spec.ts

@@ -8,7 +8,7 @@ import {
   dispatchMouseEvent,
 } from '@angular/cdk/testing';
 import {Component, FactoryProvider, Type, ValueProvider, ViewChild} from '@angular/core';
-import {ComponentFixture, fakeAsync, flush, inject, TestBed} from '@angular/core/testing';
+import {ComponentFixture, fakeAsync, flush, inject, TestBed, tick} from '@angular/core/testing';
 import {FormControl, FormsModule, ReactiveFormsModule} from '@angular/forms';
 import {
   DEC,
@@ -102,7 +102,7 @@ describe('MatDatepicker', () => {
         expect(document.querySelector('.cdk-overlay-pane.mat-datepicker-popup')).not.toBeNull();
       });
 
-      it('open touch should open dialog', () => {
+      it('touch should open dialog', () => {
         testComponent.touch = true;
         fixture.detectChanges();
 
@@ -115,6 +115,28 @@ describe('MatDatepicker', () => {
             .not.toBeNull();
       });
 
+      it('should not be able to open more than one dialog', fakeAsync(() => {
+        testComponent.touch = true;
+        fixture.detectChanges();
+
+        expect(document.querySelectorAll('.mat-datepicker-dialog').length).toBe(0);
+
+        testComponent.datepicker.open();
+        fixture.detectChanges();
+        tick(500);
+        fixture.detectChanges();
+
+        dispatchKeyboardEvent(document.querySelector('.mat-calendar-body')!, 'keydown', ENTER);
+        fixture.detectChanges();
+        tick(100);
+
+        testComponent.datepicker.open();
+        tick(500);
+        fixture.detectChanges();
+
+        expect(document.querySelectorAll('.mat-datepicker-dialog').length).toBe(1);
+      }));
+
       it('should open datepicker if opened input is set to true', fakeAsync(() => {
         testComponent.opened = true;
         fixture.detectChanges();

src/lib/datepicker/datepicker.ts

@@ -380,6 +380,14 @@ export class MatDatepicker<D> implements OnDestroy, CanColor {
 
   /** Open the calendar as a dialog. */
   private _openAsDialog(): void {
+    // Usually this would be handled by `open` which ensures that we can only have one overlay
+    // open at a time, however since we reset the variables in async handlers some overlays
+    // may slip through if the user opens and closes multiple times in quick succession (e.g.
+    // by holding down the enter key).
+    if (this._dialogRef) {
+      this._dialogRef.close();
+    }
+
     this._dialogRef = this._dialog.open<MatDatepickerContent<D>>(MatDatepickerContent, {
       direction: this._dir ? this._dir.value : 'ltr',
       viewContainerRef: this._viewContainerRef,