feat(material/dialog): support async MatDialogConfig.closePredicate

Author: Mr-KRAMA

src/material/dialog/dialog-config.ts

@@ -77,7 +77,7 @@ export class MatDialogConfig<D = any> {
     result: Result | undefined,
     config: Config,
     componentInstance: Component | null,
-  ) => boolean;
+  ) => boolean | Promise<boolean>;
 
   /** Width of the dialog. */
   width?: string = '';

src/material/dialog/dialog-ref.ts

@@ -123,10 +123,29 @@ export class MatDialogRef<T, R = any> {
   close(dialogResult?: R): void {
     const closePredicate = this._config.closePredicate;
 
-    if (closePredicate && !closePredicate(dialogResult, this._config, this.componentInstance)) {
-      return;
+    if (closePredicate) {
+      const result = closePredicate(dialogResult, this._config, this.componentInstance);
+
+      if (result instanceof Promise) {
+        result.then(canClose => {
+          if (canClose) {
+            this._performClose(dialogResult);
+          }
+        });
+        return;
+      } else if (!result) {
+        return;
+      }
     }
 
+    this._performClose(dialogResult);
+  }
+
+  /**
+   * Performs the actual dialog close operation.
+   * @param dialogResult Optional result to return to the dialog opener.
+   */
+  private _performClose(dialogResult?: R): void {
     this._result = dialogResult;
 
     // Transition the backdrop in parallel to the dialog.

src/material/dialog/dialog.spec.ts

@@ -1172,6 +1172,50 @@ describe('MatDialog', () => {
 
       overlayContainerElement.remove();
     }));
+
+    it('should support async closePredicate that returns a Promise', fakeAsync(() => {
+      let resolvePromise: (value: boolean) => void;
+      const closedSpy = jasmine.createSpy('closed spy');
+      const ref = dialog.open(PizzaMsg, {
+        closePredicate: () =>
+          new Promise<boolean>(resolve => {
+            resolvePromise = resolve;
+          }),
+        viewContainerRef: testViewContainerRef,
+      });
+
+      ref.afterClosed().subscribe(closedSpy);
+      viewContainerFixture.detectChanges();
+
+      expect(getDialogs().length).toBe(1);
+
+      // Try to close - should not close immediately
+      ref.close('test-result');
+      viewContainerFixture.detectChanges();
+      flush();
+
+      expect(getDialogs().length).toBe(1);
+      expect(closedSpy).not.toHaveBeenCalled();
+
+      // Resolve promise with false - should still not close
+      resolvePromise!(false);
+      tick();
+      viewContainerFixture.detectChanges();
+      flush();
+
+      expect(getDialogs().length).toBe(1);
+      expect(closedSpy).not.toHaveBeenCalled();
+
+      // Try to close again and resolve with true - should close
+      ref.close('test-result');
+      resolvePromise!(true);
+      tick();
+      viewContainerFixture.detectChanges();
+      flush();
+
+      expect(getDialogs().length).toBe(0);
+      expect(closedSpy).toHaveBeenCalledWith('test-result');
+    }));
   });
 
   it(