fix(material/datepicker): actions not re-rendering if swapped out while calendar is open

src/material/datepicker/datepicker-actions.spec.ts

@@ -257,6 +257,28 @@ describe('MatDatepickerActions', () => {
     expect(control.value).toBeTruthy();
     expect(onDateChange).toHaveBeenCalledTimes(1);
   }));
+
+  it('should be able to toggle the actions while the datepicker is open', fakeAsync(() => {
+    const fixture = createComponent(DatepickerWithActions);
+    fixture.componentInstance.renderActions = false;
+    fixture.detectChanges();
+
+    fixture.componentInstance.datepicker.open();
+    fixture.detectChanges();
+    tick();
+    flush();
+
+    const content = document.querySelector('.mat-datepicker-content')!;
+    expect(content.querySelector('.mat-datepicker-actions')).toBeFalsy();
+
+    fixture.componentInstance.renderActions = true;
+    fixture.detectChanges();
+    expect(content.querySelector('.mat-datepicker-actions')).toBeTruthy();
+
+    fixture.componentInstance.renderActions = false;
+    fixture.detectChanges();
+    expect(content.querySelector('.mat-datepicker-actions')).toBeFalsy();
+  }));
 });
 
 @Component({

src/material/datepicker/datepicker-base.ts

@@ -180,10 +180,6 @@ export class MatDatepickerContent<S, D = ExtractDateTypeFromSelection<S>>
   }
 
   ngOnInit() {
-    // If we have actions, clone the model so that we have the ability to cancel the selection,
-    // otherwise update the global model directly. Note that we want to assign this as soon as
-    // possible, but `_actionsPortal` isn't available in the constructor so we do it in `ngOnInit`.
-    this._model = this._actionsPortal ? this._globalModel.clone() : this._globalModel;
     this._animationState = this.datepicker.touchUi ? 'enter-dialog' : 'enter-dropdown';
   }
 
@@ -246,6 +242,25 @@ export class MatDatepickerContent<S, D = ExtractDateTypeFromSelection<S>>
       this._globalModel.updateSelection(this._model.selection, this);
     }
   }
+
+  /**
+   * Assigns a new portal containing the datepicker actions.
+   * @param portal Portal with the actions to be assigned.
+   * @param forceRerender Whether a re-render of the portal should be triggered. This isn't
+   * necessary if the portal is assigned during initialization, but it may be required if it's
+   * added at a later point.
+   */
+  _assignActions(portal: TemplatePortal<any> | null, forceRerender: boolean) {
+    // If we have actions, clone the model so that we have the ability to cancel the selection,
+    // otherwise update the global model directly. Note that we want to assign this as soon as
+    // possible, but `_actionsPortal` isn't available in the constructor so we do it in `ngOnInit`.
+    this._model = portal ? this._globalModel.clone() : this._globalModel;
+    this._actionsPortal = portal;
+
+    if (forceRerender) {
+      this._changeDetectorRef.detectChanges();
+    }
+  }
 }
 
 /** Form control that can be associated with a datepicker. */
@@ -556,6 +571,7 @@ export abstract class MatDatepickerBase<
       throw Error('A MatDatepicker can only be associated with a single actions row.');
     }
     this._actionsPortal = portal;
+    this._componentRef?.instance._assignActions(portal, true);
   }
 
   /**
@@ -565,6 +581,7 @@ export abstract class MatDatepickerBase<
   removeActions(portal: TemplatePortal): void {
     if (portal === this._actionsPortal) {
       this._actionsPortal = null;
+      this._componentRef?.instance._assignActions(null, true);
     }
   }
 
@@ -632,8 +649,8 @@ export abstract class MatDatepickerBase<
   protected _forwardContentValues(instance: MatDatepickerContent<S, D>) {
     instance.datepicker = this;
     instance.color = this.color;
-    instance._actionsPortal = this._actionsPortal;
     instance._dialogLabelId = this.datepickerInput.getOverlayLabelId();
+    instance._assignActions(this._actionsPortal, false);
   }
 
   /** Opens the overlay with the calendar. */

tools/public_api_guard/material/datepicker.md

@@ -427,6 +427,7 @@ export class MatDatepickerContent<S, D = ExtractDateTypeFromSelection<S>> extend
     readonly _animationDone: Subject<void>;
     _animationState: 'enter-dropdown' | 'enter-dialog' | 'void';
     _applyPendingSelection(): void;
+    _assignActions(portal: TemplatePortal<any> | null, forceRerender: boolean): void;
     _calendar: MatCalendar<D>;
     _closeButtonFocused: boolean;
     _closeButtonText: string;