fix: allow null and undefined in selected-item-changed event (#2281)

Author: hdamr

packages/vaadin-combo-box/src/interfaces.d.ts

@@ -54,7 +54,7 @@ export type ComboBoxFilterChangedEvent = CustomEvent<{ value: string }>;
 /**
  * Fired when the `selectedItem` property changes.
  */
-export type ComboBoxSelectedItemChangedEvent<TItem> = CustomEvent<{ value: TItem }>;
+export type ComboBoxSelectedItemChangedEvent<TItem> = CustomEvent<{ value: TItem | null | undefined }>;
 
 export interface ComboBoxEventMap<TItem> extends HTMLElementEventMap {
   'custom-value-set': ComboBoxCustomValueSetEvent;

packages/vaadin-combo-box/test/typings/combo-box.types.ts

@@ -57,7 +57,7 @@ narrowedComboBox.addEventListener('filter-changed', (event) => {
 
 narrowedComboBox.addEventListener('selected-item-changed', (event) => {
   assertType<ComboBoxSelectedItemChangedEvent<TestComboBoxItem>>(event);
-  assertType<TestComboBoxItem>(event.detail.value);
+  assertType<TestComboBoxItem | null | undefined>(event.detail.value);
 });
 
 /* ComboBoxLightElement */
@@ -96,5 +96,5 @@ narrowedComboBoxLightElement.addEventListener('filter-changed', (event) => {
 
 narrowedComboBoxLightElement.addEventListener('selected-item-changed', (event) => {
   assertType<ComboBoxSelectedItemChangedEvent<TestComboBoxItem>>(event);
-  assertType<TestComboBoxItem>(event.detail.value);
+  assertType<TestComboBoxItem | null | undefined>(event.detail.value);
 });