feat: Added support for null in useTableListener (#1227)

resolves #1228

Author: bmingles

packages/jsapi-components/src/useTableListener.test.ts

@@ -0,0 +1,48 @@
+import { renderHook } from '@testing-library/react-hooks';
+import { Evented } from '@deephaven/jsapi-types';
+import useTableListener from './useTableListener';
+
+const eventName = 'mock.event';
+
+const addEventListener = jest.fn();
+const handler = jest.fn();
+const unsubscribe = jest.fn();
+
+const evented = ({
+  addEventListener,
+} as unknown) as Evented;
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  addEventListener.mockReturnValue(unsubscribe);
+});
+
+it('should register an event listener', () => {
+  renderHook(() => useTableListener(evented, eventName, handler));
+  expect(evented.addEventListener).toHaveBeenCalledWith(eventName, handler);
+});
+
+it('should unsubscribe on unmount', () => {
+  const { unmount } = renderHook(() =>
+    useTableListener(evented, eventName, handler)
+  );
+
+  expect(unsubscribe).not.toHaveBeenCalled();
+
+  unmount();
+
+  expect(unsubscribe).toHaveBeenCalled();
+});
+
+it.each([null, undefined])(
+  'should handle null or undefined: %s',
+  nullOrUndefined => {
+    const { unmount } = renderHook(() =>
+      useTableListener(nullOrUndefined, eventName, handler)
+    );
+
+    unmount();
+
+    expect(unsubscribe).not.toHaveBeenCalled();
+  }
+);

packages/jsapi-components/src/useTableListener.ts

@@ -5,13 +5,13 @@ import Log from '@deephaven/log';
 const log = Log.module('useTableListener');
 
 export const useTableListener = (
-  eventEmitter: Evented | undefined,
+  eventEmitter: Evented | undefined | null,
   eventName: string,
   callback: EventListener
 ): void =>
   useEffect(
     function initEventEmitter() {
-      if (eventEmitter === undefined) {
+      if (eventEmitter == null) {
         log.debug2('Emitter undefined, skipping addEventListener', eventName);
         return;
       }