Fix debounce with void events (#269)

src/debounce/debounce.test.ts

@@ -569,3 +569,17 @@ test('debounce do not affect another instance of debounce', async () => {
   await wait(20);
   expect(watcherSecond).toBeCalledWith('foo');
 });
+
+test('debounced event should be triggered with undefined', async () => {
+  const trigger = createEvent();
+  const debounced = debounce({ source: trigger, timeout: 0 });
+
+  const listener = jest.fn();
+  debounced.watch(listener);
+
+  trigger();
+  await wait(0);
+
+  expect(listener).toBeCalledTimes(1);
+  expect(listener).toBeCalledWith(undefined);
+});

src/debounce/index.ts

@@ -87,9 +87,9 @@ export function debounce<T>({
   $timeoutId.reset(timerFx.done);
 
   // It's ok - nothing will ever start unless source is triggered
-  const $payload = createStore<T>(null as unknown as T, { serialize: 'ignore' }).on(
+  const $payload = createStore<T[]>([], { serialize: 'ignore' }).on(
     source,
-    (_, payload) => payload,
+    (_, payload) => [payload],
   );
 
   const $canTick = createStore(true, { serialize: 'ignore' });
@@ -130,6 +130,7 @@ export function debounce<T>({
   sample({
     source: $payload,
     clock: timerFx.done,
+    fn: ([payload]) => payload,
     target: tick,
   });