Can I drain the pending queue without running them?

Question

RepoPilot · Accepted Answer

Yes, you can drain the pending queue without running the pending tasks using the `clearQueue()` method. This discards all pending promises that are waiting to run.

According to the documentation in [readme.md:L96-L106], `limit.clearQueue()` will:

> Discard pending promises that are waiting to run. This might be useful if you want to teardown the queue at the end of your program's lifecycle or discard any function calls referencing an intermediary state of your app. Note: This does not cancel promises that are already running.

The test in [test.js:L180-L188] demonstrates this behavior:

```javascript
const limit = pLimit(1);

Array.from({length: 1}, () => limit(() => delay(1000)));
Array.from({length: 3}, () => limit(() => delay(1000)));

await Promise.resolve();
t.is(limit.pendingCount, 3);
limit.clearQueue();
t.is(limit.pendingCount, 0);
```

This shows that after calling `clearQueue()`, the `pendingCount` drops to 0, meaning all pending tasks were discarded without execution.

**Optional behavior:** If you want pending promises to be explicitly rejected instead of silently discarded, you can enable the `rejectOnClear` option when creating the limiter [index.d.ts:L115-L121]. This is useful if you're awaiting the promises with `Promise.all()` so they don't remain unresolved.

FOLLOW_UPS:
- How does `rejectOnClear` differ from normal `clearQueue()`?
- What happens to currently running promises with `clearQueue()`?
- Can I check pending count before clearing?