Can I drain the pending queue without running them?

Question

RepoPilot · Accepted Answer

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

According to [index.d.ts:L18-L26], `clearQueue()` will:
- Discard pending promises that are waiting to run
- Not cancel promises that are already running
- Optionally reject pending promises with an `AbortError` if `rejectOnClear` is enabled

Here's how it works:

**Basic usage** (pending promises never settle):
```js
limit.clearQueue();
```

**With rejectOnClear option** (pending promises are rejected):
```js
const limit = pLimit({concurrency: 1, rejectOnClear: true});
limit.clearQueue(); // Pending promises reject with AbortError
```

The test in [test.js:L186-L192] shows that after calling `clearQueue()`, the `pendingCount` immediately drops to 0:

```js
Array.from({length: 3}, () => limit(() => delay(1000)));
await Promise.resolve();
t.is(limit.pendingCount, 3);
limit.clearQueue();
t.is(limit.pendingCount, 0);
```

**Important note:** Without `rejectOnClear: true`, pending promises will never settle, so you won't be able to await them. The [recipes.md:L76-L115] example demonstrates using `clearQueue()` during graceful shutdown, where it clears pending tasks while only waiting for already-running tasks to complete.

FOLLOW_UPS:
- What happens to running promises when clearQueue is called?
- How does rejectOnClear option change the behavior?
- What's the difference between activeCount and pendingCount?