Ever considered the use of queueMicrotask?

[andreyvital]

It's available as of v11—isn't it better than process.nextTick? https://nodejs.org/api/globals.html#queuemicrotaskcallback

dataloader/src/index.js

Lines 239 to 255 in d336bd1

	const enqueuePostPromiseJob =
	typeof process === 'object' && typeof process.nextTick === 'function'
	? function (fn) {
	if (!resolvedPromise) {
	resolvedPromise = Promise.resolve();
	}
	resolvedPromise.then(() => {
	process.nextTick(fn);
	});
	}
	: typeof setImmediate === 'function'
	? function (fn) {
	setImmediate(fn);
	}
	: function (fn) {
	setTimeout(fn);
	};

Just a question...

Thanks,
A.

[victorandree]

@andreyvital I had the same thought when considering this library on something like Cloudflare Workers or Vercel (see #341).

I decided to investigate and TL;DR is that I don't think queueMicrotask can quite replicate the behavior of process.nextTick(fn) because of subtle differences in scheduling. This behavior is covered by this test: https://github.com/graphql/dataloader/blob/55c33d480cdf429a0b24cf607ddd0e892521a35b/src/__tests__/dataloader.test.js#L1004C5-L1025C5.

My understanding is this: The batch is constructed, and schedules its post-promise job, before the promises to return values are constructed. This means that the associated microtask would always be queued before those promises start resolving. I don't see a way to use the queueMicrotask to schedule its job "after" Promises. setTimeout (and setImmediate, though that's deprecated) will execute after, which is why they're the backup for process.nextTick.