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ffi: nextTick and microtasks queued in event-loop-invoked callbacks are not drained #66917
Description
Version
main
Platform
macOS
Subsystem
ffi
What steps will reproduce the bug?
This uses libuv's own timer through dlopen(null), so native code calls the callback straight from the event loop:
import { dlopen, getCurrentEventLoop } from 'node:ffi';
const { lib, functions: uv } = dlopen(null, {
uv_handle_size: { arguments: ['i32'], return: 'u64' },
uv_timer_init: { arguments: ['pointer', 'pointer'], return: 'i32' },
uv_timer_start: {
arguments: ['pointer', 'pointer', 'u64', 'u64'],
return: 'i32',
},
});
const UV_TIMER = 13;
const timer = new Uint8Array(Number(uv.uv_handle_size(UV_TIMER)) + 64);
const start = performance.now();
const t = () => `${Math.round(performance.now() - start)}ms`;
const cb = lib.registerCallback({ arguments: ['pointer'], return: 'void' }, () => {
console.log(`${t()} native timer callback`);
process.nextTick(() => console.log(`${t()} nextTick`));
queueMicrotask(() => console.log(`${t()} microtask`));
Promise.resolve().then(() => console.log(`${t()} promise.then`));
});
uv.uv_timer_init(getCurrentEventLoop(), timer);
uv.uv_timer_start(timer, cb, 10n, 0n);
setTimeout(() => console.log(`${t()} unrelated setTimeout`), 1000);How often does it reproduce? Is there a required condition?
Always
What is the expected behavior? Why is that the expected behavior?
3ms native timer callback
3ms nextTick
3ms microtask
5ms promise.then
1001ms unrelated setTimeoutNode runs its own event-loop callbacks inside InternalCallbackScope, whose Close() drains the nextTick queue and microtasks. ffi.getCurrentEventLoop() exists so native code can call back into JS from the loop, so those callbacks should get the same treatment.
What do you see instead?
0ms native timer callback
1001ms unrelated setTimeout
1002ms nextTick
1002ms microtask
1002ms promise.thenThe queued work only runs after some unrelated Node callback. If none is pending, it runs during beforeExit. Any promise-based work started inside such a callback stalls until then.
Additional information
No response
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