[feature] Missing API: Scheduler#postTask

[benjamingr]

There are a few things missing in fake-timers we need to add for Node 17 and for new browser APIs namely:

• We're missing mocking of timers/promises and scheduler.wait (in timers/promises)
• We're missing Symbol.toPrimitive on Node timers (right?)
• We're missing scheduler.postTask with a delay

None of these new APIs are particularly hard to mock but I haven't had a chance to look at them yet.

[fatso83]

I think point two is done. At least I think I had something to do with it:

$ ag -A10 toPrimitive
src/fake-timers-src.js
599:                [Symbol.toPrimitive]: function () {
600-                    return timer.id;
601-                },
602-            };
603-            return res;

[fatso83]

What is point one about? Like some example code (that we should mock) would help my feeble mind.

[SimenB]

import {setTimeout} from 'timers/promise'

[SimenB]

not sure if it's possible to mock? unless it's also available somewhere globally so we can replace it

[fatso83]

That was new. Thanks.

[benjamingr]

Seems posible @SimenB

➜  node git:(master) node
Welcome to Node.js v16.10.0.
Type ".help" for more information.
> let orig = require('timers/promises').setTimeout;
undefined
> require('timers/promises').setTimeout = function (fn) { fn(); }
[Function (anonymous)]
> require('timers/promises').setTimeout(() => console.log('foo'), 10000); // logs immediately
foo
undefined

(Of course, it should return a promise and probably just reuse the util.promisify version - this is just to show it's mockable)

[SimenB]

ESM as well? But that's promising? 😃

[thernstig]

Not having timers/promises is becoming more and more of a nuance as Node.js 18 went to LTS October 2022, meaning more and more try to use it. Especially problematic in Jest where we now are resorted to using callback-based setTimeout() etc. when the other ones are nicer to read and use.

[fatso83]

@thernstig Want to have a go? That's the best chance of finding something to scratch your itch. We accept PRs quite gladly 👍

[thernstig]

@fatso83 I try to help where I feel comfortable in the code but this is not such an area, otherwise I would already have pushed a PR.

What I wanted to highlight was that the new APIs have gone from experimental -> stable due to Node.js 18, possibly adding a new piece of information to this thread. I did not mean to sound pushy in a sense that I put any expectations on anyone to use their free time to fix it.

[benjamingr]

@itayperry wanna take a stab at it? I won't have time to take a look in the next ±2 months probably due to travel/life.

[itayperry]

Hi @benjamingr, It looks very interesting, and I'd like to try and help. I know you said it's supposed to be easy, but it seems hard.

It'd be great if you told me where to start 🚀 what's the first thing I should mock? Maybe we can even break it into very small tasks :) and then I could do a few small PRs. In that case, if I get stuck someone else could continue from where I stopped (last issue I had took me too long cause it was a bit tricky).

I'll give it a shot ⚡️

[everett1992]

Also missing AbortSignal.timeout