setTimeout cannot be util.promisify'ed

[gabmontes]

• Electron Version: 1.8.4
• Operating System (Platform and Version): macOS 10.13.5
• Last known working Electron version: ?

Expected Behavior
require('util').promisify(setTimeout)(delay).then(callback) should work as per Node.JS 8.x docs.

Actual behavior
"callback" argument must be a function error is thrown inside promisified setTimeout.

To Reproduce
Execute this in the main process:

require('util').promisify(setTimeout)(0).then(console.log('works!'))

It will throw the mentioned error.

Additional Information
The problem seems to be that setTimeout[util.promisify.custom] is not defined. Therefore util.promisify tries to promisify setTimeout as a standard callback-last function but it is a special-case callback-first one.

See:
https://nodejs.org/api/timers.html#timers_settimeout_callback_delay_args
https://nodejs.org/api/util.html#util_custom_promisified_functions

Haven't tested in v2.x or higher yet. Is there plans to eventually backport a fix for this to the 1.x versions?

Thanks!!

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[ghost]

does electron 1.8.4 include a new enough node? You might want to use pify instead.

[pronebird]

This works in node 8.11.2, but electron 1.8.4 runs node 8.2.1 AFAIK. So maybe there is some issue with this.

[gabmontes]

@pronebird you are correct. process.versions in shows the following:

{
  "http_parser": "2.7.0",
  "node": "8.2.1",
  "v8": "5.9.211.38",
  "uv": "1.13.1",
  "zlib": "1.2.11",
  "ares": "1.10.1-DEV",
  "modules": "57",
  "openssl": "1.0.2l",
  "electron": "1.8.4",
  "chrome": "59.0.3071.115",
  "atom-shell": "1.8.4"
}

And yes, Node.js v8.2.1 already supports custom promisifying setTimeout but that is not working on this Electron version.

[pronebird]

@gabmontes what happens if you print out setTimeout[util.promisify.custom]?

You know what, that's weird.

Broken in Electron v2.0.5 interactive shell (node v8.9.3):

$ electron -i
> setTimeout[util.promisify.custom]
undefined
> util.promisify(setTimeout)(1000).then(() => { console.log('hello'); }).catch(err => { console.log('err:', err); })
Promise {
  <pending>,
  domain: 
   Domain {
     domain: null,
     _events: { error: [Function: debugDomainError] },
     _eventsCount: 1,
     _maxListeners: undefined,
     members: [] } }
> err: TypeError: "callback" argument must be a function
    at setTimeout (timers.js:427:11)
    at /Users/pronebird/mullvad/mullvadvpn-app/node_modules/electron/dist/Electron.app/Contents/Resources/electron.asar/common/init.js:14:17
    at internal/util.js:227:26
    at repl:1:27
    at ContextifyScript.Script.runInContext (vm.js:59:29)
    at REPLServer.defaultEval (repl.js:242:29)
    at bound (domain.js:301:14)
    at REPLServer.runBound [as eval] (domain.js:314:12)
    at REPLServer.onLine (repl.js:442:10)
    at emitOne (events.js:116:13)

Works in node v8.11.2

$ node
> setTimeout[util.promisify.custom]
[Function]
> util.promisify(setTimeout)(1000).then(() => { console.log('hello'); }).catch(err => { console.log('err:', err); })
Promise {
  <pending>,
  domain: 
   Domain {
     domain: null,
     _events: { error: [Function: debugDomainError] },
     _eventsCount: 1,
     _maxListeners: undefined,
     members: [] } }
> hello

I think some of the custom promisify handlers haven't been properly set in Electron. It's also possible that it was a bug that was fixed in some patch release between node v8.9.3 and v.8.11.2. I don't really have any older node to verify that, but I think you have a clue how to workaround this for the time being.

[gabmontes]

@pronebird Node.JS works fine. I have tested that in several versions as 8.2.1 (to match Electron 1.8.4) and 8.11.x (LTS).

But in Electron, the required property of setTimeout is just not set:

> promisify.custom
Symbol(util.promisify.custom)
> setTimeout[promisify.custom]
undefined

Since it is not set, setTimeout is promisified as a callback-last function and breaks because you pass a number to it and it is expecting the callback function there. The error you see in Electron 2.0.5 is the same as in 1.8.4.

[davidcornu]

This sounds really similar to #13458.

[gabmontes]

@davidcornu for sure both issues have the same root cause!

[miniak]

@gabmontes Electron specific code is intercepting setTimeout, therefore setTimeout[util.promisify.custom] is being lost. I am fixing that in #13840