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timers: captureRejections for timers

Rodrigo Muino Tomonari requested to merge github/fork/jasnell/capture-rejections-timers into master

The setTimeout(), setInterval(), and setImmediate() functions are currently not implemented to handle async functions or thenable responses.

setTimeout(async () => { throw new Error('boom'); }, 1000)

Will result in an unhandled rejection that will result in an unhandled rejection warning.

Inspired by @mcollina's recent captureRejections extension for EventEmitter, this implements a similar capability for timers.

const timers = require('timers')
timers.captureRejections = true;

setTimeout(async () => { throw new Error('boom'); }, 1000)

process.on('error', (err) => /* handle here */)

Whether or not this is desirable behavior vs. crashing immediately is a matter that can (and should) be debated.

An alternative approach here would be to make the timer objects into thenables (which I believe has been discussed before)... such that that thenable would reject when an error is thrown, and resolves when cleared.

const i = setInterval(async () => { throw new Error('foo'); }, 1000);

// Only used when function returns a thenable...
i.then(
  () => { /** called when clearInterval(i) is called **/ },
  (err) => { /** called when throws **/ })

This approach has some API weirdness that would need to be figured out.

/cc @mcollina @BridgeAR

Checklist
  • make -j4 test (UNIX), or vcbuild test (Windows) passes
  • tests and/or benchmarks are included
  • documentation is changed or added
  • commit message follows commit guidelines

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