Bull: Promise.reject results in UnhandledRejectionError

[stephenprater]

Description

Calling Promise.reject() from within a handler function results in an UnhandledRejectionError

Minimal, Working Test code to reproduce the issue.

const Queue = require('bull');

const queue = new Queue('test');
queue.process('job', 1, job => {
  console.log('tryna process');
  Promise.reject(new Error('oh no'));
});

queue.add('job', {});

setInterval(() => console.log('tick'), 1000);

Output:

tryna process
(node:62747) UnhandledPromiseRejectionWarning: Error: oh no
    at Queue.<anonymous> (/Users/stephenprater/src/fandango/hermes/test.js:6:18)
    at handlers.<computed> (/Users/stephenprater/src/fandango/hermes/node_modules/bull/lib/queue.js:656:42)
    at Queue.processJob (/Users/stephenprater/src/fandango/hermes/node_modules/bull/lib/queue.js:1050:22)
    at processTicksAndRejections (internal/process/task_queues.js:93:5)
(node:62747) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:62747) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
tick
tick
tick
tick

Bull version

3.12.1

Additional information

Using done(new Error('oh no') does not result in this error.

[stephenprater]

Duh. return Promise.reject(new Error('oh no'))

[Hikariii]

Don't get your duh... It's completely valid to return a rejection: https://github.com/OptimalBits/bull#using-promises
This should be handled by bull imho

[manast]

@Hikariii is it not handled? I think the original code was lacking a return, therefore the "Duh". :)

[Hikariii]

Nope it is not. Throwing an error goes fine, but returning a rejected promise with an error gives an unhandled promise rejection error.