chore(js): allow unhandledRejection plugin to be loaded more than once

[BethanyBerkowitz]

Status

READY

Description

Part of #1163

This PR makes it safe to load the unhandledRejection plugin more than once.

If loaded with enableUnhandledRejection true, it will add a listener if one has not already been added
If loaded with enableUnhandledRejection false, it will remove the listener if it exists
However, the client itself still only loads the plugin once, so this PR should not cause any user-facing change in behavior.

Related PRs

#1170 does the same with unhandledException

Todos

• Tests
• Documentation

Steps to Test or Reproduce

Unit tests mostly cover it, however I also tested manually using the sails example app. Any node-based example app would be fine, you just need to trigger a promise rejection where the middleware will not pick it up. eg

Honeybadger.configure({
  apiKey: process.env.HONEYBADGER_API_KEY, 
  enableUncaught: false,
  enableUnhandledRejection: true,
})


function reject() {
  Promise.reject(new Error('error within a promise'))
}

setTimeout(reject, 500)

I tested with enableUnhandledRejection: true and false.

[joshuap]

This looks good to me. If it's not urgent, it would be great if @subzero10 could also review when he's back from vacation.