discord.js - Imagine an app•3d ago

How to handle unhandled rejections?

My app usually crashes when a very weird unhandled rejection occurs, usually when it's an event where I don't have a general error handler. So how can I catch unhandled rejections effectively? (Maybe even do something with it like send it with a Webhook or log it)

25 Replies

d.js toolkit•3d ago

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treble/luna•3d ago

Catch them properly, either by try catch or just chaining a .catch to your promises

LukeZOP•3d ago

Oh well, nevermind 😂 I will give that one a try: https://discordjs.guide/popular-topics/errors.html#how-to-diagnose-api-errors

discord.js Guide

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LukeZOP•3d ago

Not really possible. I'd have to make a handler just for that which is a bit too complicated to implement

monbrey•3d ago

Yes, your errors should be handled Thats how that works

LukeZOP•3d ago

Well, I'm dynamically loading my event listeners. I'd have to manually wrap the whole event function in a try {} catch {} Imma try this one first

treble/luna•3d ago

You're gonna have to find a way, or live with your curremt issue

monbrey•3d ago

no you dont You can catch the error at the promise that throws it

LukeZOP•3d ago

Oooh, I think I'm gonna do it like this (if the one from. The guide doesn't work properly)

// Handler Function
export default async handler(eventFunc: Function, ...args) {
  try {
    await eventFunc(...args);
  } catch (e) { /* ... */ }
}

// Use the handler in the index
// In the loop where I import the event function
client.addEventListener(event, handlerFunc.bind(null, eventFunc, ...args));

// Handler Function
export default async handler(eventFunc: Function, ...args) {
  try {
    await eventFunc(...args);
  } catch (e) { /* ... */ }
}

// Use the handler in the index
// In the loop where I import the event function
client.addEventListener(event, handlerFunc.bind(null, eventFunc, ...args));

Maybe like this idk I will see I know, but I sometimes have random rejections on promises that usually don't reject and if I'd handle all promises, my code would be flooded with try-catches. That seems not very practical to me and there has to be an easier and better solution.

monbrey•3d ago

nope

LukeZOP•3d ago

What nope?

Unknown User•3d ago

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LukeZOP•3d ago

So try-catch on every promise. :FeelsDonkMan: Btw. It's usually the functions themselves rejecting because of some edge case scenario I didn't think of

monbrey•3d ago

I mean, you can propagate errors upwards, but generally catching at the source will give you the best granularity and information to debug A higher level handler is fine to catch the ones youve missed

ethan<333•3d ago

process
  .on("unhandledRejection", (err: Error) => logger.error(inspect(err), "unhandledRejection"))
  .on("uncaughtException", (err: Error) => logger.error(inspect(err), "uncaughtException"))
  .on("error", (err: Error) => logger.error(inspect(err), "error"))
  .on("warning", (err: Error) => logger.error(inspect(err), "warning"));

process
  .on("unhandledRejection", (err: Error) => logger.error(inspect(err), "unhandledRejection"))
  .on("uncaughtException", (err: Error) => logger.error(inspect(err), "uncaughtException"))
  .on("error", (err: Error) => logger.error(inspect(err), "error"))
  .on("warning", (err: Error) => logger.error(inspect(err), "warning"));

LukeZOP•3d ago

👀

ethan<333•3d ago

but it is generally easier to catch bugs when you .catch the promise instead of doing it on a higher level like the above code

LukeZOP•3d ago

yeah I thought that too -# Not always possible though

ethan<333•3d ago

its always possible

Amgelo•3d ago

not a recommended practice

ethan<333•3d ago

im aware, hence my warning above

Amgelo•3d ago

yeah but it's not only easier, it's better

ethan<333•3d ago

how is it easier to go through an entire codebase and add some code to the end of every promise than just using the code i sent there's pros and cons to it

Amgelo•3d ago

I'm quoting you, just adding the fact that it's also better

ethan<333•3d ago

ah apols high-level .catch: takes no time but less efficient low-level .catch: takes a long time but very efficient

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How to handle unhandled rejections?