Customizing Validation Errors in Payload CMS (beforeValidate Hook)

[rozenteno]

Howdy everyone! 👋🏼

I'm looking for help on how to customize error responses triggered during validation in Payload CMS.
Instead of returning my custom error, the API always responds with a static 500 Internal Server Error.

My Case:
I have a purchasedTickets field where I store purchased tickets as a JSON array. Before saving a new purchase, I check if any of the newTickets already exist in purchasedTickets. If they do, I want to prevent the update and return a structured error response.

fields: [ { name: "purchasedTickets", type: "json", defaultValue: [], }, ],

Here’s my current beforeValidate hook:
hooks: {beforeValidate: [ async ({ data, originalDoc, req }) => { if (data.newTickets) { const duplicateTickets = data.newTickets.filter((ticket) => originalDoc.purchasedTickets.some( (existingTicket) => existingTicket.ticket === ticket.ticket ) ); if (duplicateTickets.length > 0) { console.log("❌ Duplicate tickets detected:", duplicateTickets); if (req?.res) { req.res.status(400).json({ errors: [ { message: "Some of the new tickets already exist in the purchased tickets." } ], }); } throw new Error( "Some of the new tickets already exist in the purchased tickets Error 84." ); } } }, ], }

Issues I'm Facing:

1️⃣ req.res is undefined – I tried sending a response manually, but req.res does not exist in Payload CMS requests.
2️⃣ Payload CMS still returns a 500 Internal Server Error instead of my structured error message.
3️⃣ Ideally, I want to return a 400 Bad Request with a JSON response like this:
{ "errorCode": 400, "message": "Some of the new tickets already exist in the purchased tickets." }
4️⃣ If beforeValidate isn't the right place, what hook should I use to properly stop the update and send a custom response?

Questions:

1. How can I correctly stop the update and return a custom error response in Payload CMS?
2. Is there a better way to handle validation errors without getting a generic 500 error?

Would love any guidance from the community! 🚀 Thanks in advance! 🙌🏼