How to import fastify error codes?

[Eomm]

Discussed in #3842

^{Originally posted by teemupiiroinenwirepas April 20, 2022}
We would like to map fastify error codes from https://github.com/fastify/fastify/blob/main/lib/errors.js to our own error codes, but we cannot find a way how to import the codes. How the importing should be done, or how the error code mapping should be done to the application specific error codes?

Br,
Teemu

---

We should:

• export the errors from this utility https://github.com/fastify/fastify/blob/main/lib/errors.js
• generate/update the corresponding page https://github.com/fastify/fastify/blob/main/docs/Reference/Errors.md
• generate/update the typescript interface as well

[Uzlopak]

Also dont forget that fastify plugins have their own errors. Maybe we should register those errors also?

[fitiskin]

I'd like to do this. Assign it to me please, if @teemupiiroinenwirepas don't mind.

[Eomm]

Maybe we should register those errors also?

This integration would be nice, but it should be transparent for the @fastify/errors users

[mcollina]

Let's not include plugins.

[fitiskin]

I can't understand how this frameworkErrors example is supposed to work while we can't import FST_ERR_BAD_URL directly.

[fitiskin]

Should we export only error codes (string names) or the errors produced by createError?

Error codes:

const fastify = require('fastify')

exampleErrorHandler((err) => {
    if (err.code === fastify.errorCodes.FST_ERR_NOT_FOUND) {
        //
    }
})

Errors:

const fastify = require('fastify')

exampleErrorHandler((err) => {
    if (err instanceof fastify.errorCodes.FST_ERR_NOT_FOUND) {
        //
    }
})

As I guess we shouldn't export the appendStackTrace utility function.

[Eomm]

Should we export only #3842 (reply in thread) (string names) or the errors produced by createError?

The latter 👍🏽

As I guess we shouldn't export the appendStackTrace utility function.

Yes, there is not value for the user getting it