FST_ERR_DEC_ALREADY_PRESENT error when set trustProxy to true

[Dafyh]

Describe the bug
If the trustProxy option is set to true, the following error occurs: FST_ERR_DEC_ALREADY_PRESENT.

To Reproduce
Steps to reproduce the behavior:

'use strict'
const tap = require('tap')
const fastify = require('fastify')
const plugin = require('../')

tap.test('Plugin#Decoration', scope => {
  scope.test('Throw a FST_ERR_DEC_ALREADY_PRESENT error', async t => {
    await fastify({ trustProxy: true }).register(plugin).ready()
  })
})

Expected behavior
Should not return any errors.

Screenshots

[metcoder95]

Thanks for the report!

We can provide two properties at the same time, if the request.ip has been already set, we can just skip it.

The second one can always be set, something like realIp or inferredIp (or similar).

Would you like to submit a PR?

[Dafyh]

Yes, I can do a PR.

However, we could redefine the getter ip in the hook preHandler instead of adding a property in the case where trustProxy is true (ip, ips, hostname and protocol are present) ?

[Dafyh]

For example :

const isTrustProxyOn = [
  'ip',
  'ips',
  'hostname',
  'protocol'
].every((key) => instance.hasRequestDecorator(key))

if (isTrustProxyOn) {
  async function redefineIpDecorator (request) {
    Object.defineProperty(request, 'ip', {
      get () {
        return ipDecorator.getter.apply(request)
      }
    })
  }

  instance.addHook('preHandler', redefineIpDecorator)
} else {
  instance.decorateRequest('ip', ipDecorator)
}

Where ipDecorator is the object with the getter.

[metcoder95]

sgtm. i’d just recommend to not re define the property but rather just assign it.

let’s also document this in the documentation

[Dafyh]

Unfortunately, I can't assign a value as the setter is not implemented (TypeError). We could also propose a PR on fastify, but the simplest solution would be to redefine the property into fastify-ip 😊.

I will do a PR in any cases.

see

[metcoder95]

ah good callout, then that's fine 👍

[fraxken]

Thanks for the fast answer and the release ❤️ 🚀

[Dafyh]

Thanks 👍.