[BUG]: path must be a string, array of strings, or regular expression

[jamessan85]

Tracer Version(s)

5.55.0

Node.js Version(s)

18.20.8

Bug Report

I've come across a weird edge case to do with express, express-validator and dd-trace where when I submit a form action POST request I get the error thrown from path-to-regexp - path must be a string, array of strings, or regular expression. This is working fine in dd-trace 5.45.0

Reproduction Code

Create a route in express.js

validator.js

import { check } from 'express-validator';

const usersValidator = [check('name').isAlpha().withMessage('isAlpha')];

export default usersValidator; 

router.js

import app from 'express';
import usersValidator from './validator';

const router = app.Router();

router.post('/users', [usersValidator], (req, res) => res.send('OK'));

export default router;

If you remove the array in the middleware like so router.post('/users', usersValidator, (req, res) => res.send('OK')); it works fine.

Error Logs

No response

Tracer Config

No response

Operating System

No response

Bundling

No Bundling

[BridgeAR]

Thank you for the good bug report! I believe I know where this regressed and how to fix it.
I won't get to it today but in the next few days (so likely with the next release).