How to get the full URL of an express request, with placeholders as-is?

Question

I am using express.Router instances create routes and bind them to base routes with app.use(), and I use placeholders in those routes to populate the req.params object. A complete route might look like /user/:id/profile -- I'm looking for the way to get that /user/:id/profile string.

Here's an example server:

const express = require('express');
const router = express.Router({ mergeParams: true });

const app = express();

router.get('/profile', (req, res) => {
        console.log(req.url);                // prints "/profile"
        console.log(req.baseUrl);            // prints "/user/foo"
        console.log(req.originalUrl);        // prints "/user/foo/profile"
        console.log(req.route.path);         // prints "/profile"
        res.send(`hello ${req.params.id}`);
});

app.use('/user/:id', router);

app.listen(49500, () => {
        console.log('listening');
});

curl localhost:49500/user/foo/profile returns hello foo and logs the values shown above in the example script, but nothing I've found gives me /user/:id/profile, and I've checked req and res.

There have been similar questions posted to SO, but the key difference here is I am looking for a way to preserve the placeholders.

Edited to add: I'm running express 4.17.2 (latest version at the time of this post) in node 17.0.1.