Deno's URLPattern.exec(string) implementation differs from the node polyfill

[NextLegacy]

Version: Deno 2.2.1

Heyy everyone,
It seems like Deno's URLPattern.exec(string) implementation differs from the node polyfill, which is causing some libraries to behave inconsistently or even break when running in Deno.

Reproduction:

const pattern = ":protocol://:domain(.*)::port?/:locale(de)?/:path(.*)?";
const url = "https://localhost:5173/de";

const urlpattern = new URLPattern(pattern);
const match = urlpattern.exec(url);

console.log(match);

Expected Behavior (Chrome/Node Polyfill):

{
  "inputs": ["https://localhost:5173/de"],
  "protocol": { "input": "https", "groups": { "protocol": "https" } },
  "username": { "input": "", "groups": { "0": "" } },
  "password": { "input": "", "groups": { "0": "" } },
  "hostname": { "input": "localhost", "groups": { "domain": "localhost" } },
  "port": { "input": "5173", "groups": { "port": "5173" } },
  "pathname": { "input": "/de", "groups": { "locale": "de", "path": undefined } },
  "search": { "input": "", "groups": { "0": "" } },
  "hash": { "input": "", "groups": { "0": "" } }
}

Actual Behavior (Deno):

{
  "inputs": ["https://localhost:5173/de"],
  "protocol": { "input": "https", "groups": { "protocol": "https" } },
  "username": { "input": "", "groups": { "0": "" } },
  "password": { "input": "", "groups": { "0": "" } },
  "hostname": { "input": "localhost", "groups": { "0": "localhost" } },
  "port": { "input": "5173", "groups": { "port": "5173" } },
  "pathname": { "input": "/de", "groups": { "locale": "de", "path": undefined } },
  "search": { "input": "", "groups": { "0": "" } },
  "hash": { "input": "", "groups": { "0": "" } }
}

Difference:

In Deno, the hostname.groups object does not contain the expected named group (domain), while in Chrome/Node's polyfill, it does ("groups": { "domain": "localhost" }). This discrepancy is causing some libraries that rely on the expected output format to break.

Is this an intentional difference, or could it be a bug in Deno’s implementation?

Thanks in advance!

[marvinhagemeister]

Can confirm the issue. Something is off with the groups property.

[samuelstroschein]

Node's spec implementation (released in v23) yields the same result as the polyfill, further indicating that Deno's implementation has a bug.

import { URLPattern } from "node:url";

const pattern = ":protocol://:domain(.*)::port?/:locale(de)?/:path(.*)?";
const url = "https://localhost:5173/de";

const urlpattern = new URLPattern(pattern);
const match = urlpattern.exec(url);

console.log(match);

{
  inputs: [ 'https://localhost:5173/de' ],
  protocol: { input: 'https', groups: { protocol: 'https' } },
  username: { input: '', groups: { '0': '' } },
  password: { input: '', groups: { '0': '' } },
  hostname: { input: 'localhost', groups: { domain: 'localhost' } },
  port: { input: '5173', groups: { port: '5173' } },
  pathname: { input: '/de', groups: { path: undefined, locale: 'de' } },
  search: { input: '', groups: { '0': '' } },
  hash: { input: '', groups: { '0': '' } }
}