url: allow extension of user provided URL objects

doc/api/url.md

@@ -1226,6 +1226,11 @@ pathToFileURL('/some/path%.c');       // Correct:   file:///some/path%25.c (POSI
 added:
   - v15.7.0
   - v14.18.0
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/46989
+    description: The returned object will also contain all the own enumerable
+                 properties of the `url` argument.
 -->
 
 * `url` {URL} The [WHATWG URL][] object to convert to an options object.

lib/internal/url.js

@@ -1084,26 +1084,32 @@ function domainToUnicode(domain) {
   return _domainToUnicode(`${domain}`);
 }
 
-// Utility function that converts a URL object into an ordinary
-// options object as expected by the http.request and https.request
-// APIs.
+/**
+ * Utility function that converts a URL object into an ordinary options object
+ * as expected by the `http.request` and `https.request` APIs.
+ * @param {URL} url
+ * @returns {Record<string, unknown>}
+ */
 function urlToHttpOptions(url) {
+  const { hostname, pathname, port, username, password, search } = url;
   const options = {
+    __proto__: null,
+    ...url, // In case the url object was extended by the user.
     protocol: url.protocol,
-    hostname: url.hostname && StringPrototypeStartsWith(url.hostname, '[') ?
-      StringPrototypeSlice(url.hostname, 1, -1) :
-      url.hostname,
+    hostname: hostname && StringPrototypeStartsWith(hostname, '[') ?
+      StringPrototypeSlice(hostname, 1, -1) :
+      hostname,
     hash: url.hash,
-    search: url.search,
-    pathname: url.pathname,
-    path: `${url.pathname || ''}${url.search || ''}`,
+    search: search,
+    pathname: pathname,
+    path: `${pathname || ''}${search || ''}`,
     href: url.href,
   };
-  if (url.port !== '') {
-    options.port = Number(url.port);
+  if (port !== '') {
+    options.port = Number(port);
   }
-  if (url.username || url.password) {
-    options.auth = `${decodeURIComponent(url.username)}:${decodeURIComponent(url.password)}`;
+  if (username || password) {
+    options.auth = `${decodeURIComponent(username)}:${decodeURIComponent(password)}`;
   }
   return options;
 }

test/parallel/test-http-client-request-options.js

@@ -0,0 +1,27 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('node:assert');
+const http = require('node:http');
+
+const headers = { foo: 'Bar' };
+const server = http.createServer(common.mustCall((req, res) => {
+  assert.strictEqual(req.url, '/ping?q=term');
+  assert.strictEqual(req.headers?.foo, headers.foo);
+  req.resume();
+  req.on('end', () => {
+    res.writeHead(200);
+    res.end('pong');
+  });
+}));
+
+server.listen(0, common.localhostIPv4, () => {
+  const { address, port } = server.address();
+  const url = new URL(`http://${address}:${port}/ping?q=term`);
+  url.headers = headers;
+  const clientReq = http.request(url);
+  clientReq.on('close', common.mustCall(() => {
+    server.close();
+  }));
+  clientReq.end();
+});