Implement URL.from

doc/api/url.md

@@ -525,6 +525,45 @@ console.log(JSON.stringify(myURLs));
 // Prints ["https://www.example.com/","https://test.example.org/"]
 ```
 
+#### Static: URL.from(input)
+
+* `input` {Object}
+  * `protocol` {string} any valid protocol. See [`url.protocol`][].
+  * `username` {string} any valid username. See [`url.username`][].
+  * `password` {string} any valid password. See [`url.password`][].
+  * `host` {string} any valid host. See [`url.host`][].
+  * `port` {string|number} any valid port. See [`url.port`][].
+  * `query` {string} is a string representing the query.
+    It gets parsed into a valid [`URLSearchParams`][] and used inside of
+    the [`url.href`][] and [`url.search`][].
+  * `path` {string[]} unlike [`url.pathname`][] it is not a string,
+    but rather an array representing the path.
+  * `fragment` {string} represents the fragment (part after `#`).
+
+Creates a new `URL` instance based on the input object.
+
+```js
+const myURL = URL.from({
+  protocol: 'http',
+  username: 'root',
+  password: '1234',
+  port: '3000',
+  host: 'localhost',
+  path: ['main'],
+  fragment: 'app',
+  query: 'el=%3Cdiv%20%2F%3E',
+});
+// http://root:1234@localhost:3000/main?el=%3Cdiv%20%2F%3E#app
+```
+
+All properties are optional in case you want to build your url object
+gradually.
+
+```js
+const myURL = URL.from();
+// :
+```
+
 ### Class: URLSearchParams
 <!-- YAML
 added:

lib/internal/url.js

@@ -320,6 +320,64 @@ class URL {
           onParseError);
   }
 
+  static from(input) {
+    input = input || {};
+
+    const {
+      username = '',
+      password = '',
+      host = null,
+      port = null,
+      query = null,
+      path = [],
+      fragment = null,
+    } = input;
+    const protocol = `${input.protocol || ''}:`;
+
+    let flags = 0;
+
+    if (
+      protocol === 'file:' ||
+      protocol === 'https:' ||
+      protocol === 'wss:' ||
+      protocol === 'http:' ||
+      protocol === 'ftp:' ||
+      protocol === 'ws:' ||
+      protocol === 'gopher:'
+    )
+      flags |= URL_FLAGS_SPECIAL;
+    else if (!host)
+      flags |= URL_FLAGS_CANNOT_BE_BASE;
+
+    if (path.length)
+      flags |= URL_FLAGS_HAS_PATH;
+    if (host)
+      flags |= URL_FLAGS_HAS_HOST;
+    if (query)
+      flags |= URL_FLAGS_HAS_QUERY;
+    if (username)
+      flags |= URL_FLAGS_HAS_USERNAME;
+    if (password)
+      flags |= URL_FLAGS_HAS_PASSWORD;
+    if (fragment)
+      flags |= URL_FLAGS_HAS_FRAGMENT;
+
+    // TODO: maybe don't need to support this since it was used for
+    // the host setter hack at src/node_url.cc:1816
+    if (port == '-1') // eslint-disable-line eqeqeq
+      flags |= URL_FLAGS_IS_DEFAULT_SCHEME_PORT;
+
+    const self = Object.create(URL.prototype);
+    self[context] = new URLContext();
+
+    onParseComplete.apply(self, [
+      flags, protocol, username, password,
+      host, port, path, query, fragment
+    ]);
+
+    return self;
+  }
+
   get [special]() {
     return (this[context].flags & URL_FLAGS_SPECIAL) !== 0;
   }

test/parallel/test-whatwg-url-from.js

@@ -0,0 +1,91 @@
+'use strict';
+
+require('../common');
+
+const assert = require('assert');
+const { URL } = require('url');
+
+function t(expectedUrl, actualConfig) {
+  const url = URL.from(actualConfig);
+  assert.strictEqual(String(url), expectedUrl);
+}
+
+t(':', {});
+t(':', []);
+t(':', undefined);
+t(':', null);
+t(':', false);
+t(':', 0);
+t(':', 42);
+t(':', new Date());
+t(':', class {});
+t(':', 'str');
+t(':', new RegExp());
+t(':', Symbol());
+t('https://nodejs.org', new Proxy({}, {
+  get(target, p) {
+    if (p === 'protocol')
+      return 'https';
+    else if (p === 'host')
+      return 'nodejs.org';
+  }
+}));
+
+t('https://nodejs.org', {
+  protocol: 'https',
+  host: 'nodejs.org'
+});
+
+t('https://[email protected]', {
+  protocol: 'https',
+  host: 'site.com',
+  username: 'root'
+});
+
+t('https://:[email protected]', {
+  protocol: 'https',
+  host: 'site.com',
+  password: '1234'
+});
+
+t('https://root:[email protected]', {
+  protocol: 'https',
+  host: 'site.com',
+  username: 'root',
+  password: '1234'
+});
+
+t('https://site.com?a=1&b=2', {
+  protocol: 'https',
+  host: 'site.com',
+  query: 'a=1&b=2'
+});
+
+t('https://site.com/one/two', {
+  protocol: 'https',
+  host: 'site.com',
+  path: ['one', 'two']
+});
+
+t('http://localhost:3000', {
+  protocol: 'http',
+  host: 'localhost',
+  port: '3000',
+});
+
+t('http://localhost#fr', {
+  protocol: 'http',
+  host: 'localhost',
+  fragment: 'fr'
+});
+
+t('http://root:1234@localhost:3000/main?el=%3Cdiv%20%2F%3E#app', {
+  protocol: 'http',
+  username: 'root',
+  password: '1234',
+  port: '3000',
+  host: 'localhost',
+  path: ['main'],
+  fragment: 'app',
+  query: 'el=%3Cdiv%20%2F%3E'
+});