Add fileURLToPath

README.md

@@ -106,3 +106,10 @@ an anchor tag.  Examples:
     url.resolve('/one/two/three', 'four')         // '/one/two/four'
     url.resolve('http://example.com/', '/one')    // 'http://example.com/one'
     url.resolve('http://example.com/one', '/two') // 'http://example.com/two'
+
+### url.fileURLToPath(url)
+
+Take a string or WHATWG `URL` object representing a filepath, and return the POSIX
+filepath as a string.
+
+    url.fileURLToPath('file:///etc/hosts')         // '/etc/hosts'

test/index.js

@@ -2055,3 +2055,74 @@ relativeTests2.forEach(function (relativeTest) {
     assert.equal(actual, expected, 'format(' + relativeTest[1] + ') == ' + expected + '\nactual:' + actual);
   });
 });
+
+var fileURLToPathTestCases = [
+  // Lowercase ascii alpha
+  { path: '/foo', fileURL: 'file:///foo' },
+  // Uppercase ascii alpha
+  { path: '/FOO', fileURL: 'file:///FOO' },
+  // dir
+  { path: '/dir/foo', fileURL: 'file:///dir/foo' },
+  // trailing separator
+  { path: '/dir/', fileURL: 'file:///dir/' },
+  // dot
+  { path: '/foo.mjs', fileURL: 'file:///foo.mjs' },
+  // space
+  { path: '/foo bar', fileURL: 'file:///foo%20bar' },
+  // question mark
+  { path: '/foo?bar', fileURL: 'file:///foo%3Fbar' },
+  // number sign
+  { path: '/foo#bar', fileURL: 'file:///foo%23bar' },
+  // ampersand
+  { path: '/foo&bar', fileURL: 'file:///foo&bar' },
+  // equals
+  { path: '/foo=bar', fileURL: 'file:///foo=bar' },
+  // colon
+  { path: '/foo:bar', fileURL: 'file:///foo:bar' },
+  // semicolon
+  { path: '/foo;bar', fileURL: 'file:///foo;bar' },
+  // percent
+  { path: '/foo%bar', fileURL: 'file:///foo%25bar' },
+  // backslash
+  { path: '/foo\\bar', fileURL: 'file:///foo%5Cbar' },
+  // backspace
+  { path: '/foo\bbar', fileURL: 'file:///foo%08bar' },
+  // tab
+  { path: '/foo\tbar', fileURL: 'file:///foo%09bar' },
+  // newline
+  { path: '/foo\nbar', fileURL: 'file:///foo%0Abar' },
+  // carriage return
+  { path: '/foo\rbar', fileURL: 'file:///foo%0Dbar' },
+  // latin1
+  { path: '/fóóbàr', fileURL: 'file:///f%C3%B3%C3%B3b%C3%A0r' },
+  // Euro sign (BMP code point)
+  { path: '/€', fileURL: 'file:///%E2%82%AC' },
+  // Rocket emoji (non-BMP code point)
+  { path: '/🚀', fileURL: 'file:///%F0%9F%9A%80' }
+];
+
+fileURLToPathTestCases.forEach(function (fileURLToPathTestCase) {
+  test('fileURLToPath(' + fileURLToPathTestCase.fileURL + ')', function () {
+    var fromString = url.fileURLToPath(fileURLToPathTestCase.fileURL);
+    assert.strictEqual(fromString, fileURLToPathTestCase.path);
+    var fromURL = url.fileURLToPath(new URL(fileURLToPathTestCase.fileURL));
+    assert.strictEqual(fromURL, fileURLToPathTestCase.path);
+  });
+});
+
+[
+  'https://host/y',
+  'file://host/a',
+  new URL('https://host/y'),
+  'file:///a%2F/',
+  '',
+  null,
+  undefined,
+  1,
+  {},
+  true
+].forEach(function (val) {
+  test('fileURLToPath(' + val + ')', function () {
+    assert['throws'](function () { url.fileURLToPath(val); }, TypeError);
+  });
+});

url.js

@@ -770,4 +770,38 @@ exports.resolve = urlResolve;
 exports.resolveObject = urlResolveObject;
 exports.format = urlFormat;
 
+function isURLInstance(fileURLOrPath) {
+  return fileURLOrPath != null && fileURLOrPath.href && fileURLOrPath.origin;
+}
+
+function getPathFromURLPosix(url) {
+  if (url.hostname !== '') {
+    throw new TypeError('File URL host must be "localhost" or empty on darwin');
+  }
+  var pathname = url.pathname;
+  for (var n = 0; n < pathname.length; n++) {
+    if (pathname[n] === '%') {
+      var third = pathname.codePointAt(n + 2) | 0x20;
+      if (pathname[n + 1] === '2' && third === 102) {
+        throw new TypeError('File URL path must not include encoded / characters');
+      }
+    }
+  }
+  return decodeURIComponent(pathname);
+}
+
+function fileURLToPath(path) {
+  if (typeof path === 'string') {
+    path = new URL(path);
+  } else if (!isURLInstance(path)) {
+    throw new TypeError('The "path" argument must be of type string or an instance of URL. Received ' + path);
+  }
+  if (path.protocol !== 'file:') {
+    throw new TypeError('The URL must be of scheme file');
+  }
+  return getPathFromURLPosix(path);
+}
+
+exports.fileURLToPath = fileURLToPath;
+
 exports.Url = Url;