dart:io | Add Link class, as sibling to File and Directory.

tests/standalone/io/link_test.dart

+// Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import "dart:io";
+import "dart:isolate";
+
+// Test the dart:io Link class.
+
+testCreateSync() {
+  Path base = new Path(new Directory('').createTempSync().path);
+  String link = base.append('link').toNativePath();
+  String target = base.append('target').toNativePath();
+  new Directory(target).createSync();
+  new Link(link).createSync(target);
+
+  Expect.equals(FileSystemEntityType.DIRECTORY,
+                FileSystemEntity.typeSync(link));
+  Expect.equals(FileSystemEntityType.DIRECTORY,
+                FileSystemEntity.typeSync(target));
+  Expect.equals(FileSystemEntityType.LINK,
+                FileSystemEntity.typeSync(link, followLinks: false));
+  Expect.equals(FileSystemEntityType.DIRECTORY,
+                FileSystemEntity.typeSync(target, followLinks: false));
+  Expect.isTrue(FileSystemEntity.isLinkSync(link));
+  Expect.isFalse(FileSystemEntity.isLinkSync(target));
+  Expect.isTrue(new Directory(link).existsSync());
+  Expect.isTrue(new Directory(target).existsSync());
+  Expect.isTrue(new Link(link).existsSync());
+  Expect.isFalse(new Link(target).existsSync());
+
+  String createdThroughLink =
+      base.append('link/createdThroughLink').toNativePath();
+  String createdDirectly = base.append('target/createdDirectly').toNativePath();
+  new Directory(createdThroughLink).createSync();
+  new Directory(createdDirectly).createSync();
+  Expect.isTrue(new Directory(createdThroughLink).existsSync());
+  Expect.isTrue(new Directory(createdDirectly).existsSync());
+  Expect.isTrue(new Directory.fromPath(base.append('link/createdDirectly'))
+                .existsSync());
+  Expect.isTrue(new Directory.fromPath(base.append('target/createdThroughLink'))
+                .existsSync());
+  Expect.equals(FileSystemEntityType.DIRECTORY,
+                FileSystemEntity.typeSync(createdThroughLink,
+                                          followLinks: false));
+  Expect.equals(FileSystemEntityType.DIRECTORY,
+                FileSystemEntity.typeSync(createdDirectly, followLinks: false));
+
+  new Directory.fromPath(base).deleteSync(recursive: true);
+}
+
+
+main() {
+  testCreateSync();
+}