Handle deleting broken symlinks on Windows.

utils/pub/entrypoint.dart

 // Copyright (c) 2012, 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.
 
 library entrypoint;
 
 import 'dart:async';
 
 import '../../pkg/pathos/lib/path.dart' as path;
 
@@ skipping 280 matching lines @@
         });
       }).toList());
     }).then(flatten);
   }
 
   /// Creates a symlink to the `packages` directory in [dir]. Will replace one
   /// if already there.
   Future _linkSecondaryPackageDir(String dir) {
     return defer(() {
       var symlink = path.join(dir, 'packages');
-      if (fileExists(symlink)) {
+      // The order of if tests is significant here. fileExists() will return
+      // true for a symlink (broken or not) but deleteFile() cannot be used
+      // to delete a broken symlink on Windows. So we test for the directory
+      // first since deleteDir() does work on symlinks.
+      // TODO(rnystrom): Make deleteFile() work for symlinks on Windows so this
+      // doesn't matter.
+      if (dirExists(symlink)) {
+        deleteDir(symlink);
+      } else if (fileExists(symlink)) {
         deleteFile(symlink);
-      } else if (dirExists(symlink)) {
-        deleteDir(symlink);
       }
       return createSymlink(packagesDir, symlink, relative: true);
     });
   }
 }