Don't warn on the absence of "lib" in the root package.

utils/pub/io.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.
 
 /**
  * Helper functionality to make working with IO easier.
  */
 #library('io');
 
 #import('dart:io');
@@ skipping 335 matching lines @@
     }
 
     // It's a new style package, so symlink to the 'lib' directory. But only
     // if the package actually *has* one. Otherwise, we won't create a
     // symlink at all.
     from = join(from, 'lib');
     return dirExists(from).chain((exists) {
       if (exists) {
         return createSymlink(from, to);
       } else {
-        printError('Warning: Package "$name" does not have a "lib" directory.');
+        // It's OK for the self link (i.e. the root package) to not have a lib
+        // directory since it may just be a leaf application that only has
+        // code in bin or web.
+        if (!isSelfLink) {
+          printError(
+              'Warning: Package "$name" does not have a "lib" directory.');
+        }
+
         return new Future.immediate(to);
       }
     });
   });
 }
 
 /**
  * Given [entry] which may be a [String], [File], or [Directory] relative to
  * the current working directory, returns its full canonicalized path.
  */
@@ skipping 400 matching lines @@
   return new Directory(entry);
 }
 
 /**
  * Gets a [Uri] for [uri], which can either already be one, or be a [String].
  */
 Uri _getUri(uri) {
   if (uri is Uri) return uri;
   return new Uri.fromString(uri);
 }