Make a bunch of stuff in pub synchronous.

utils/pub/validator/name.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 name_validator;
 
 import 'dart:async';
 import 'dart:io';
 
 import '../../../pkg/path/lib/path.dart' as path;
 import '../entrypoint.dart';
 import '../io.dart';
+import '../utils.dart';
 import '../validator.dart';
 
 /// Dart reserved words, from the Dart spec.
 final _RESERVED_WORDS = [
   "abstract", "as", "dynamic", "export", "external", "factory", "get",
   "implements", "import", "library", "operator", "part", "set", "static",
   "typedef"
 ];
 
 /// A validator that validates the name of the package and its libraries.
@@ skipping 17 matching lines @@
             'the name of the package, "${entrypoint.root.name}".\n'
             'This helps users know what library to import.');
       }
     });
   }
 
   /// Returns a list of all libraries in the current package as paths relative
   /// to the package's root directory.
   Future<List<String>> get _libraries {
     var libDir = join(entrypoint.root.dir, "lib");
-    return dirExists(libDir).then((libDirExists) {
-      if (!libDirExists) return [];
+    return defer(() {
+      if (!dirExists(libDir)) return [];
       return listDir(libDir, recursive: true);
     }).then((files) {
       return files
           .map((file) => relativeTo(file, dirname(libDir)))
           .where((file) => !splitPath(file).contains("src") &&
                            path.extension(file) == '.dart')
           .toList();
     });
   }
 
@@ skipping 23 matching lines @@
       builder
         ..add(source.substring(lastMatchEnd, match.start + 1))
         ..add("_")
         ..add(match.group(1).toLowerCase());
       lastMatchEnd = match.end;
     }
     builder.add(source.substring(lastMatchEnd));
     return builder.toString().toLowerCase();
   }
 }