Make a bunch of stuff in pub synchronous.

utils/pub/utils.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.
 
 /// Generic utility functions. Stuff that should possibly be in core.
 library utils;
 
 import 'dart:async';
 import 'dart:crypto';
 import 'dart:isolate';
@@ skipping 127 matching lines @@
   return false;
 }
 
 /// Returns the hex-encoded sha1 hash of [source].
 String sha1(String source) {
   var sha = new SHA1();
   sha.add(source.charCodes);
   return CryptoUtils.bytesToHex(sha.close());
 }
 
+/// Invokes the given callback asynchronously. Returns a [Future] that completes
+/// to the result of [callback].
+///
+/// This is also used to wrap synchronous code that may thrown an exception to
+/// ensure that methods that have both sync and async code only report errors
+/// asynchronously.
+Future defer(callback()) {
+  return new Future.immediate(null).then((_) => callback());
+}
+
 /// Returns a [Future] that completes in [milliseconds].
 Future sleep(int milliseconds) {
   var completer = new Completer();
   new Timer(milliseconds, (_) => completer.complete());
   return completer.future;
 }
 
 /// Configures [future] so that its result (success or exception) is passed on
 /// to [completer].
 void chainToCompleter(Future future, Completer completer) {
@@ skipping 142 matching lines @@
 
 /// Add all key/value pairs from [source] to [destination], overwriting any
 /// pre-existing values.
 void mapAddAll(Map destination, Map source) =>
   source.forEach((key, value) => destination[key] = value);
 
 /// Decodes a URL-encoded string. Unlike [decodeUriComponent], this includes
 /// replacing `+` with ` `.
 String urlDecode(String encoded) =>
   decodeUriComponent(encoded.replaceAll("+", " "));