Work around issue 7218 in Pub.

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 628 matching lines @@
 }
 
 /// Spawns the process located at [executable], passing in [args]. Returns a
 /// [Future] that will complete with the [Process] once it's been started.
 ///
 /// The spawned process will inherit its parent's environment variables. If
 /// [environment] is provided, that will be used to augment (not replace) the
 /// the inherited variables.
 Future<Process> startProcess(String executable, List<String> args,
     {workingDir, Map<String, String> environment}) =>
-  _doProcess(Process.start, executable, args, workingDir, environment);
+  _doProcess(Process.start, executable, args, workingDir, environment)
+    .transform((process) => new _WrappedProcess(process));
+
+/// A wrapper around [Process] that buffers the stdout and stderr to avoid
+/// running into issue 7218.
+class _WrappedProcess implements Process {
+  final Process _process;
+  final InputStream stderr;
+  final InputStream stdout;
+
+  OutputStream get stdin => _process.stdin;
+
+  void set onExit(void callback(int exitCode)) {
+    _process.onExit = callback;
+  }
+
+  _WrappedProcess(Process process)
+    : _process = process,
+      stderr = wrapInputStream(process.stderr),
+      stdout = wrapInputStream(process.stdout);
+
+  bool kill([ProcessSignal signal = ProcessSignal.SIGTERM]) =>
+    _process.kill(signal);
+}
 
 /// Calls [fn] with appropriately modified arguments. [fn] should have the same
 /// signature as [Process.start], except that the returned [Future] may have a
 /// type other than [Process].
 Future _doProcess(Function fn, String executable, List<String> args, workingDir,
     Map<String, String> environment) {
   // TODO(rnystrom): Should dart:io just handle this?
   // Spawning a process on Windows will not look for the executable in the
   // system path. So, if executable looks like it needs that (i.e. it doesn't
   // have any path separators in it), then spawn it through a shell.
@@ skipping 152 matching lines @@
  * directory or a path. Returns whether or not the extraction was successful.
  */
 Future<bool> extractTarGz(InputStream stream, destination) {
   destination = _getPath(destination);
 
   if (Platform.operatingSystem == "windows") {
     return _extractTarGzWindows(stream, destination);
   }
 
   var completer = new Completer<int>();
-  var processFuture = Process.start("tar",
+  var processFuture = startProcess("tar",
       ["--extract", "--gunzip", "--directory", destination]);
   processFuture.then((process) {
     process.onExit = completer.complete;
     stream.pipe(process.stdin);
     process.stdout.pipe(stdout, close: false);
     process.stderr.pipe(stderr, close: false);
   });
   processFuture.handleException((error) {
     completer.completeException(error, processFuture.stackTrace);
     return true;
@@ skipping 196 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);
 }