Close stdout and stderr before exiting Pub.

sdk/lib/_internal/pub/bin/pub.dart

 // Copyright (c) 2013, 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.
 
 import 'dart:async';
 import 'dart:io';
 import 'dart:math' as math;
 
 import 'package:args/args.dart';
 import 'package:path/path.dart' as path;
 
 import '../lib/src/command.dart';
 import '../lib/src/exit_codes.dart' as exit_codes;
 import '../lib/src/io.dart';
 import '../lib/src/log.dart' as log;
 import '../lib/src/sdk.dart' as sdk;
 import '../lib/src/utils.dart';
 
 final pubArgParser = initArgParser();
 
 void main() {
   ArgResults options;
 
   try {
     options = pubArgParser.parse(new Options().arguments);
   } on FormatException catch (e) {
     log.error(e.message);
     log.error('Run "pub help" to see available options.');
-    exit(exit_codes.USAGE);
+    flushThenExit(exit_codes.USAGE);
+    return;
   }
 
   if (options['version']) {
     log.message('Pub ${sdk.version}');
     return;
   }
 
   if (options['help']) {
     printUsage();
     return;
   }
 
   if (options.command == null) {
     if (options.rest.isEmpty) {
       // No command was chosen.
       printUsage();
     } else {
       log.error('Could not find a command named "${options.rest[0]}".');
       log.error('Run "pub help" to see available commands.');
-      exit(exit_codes.USAGE);
+      flushThenExit(exit_codes.USAGE);
+      return;
     }
     return;
   }
 
   if (options['trace']) {
     log.recordTranscript();
   }
 
   switch (options['verbosity']) {
     case 'normal': log.showNormal(); break;
@@ skipping 59 matching lines @@
 
 /// Checks that pub is running on a supported platform. If it isn't, it prints
 /// an error message and exits. Completes when the validation is done.
 Future validatePlatform() {
   return new Future.sync(() {
     if (Platform.operatingSystem != 'windows') return;
 
     return runProcess('ver', []).then((result) {
       if (result.stdout.join('\n').contains('XP')) {
         log.error('Sorry, but pub is not supported on Windows XP.');
-        exit(exit_codes.USAGE);
+        return flushThenExit(exit_codes.USAGE);
       }
     });
   });
 }
 
 /// Displays usage information for the app.
 void printUsage([String description = 'Pub is a package manager for Dart.']) {
   // Build up a buffer so it shows up as a single log entry.
   var buffer = new StringBuffer();
   buffer.write(description);
@@ skipping 24 matching lines @@
   for (var name in names) {
     buffer.write('  ${padRight(name, length)}   '
         '${PubCommand.commands[name].description}\n');
   }
 
   buffer.write('\n');
   buffer.write(
       'Use "pub help [command]" for more information about a command.');
   log.message(buffer.toString());
 }