Refactor command code and add support for --help and --version.

utils/pub/pub.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.
 
 /**
  * The main entrypoint for the pub command line application.
  */
 #library('pub');
 
 #import('../yaml/yaml.dart');
 
 #import('io.dart');
 #import('utils.dart');
 
 #source('cache.dart');
 #source('command_list.dart');
 #source('command_update.dart');
+#source('command_version.dart');
 #source('package.dart');
 
-Map<String, PubCommand> commands;
-PackageCache cache;
-
 main() {
   final args = new Options().arguments;
 
   // TODO(rnystrom): In addition to explicit "help" and "version" commands,
   // should also add special-case support for --help and --version arguments to
   // be consistent with other Unix apps.
-  commands = {
-    'list': new PubCommand('print the contents of repositories', commandList),
-    'update': new PubCommand("update a package's dependencies", commandUpdate),
-    'version': new PubCommand('print Pub version', commandVersion)
+  final commands = {
+    'list': new ListCommand(),
+    'update': new UpdateCommand(),
+    'version': new VersionCommand()
   };
 
   if (args.length == 0) {
-    showUsage();
+    printUsage(commands);
     return;
   }
 
+  // For consistency with expected unix idioms, support --help, -h, and
+  // --version in addition to the regular commands.
+  if (args.length == 1) {
+    if (args[0] == '--help' || args[0] == '-h') {
+      printUsage(commands);
+      return;
+    }
+
+    if (args[0] == '--version') {
+      printVersion();
+      return;
+    }
+  }
+
   // TODO(rnystrom): Hack. This is temporary code to allow the pub tests to
   // pass in relevant paths. Eventually these should be either environment
   // variables or at least a cleaner arg parser.
   var cacheDir;
   for (var i = 0; i < args.length; i++) {
     if (args[i].startsWith('--cachedir=')) {
       cacheDir = args[i].substring('--cachedir='.length);
       args.removeRange(i, 1);
       break;
     }
   }
 
   // TODO(rnystrom): Do we want this to be global?
-  cache = new PackageCache(cacheDir);
-
-  var options = new PubOptions(cacheDir);
+  final cache = new PackageCache(cacheDir);
 
   // Select the command.
   final command = commands[args[0]];
   if (command == null) {
     print('Unknown command "${args[0]}".');
     print('Run "pub help" to see available commands.');
     exit(64); // See http://www.freebsd.org/cgi/man.cgi?query=sysexits.
     return;
   }
 
   args.removeRange(0, 1);
-  command.function(options, args);
+  command.run(cache, args);
 }
 
 /** Displays usage information for the app. */
-void showUsage() {
+void printUsage(Map<String, PubCommand> commands) {
   print('Pub is a package manager for Dart.');
   print('');
   print('Usage:');
   print('');
   print('  pub command [arguments]');
   print('');
   print('The commands are:');
   print('');
 
   // Show the commands sorted.
   // TODO(rnystrom): A sorted map would be nice.
   int length = 0;
   final names = <String>[];
   for (final command in commands.getKeys()) {
     length = Math.max(length, command.length);
     names.add(command);
   }
 
   names.sort((a, b) => a.compareTo(b));
 
   for (final name in names) {
     print('  ${padRight(name, length)}   ${commands[name].description}');
   }
 
   print('');
   print('Use "pub help [command]" for more information about a command.');
 }
 
-/** Displays pub version information. */
-void commandVersion(PubOptions options, List<String> args) {
-  // TODO(rnystrom): Store some place central.
+void printVersion() {
   print('Pub 0.0.0');
 }
 
 /**
  * Gets the package that contains the current working directory. In other words,
  * finds the package that the user is currently "in".
  */
 Future<Package> getWorkingPackage() {
   // TODO(rnystrom): Will eventually need better logic to walk up
   // subdirectories until we hit one that looks package-like. For now, just
   // assume the cwd is it.
   return Package.load(workingDir);
 }
 
-typedef void CommandFunction(PubOptions options, List<String> args);
+class PubCommand {
+  PackageCache cache;
 
-class PubCommand {
-  final String description;
-  final CommandFunction function;
+  abstract String get description();
 
-  PubCommand(this.description, this.function);
+  void run(PackageCache cache_, List<String> args) {
+    cache = cache_;
+
+    // TODO(rnystrom): Each command should define the arguments it expects and
+    // we can handle them generically here.
+
+    onRun();
+  }
+
+  abstract void onRun();
 }
-
-class PubOptions {
-  final String cacheDir;
-
-  PubOptions(this.cacheDir);
-}