Fix error reporting on invalid command line args.

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 '../../pkg/args/lib/args.dart';
@@ skipping 41 matching lines @@
     help: 'Prints the version of Pub');
   parser.addFlag('trace', help: 'Prints a stack trace when an error occurs');
   return parser;
 }
 
 main() {
   var globalOptions;
   try {
     globalOptions = pubArgParser.parse(new Options().arguments);
   } on FormatException catch (e) {
-    printUsage(description: e.message);
-    return;
+    printError(e.message);
+    printError('Run "pub help" to see available options.');
+    exit(exit_codes.USAGE);
   }
 
   if (globalOptions['version']) {
     printVersion();
     return;
   }
 
   if (globalOptions['help'] || globalOptions.rest.isEmpty) {
     printUsage();
     return;
@@ skipping 14 matching lines @@
 
   var cache = new SystemCache(cacheDir);
   cache.register(new SdkSource(sdkDir));
   cache.register(new GitSource());
   cache.register(new HostedSource());
   cache.sources.setDefault('hosted');
 
   // Select the command.
   var command = pubCommands[globalOptions.rest[0]];
   if (command == null) {
-    printError('Unknown command "${globalOptions.rest[0]}".');
+    printError('Could not find a command named "${globalOptions.rest[0]}".');
     printError('Run "pub help" to see available commands.');
     exit(exit_codes.USAGE);
     return;
   }
 
   var commandArgs =
       globalOptions.rest.getRange(1, globalOptions.rest.length - 1);
   command.run(cache, globalOptions, commandArgs);
 }
 
 /** Displays usage information for the app. */
 void printUsage([String description = 'Pub is a package manager for Dart.']) {
   print(description);
   print('');
   print('Usage: pub command [arguments]');
   print('');
   print('Global options:');
   print(pubArgParser.getUsage());
   print('');
-  print('The commands are:');
 
   // Show the commands sorted.
+  print('Available commands:');
+
   // TODO(rnystrom): A sorted map would be nice.
   int length = 0;
   var names = <String>[];
   for (var command in pubCommands.keys) {
     length = max(length, command.length);
     names.add(command);
   }
 
   names.sort((a, b) => a.compareTo(b));
 
@@ skipping 12 matching lines @@
 abstract class PubCommand {
   SystemCache cache;
   ArgResults globalOptions;
   ArgResults commandOptions;
 
   Entrypoint entrypoint;
 
   /**
    * A one-line description of this command.
    */
-  abstract String get description;
+  String get description;
 
   /**
    * How to invoke this command (e.g. `"pub install [package]"`).
    */
-  abstract String get usage;
+  String get usage;
 
   /// Whether or not this command requires [entrypoint] to be defined. If false,
   /// Pub won't look for a pubspec and [entrypoint] will be null when the
   /// command runs.
   bool get requiresEntrypoint => true;
 
   /**
    * Override this to define command-specific options. The results will be made
    * available in [commandOptions].
    */
   ArgParser get commandParser => new ArgParser();
 
   void run(SystemCache cache_, ArgResults globalOptions_,
       List<String> commandArgs) {
     cache = cache_;
     globalOptions = globalOptions_;
 
     try {
      commandOptions = commandParser.parse(commandArgs);
     } on FormatException catch (e) {
-      this.printUsage(description: e.message);
+      printError(e.message);
+      printError('Use "pub help" for more information.');
       exit(exit_codes.USAGE);
     }
 
     handleError(error, trace) {
       // This is basically the top-level exception handler so that we don't
       // spew a stack trace on our users.
       var message = error.toString();
 
       // TODO(rnystrom): The default exception implementation class puts
       // "Exception:" in the output, so strip that off.
@@ skipping 48 matching lines @@
     // Explicitly exit on success to ensure that any dangling dart:io handles
     // don't cause the process to never terminate.
     future.then((_) => exit(0));
   }
 
   /**
    * Override this to perform the specific command. Return a future that
    * completes when the command is done or fails if the command fails. If the
    * command is synchronous, it may return `null`.
    */
-  abstract Future onRun();
+  Future onRun();
 
   /** Displays usage information for this command. */
   void printUsage([String description]) {
     if (description == null) description = this.description;
     print(description);
     print('');
     print('Usage: $usage');
 
     var commandUsage = commandParser.getUsage();
     if (!commandUsage.isEmpty) {
       print('');
       print(commandUsage);
     }
   }
 
   /// Returns the appropriate exit code for [exception], falling back on 1 if no
   /// appropriate exit code could be found.
   int _chooseExitCode(exception) {
     if (exception is HttpException || exception is HttpParserException ||
         exception is SocketIOException || exception is PubHttpException) {
       return exit_codes.UNAVAILABLE;
     } else if (exception is FormatException) {
       return exit_codes.DATA;
     } else {
       return 1;
     }
   }
 }