Rationalize arg handling for pub build and serve.

sdk/lib/_internal/pub/lib/src/command/serve.dart

Index: sdk/lib/_internal/pub/lib/src/command/serve.dart
diff --git a/sdk/lib/_internal/pub/lib/src/command/serve.dart b/sdk/lib/_internal/pub/lib/src/command/serve.dart
index f7c140a778f7d45b40f6ae85490627ec882459c9..a2cc64e5400ae0c72e417f373f0818f08a8720a6 100644
--- a/sdk/lib/_internal/pub/lib/src/command/serve.dart
+++ b/sdk/lib/_internal/pub/lib/src/command/serve.dart
@@ -8,25 +8,22 @@ import 'dart:async';
 import 'dart:math' as math;
 
 import 'package:barback/barback.dart';
-import 'package:path/path.dart' as p;
 
 import '../barback/build_environment.dart';
 import '../barback/pub_package_provider.dart';
-import '../command.dart';
-import '../io.dart';
 import '../log.dart' as log;
 import '../utils.dart';
+import 'barback.dart';
 
 final _arrow = getSpecial('\u2192', '=>');
 
 /// Handles the `serve` pub command.
-class ServeCommand extends PubCommand {
+class ServeCommand extends BarbackCommand {
   String get description =>
       'Run a local web development server.\n\n'
       'By default, this serves "web/" and "test/", but an explicit list of \n'
       'directories to serve can be provided as well.';
   String get usage => "pub serve [directories...]";
-  final takesArguments = true;
 
   PubPackageProvider _provider;
 
@@ -51,8 +48,9 @@ class ServeCommand extends PubCommand {
   /// `true` if the admin server URL should be displayed on startup.
   bool get logAdminUrl => commandOptions['log-admin-url'];
 
-  /// The build mode.
-  BarbackMode get mode => new BarbackMode(commandOptions['mode']);
+  BarbackMode get defaultMode => BarbackMode.DEBUG;
+
+  List<String> get defaultSourceDirectories => ["web", "test"];
 
   /// This completer is used to keep pub running (by not completing) and to
   /// pipe fatal errors to pub's top-level error-handling machinery.
@@ -78,24 +76,20 @@ class ServeCommand extends PubCommand {
         help: 'Compile Dart to JavaScript.');
     commandParser.addFlag('force-poll', defaultsTo: false,
         help: 'Force the use of a polling filesystem watcher.');
-    commandParser.addOption('mode', defaultsTo: BarbackMode.DEBUG.toString(),
-        help: 'Mode to run transformers in.');
   }
 
-  Future onRun() {
+  Future onRunTransformerCommand() {
     var port = parseInt(commandOptions['port'], 'port');
     var adminPort = commandOptions['admin-port'] == null ? null :
         parseInt(commandOptions['admin-port'], 'admin port');
 
-    var directories = _parseDirectoriesToServe();
-
     var watcherType = commandOptions['force-poll'] ?
         WatcherType.POLLING : WatcherType.AUTO;
 
     return BuildEnvironment.create(entrypoint, hostname, port, mode,
         watcherType, useDart2JS: useDart2JS).then((environment) {
 
-      var directoryLength = directories.map((dir) => dir.length)
+      var directoryLength = sourceDirectories.map((dir) => dir.length)
           .reduce(math.max);
 
       return environment.startAdminServer(adminPort).then((server) {
@@ -113,7 +107,7 @@ class ServeCommand extends PubCommand {
         // that we don't log spurious build results in the middle of listing
         // out the bound servers.
         environment.pauseUpdates();
-        return Future.forEach(directories, (directory) {
+        return Future.forEach(sourceDirectories, (directory) {
           return _startServer(environment, directory, directoryLength);
         });
       }).then((_) {
@@ -178,50 +172,6 @@ class ServeCommand extends PubCommand {
     });
   }
 
-  /// Returns the set of directories that will be served from servers exposed
-  /// to the user.
-  ///
-  /// Throws a [UsageException] if the command-line arguments are invalid.
-  List<String> _parseDirectoriesToServe() {
-    if (commandOptions.rest.isEmpty) {
-      var directories = ['web', 'test'].where(dirExists).toList();
-      if (directories.isNotEmpty) return directories;
-      usageError(
-          'Your package must have "web" and/or "test" directories to serve,\n'
-          'or you must pass in directories to serve explicitly.');
-    }
-
-    var directories = commandOptions.rest.map(p.normalize).toList();
-    var invalid = directories.where((dir) => !p.isWithin('.', dir));
-    if (invalid.isNotEmpty) {
-      usageError("${_directorySentence(invalid, "isn't", "aren't")} in this "
-          "package.");
-    }
-
-    var nonExistent = directories.where((dir) => !dirExists(dir));
-    if (nonExistent.isNotEmpty) {
-      usageError("${_directorySentence(nonExistent, "doesn't", "don't")} "
-          "exist.");
-    }
-
-    return directories;
-  }
-
-  /// Converts a list of [directoryNames] to a sentence.
-  ///
-  /// After the list of directories, [singularVerb] will be used if there is
-  /// only one directory and [pluralVerb] will be used if there are more than
-  /// one.
-  String _directorySentence(Iterable<String> directoryNames,
-      String singularVerb, String pluralVerb) {
-    var directories = pluralize('Directory', directoryNames.length,
-        plural: 'Directories');
-    var names = toSentence(ordered(directoryNames).map((dir) => '"$dir"'));
-    var verb = pluralize(singularVerb, directoryNames.length,
-        plural: pluralVerb);
-    return "$directories $names $verb";
-  }
-
   /// Reports [error] and exits the server.
   void _fatalError(error, [stackTrace]) {
     if (_completer.isCompleted) return;