Rationalize arg handling for pub build and serve.

sdk/lib/_internal/pub/test/barback/fails_if_no_default_dirs_test.dart

Index: sdk/lib/_internal/pub/test/barback/fails_if_no_default_dirs_test.dart
diff --git a/sdk/lib/_internal/pub/test/barback/fails_if_no_default_dirs_test.dart b/sdk/lib/_internal/pub/test/barback/fails_if_no_default_dirs_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..3b0aa972f1aa9f6505e92a1a81da90e5753b9a32
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/barback/fails_if_no_default_dirs_test.dart
@@ -0,0 +1,27 @@
+// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS d.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 'package:scheduled_test/scheduled_test.dart';
+
+import '../../lib/src/exit_codes.dart' as exit_codes;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+
+main() {
+  initConfig();
+
+  setUp(() {
+    d.appDir().create();
+  });
+
+  pubBuildAndServeShouldFail("if no directories were passed and no default "
+          "ones exist",
+      args: [],
+      buildError: 'Your package must have a "web" directory,\n'
+          'or you must specify the source directories.',
+      serveError: 'Your package must have "web" and/or "test" directories,\n'
+          'or you must specify the source directories.',
+      exitCode: exit_codes.DATA);
+}