Support serving from multiple directories using "pub serve".

sdk/lib/_internal/pub/test/serve/roots/throws_an_error_if_custom_roots_dont_exist_test.dart

Index: sdk/lib/_internal/pub/test/serve/roots/throws_an_error_if_custom_roots_dont_exist_test.dart
diff --git a/sdk/lib/_internal/pub/test/serve/roots/throws_an_error_if_custom_roots_dont_exist_test.dart b/sdk/lib/_internal/pub/test/serve/roots/throws_an_error_if_custom_roots_dont_exist_test.dart
new file mode 100644
index 0000000000000000000000000000000000000000..440043b742b7cb193cd0a7bb1e5600227be2af5b
--- /dev/null
+++ b/sdk/lib/_internal/pub/test/serve/roots/throws_an_error_if_custom_roots_dont_exist_test.dart
@@ -0,0 +1,26 @@
+// 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.
+
+library pub_tests;
+
+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();
+  integration("throws an error if custom roots don't exist", () {

[Bob Nystrom, 2014/02/19 00:36:52]

Is this the behavior we want? What if the user fires up pub serve and then
creates the directory afterwards?

[nweiz, 2014/02/19 01:25:58]

The watcher package doesn't support that. We currently allow this for "pub
serve", but if you create the directory after the fact no changes in it will
ever be registered.

We could theoretically support this by watching the parent directory to see when
the child directories were created, then watching those, but that sounds like
more pain than it's worth.

[Bob Nystrom, 2014/02/19 01:50:55]

Ah good point. Let's not worry about that then.

+    d.dir(appPath, [
+      d.appPubspec()
+    ]).create();
+
+    var server = startPubServe(args: ["foo", "bar"]);

[Bob Nystrom, 2014/02/19 00:36:52]

Add a third directory that does exist to ensure that we only show errors for the
missing ones, and that we do show errors even if some are missing.

[nweiz, 2014/02/19 01:25:58]

Done.

+    server.stderr.expect('Directories "bar/" and "foo/" don\'t exist.');

[Bob Nystrom, 2014/02/19 00:36:52]

Remove the "/" from the names. We don't use them when referring to directories
elsewhere, and it will be wrong on Windows.

[nweiz, 2014/02/19 01:25:58]

Done.

+    server.shouldExit(exit_codes.USAGE);
+  });
+}