Add a validator for top-level directory names.

utils/pub/validator/directory.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.
+
+library directory_validator;
+
+import '../entrypoint.dart';
+import '../io.dart';
+import '../validator.dart';
+
+/// A validator that validates a package's top-level directories.
+class DirectoryValidator extends Validator {
+  DirectoryValidator(Entrypoint entrypoint)
+    : super(entrypoint);
+
+  static final _PLURAL_NAMES = ["tools", "tests", "docs", "examples"];
+
+  Future validate() {
+    return listDir(entrypoint.root.dir).chain((dirs) {
+      return Futures.wait(dirs.map((dir) {
+        return dirExists(dir).transform((exists) {
+          if (!exists) return;
+
+          dir = basename(dir);
+          if (_PLURAL_NAMES.contains(dir)) {
+            // Cut off the "s"
+            var singularName = dir.substring(0, dir.length - 1);
+            warnings.add('Rename the top-level "$dir" directory to '
+                    '"$singularName".\n'
+                'The Pub layout convention is to use singular directory '
+                    'names.\n'
+                'Plural names won\'t be correctly identified by Pub and other '
+                    'tools.');

[Bob Nystrom, 2013/01/03 23:18:54]

How about:

''Rename the top-level "$dir" directory to "$singularName".\n'
'This enables Dart scripts within that directory to use "package:" imports.'

Ditto for below. Better?

[nweiz, 2013/01/04 00:25:15]

That doesn't really make sense for "doc", and I think a lot of people will have
non-Dart tool scripts. This will also be relevant if/when we list examples/docs
on pub.dartlang.org or add bin files to the users path. I feel like being a
little vague about the consequences makes sense here.

+          }
+
+          if (dir.contains(new RegExp(r"^samples?$"))) {
+            warnings.add('Rename the top-level "$dir" directory to "example".\n'
+                'This allows Pub to find your examples and create "packages" '
+                    'directories for them.\n');
+          }
+        });
+      }));
+    });
+  }
+}