Add validation infrastructure for "pub lish".

utils/pub/validator/pubspec_field.dart

Index: utils/pub/validator/pubspec_field.dart
diff --git a/utils/pub/validator/pubspec_field.dart b/utils/pub/validator/pubspec_field.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4c63d9bbec02cbc7e430f283fe3b76c1cb1e9475
--- /dev/null
+++ b/utils/pub/validator/pubspec_field.dart
@@ -0,0 +1,48 @@
+// 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 pubspec_field_validator;
+
+import '../entrypoint.dart';
+import '../system_cache.dart';
+import '../validator.dart';
+
+/// A validator that checks that the pubspec has valid "author" and "homepage"
+/// fields.
+class PubspecFieldValidator extends Validator {
+  PubspecFieldValidator(Entrypoint entrypoint)
+    : super(entrypoint);
+
+  Future validate() {
+    // The types of all fields are validated when the pubspec is parsed.
+    var pubspec = entrypoint.root.pubspec;
+    var author = pubspec.fields['author'];
+    var authors = pubspec.fields['authors'];
+    if (author == null && authors == null) {
+      errors.add('pubspec.yaml is missing an "author" or "authors" field.');
+    } else {
+      if (authors == null) authors = [author];
+
+      var hasName = new RegExp(r"^ *[^< ]");
+      var hasEmail = new RegExp(r"<[^>]+> *$");
+      for (var authorName in authors) {
+        if (!hasName.hasMatch(authorName)) {
+          warnings.add('Author "$authorName" in pubspec.yaml is missing a '
+              'name.');
+        }
+        if (!hasEmail.hasMatch(authorName)) {
+          warnings.add('Author "$authorName" in pubspec.yaml is missing an '
+              'email address (e.g. "name <email>").');
+        }
+      }
+    }
+
+    var homepage = pubspec.fields['homepage'];
+    if (homepage == null) {
+      errors.add('pubspec.yaml is missing a "homepage" field.');
+    }
+
+    return new Future.immediate(null);
+  }
+}