add a comment to the generated lock file

utils/pub/lock_file.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 lock_file;
 
 import 'dart:json' as json;
 import 'package.dart';
 import 'source_registry.dart';
 import 'utils.dart';
 import 'version.dart';
 import '../../pkg/yaml/lib/yaml.dart';
 
 /// A parsed and validated `pubspec.lock` file.
 class LockFile {
+  
+  /// comment to append at start of lock file 
+  static final comment = "# Generated by pub. See: http://pub.dartlang.org/doc/glossary.html#lockfile";

[Bob Nystrom, 2013/01/31 22:17:44]

It's probably not worth making a constant for this. I'd just put the string
inline below.

[keertip, 2013/01/31 22:40:41]

Done.

+  
   /// The packages this lockfile pins.
   Map<String, PackageId> packages;
 
   LockFile._(this.packages);
 
   LockFile.empty()
     : packages = <String, PackageId>{};
 
   /// Parses the lockfile whose text is [contents].
   factory LockFile.parse(String contents, SourceRegistry sources) {
     var packages = <String, PackageId>{};
 
     if (contents.trim() == '') return new LockFile.empty();
-
-    var parsed = loadYaml(contents);
+    // remove comment before parsing
+    var parsed = loadYaml(contents.replaceAll(comment, ''));

[Bob Nystrom, 2013/01/31 22:17:44]

This shouldn't be necessary. YAML supports comments and should ignore them
automatically.

[keertip, 2013/01/31 22:40:41]

Removed.

On 2013/01/31 22:17:44, Bob Nystrom wrote:

 
     if (parsed.containsKey('packages')) {
       var packageEntries = parsed['packages'];
 
       packageEntries.forEach((name, spec) {
         // Parse the version.
         if (!spec.containsKey('version')) {
           throw new FormatException('Package $name is missing a version.');
         }
         var version = new Version.parse(spec['version']);
@@ skipping 37 matching lines @@
     packages.forEach((name, id) {
       packagesObj[name] = {
         'version': id.version.toString(),
         'source': id.source.name,
         'description': id.description
       };
     });
 
     // TODO(nweiz): Serialize using the YAML library once it supports
     // serialization. For now, we use JSON, since it's a subset of YAML anyway.
-    return json.stringify({'packages': packagesObj});
+    var lockFileString = json.stringify({'packages': packagesObj});
+    return '$comment $lockFileString';

[Bob Nystrom, 2013/01/31 22:17:44]

I'd use a multiline string here:

return '''
# Generated by pub...
${json.stringify({'packages': packagesObj})}
''';

[keertip, 2013/01/31 22:40:41]

Done.

   }
 }