anchor.diff:        String packageName = pubspecMap['name'];
         assert(packageName != null && packageName.length > 0);
   
  -      String version = pubspecMap['version'];
  -      if (version == null) version = '';
  +      var versionString = pubspecMap['version'];
  +      var version = (versionString == null) ?
  +          null : new Version.parse(versionString);
   
         var deps = Dependency.getDependencies(pubspecMap);
   
  
positive.code: import 'package:yaml/yaml.dart' as yaml;
  
  import 'dependency.dart';
  
  class VizPackage extends Comparable {
    final String path;
    final String name;
    final String version;
    final Set<Dependency> dependencies;
    bool isPrimary = false;
  
  
negative.code:     var newLine = (escapeLabels) ? r'\n' : '\n';
  
      var label = name;
      if (version != null) {
        label = label + '$newLine$version';
      }
  
  