anchor.diff:      for (var package in packages) {
         var packageName = path.basename(package.path);
         var realPath = package.resolveSymbolicLinksSync();
  -      result[packageName] =
  -          [PhysicalResourceProvider.INSTANCE.getFolder(realPath)];
  +      result[packageName] = [
  +        PhysicalResourceProvider.INSTANCE.getFolder(realPath)
  +      ];
       }
       return result;
     }
  
positive.code:       if (packages != null) {
          packageMap = _getPackageMap(packages);
        } else {
  
          // Fall back to pub list-dir.
  
          PubPackageMapProvider pubPackageMapProvider =
  
negative.code: 
      Map<String, List<fileSystem.Folder>> folderMap =
          new Map<String, List<fileSystem.Folder>>();
      packages.asMap().forEach((String packagePath, Uri uri) {
        folderMap[packagePath] = [
          PhysicalResourceProvider.INSTANCE.getFolder(path.fromUri(uri))
        ];
      });
      return folderMap;
    }
  