anchor.diff:      }
   
       return null;
  +  }
  +
  +  Map<String, List<fileSystem.Folder>> _getPackageMap(Packages packages) {
  +    if (packages == null) {
  +      return null;
  +    }
  +
  +    Map<String, List<fileSystem.Folder>> folderMap =
  +        new Map<String, List<fileSystem.Folder>>();
  +    packages.asMap().forEach((String path, Uri uri) {
  +      folderMap[path] = [PhysicalResourceProvider.INSTANCE.getFolder(uri.path)];
  +    });
  +    return folderMap;
     }
   
     void _processAnalysisOptions(CommandLineOptions options) {
  
positive.code:   /// [SourceFactory] that has been configured accordingly.
    SourceFactory _chooseUriResolutionPolicy(
        CommandLineOptions options, Map<String, String> customUrlMappings) {
      List<UriResolver> resolvers = [
        new CustomUriResolver(customUrlMappings),
        new DartUriResolver(sdk)
      ];
  
      Packages packages;
  
      if (options.packageConfigPath != null) {
        String packageConfigPath = options.packageConfigPath;
        Uri fileUri = new Uri.file(packageConfigPath);
  
negative.code:       // Look for .packages.
        packages = _discoverPackagespec(new Uri.directory(cwd.path));
  
        if (packages != null) {
          packageMap = _getPackageMap(packages);
        } else {
  
          // Fall back to pub list-dir.
  
          PubPackageMapProvider pubPackageMapProvider =
              new PubPackageMapProvider(PhysicalResourceProvider.INSTANCE, sdk);
          PackageMapInfo packageMapInfo =
              pubPackageMapProvider.computePackageMap(cwd);
          packageMap = packageMapInfo.packageMap;
  
          packageUriResolver = new PackageMapUriResolver(
              PhysicalResourceProvider.INSTANCE, packageMap);
        }
      }
  
      // Now, build our resolver list.
  
      // Custom and 'dart:' URIs come first.
      List<UriResolver> resolvers = [
        new CustomUriResolver(customUrlMappings),
        new DartUriResolver(sdk)
      ];
  
      // Next SdkExts.
      if (packageMap != null) {
        resolvers.add(new SdkExtUriResolver(packageMap));
      }
  
      // Then package URIs.
      if (packageUriResolver != null) {
        resolvers.add(packageUriResolver);
      }
  
      // Finally files.
      resolvers.add(new FileUriResolver());
  
      return new SourceFactory(resolvers, packages);
    }
  
  