@Nullable
  public SourceFolder addSourceFolder(@NotNull final VirtualFile file, boolean isTestSource, String packagePrefix) {
    return addSourceFolder(file, isTestSource ? JavaSourceRootType.TEST_SOURCE : JavaSourceRootType.SOURCE,
                           JpsJavaExtensionService.getInstance().createSourceRootProperties(packagePrefix));
  }
@Nullable
  public SourceFolder addSourceFolder(@NotNull final VirtualFile file, boolean isTestSource, String packagePrefix)