f.hs

parseNested :: FilePath -> Parser ()
parseNested path = do
  txt <- readBuf path
  oldBase <- gets (_psCurrentPath)
  setCurrentPath (takeDirectory path)
  r <- lift $ runParserT principleFile' path txt
  case r of
    Left bundle -> liftIO $ throwIO (CpeNestedError bundle)
    Right ()    -> setCurrentPath oldBase