Getting a path to a source file

It’s sometimes convenient to get an absolute path to a source file for logging. Template Haskell allows you to do it.

{-# LANGUAGE TemplateHaskell #-}

import Control.Monad
import Data.Functor
import Language.Haskell.TH
import System.Directory
import System.FilePath

filePath :: String
filePath = $(liftM2 (</>) (runIO getCurrentDirectory) (loc_filename <$> location) >>= litE . stringL)

If you’re thinking about using this for logging, you may be interested in monad-logger.