.dir-locals.el

((haskell-mode . ((haskell-indent-spaces . 4)
                  (haskell-process-use-ghci . t)
                  (haskell-process-args-cabal-repl . ("-ferror-spans -fno-diagnostics-show-caret -fshow-loaded-modules"))
                  (haskell-process-args-stack-ghci . ("--ghc-options=-ferror-spans" "--ghc-options=-fno-diagnostics-show-caret" "--ghc-options=-fshow-loaded-modules"))
                  ))
 (hamlet-mode . ((hamlet/basic-offset . 4)
                 (haskell-process-use-ghci . t))))