Code to fix ghc-mod, flymake, haskell-mode when used with yesod

gistfile1.el

;; Add this code to your .emacs file so it will be loaded at start, after installing ghc-mod

;; This code checks the parent folders of new haskell buffers to see if they contain .cabal
;; files. If so, it changes the working directory of the buffer to point to that directory.

(defun change-to-cabal-directory ()
  (if (buffer-file-name)
      (change-to-cabal-directory-from-directory (file-name-directory buffer-file-name))))

(defun change-to-cabal-directory-from-directory (directory) 
            (if (file-accessible-directory-p directory)
                (if (find-cabal-files directory)
                  (cd directory)
                  (let ((parent-directory (file-name-directory
                         (directory-file-name directory))))
                      (if (string= parent-directory directory)
                          nil
                          (change-to-cabal-directory-from-directory
                                parent-directory))))))

(defun find-cabal-files (directory)
  (let ((file-list (directory-files directory)))
  (delq nil
    (mapcar (lambda (file) 
              (if (> (length file) 6)
                  (string= (substring file (- 0 6)) ".cabal")
                  nil)) 
            file-list))))

;; From the ghc-mod instructions
(autoload 'ghc-init "ghc" nil t)
;; This should replace the call to add-hook from the ghc-mod instructions:
(add-hook 'haskell-mode-hook (lambda () (ghc-init) (change-to-cabal-directory) (flymake-mode)))