Error on "C-c C-l"

[budsbenzer]

Hello,

I seem to have the same issue as reported in this issue. However, I am willing to help you debug it. ;)

I am using haskell-mode version 20150727.354 from ELPA, on GNU Emacs 24.5.1.

Whenever I try to launch a new Haskell session via C-c C-l, I get the message haskell-utils-read-directory-name: Wrong type argument: arrayp, nil. On following invocations of C-c C-l, the message is haskell-session-current-dir: No current directory.

The backtrace for the first invocation of C-c C-l:

Debugger entered--Lisp error: (wrong-type-argument arrayp nil)
  file-truename(nil)
  haskell-utils-read-directory-name("Cabal dir: " nil)
  haskell-cabal-get-dir()
  haskell-session-cabal-dir(((name . "haskell") (process (name . "haskell") (is-restarting) (current-command) (suggested-imported) (sent-stdin) (evaluating) (session (name . "haskell") #1))))
  haskell-process-start(((name . "haskell") (process (name . "haskell") (is-restarting) (current-command) (suggested-imported) (sent-stdin) (evaluating) (session (name . "haskell") #1))))
  haskell-session-make("haskell")
  haskell-session-new-assume-from-cabal()
  haskell-session()
  haskell-process-load-file()
  haskell-process-load-or-reload(nil)
  #<subr call-interactively>(haskell-process-load-or-reload nil nil)
  ad-Advice-call-interactively(#<subr call-interactively> haskell-process-load-or-reload nil nil)
  apply(ad-Advice-call-interactively #<subr call-interactively> (haskell-process-load-or-reload nil nil))
  call-interactively(haskell-process-load-or-reload nil nil)
  command-execute(haskell-process-load-or-reload)

If you need more information, please tell me.

[ocecaco]

A quick way to fix this problem is to set haskell-process-load-or-reload-prompt to t. Then it will ask you for a directory. This problem only occurs for me when I'm working on files which are not in a Cabal project.

What I've found out from some debugging today: The reason for this error is that when haskell-process-load-or-reload-prompt is nil, it doesn't ask for a directory, instead it returns the default directory passed as the 2nd argument to haskell-utils-read-directory-name. The second argument is nil as you can see which causes the error later on.

EDIT: When the file is in a Cabal project, the 2nd argument receives the directory of the Cabal project as default directory and not nil.