flycheck-stack

A flycheck checker that uses stack ghci

Requirements

• stack
• haskell-mode
• flycheck

You can use it with any stack project, or any random file that isn't in a stack project, in which case it'll use the global configuration.

Installing

Grab the repo:

$ git clone [email protected]:chrisdone/flycheck-stack.git

Add the following to your ~/.emacs:

(add-to-list 'load-path "/path/to/flycheck-stack")
(require 'flycheck-stack)

Enable flycheck in your haskell-mode with M-x flycheck-mode. Done!

Other configurations

Enable it for all Haskell files:

(add-hook 'haskell-mode-hook 'haskell-mode-flycheck-stack)
(defun haskell-mode-flycheck-stack ()
  (flycheck-select-checker 'stack)
  (flycheck-mode))

Annoyed by the constant checking? Customize the following variable (removing things you don't like):

(setq flycheck-check-syntax-automatically '(save idle-change new-line mode-enabled))

Prefer to trigger it manually?

(define-key haskell-mode-map [f5] 'flycheck-buffer)

Usage

Basic

When flycheck tries to do a check, the first time for a project you'll see this in your minibuffer:

Booting up stack ghci ...

Then in a moment:

Booted up stack ghci!

Then it's ready for doing checks.

Switching targets

Some packages have different files and settings for each target in the .cabal file, and some stack projects have multiple packages. For this reason stack has a fairly elaborate means of specifying targets.

Use M-x flycheck-stack-targets to set the targets. Examples:

• M-x flycheck-stack-targets RET my-package1 other-package -- Load up two packages.
• M-x flycheck-stack-targets RET my-package1:test:my-test-suite -- Load up just my-test-suite from the my-package1 package.
• M-x flycheck-stack-targets RET my-package1:my-test-suite -- Load up just my-test-suite from the my-package1 package because it's obvious that it's the test suite.
• Finally, M-x flycheck-stack-targets RET :my-test-suite -- Load up just my-test-suite from the my-package1 package because it's obvious which one we mean.

Failure to start up

If the stack ghci fails to start, it'll bring up the buffer with the output. At this point, you can just run the command in your terminal to see what the problem is. If it works in the terminal, it should work in Emacs.