flycheck-mode hook and dir-locals

[themoritz]

This is more of a note for everyone using a .dir-locals.el file to set dante-target.

When using dante with the recommended entry in my .emacs file as described in the readme, I had an issue where every time I opened a .hs file, the dante-target variable would be overwritten to nil and subsequently dante fails because cabal can't handle multiple targets. This prevented me from using Emacs' dir-locals feature to tell dante which target to use.

The workaround was to remove the following flycheck-mode hook (I don't understand why this fixes the problem or why flycheck keeps working without this line):

(add-hook 'haskell-mode-hook 'flycheck-mode)

[themoritz]

Just learned that the order of the hooks matters. The issue is only there if the flycheck-mode hook comes after the dante-mode hook.

[michalrus]

Emacs is depressing. #ihatemyeditor

Thank you very much, tho.

[joehealy]

Did you get to the bottom of why the flycheck-mode hook was needed?

[michalrus]

No, right now I have an “if it works I freakin’ don’t care” relation w/ Emacs. :throw_up:

But I think I remember a similar problem with Scala and its ENSIME. Maybe let’s… /cc @fommil?

[fommil]

hmm, I think this sounds familiar as documented Emacs behaviour due to the load order of .dir-locals.el. The relevant part of my init.el points at https://emacs.stackexchange.com/questions/7743 as an example, also see the docs of hack-local-variables-hook.

[fommil]

btw, it sounds hacky, but I'm actually fine with the Emacs approach. I don't believe anybody has solved the generic problem of load order for any customisable system automatically. Even my xbox computer games have a "load order" for mods, which is the same problem, in a different guise. When customising a core tool, we have to open up the hood sometimes.

FYI additional thing... when I load whitespace-mode and want to use local variables I use this alternative function instead of the default hook loader.

(defun whitespace-mode-with-local-variables ()
  "A variant of `whitespace-mode' that can see local variables."
  (add-hook 'hack-local-variables-hook 'whitespace-mode nil t))

Which is the escape hatch.

[fommil]

the other thing dante could do would be to make dante-target buffer local by default, e.g. https://stackoverflow.com/questions/21917049 i.e. call (make-variable-buffer-local 'dante-target) immediately after defining it.

(users must then use setq-default instead of setq) and also add to the safe-local-variable list. Example from another project: Wilfred/ag.el#145

I recommend that anything project-specific be made buffer local in a similar fashion.

[themoritz]

@joehealy I actually found out that the hook wasn't really necessary for me in the first place. 😕

[michalrus]

@fommil, thank you for all the details! =)

[fommil]

@michalrus no problem, I hope to one day be a) a haskell developer b) using this mode.

[michalrus]

I very much recommend the switch. It’s been an amazing experience so far for me. ^.^

[fommil]

it's my employers who need to be convinced...