Problems trying to turn on auto-fill in a directory local way

Question

I am inexperienced in Emacs and very new to directory-local variables, so please forgive any obvious things I may be missing.

I am trying to have auto-fill mode activated for all the files in a certain directory. In this directory, I have a .dir-locals.el file which contains:

((nil . ((eval add-hook 'text-mode-hook 'turn-on-auto-fill)
     (truncate-lines . nil)))
)

(FYI I have truncate-lines set to t in my .emacs file, so that's its "default" value for me.)

After saving this .dir-locals.el file, when opening a text file with Emacs in this directory, I find that truncate-lines is indeed turned off. However, auto-fill isn't working: the lines I'm writing don't break into new lines. (My fill-column value is 70.)

When I do C-h v text-mode-hook I get:

text-mode-hook's value is 
(turn-on-auto-fill text-mode-hook-identify)
...

but when I don't include the "eval add-hook..." in the .dir-locals.el file, the words turn-on-auto-fill don't appear in the text-mode-hook's value, so the .el file I have appears to be setting something, it just isn't working.

When I do M-x auto-fill-mode, then auto-fill does start working.

Any ideas why auto-fill isn't working for me from my directory local file? Alternatively, any suggestions for an alternative way to active auto-fill-mode for and only for the files in my directory?

Answer 1

The directory local variables are set after the major mode command run. Otherwise the major-mode dependent file local variables would not work.

Therefore, you just buffer-locally add turn-on-auto-fill to text-mode-hook. But the hook is not run again and your configuration is without effect.

If you want to deactivate truncate-lines for all major modes and activate auto-fill-mode just for text-mode in a certain directory (and its sub-directories) you can put the following list into your .dir-locals.el-file:

((nil . ((truncate-lines . t)))
 (text-mode . ((eval . (turn-on-auto-fill)))))