Set variables based on path without using directory-local variables

Question

I want to set variables, in particular, compile-command and tabbing related variables based on the path of the file I'm editing.

In my .vimrc I use the following to do this.

autocmd BufRead,BufNewFile */path/*.ext set tabbing-setting
autocmd BufRead,BufNewFile */path/*.ext set makeprg=build.sh

These cause vim to run the set ... commands whenever I create or read a file that matches the pattern */path/*.ext.

I don't want to use directory-local variables because I want this to live with the rest of my emacs configuration.

Answer 1

Directory-local variables were actually designed for this use case as well. Read the docs, especially at the end, where it discusses dir-locals-set-directory-class. The idea here is that you can keep the directory-local settings somewhere other than in the .dir-locals.el file.

Another way to accomplish this same thing is to make settings directory-dependent in the relevant mode hooks. For example, something like:

(defun my-set-c-style ()
  (if (buffer-file-name)
      (cond
       ((string-match "/some/random/path" (buffer-file-name))
        (c-set-style "BSD")
        (make-local-variable 'c-basic-offset)
        (setq c-basic-offset 4)))
... you get the idea

This function would be attached to c-mode-hook.

The advantage of the directory-local approach is that you can keep all the settings related to a project in one spot. The advantage of the second approach is that it can also be used for things that you can't do via directory-locals, for example binding a key.