[Fix #24] Run nameless--after-hack-local-variables just once

[nickdrozd]

The suggested use of nameless is

(add-hook 'emacs-lisp-mode-hook #'nameless-mode)

Prior to this change, running nameless in this way would cause nameless--after-hack-local-variables to get run twice on opening a file: once when running run-hooks, and once again when running hack-local-variables-hook. This operation is slow on large files, and running it twice is even slower.

You might think that it would suffice to simply remove the direct call to nameless--after-hack-local-variables in nameless-mode, but then nameless-mode would fail to "toggle" when run interactively. Instead, we just check whether the function is being called interatively, "toggling" if it is, then add the function to hack-local-variables-hook. There are probably more elegant ways to do this, but the basic idea is probably the same in all cases.

To time this change, I used

(defun nameless-benchmark ()
  (interactive)
  (benchmark 5 '(progn
                  (find-file "~/emacs/lisp/org/org.el")
                  (kill-buffer "org.el"))))

(org.el is just shy of 25_000 lines.)

Here are the results of running that twice on master and twice with this change (times recorded on my crappy little Thinkpad):

• Before

Elapsed time: 107.945053s (34.001933s in 213 GCs)
Elapsed time: 107.498577s (33.706725s in 215 GCs)

• After

Elapsed time: 56.372983s (18.334976s in 115 GCs)
Elapsed time: 56.753919s (18.720507s in 116 GCs)

The time is cut in half. This is not surprising, as the expensive operation is being executed half as often.

[nickdrozd]

As I mentioned in that issue, my understanding of hooks and local variables is hazy, so I might be missing something subtle. That said, this seems to work locally.

[Malabarba]

Thanks for this! The only negative side-effect I can see is that if someone has some code that calls this mode non-interactively it will stop working with this change. Ideally, instead of checking for (called-interactively-p 'any), we would have a way of checking if local variables have already been loaded in this file. Do you know if there's a way of checking for that?

[nickdrozd]

I don't know. There must be something. But whatever the exact solution, I think it will look something like this: adding the hack-locals hook if called from a hook, and changing the display immediately if called directly.