I used to use delete-trailing-whitespace in my local-file-write-hooks for any source file I edited, but I had to disable it a while back. Many files containing legacy source were extremely messy in this regard, and it made making simple fixes harder to track, since there was a large amount of noise in the diff from the whitespace changes.

But I just solved this. Here at Digg, we document all new code with phpDocumentor. Leveraging this, I wrote a new function to examine the header of the source file and strip whitespace if I have an @author tag.

(defun maybe-delete-trailing-whitespace ()
  "Delete trailing whitespace if I am the author of this file."
  (interactive)
  (and (delete-trailing-whitespacep) (delete-trailing-whitespace)))

(defun delete-trailing-whitespacep ()
  "Should we delete trailing whitespace when saving this file?"
  (save-excursion
    (goto-char (point-min))
    (next-line 25)
    (let ((pos (point)))
      (goto-char (point-min))
      (re-search-forward (concat "@author +" user-full-name) pos t))))

(defun progmodes-write-hooks ()
  "Hooks which run on file write for programming modes"
  (prog1 nil
    (set-buffer-file-coding-system 'utf-8-unix)
    (untabify-buffer)
    (copyright-update)
    (maybe-delete-trailing-whitespace)))

(defun progmodes-hooks ()
  "Hooks for all programming modes"
  (add-hook 'local-write-file-hooks 'progmodes-write-hooks))

(add-hook 'php-mode-hook 'progmodes-hooks)
(add-hook 'js2-mode-hook 'progmodes-hooks)
;; Repeat for any other mode for editing source

It works a treat, happily stripping trailing whitespace if I’m listed as an author in the header, and leaving it unmolested otherwise. I’m not entirely satisfied with delete-trailing-whitespacep, which feels a little graceless. Maybe someone knows a better way to do it?

This entry was posted on Friday, August 15th, 2008 at 1:51 pm and is filed under Code. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.