bug#17064: 24.3.50; Enhancement request: dired: fontification of symlinks

[Lars Ingebrigtsen <larsi@gnus.org>]

Michael Heerdegen <michael_heerdegen@web.de> writes:

> in dired, symlinks look like
>
>   symlink -> target
>
> where the whole thing is fontified with dired-symlink-face.  But I
> already know from the -> that I have a symlink, it would be more useful
> to know whether TARGET is a directory, which is what I normally see for
> non symlink files in dired by fontification with dired-directory-face.
>
> My proposal: fontify only the first part "symlink ->" with
> dired-symlink-face.  Fontify "target" according to its truename type.

Sounds good to me.

> (cl-callf nconc dired-font-lock-keywords
>   `((,dired-re-sym
>      ((lambda (end) (when (let ((file (dired-file-name-at-point)))
> 		       (file-directory-p (file-truename file)))
> 		 (search-forward-regexp "\\(.+-> ?\\)\\(.+\\)" end t)))
>       (dired-move-to-filename)
>       nil
>       (1 dired-symlink-face)
>       (2 dired-directory-face)))

[...]

> Or could this have any bad side effects?  Is it maybe too heavy to call
> `file-truename'?

Normally, there aren't many symlinks in a buffer, so I think the
performance impact would be negligible.

I've added a modified version of your code to Emacs 27 -- more error
checking was necessary, because symlinks may be circular etc.

-- 
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   bloggy blog: http://lars.ingebrigtsen.no