Re: Problem mit symlinks, locate-library and load-history [Was: <Something else>]

[Alan Mackenzie]

Hi, Richard!

On Mon, 20 Mar 2006, Richard Stallman wrote:

[ This was in the context of eval-after-load not finding an already
loaded file, because of confusion between suffixes ".el" and ".elc" and
confusion between symbolic links and true names. ] 

>It could be useful to define a subroutine to do
>             (assoc (file-truename (locate-library file)) load-history)))
>except do it correctly.

>Would someone like to do that, and ack?

Thinking about this a little more, there is confusion in the above,
certainly when used in eval-after-load:  There is NO REASON why a loaded
file should have to be in load-path, and it seems that (locate-library
file) was used mainly to give a convenient search key for `alloc'.

I therefore propose the following function loaded-filename which does
nothing but search load-history for a file.  It can be called like
this:

(loaded-filename "font-lock.el") => "/home/acm/emacs/emacs/lisp/font-lock.elc"
  (any suffix in `load-suffixes' will do in place of the .el).

(loaded-filename "font-lock") => "/home/acm/emacs/emacs/lisp/font-lock.elc"
  (There needn't be a suffix on the name).

(loaded-filename "font-lock.el" t) => nil
  ("font-lock.el", as such, has not been loaded)

(loaded-filename "~/emacs/emacs/lisp/font-lock") =>
"/home/acm/emacs/emacs/lisp/font-lock.elc"

The functions work fine in GNU.  I'm not sure about MS-Windows (case
folding?) or VMS (version numbers?).

#########################################################################
(defun load-history-filename-element (filename &optional exact-suffix)
  "Get the load-history element which matches the loaded Elisp file FILENAME.
Return nil if the file isn't found.  The parameters have the same meaning as
those of the function `loaded-filename'."
  (let* (supplied-basename-sans-ext
         supplied-extension             ; e.g. ".el" or "", NOT "el".
         regexp
         (loads load-history)
         (load-elt (and loads (car loads))))

    (if (file-name-absolute-p filename)
        (progn
          (setq filename (file-truename filename))
          (setq supplied-basename-sans-ext
                (file-name-sans-extension (file-name-nondirectory filename))))
      (if (file-name-directory filename)
          (error "loaded-filename: Relative file name has directory parts: %s" 
filename))
      (setq supplied-basename-sans-ext (file-name-sans-extension filename)))
    (setq supplied-extension
          (if (file-name-extension filename)
              (concat "." (file-name-extension filename))
            ""))
    (setq regexp
          (concat (if (file-name-absolute-p filename) "^" "")
                  (if exact-suffix
                      (regexp-quote filename)
                    (concat supplied-basename-sans-ext
                            (regexp-opt (cons supplied-extension 
load-suffixes))))
                  "$"))

    (while (and loads
                (or (null (car load-elt))
                    (not (string-match regexp (car load-elt)))
                    (not (string= supplied-basename-sans-ext
                                  (file-name-sans-extension
                                   (file-name-nondirectory (car load-elt)))))))
      (setq loads (cdr loads)
            load-elt (and loads (car loads))))
    load-elt))

(defun loaded-filename (filename &optional exact-suffix)
  "Get the absolute file name from which Elisp file FILENAME was loaded.
Return nil if the file isn't found.  The returned file name will be a true
name \(i.e. with all its symbolic links having been chased out).

FILENAME is a string.  It may be an absolute file name like
\"/usr/local/bin/emacs/lisp/foobar\", or a bare file name like \"foobar\" or
\"foobar.el\".  It may not be a relative name containing a \"/\".

If EXACT-SUFFIX is non-nil, the function searches only for FILENAME.
Otherwise it also searches for the file names formed by replacing FILENAME's
suffix, if any, by each of the suffixes in `load-suffixes'."
  (let ((elt (load-history-filename-element filename exact-suffix)))
    (and elt (car elt))))
#########################################################################

-- 
Alan Mackenzie (Munich, Germany)