--- /dev/null
+;;; shadow.el --- Locate Emacs Lisp file shadowings.
+
+;; Copyright (C) 1995 Free Software Foundation, Inc.
+
+;; Author: Terry Jones <terry@santafe.edu>
+;; Keywords: lisp
+;; Created: 15 December 1995
+
+;; This file is part of GNU Emacs.
+
+;; GNU Emacs is free software; you can redistribute it and/or modify
+;; it under the terms of the GNU General Public License as published by
+;; the Free Software Foundation; either version 2, or (at your option)
+;; any later version.
+
+;; GNU Emacs is distributed in the hope that it will be useful,
+;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+;; GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License
+;; along with GNU Emacs; see the file COPYING. If not, write to
+;; the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
+
+;;; Commentary:
+;;
+;; The functions in this file detect (`find-emacs-lisp-shadows')
+;; and display (`list-load-path-shadows') potential load-path
+;; problems that arise when Emacs Lisp files "shadow" each other.
+;;
+;; For example, a file XXX.el early in one's load-path will shadow
+;; a file with the same name in a later load-path directory. When
+;; this is unintentional, it may result in problems that could have
+;; been easily avoided. This occurs often (to me) when installing a
+;; new version of emacs and something in the site-lisp directory
+;; has been updated and added to the emacs distribution. The old
+;; version, now outdated, shadows the new one. This is obviously
+;; undesirable.
+;;
+;; The `list-load-path-shadows' function was run when you installed
+;; this version of emacs. To run it by hand in emacs:
+;;
+;; M-x load-library RET shadow RET
+;; M-x list-load-path-shadows
+;;
+;; or run it non-interactively via:
+;;
+;; emacs -batch -l shadow.el -f list-load-path-shadows
+;;
+;; Thanks to Francesco Potorti` <pot@cnuce.cnr.it> for suggestions,
+;; rewritings & speedups.
+
+;;; Code:
+\f
+(defun find-emacs-lisp-shadows (&optional path)
+ "Return a list of Emacs Lisp files that create shadows.
+This function does the work for `list-load-path-shadows'.
+
+We traverse PATH looking for shadows, and return a \(possibly empty\)
+even-length list of files. A file in this list at position 2i shadows
+the file in position 2i+1. Emacs Lisp file suffixes \(.el and .elc\)
+are stripped from the file names in the list.
+
+See the documentation for `list-load-path-shadows' for further information."
+
+ (or path (setq path load-path))
+
+ (let (true-names ; List of dirs considered.
+ shadows ; List of shadowings, to be returned.
+ files ; File names ever seen, with dirs.
+ dir ; The dir being currently scanned.
+ curr-files ; This dir's Emacs Lisp files.
+ orig-dir ; Where the file was first seen.
+ files-seen-this-dir ; Files seen so far in this dir.
+ file) ; The current file.
+
+
+ (while path
+
+ (setq dir (file-truename (or (car path) ".")))
+ (if (member dir true-names)
+ ;; We have already considered this PATH redundant directory.
+ ;; Show the redundancy if we are interactiver, unless the PATH
+ ;; dir is nil or "." (these redundant directories are just a
+ ;; result of the current working directory, and are therefore
+ ;; not always redundant).
+ (or noninteractive
+ (and (car path)
+ (not (string= (car path) "."))
+ (message "Ignoring redundant directory '%s'." (car path))))
+
+ (setq true-names (append true-names (list dir)))
+ (setq dir (or (car path) "."))
+ (setq curr-files (if (file-accessible-directory-p dir)
+ (directory-files dir nil ".\\.elc?$" t)))
+ (and curr-files
+ (not noninteractive)
+ (message "Checking %d files in '%s' ..." (length curr-files) dir))
+
+ (setq files-seen-this-dir nil)
+
+ (while curr-files
+
+ (setq file (car curr-files))
+ (setq file (substring
+ file 0 (if (string= (substring file -1) "c") -4 -3)))
+
+ ;; 'file' now contains the current file name, with no suffix.
+ (if (member file files-seen-this-dir)
+ nil
+
+ ;; File has not been seen yet in this directory.
+ ;; This test prevents us declaring that XXX.el shadows
+ ;; XXX.elc (or vice-versa) when they are in the same directory.
+ (setq files-seen-this-dir (cons file files-seen-this-dir))
+
+ (if (setq orig-dir (assoc file files))
+ ;; This file was seen before, we have a shadowing.
+ (setq shadows
+ (append shadows
+ (list (concat (cdr orig-dir) "/" file)
+ (concat dir "/" file))))
+
+ ;; Not seen before, add it to the list of seen files.
+ (setq files (cons (cons file dir) files))))
+
+ (setq curr-files (cdr curr-files))))
+ (setq path (cdr path)))
+
+ ;; Return the list of shadowings.
+ shadows))
+
+\f
+;;;###autoload
+(defun list-load-path-shadows ()
+
+ "Display a list of Emacs Lisp files that create shadows.
+
+This function lists potential load-path problems. Directories in the
+`load-path' variable are searched, in order, for Emacs Lisp
+files. When a previously encountered file name is re-located, a
+message is displayed indicating that the later file is \"shadowed\" by
+the earlier.
+
+For example, suppose `load-path' is set to
+
+\(\"/usr/gnu/emacs/site-lisp\" \"/usr/gnu/emacs/share/emacs/19.30/lisp\"\)
+
+and that each of these directories contains a file called XXX.el. Then
+XXX.el in the site-lisp directory is referred to by all of:
+\(require 'XXX\), \(autoload .... \"XXX\"\), \(load-library \"XXX\"\) etc.
+
+The first XXX.el file prevents emacs from seeing the second \(unless
+the second is loaded explicitly via load-file\).
+
+When not intended, such shadowings can be the source of subtle
+problems. For example, the above situation may have arisen because the
+XXX package was not distributed with versions of emacs prior to
+19.30. An emacs maintainer downloaded XXX from elsewhere and installed
+it. Later, XXX was updated and included in the emacs distribution.
+Unless the emacs maintainer checks for this, the new version of XXX
+will be hidden behind the old \(which may no longer work with the new
+emacs version\).
+
+This function performs these checks and flags all possible
+shadowings. Because a .el file may exist without a corresponding .elc
+\(or vice-versa\), these suffixes are essentially ignored. A file
+XXX.elc in an early directory \(that does not contain XXX.el\) is
+considered to shadow a later file XXX.el, and vice-versa.
+
+When run interactively, the shadowings \(if any\) are displayed in a
+buffer called `*Shadows*'. Shadowings are located by calling the
+\(non-interactive\) companion function, `find-emacs-lisp-shadows'."
+
+ (interactive)
+ (let* ((shadows (find-emacs-lisp-shadows))
+ (n (/ (length shadows) 2))
+ (msg (format "%s Emacs Lisp load-path shadowing%s found."
+ (if (zerop n) "No" (concat "\n" (number-to-string n)))
+ (if (= n 1) " was" "s were"))))
+ (if (interactive-p)
+ (save-excursion
+ ;; We are interactive.
+ ;; Create the *Shadows* buffer and display shadowings there.
+ (let ((output-buffer (get-buffer-create "*Shadows*")))
+ (display-buffer output-buffer)
+ (set-buffer output-buffer)
+ (erase-buffer)
+ (while shadows
+ (insert (format "%s shadows %s\n" (car shadows) (car (cdr shadows))))
+ (setq shadows (cdr (cdr shadows))))
+ (insert msg "\n")))
+ ;; We are non-interactive, print shadows via message.
+ (while shadows
+ (message (format "%s shadows %s" (car shadows) (car (cdr shadows))))
+ (setq shadows (cdr (cdr shadows))))
+ (message msg))))
+
+(provide 'shadow)
+
+;;; shadow.el ends here
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