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lisp/emacs-lisp/shadow.el

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+;;; 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+;; version, now outdated, shadows the new one.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:
+
+(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))
+
+
+;;;###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