lisp/emacs-lisp/shadow.el

   1 ;;; shadow.el --- locate Emacs Lisp file shadowings
   2
   3 ;; Copyright (C) 1995 Free Software Foundation, Inc.
   4
   5 ;; Author: Terry Jones <terry@santafe.edu>
   6 ;; Keywords: lisp
   7 ;; Created: 15 December 1995
   8
   9 ;; This file is part of GNU Emacs.
  10
  11 ;; GNU Emacs is free software; you can redistribute it and/or modify
  12 ;; it under the terms of the GNU General Public License as published by
  13 ;; the Free Software Foundation; either version 2, or (at your option)
  14 ;; any later version.
  15
  16 ;; GNU Emacs is distributed in the hope that it will be useful,
  17 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  18 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  19 ;; GNU General Public License for more details.
  20
  21 ;; You should have received a copy of the GNU General Public License
  22 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  23 ;; Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  24 ;; Boston, MA 02111-1307, USA.
  25
  26 ;;; Commentary:
  27
  28 ;; The functions in this file detect (`find-emacs-lisp-shadows')
  29 ;; and display (`list-load-path-shadows') potential load-path
  30 ;; problems that arise when Emacs Lisp files "shadow" each other.
  31 ;;
  32 ;; For example, a file XXX.el early in one's load-path will shadow
  33 ;; a file with the same name in a later load-path directory.  When
  34 ;; this is unintentional, it may result in problems that could have
  35 ;; been easily avoided.  This occurs often (to me) when installing a
  36 ;; new version of emacs and something in the site-lisp directory
  37 ;; has been updated and added to the emacs distribution.  The old
  38 ;; version, now outdated, shadows the new one. This is obviously
  39 ;; undesirable.
  40 ;;
  41 ;; The `list-load-path-shadows' function was run when you installed
  42 ;; this version of emacs. To run it by hand in emacs:
  43 ;;
  44 ;;     M-x load-library RET shadow RET
  45 ;;     M-x list-load-path-shadows
  46 ;;
  47 ;; or run it non-interactively via:
  48 ;;
  49 ;;     emacs -batch -l shadow.el -f list-load-path-shadows
  50 ;;
  51 ;; Thanks to Francesco Potorti` <pot@cnuce.cnr.it> for suggestions,
  52 ;; rewritings & speedups.
  53
  54 ;;; Code:
  55 \f
  56 (defgroup lisp-shadow nil
  57   "Locate Emacs Lisp file shadowings."
  58   :prefix "shadows-"
  59   :group 'lisp)
  60
  61 (defcustom shadows-compare-text-p nil
  62   "*If non-nil, then shadowing files are reported only if their text differs.
  63 This is slower, but filters out some innocuous shadowing."
  64   :type 'boolean
  65   :group 'lisp-shadow)
  66
  67 (defun find-emacs-lisp-shadows (&optional path)
  68   "Return a list of Emacs Lisp files that create shadows.
  69 This function does the work for `list-load-path-shadows'.
  70
  71 We traverse PATH looking for shadows, and return a \(possibly empty\)
  72 even-length list of files.  A file in this list at position 2i shadows
  73 the file in position 2i+1.  Emacs Lisp file suffixes \(.el and .elc\)
  74 are stripped from the file names in the list.
  75
  76 See the documentation for `list-load-path-shadows' for further information."
  77
  78   (or path (setq path load-path))
  79
  80   (let (true-names                      ; List of dirs considered.
  81         shadows                         ; List of shadowings, to be returned.
  82         files                           ; File names ever seen, with dirs.
  83         dir                             ; The dir being currently scanned.
  84         curr-files                      ; This dir's Emacs Lisp files.
  85         orig-dir                        ; Where the file was first seen.
  86         files-seen-this-dir             ; Files seen so far in this dir.
  87         file)                           ; The current file.
  88
  89
  90     (while path
  91
  92       (setq dir (directory-file-name (file-truename (or (car path) "."))))
  93       (if (member dir true-names)
  94           ;; We have already considered this PATH redundant directory.
  95           ;; Show the redundancy if we are interactiver, unless the PATH
  96           ;; dir is nil or "." (these redundant directories are just a
  97           ;; result of the current working directory, and are therefore
  98           ;; not always redundant).
  99           (or noninteractive
 100               (and (car path)
 101                    (not (string= (car path) "."))
 102                    (message "Ignoring redundant directory %s" (car path))))
 103
 104         (setq true-names (append true-names (list dir)))
 105         (setq dir (directory-file-name (or (car path) ".")))
 106         (setq curr-files (if (file-accessible-directory-p dir)
 107                              (directory-files dir nil ".\\.elc?$" t)))
 108         (and curr-files
 109              (not noninteractive)
 110              (message "Checking %d files in %s..." (length curr-files) dir))
 111
 112         (setq files-seen-this-dir nil)
 113
 114         (while curr-files
 115
 116           (setq file (car curr-files))
 117           (setq file (substring
 118                       file 0 (if (string= (substring file -1) "c") -4 -3)))
 119
 120           ;; FILE now contains the current file name, with no suffix.
 121           (unless (or (member file files-seen-this-dir)
 122                       ;; Ignore these files.
 123                       (member file '("subdirs")))
 124             ;; File has not been seen yet in this directory.
 125             ;; This test prevents us declaring that XXX.el shadows
 126             ;; XXX.elc (or vice-versa) when they are in the same directory.
 127             (setq files-seen-this-dir (cons file files-seen-this-dir))
 128
 129             (if (setq orig-dir (assoc file files))
 130                 ;; This file was seen before, we have a shadowing.
 131                 ;; Report it unless the files are identical.
 132                 (let ((base1 (concat (cdr orig-dir) "/" file))
 133                       (base2 (concat dir "/" file)))
 134                   (if (not (and shadows-compare-text-p
 135                                 (shadow-same-file-or-nonexistent
 136                                  (concat base1 ".el") (concat base2 ".el"))
 137                                 ;; This is a bit strict, but safe.
 138                                 (shadow-same-file-or-nonexistent
 139                                  (concat base1 ".elc") (concat base2 ".elc"))))
 140                       (setq shadows
 141                             (append shadows (list base1 base2)))))
 142
 143               ;; Not seen before, add it to the list of seen files.
 144               (setq files (cons (cons file dir) files))))
 145
 146           (setq curr-files (cdr curr-files))))
 147         (setq path (cdr path)))
 148
 149     ;; Return the list of shadowings.
 150     shadows))
 151
 152 ;; Return true if neither file exists, or if both exist and have identical
 153 ;; contents.
 154 (defun shadow-same-file-or-nonexistent (f1 f2)
 155   (let ((exists1 (file-exists-p f1))
 156         (exists2 (file-exists-p f2)))
 157     (or (and (not exists1) (not exists2))
 158         (and exists1 exists2
 159              (or (equal (file-truename f1) (file-truename f2))
 160                  ;; As a quick test, avoiding spawning a process, compare file
 161                  ;; sizes.
 162                  (and (= (nth 7 (file-attributes f1))
 163                          (nth 7 (file-attributes f2)))
 164                       (eq 0 (call-process "cmp" nil nil nil "-s" f1 f2))))))))
 165 \f
 166 ;;;###autoload
 167 (defun list-load-path-shadows ()
 168   "Display a list of Emacs Lisp files that shadow other files.
 169
 170 This function lists potential load-path problems.  Directories in the
 171 `load-path' variable are searched, in order, for Emacs Lisp
 172 files.  When a previously encountered file name is found again, a
 173 message is displayed indicating that the later file is \"hidden\" by
 174 the earlier.
 175
 176 For example, suppose `load-path' is set to
 177
 178 \(\"/usr/gnu/emacs/site-lisp\" \"/usr/gnu/emacs/share/emacs/19.30/lisp\"\)
 179
 180 and that each of these directories contains a file called XXX.el.  Then
 181 XXX.el in the site-lisp directory is referred to by all of:
 182 \(require 'XXX\), \(autoload .... \"XXX\"\), \(load-library \"XXX\"\) etc.
 183
 184 The first XXX.el file prevents emacs from seeing the second \(unless
 185 the second is loaded explicitly via load-file\).
 186
 187 When not intended, such shadowings can be the source of subtle
 188 problems.  For example, the above situation may have arisen because the
 189 XXX package was not distributed with versions of emacs prior to
 190 19.30.  An emacs maintainer downloaded XXX from elsewhere and installed
 191 it.  Later, XXX was updated and included in the emacs distribution.
 192 Unless the emacs maintainer checks for this, the new version of XXX
 193 will be hidden behind the old \(which may no longer work with the new
 194 emacs version\).
 195
 196 This function performs these checks and flags all possible
 197 shadowings.  Because a .el file may exist without a corresponding .elc
 198 \(or vice-versa\), these suffixes are essentially ignored.  A file
 199 XXX.elc in an early directory \(that does not contain XXX.el\) is
 200 considered to shadow a later file XXX.el, and vice-versa.
 201
 202 When run interactively, the shadowings \(if any\) are displayed in a
 203 buffer called `*Shadows*'.  Shadowings are located by calling the
 204 \(non-interactive\) companion function, `find-emacs-lisp-shadows'."
 205
 206   (interactive)
 207   (let* ((path (copy-sequence load-path))
 208         (tem path)
 209         toplevs)
 210     ;; If we can find simple.el in two places,
 211     (while tem
 212       (if (file-exists-p (expand-file-name "simple.el" (car tem)))
 213           (setq toplevs (cons (car tem) toplevs)))
 214       (setq tem (cdr tem)))
 215     (if (> (length toplevs) 1)
 216         ;; Cut off our copy of load-path right before
 217         ;; the last directory which has simple.el in it.
 218         ;; This avoids loads of duplications between the source dir
 219         ;; and the dir where these files were copied by installation.
 220         (let ((break (car toplevs)))
 221           (setq tem path)
 222           (while tem
 223             (if (eq (nth 1 tem) break)
 224                 (progn
 225                   (setcdr tem nil)
 226                   (setq tem nil)))
 227             (setq tem (cdr tem)))))
 228
 229     (let* ((shadows (find-emacs-lisp-shadows path))
 230            (n (/ (length shadows) 2))
 231            (msg (format "%s Emacs Lisp load-path shadowing%s found"
 232                         (if (zerop n) "No" (concat "\n" (number-to-string n)))
 233                         (if (= n 1) " was" "s were"))))
 234       (if (interactive-p)
 235           (save-excursion
 236             ;; We are interactive.
 237             ;; Create the *Shadows* buffer and display shadowings there.
 238             (let ((output-buffer (get-buffer-create "*Shadows*")))
 239               (display-buffer output-buffer)
 240               (set-buffer output-buffer)
 241               (erase-buffer)
 242               (while shadows
 243                 (insert (format "%s hides %s\n" (car shadows)
 244                                 (car (cdr shadows))))
 245                 (setq shadows (cdr (cdr shadows))))
 246               (insert msg "\n")))
 247         ;; We are non-interactive, print shadows via message.
 248         (when shadows
 249           (message "This site has duplicate Lisp libraries with the same name.
 250 If a locally-installed Lisp library overrides a library in the Emacs release,
 251 that can cause trouble, and you should probably remove the locally-installed
 252 version unless you know what you are doing.\n")
 253           (while shadows
 254             (message "%s hides %s" (car shadows) (car (cdr shadows)))
 255             (setq shadows (cdr (cdr shadows))))
 256           (message "%s" msg))))))
 257
 258 (provide 'shadow)
 259
 260 ;;; arch-tag: 0480e8a7-62ed-4a12-a9f6-f44ded9b0830
 261 ;;; shadow.el ends here