lisp/loadhist.el

   1 ;;; loadhist.el --- lisp functions for working with feature groups
   2
   3 ;; Copyright (C) 1995, 1998, 2000, 2002, 2003, 2004,
   4 ;;   2005 Free Software Foundation, Inc.
   5
   6 ;; Author: Eric S. Raymond <esr@snark.thyrsus.com>
   7 ;; Maintainer: FSF
   8 ;; Keywords: internal
   9
  10 ;; This file is part of GNU Emacs.
  11
  12 ;; GNU Emacs is free software; you can redistribute it and/or modify
  13 ;; it under the terms of the GNU General Public License as published by
  14 ;; the Free Software Foundation; either version 2, or (at your option)
  15 ;; any later version.
  16
  17 ;; GNU Emacs is distributed in the hope that it will be useful,
  18 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
  19 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20 ;; GNU General Public License for more details.
  21
  22 ;; You should have received a copy of the GNU General Public License
  23 ;; along with GNU Emacs; see the file COPYING.  If not, write to the
  24 ;; Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
  25 ;; Boston, MA 02110-1301, USA.
  26
  27 ;;; Commentary:
  28
  29 ;; These functions exploit the load-history system variable.
  30 ;; Entry points include `unload-feature', `symbol-file', and
  31 ;; `feature-file', documented in the Emacs Lisp manual.
  32
  33 ;;; Code:
  34
  35 (defun feature-symbols (feature)
  36   "Return the file and list of definitions associated with FEATURE.
  37 The value is actually the element of `load-history'
  38 for the file that did (provide FEATURE)."
  39    (catch 'foundit
  40      (mapc (lambda (x)
  41              (if (member (cons 'provide feature) (cdr x))
  42                  (throw 'foundit x)))
  43            load-history)
  44      nil))
  45
  46 (defun feature-file (feature)
  47   "Return the file name from which a given FEATURE was loaded.
  48 Actually, return the load argument, if any; this is sometimes the name of a
  49 Lisp file without an extension.  If the feature came from an `eval-buffer' on
  50 a buffer with no associated file, or an `eval-region', return nil."
  51   (if (not (featurep feature))
  52       (error "%S is not a currently loaded feature" feature)
  53     (car (feature-symbols feature))))
  54
  55 (defun file-loadhist-lookup (file)
  56   "Return the `load-history' element for FILE.
  57 FILE can be a file name, or a library name.
  58 A library name is equivalent to the file name that `load-library' would load."
  59   ;; First look for FILE as given.
  60   (let ((symbols (assoc file load-history)))
  61     ;; Try converting a library name to an absolute file name.
  62     (and (null symbols)
  63          (let ((absname
  64                 (locate-file file load-path load-suffixes)))
  65            (and absname (not (equal absname file))
  66                 (setq symbols (cdr (assoc absname load-history))))))
  67     symbols))
  68
  69 (defun file-provides (file)
  70   "Return the list of features provided by FILE as it was loaded.
  71 FILE can be a file name, or a library name.
  72 A library name is equivalent to the file name that `load-library' would load."
  73   (let ((symbols (file-loadhist-lookup file))
  74         provides)
  75     (mapc (lambda (x)
  76             (if (and (consp x) (eq (car x) 'provide))
  77                 (setq provides (cons (cdr x) provides))))
  78           symbols)
  79     provides))
  80
  81 (defun file-requires (file)
  82   "Return the list of features required by FILE as it was loaded.
  83 FILE can be a file name, or a library name.
  84 A library name is equivalent to the file name that `load-library' would load."
  85   (let ((symbols (file-loadhist-lookup file))
  86         requires)
  87     (mapc (lambda (x)
  88             (if (and (consp x) (eq (car x) 'require))
  89                 (setq requires (cons (cdr x) requires))))
  90           symbols)
  91     requires))
  92
  93 (defsubst file-set-intersect (p q)
  94   "Return the set intersection of two lists."
  95   (let ((ret nil))
  96     (dolist (x p ret)
  97       (if (memq x q) (setq ret (cons x ret))))
  98     ret))
  99
 100 (defun file-dependents (file)
 101   "Return the list of loaded libraries that depend on FILE.
 102 This can include FILE itself.
 103 FILE can be a file name, or a library name.
 104 A library name is equivalent to the file name that `load-library' would load."
 105   (let ((provides (file-provides file))
 106         (dependents nil))
 107     (dolist (x load-history dependents)
 108       (if (file-set-intersect provides (file-requires (car x)))
 109           (setq dependents (cons (car x) dependents))))
 110     dependents))
 111
 112 (defun read-feature (prompt)
 113   "Read a feature name \(string\) from the minibuffer.
 114 Prompt with PROMPT and completing from `features', and
 115 return the feature \(symbol\)."
 116   (intern (completing-read prompt
 117                            (mapcar (lambda (feature)
 118                                      (list (symbol-name feature)))
 119                                    features)
 120                            nil t)))
 121
 122 (defvaralias 'loadhist-hook-functions 'unload-feature-special-hooks)
 123 (defvar unload-feature-special-hooks
 124   '(after-change-functions
 125     after-insert-file-functions auto-fill-function
 126     before-change-functions blink-paren-function
 127     buffer-access-fontify-functions command-line-functions
 128     comment-indent-function kill-buffer-query-functions
 129     kill-emacs-query-functions lisp-indent-function
 130     mouse-position-function
 131     redisplay-end-trigger-functions temp-buffer-show-function
 132     window-scroll-functions window-size-change-functions
 133     write-region-annotate-functions)
 134   "A list of special hooks from Info node `(elisp)Standard Hooks'.
 135
 136 These are symbols with hook-type values whose names don't end in
 137 `-hook' or `-hooks', from which `unload-feature' tries to remove
 138 pertinent symbols.")
 139
 140 (defvar unload-hook-features-list nil
 141   "List of features of the package being unloaded.
 142
 143 This is meant to be used by FEATURE-unload-hook hooks, see the
 144 documentation of `unload-feature' for details.")
 145
 146 ;;;###autoload
 147 (defun unload-feature (feature &optional force)
 148   "Unload the library that provided FEATURE, restoring all its autoloads.
 149 If the feature is required by any other loaded code, and prefix arg FORCE
 150 is nil, raise an error.
 151
 152 This function tries to undo modifications made by the package to
 153 hooks.  Packages may define a hook FEATURE-unload-hook that is called
 154 instead of the normal heuristics for doing this.  Such a hook should
 155 undo all the relevant global state changes that may have been made by
 156 loading the package or executing functions in it.  It has access to
 157 the package's feature list (before anything is unbound) in the
 158 variable `unload-hook-features-list' and could remove features from it
 159 in the event that the package has done something normally-ill-advised,
 160 such as redefining an Emacs function."
 161   (interactive (list (read-feature "Feature: ") current-prefix-arg))
 162   (unless (featurep feature)
 163     (error "%s is not a currently loaded feature" (symbol-name feature)))
 164   (unless force
 165     (let* ((file (feature-file feature))
 166            (dependents (delete file (copy-sequence (file-dependents file)))))
 167       (when dependents
 168         (error "Loaded libraries %s depend on %s"
 169                (prin1-to-string dependents) file))))
 170   (let* ((unload-hook-features-list (feature-symbols feature))
 171          (file (pop unload-hook-features-list))
 172          (unload-hook (intern-soft (concat (symbol-name feature)
 173                                            "-unload-hook"))))
 174     ;; Try to avoid losing badly when hooks installed in critical
 175     ;; places go away.  (Some packages install things on
 176     ;; `kill-buffer-hook', `activate-menubar-hook' and the like.)
 177     ;; First off, provide a clean way for package FOO to arrange
 178     ;; this by adding hooks on the variable `FOO-unload-hook'.
 179     (if unload-hook
 180         (run-hooks unload-hook)
 181       ;; Otherwise, do our best.  Look through the obarray for symbols
 182       ;; which seem to be hook variables or special hook functions and
 183       ;; remove anything from them which matches the feature-symbols
 184       ;; about to get zapped.  Obviously this won't get anonymous
 185       ;; functions which the package might just have installed, and
 186       ;; there might be other important state, but this tactic
 187       ;; normally works.
 188       (mapatoms
 189        (lambda (x)
 190          (when (and (boundp x)
 191                     (or (and (consp (symbol-value x)) ; Random hooks.
 192                              (string-match "-hooks?\\'" (symbol-name x)))
 193                         (memq x unload-feature-special-hooks))) ; Known abnormal hooks etc.
 194            (dolist (y unload-hook-features-list)
 195              (when (and (eq (car-safe y) 'defun)
 196                         (not (get (cdr y) 'autoload)))
 197                (remove-hook x (cdr y)))))))
 198       ;; Remove any feature-symbols from auto-mode-alist as well.
 199       (dolist (y unload-hook-features-list)
 200         (when (and (eq (car-safe y) 'defun)
 201                    (not (get (cdr y) 'autoload)))
 202           (setq auto-mode-alist
 203                 (rassq-delete-all (cdr y) auto-mode-alist)))))
 204     (when (fboundp 'elp-restore-function) ; remove ELP stuff first
 205       (dolist (elt unload-hook-features-list)
 206         (when (symbolp elt)
 207           (elp-restore-function elt))))
 208     (dolist (x unload-hook-features-list)
 209       (if (consp x)
 210           (cond
 211            ;; Remove any feature names that this file provided.
 212            ((eq (car x) 'provide)
 213             (setq features (delq (cdr x) features)))
 214            ((eq (car x) 'defun)
 215             (let ((fun (cdr x)))
 216               (when (fboundp fun)
 217                 (when (fboundp 'ad-unadvise)
 218                   (ad-unadvise fun))
 219                 (fmakunbound fun)
 220                 (let ((aload (get fun 'autoload)))
 221                   (when aload
 222                     (fset fun (cons 'autoload aload))))))))
 223         ;; Kill local values as much as possible.
 224         (dolist (buf (buffer-list))
 225           (with-current-buffer buf
 226             (kill-local-variable x)))
 227         ;; Get rid of the default binding if we can.
 228         (unless (local-variable-if-set-p x)
 229           (makunbound x))))
 230     ;; Delete the load-history element for this file.
 231     (setq load-history (delq (assoc file load-history) load-history))))
 232
 233 (provide 'loadhist)
 234
 235 ;;; arch-tag: 70bb846a-c413-4f01-bf88-78dba4ac0798
 236 ;;; loadhist.el ends here