lisp/loadhist.el

   1 ;;; loadhist.el --- lisp functions for working with feature groups
   2
   3 ;; Copyright (C) 1995, 1998, 2000-2015 Free Software Foundation, Inc.
   4
   5 ;; Author: Eric S. Raymond <esr@snark.thyrsus.com>
   6 ;; Maintainer: emacs-devel@gnu.org
   7 ;; Keywords: internal
   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 3 of the License, or
  14 ;; (at your option) 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.  If not, see <http://www.gnu.org/licenses/>.
  23
  24 ;;; Commentary:
  25
  26 ;; These functions exploit the load-history system variable.
  27 ;; Entry points include `unload-feature', `symbol-file', and
  28 ;; `feature-file', documented in the Emacs Lisp manual.
  29
  30 ;;; Code:
  31
  32 (defun feature-symbols (feature)
  33   "Return the file and list of definitions associated with FEATURE.
  34 The value is actually the element of `load-history'
  35 for the file that did (provide FEATURE)."
  36   (catch 'foundit
  37     (let ((element (cons 'provide feature)))
  38       (dolist (x load-history nil)
  39         (when (member element (cdr x))
  40           (throw 'foundit x))))))
  41
  42 (defun feature-file (feature)
  43   "Return the file name from which a given FEATURE was loaded.
  44 Actually, return the load argument, if any; this is sometimes the name of a
  45 Lisp file without an extension.  If the feature came from an `eval-buffer' on
  46 a buffer with no associated file, or an `eval-region', return nil."
  47   (if (not (featurep feature))
  48       (error "%S is not a currently loaded feature" feature)
  49     (car (feature-symbols feature))))
  50
  51 (defun file-loadhist-lookup (file)
  52   "Return the `load-history' element for FILE.
  53 FILE can be a file name, or a library name.
  54 A library name is equivalent to the file name that `load-library' would load."
  55   ;; First look for FILE as given.
  56   (let ((symbols (assoc file load-history)))
  57     ;; Try converting a library name to an absolute file name.
  58     (and (null symbols)
  59          (let ((absname
  60                 (locate-file file load-path (get-load-suffixes))))
  61            (and absname (not (equal absname file))
  62                 (setq symbols (cdr (assoc absname load-history))))))
  63     symbols))
  64
  65 (defun file-provides (file)
  66   "Return the list of features provided by FILE as it was loaded.
  67 FILE can be a file name, or a library name.
  68 A library name is equivalent to the file name that `load-library' would load."
  69   (let (provides)
  70     (dolist (x (file-loadhist-lookup file) provides)
  71       (when (eq (car-safe x) 'provide)
  72         (push (cdr x) provides)))))
  73
  74 (defun file-requires (file)
  75   "Return the list of features required by FILE as it was loaded.
  76 FILE can be a file name, or a library name.
  77 A library name is equivalent to the file name that `load-library' would load."
  78   (let (requires)
  79     (dolist (x (file-loadhist-lookup file) requires)
  80       (when (eq (car-safe x) 'require)
  81         (push (cdr x) requires)))))
  82
  83 (defsubst file-set-intersect (p q)
  84   "Return the set intersection of two lists."
  85   (let (ret)
  86     (dolist (x p ret)
  87       (when (memq x q) (push x ret)))))
  88
  89 (defun file-dependents (file)
  90   "Return the list of loaded libraries that depend on FILE.
  91 This can include FILE itself.
  92 FILE can be a file name, or a library name.
  93 A library name is equivalent to the file name that `load-library' would load."
  94   (let ((provides (file-provides file))
  95         (dependents nil))
  96     (dolist (x load-history dependents)
  97       (when (file-set-intersect provides (file-requires (car x)))
  98         (push (car x) dependents)))))
  99
 100 (defun read-feature (prompt &optional loaded-p)
 101   "Read feature name from the minibuffer, prompting with string PROMPT.
 102 If optional second arg LOADED-P is non-nil, the feature must be loaded
 103 from a file."
 104   (intern (completing-read
 105            prompt
 106            (mapcar #'symbol-name
 107                    (if loaded-p
 108                        (delq nil
 109                              (mapcar
 110                               (lambda (x) (and (feature-file x) x))
 111                               features))
 112                      features)))))
 113
 114 (defvaralias 'loadhist-hook-functions 'unload-feature-special-hooks)
 115 (defvar unload-feature-special-hooks
 116   '(after-change-functions after-insert-file-functions
 117     after-make-frame-functions auto-coding-functions
 118     auto-fill-function before-change-functions
 119     blink-paren-function buffer-access-fontify-functions
 120     choose-completion-string-functions
 121     comint-output-filter-functions command-line-functions
 122     comment-indent-function compilation-finish-functions
 123     delete-frame-functions disabled-command-function
 124     fill-nobreak-predicate find-directory-functions
 125     find-file-not-found-functions
 126     font-lock-beginning-of-syntax-function
 127     font-lock-fontify-buffer-function
 128     font-lock-fontify-region-function
 129     font-lock-mark-block-function
 130     font-lock-syntactic-face-function
 131     font-lock-unfontify-buffer-function
 132     font-lock-unfontify-region-function
 133     kill-buffer-query-functions kill-emacs-query-functions
 134     lisp-indent-function mouse-position-function
 135     redisplay-end-trigger-functions suspend-tty-functions
 136     temp-buffer-show-function window-scroll-functions
 137     window-size-change-functions write-contents-functions
 138     write-file-functions write-region-annotate-functions)
 139   "A list of special hooks from Info node `(elisp)Standard Hooks'.
 140
 141 These are symbols with hooklike values whose names don't end in
 142 `-hook' or `-hooks', from which `unload-feature' should try to remove
 143 pertinent symbols.")
 144
 145 (define-obsolete-variable-alias 'unload-hook-features-list
 146     'unload-function-defs-list "22.2")
 147 (defvar unload-function-defs-list nil
 148   "List of definitions in the Lisp library being unloaded.
 149
 150 This is meant to be used by `FEATURE-unload-function'; see the
 151 documentation of `unload-feature' for details.")
 152
 153 (defun unload--set-major-mode ()
 154   (save-current-buffer
 155     (dolist (buffer (buffer-list))
 156       (set-buffer buffer)
 157       (let ((proposed major-mode))
 158         ;; Look for a predecessor mode not defined in the feature we're processing
 159         (while (and proposed (rassq proposed unload-function-defs-list))
 160           (setq proposed (get proposed 'derived-mode-parent)))
 161         (unless (eq proposed major-mode)
 162           ;; Two cases: either proposed is nil, and we want to switch to fundamental
 163           ;; mode, or proposed is not nil and not major-mode, and so we use it.
 164           (funcall (or proposed 'fundamental-mode)))))))
 165
 166 ;;;###autoload
 167 (defun unload-feature (feature &optional force)
 168   "Unload the library that provided FEATURE.
 169 If the feature is required by any other loaded code, and prefix arg FORCE
 170 is nil, raise an error.
 171
 172 Standard unloading activities include restoring old autoloads for
 173 functions defined by the library, undoing any additions that the
 174 library has made to hook variables or to `auto-mode-alist', undoing
 175 ELP profiling of functions in that library, unproviding any features
 176 provided by the library, and canceling timers held in variables
 177 defined by the library.
 178
 179 If a function `FEATURE-unload-function' is defined, this function
 180 calls it with no arguments, before doing anything else.  That function
 181 can do whatever is appropriate to undo the loading of the library.  If
 182 `FEATURE-unload-function' returns non-nil, that suppresses the
 183 standard unloading of the library.  Otherwise the standard unloading
 184 proceeds.
 185
 186 `FEATURE-unload-function' has access to the package's list of
 187 definitions in the variable `unload-function-defs-list' and could
 188 remove symbols from it in the event that the package has done
 189 something strange, such as redefining an Emacs function."
 190   (interactive
 191    (list
 192     (read-feature "Unload feature: " t)
 193     current-prefix-arg))
 194   (unless (featurep feature)
 195     (error "%s is not a currently loaded feature" (symbol-name feature)))
 196   (unless force
 197     (let* ((file (feature-file feature))
 198            (dependents (delete file (copy-sequence (file-dependents file)))))
 199       (when dependents
 200         (error "Loaded libraries %s depend on %s"
 201                (prin1-to-string dependents) file))))
 202   (let* ((unload-function-defs-list (feature-symbols feature))
 203          (file (pop unload-function-defs-list))
 204          ;; If non-nil, this is a symbol for which we should
 205          ;; restore a previous autoload if possible.
 206          restore-autoload
 207          (name (symbol-name feature))
 208          (unload-hook (intern-soft (concat name "-unload-hook")))
 209          (unload-func (intern-soft (concat name "-unload-function"))))
 210     ;; If FEATURE-unload-function is defined and returns non-nil,
 211     ;; don't try to do anything more; otherwise proceed normally.
 212     (unless (and (fboundp unload-func)
 213                  (funcall unload-func))
 214       ;; Try to avoid losing badly when hooks installed in critical
 215       ;; places go away.  (Some packages install things on
 216       ;; `kill-buffer-hook', `activate-menubar-hook' and the like.)
 217       (if unload-hook
 218           ;; First off, provide a clean way for package FOO to arrange
 219           ;; this by adding hooks on the variable `FOO-unload-hook'.
 220           ;; This is obsolete; FEATURE-unload-function should be used now.
 221           (run-hooks unload-hook)
 222         ;; Otherwise, do our best.  Look through the obarray for symbols
 223         ;; which seem to be hook variables or special hook functions and
 224         ;; remove anything from them which matches the feature-symbols
 225         ;; about to get zapped.  Obviously this won't get anonymous
 226         ;; functions which the package might just have installed, and
 227         ;; there might be other important state, but this tactic
 228         ;; normally works.
 229         (mapatoms
 230          (lambda (x)
 231            (when (and (boundp x)
 232                       (or (and (consp (symbol-value x)) ; Random hooks.
 233                                (string-match "-hooks?\\'" (symbol-name x)))
 234                           (memq x unload-feature-special-hooks)))       ; Known abnormal hooks etc.
 235              (dolist (y unload-function-defs-list)
 236                (when (and (eq (car-safe y) 'defun)
 237                           (not (get (cdr y) 'autoload)))
 238                  (remove-hook x (cdr y)))))))
 239         ;; Remove any feature-symbols from auto-mode-alist as well.
 240         (dolist (y unload-function-defs-list)
 241           (when (and (eq (car-safe y) 'defun)
 242                      (not (get (cdr y) 'autoload)))
 243             (setq auto-mode-alist
 244                   (rassq-delete-all (cdr y) auto-mode-alist)))))
 245
 246       ;; Change major mode in all buffers using one defined in the feature being unloaded.
 247       (unload--set-major-mode)
 248
 249       (when (fboundp 'elp-restore-function) ; remove ELP stuff first
 250         (dolist (elt unload-function-defs-list)
 251           (when (symbolp elt)
 252             (elp-restore-function elt))))
 253
 254       (dolist (x unload-function-defs-list)
 255         (if (consp x)
 256             (pcase (car x)
 257               ;; Remove any feature names that this file provided.
 258               (`provide
 259                (setq features (delq (cdr x) features)))
 260               ((or `defun `autoload)
 261                (let ((fun (cdr x)))
 262                  (when (fboundp fun)
 263                    (when (fboundp 'ad-unadvise)
 264                      (ad-unadvise fun))
 265                    (let ((aload (get fun 'autoload)))
 266                      (if (and aload (eq fun restore-autoload))
 267                          (fset fun (cons 'autoload aload))
 268                        (fmakunbound fun))))))
 269               ;; (t . SYMBOL) comes before (defun . SYMBOL)
 270               ;; and says we should restore SYMBOL's autoload
 271               ;; when we undefine it.
 272               (`t (setq restore-autoload (cdr x)))
 273               ((or `require `defface) nil)
 274               (_ (message "Unexpected element %s in load-history" x)))
 275           ;; Kill local values as much as possible.
 276           (dolist (buf (buffer-list))
 277             (with-current-buffer buf
 278               (if (and (boundp x) (timerp (symbol-value x)))
 279                   (cancel-timer (symbol-value x)))
 280               (kill-local-variable x)))
 281           (if (and (boundp x) (timerp (symbol-value x)))
 282               (cancel-timer (symbol-value x)))
 283           ;; Get rid of the default binding if we can.
 284           (unless (local-variable-if-set-p x)
 285             (makunbound x))))
 286       ;; Delete the load-history element for this file.
 287       (setq load-history (delq (assoc file load-history) load-history))))
 288   ;; Don't return load-history, it is not useful.
 289   nil)
 290
 291 (provide 'loadhist)
 292
 293 ;;; loadhist.el ends here