1;;; loadhist.el --- lisp functions for working with feature groups
2
3;; Copyright (C) 1995, 1998, 2000, 2001, 2002, 2003, 2004,
4;;   2005, 2006, 2007 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(eval-when-compile (require 'cl))
36
37(defun feature-symbols (feature)
38  "Return the file and list of definitions associated with FEATURE.
39The value is actually the element of `load-history'
40for the file that did (provide FEATURE)."
41   (catch 'foundit
42     (mapc (lambda (x)
43	     (if (member (cons 'provide feature) (cdr x))
44		 (throw 'foundit x)))
45	   load-history)
46     nil))
47
48(defun feature-file (feature)
49  "Return the file name from which a given FEATURE was loaded.
50Actually, return the load argument, if any; this is sometimes the name of a
51Lisp file without an extension.  If the feature came from an `eval-buffer' on
52a buffer with no associated file, or an `eval-region', return nil."
53  (if (not (featurep feature))
54      (error "%S is not a currently loaded feature" feature)
55    (car (feature-symbols feature))))
56
57(defun file-loadhist-lookup (file)
58  "Return the `load-history' element for FILE.
59FILE can be a file name, or a library name.
60A library name is equivalent to the file name that `load-library' would load."
61  ;; First look for FILE as given.
62  (let ((symbols (assoc file load-history)))
63    ;; Try converting a library name to an absolute file name.
64    (and (null symbols)
65	 (let ((absname
66		(locate-file file load-path (get-load-suffixes))))
67	   (and absname (not (equal absname file))
68		(setq symbols (cdr (assoc absname load-history))))))
69    symbols))
70
71(defun file-provides (file)
72  "Return the list of features provided by FILE as it was loaded.
73FILE can be a file name, or a library name.
74A library name is equivalent to the file name that `load-library' would load."
75  (let ((symbols (file-loadhist-lookup file))
76	provides)
77    (mapc (lambda (x)
78	    (if (and (consp x) (eq (car x) 'provide))
79		(setq provides (cons (cdr x) provides))))
80	  symbols)
81    provides))
82
83(defun file-requires (file)
84  "Return the list of features required by FILE as it was loaded.
85FILE can be a file name, or a library name.
86A library name is equivalent to the file name that `load-library' would load."
87  (let ((symbols (file-loadhist-lookup file))
88	requires)
89    (mapc (lambda (x)
90	    (if (and (consp x) (eq (car x) 'require))
91		(setq requires (cons (cdr x) requires))))
92	  symbols)
93    requires))
94
95(defsubst file-set-intersect (p q)
96  "Return the set intersection of two lists."
97  (let ((ret nil))
98    (dolist (x p ret)
99      (if (memq x q) (setq ret (cons x ret))))
100    ret))
101
102(defun file-dependents (file)
103  "Return the list of loaded libraries that depend on FILE.
104This can include FILE itself.
105FILE can be a file name, or a library name.
106A library name is equivalent to the file name that `load-library' would load."
107  (let ((provides (file-provides file))
108	(dependents nil))
109    (dolist (x load-history dependents)
110      (if (file-set-intersect provides (file-requires (car x)))
111	  (setq dependents (cons (car x) dependents))))
112    dependents))
113
114(defun read-feature (prompt &optional loaded-p)
115  "Read feature name from the minibuffer, prompting with string PROMPT.
116If optional second arg LOADED-P is non-nil, the feature must be loaded
117from a file."
118  (intern
119   (completing-read prompt
120		    (cons nil features)
121		    (and loaded-p
122			 #'(lambda (f)
123			     (and f	; ignore nil
124				  (feature-file f))))
125		    loaded-p)))
126
127(defvaralias 'loadhist-hook-functions 'unload-feature-special-hooks)
128(defvar unload-feature-special-hooks
129  '(after-change-functions
130    after-insert-file-functions auto-fill-function
131    before-change-functions blink-paren-function
132    buffer-access-fontify-functions command-line-functions
133    comment-indent-function kill-buffer-query-functions
134    kill-emacs-query-functions lisp-indent-function
135    mouse-position-function
136    redisplay-end-trigger-functions temp-buffer-show-function
137    window-scroll-functions window-size-change-functions
138    write-region-annotate-functions)
139  "A list of special hooks from Info node `(elisp)Standard Hooks'.
140
141These are symbols with hook-type values whose names don't end in
142`-hook' or `-hooks', from which `unload-feature' tries to remove
143pertinent symbols.")
144
145(defvar unload-hook-features-list nil
146  "List of features of the package being unloaded.
147
148This is meant to be used by FEATURE-unload-hook hooks, see the
149documentation of `unload-feature' for details.")
150
151;;;###autoload
152(defun unload-feature (feature &optional force)
153  "Unload the library that provided FEATURE, restoring all its autoloads.
154If the feature is required by any other loaded code, and prefix arg FORCE
155is nil, raise an error.
156
157This function tries to undo modifications made by the package to
158hooks.  Packages may define a hook FEATURE-unload-hook that is called
159instead of the normal heuristics for doing this.  Such a hook should
160undo all the relevant global state changes that may have been made by
161loading the package or executing functions in it.  It has access to
162the package's feature list (before anything is unbound) in the
163variable `unload-hook-features-list' and could remove features from it
164in the event that the package has done something normally-ill-advised,
165such as redefining an Emacs function."
166  (interactive
167   (list
168    (read-feature "Unload feature: " t)
169    current-prefix-arg))
170  (unless (featurep feature)
171    (error "%s is not a currently loaded feature" (symbol-name feature)))
172  (unless force
173    (let* ((file (feature-file feature))
174	   (dependents (delete file (copy-sequence (file-dependents file)))))
175      (when dependents
176	(error "Loaded libraries %s depend on %s"
177	       (prin1-to-string dependents) file))))
178  (let* ((unload-hook-features-list (feature-symbols feature))
179         (file (pop unload-hook-features-list))
180	 ;; If non-nil, this is a symbol for which we should
181	 ;; restore a previous autoload if possible.
182	 restore-autoload
183         (unload-hook (intern-soft (concat (symbol-name feature)
184                                           "-unload-hook"))))
185    ;; Try to avoid losing badly when hooks installed in critical
186    ;; places go away.  (Some packages install things on
187    ;; `kill-buffer-hook', `activate-menubar-hook' and the like.)
188    ;; First off, provide a clean way for package FOO to arrange
189    ;; this by adding hooks on the variable `FOO-unload-hook'.
190    (if unload-hook
191        (run-hooks unload-hook)
192      ;; Otherwise, do our best.  Look through the obarray for symbols
193      ;; which seem to be hook variables or special hook functions and
194      ;; remove anything from them which matches the feature-symbols
195      ;; about to get zapped.  Obviously this won't get anonymous
196      ;; functions which the package might just have installed, and
197      ;; there might be other important state, but this tactic
198      ;; normally works.
199      (mapatoms
200       (lambda (x)
201         (when (and (boundp x)
202		    (or (and (consp (symbol-value x)) ; Random hooks.
203			     (string-match "-hooks?\\'" (symbol-name x)))
204			(memq x unload-feature-special-hooks)))	; Known abnormal hooks etc.
205	   (dolist (y unload-hook-features-list)
206	     (when (and (eq (car-safe y) 'defun)
207			(not (get (cdr y) 'autoload)))
208	       (remove-hook x (cdr y)))))))
209      ;; Remove any feature-symbols from auto-mode-alist as well.
210      (dolist (y unload-hook-features-list)
211	(when (and (eq (car-safe y) 'defun)
212		   (not (get (cdr y) 'autoload)))
213	  (setq auto-mode-alist
214		(rassq-delete-all (cdr y) auto-mode-alist)))))
215    (when (fboundp 'elp-restore-function) ; remove ELP stuff first
216      (dolist (elt unload-hook-features-list)
217	(when (symbolp elt)
218	  (elp-restore-function elt))))
219
220    (dolist (x unload-hook-features-list)
221      (if (consp x)
222	  (case (car x)
223	   ;; Remove any feature names that this file provided.
224	   (provide
225	    (setq features (delq (cdr x) features)))
226	   ((defun autoload)
227	    (let ((fun (cdr x)))
228	      (when (fboundp fun)
229		(when (fboundp 'ad-unadvise)
230		  (ad-unadvise fun))
231		(let ((aload (get fun 'autoload)))
232		  (if (and aload (eq fun restore-autoload))
233                      (fset fun (cons 'autoload aload))
234                    (fmakunbound fun))))))
235	   ;; (t . SYMBOL) comes before (defun . SYMBOL)
236	   ;; and says we should restore SYMBOL's autoload
237	   ;; when we undefine it.
238	   ((t) (setq restore-autoload (cdr x)))
239           ((require defface) nil)
240	   (t (message "Unexpected element %s in load-history" x)))
241	;; Kill local values as much as possible.
242	(dolist (buf (buffer-list))
243	  (with-current-buffer buf
244            (if (and (boundp x) (timerp (symbol-value x)))
245                (cancel-timer (symbol-value x)))
246	    (kill-local-variable x)))
247        (if (and (boundp x) (timerp (symbol-value x)))
248            (cancel-timer (symbol-value x)))
249	;; Get rid of the default binding if we can.
250	(unless (local-variable-if-set-p x)
251	  (makunbound x))))
252    ;; Delete the load-history element for this file.
253    (setq load-history (delq (assoc file load-history) load-history)))
254  ;; Don't return load-history, it is not useful.
255  nil)
256
257(provide 'loadhist)
258
259;; arch-tag: 70bb846a-c413-4f01-bf88-78dba4ac0798
260;;; loadhist.el ends here
261