;;; emacs-lock.el --- protect buffers against killing or exiting -*- lexical-binding: t -*-
;; Copyright (C) 2011-2019 Free Software Foundation, Inc.
;; Author: Juanma Barranquero <lekktu@gmail.com>
;; Inspired by emacs-lock.el by Tom Wurgler <twurgler@goodyear.com>
;; Maintainer: emacs-devel@gnu.org
;; Keywords: extensions, processes
;; 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 3 of the License, 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. If not, see <https://www.gnu.org/licenses/>.
;;; Commentary:
;; This package defines a minor mode Emacs Lock to mark a buffer as
;; protected against accidental killing, or exiting Emacs, or both.
;; Buffers associated with inferior modes, like shell or telnet, can
;; be treated specially, by auto-unlocking them if their inferior
;; processes are dead.
;;; Code:
(defgroup emacs-lock nil
"Emacs-Lock mode."
:version "24.1"
:group 'convenience)
(defcustom emacs-lock-default-locking-mode 'all
"Default locking mode of Emacs-Locked buffers.
Its value is used as the default for `emacs-lock-mode' (which
see) the first time that Emacs Lock mode is turned on in a buffer
without passing an explicit locking mode.
Possible values are:
exit -- Emacs cannot exit while the buffer is locked
kill -- the buffer cannot be killed, but Emacs can exit as usual
all -- the buffer is locked against both actions
nil -- the buffer is not locked"
:type '(choice
(const :tag "Do not allow Emacs to exit" exit)
(const :tag "Do not allow killing the buffer" kill)
(const :tag "Do not allow killing the buffer or exiting Emacs" all)
(const :tag "Do not lock the buffer" nil))
:group 'emacs-lock
:version "24.1")
;; Note: as auto-unlocking can lead to data loss, it would be better
;; to default to nil; but the value below is for compatibility with
;; the old emacs-lock.el.
(defcustom emacs-lock-unlockable-modes '((shell-mode . all)
(telnet-mode . all))
"Alist of auto-unlockable modes.
Each element is a pair (MAJOR-MODE . ACTION), where ACTION is
one of `kill', `exit' or `all'. Buffers with matching major
modes are auto-unlocked for the specific action if their
inferior processes are not alive. If this variable is t, all
buffers associated to inferior processes are auto-unlockable
for both actions (NOT RECOMMENDED)."
:type '(choice
(const :tag "All buffers with inferior processes" t)
(repeat :tag "Selected modes"
(cons :tag "Set auto-unlock for"
(symbol :tag "Major mode")
(radio
(const :tag "Allow exiting" exit)
(const :tag "Allow killing" kill)
(const :tag "Allow both" all)))))
:group 'emacs-lock
:version "24.1")
(defcustom emacs-lock-locked-buffer-functions nil
"Abnormal hook run when Emacs Lock prevents exiting Emacs, or killing a buffer.
The functions get one argument, the first locked buffer found."
:type 'hook
:group 'emacs-lock
:version "24.3")
(define-obsolete-variable-alias 'emacs-lock-from-exiting
'emacs-lock-mode "24.1")
(defvar-local emacs-lock-mode nil
"If non-nil, the current buffer is locked.
It can be one of the following values:
exit -- Emacs cannot exit while the buffer is locked
kill -- the buffer cannot be killed, but Emacs can exit as usual
all -- the buffer is locked against both actions
nil -- the buffer is not locked
See also `emacs-lock-unlockable-modes', which exempts buffers under
some major modes from being locked under some circumstances.")
(put 'emacs-lock-mode 'permanent-local t)
(defvar-local emacs-lock--old-mode nil
"Most recent locking mode set on the buffer.
Internal use only.")
(put 'emacs-lock--old-mode 'permanent-local t)
(defvar-local emacs-lock--try-unlocking nil
"Non-nil if current buffer should be checked for auto-unlocking.
Internal use only.")
(put 'emacs-lock--try-unlocking 'permanent-local t)
(defun emacs-lock-live-process-p (buffer-or-name)
"Return t if BUFFER-OR-NAME is associated with a live process."
(process-live-p (get-buffer-process buffer-or-name)))
(defun emacs-lock--can-auto-unlock (action)
"Return t if the current buffer can auto-unlock for ACTION.
ACTION must be one of `kill' or `exit'.
See `emacs-lock-unlockable-modes'."
(and emacs-lock--try-unlocking
(not (emacs-lock-live-process-p (current-buffer)))
(or (eq emacs-lock-unlockable-modes t)
(let ((unlock (cdr (assq major-mode emacs-lock-unlockable-modes))))
(or (eq unlock 'all) (eq unlock action))))))
(defun emacs-lock--exit-locked-buffer ()
"Return the first exit-locked buffer found."
(save-current-buffer
(catch :found
(dolist (buffer (buffer-list))
(set-buffer buffer)
(unless (or (emacs-lock--can-auto-unlock 'exit)
(memq emacs-lock-mode '(nil kill)))
(throw :found buffer)))
nil)))
(defun emacs-lock--kill-emacs-hook ()
"Signal an error if any buffer is exit-locked.
Used from `kill-emacs-hook' (which see)."
(let ((locked (emacs-lock--exit-locked-buffer)))
(when locked
(run-hook-with-args 'emacs-lock-locked-buffer-functions locked)
(error "Emacs cannot exit because buffer %S is locked"
(buffer-name locked)))))
(defun emacs-lock--kill-emacs-query-functions ()
"Display a message if any buffer is exit-locked.
Return a value appropriate for `kill-emacs-query-functions' (which see)."
(let ((locked (emacs-lock--exit-locked-buffer)))
(if (not locked)
t
(run-hook-with-args 'emacs-lock-locked-buffer-functions locked)
(message "Emacs cannot exit because buffer %S is locked"
(buffer-name locked))
nil)))
(defun emacs-lock--kill-buffer-query-functions ()
"Display a message if the current buffer is kill-locked.
Return a value appropriate for `kill-buffer-query-functions' (which see)."
(if (or (emacs-lock--can-auto-unlock 'kill)
(memq emacs-lock-mode '(nil exit)))
t
(run-hook-with-args 'emacs-lock-locked-buffer-functions (current-buffer))
(message "Buffer %S is locked and cannot be killed" (buffer-name))
nil))
(defun emacs-lock--set-mode (mode arg)
"Setter function for `emacs-lock-mode'."
(setq emacs-lock-mode
(cond ((memq arg '(all exit kill))
;; explicit locking mode arg, use it
arg)
((and (eq arg current-prefix-arg) (consp current-prefix-arg))
;; called with C-u M-x emacs-lock-mode, so ask the user
(intern (completing-read "Locking mode: "
'("all" "exit" "kill")
nil t nil nil
(symbol-name
emacs-lock-default-locking-mode))))
((eq mode t)
;; turn on, so use previous setting, or customized default
(or emacs-lock--old-mode emacs-lock-default-locking-mode))
(t
;; anything else (turn off)
mode))))
;;;###autoload
(define-minor-mode emacs-lock-mode
"Toggle Emacs Lock mode in the current buffer.
If called with a plain prefix argument, ask for the locking mode
to be used.
Initially, if the user does not pass an explicit locking mode, it
defaults to `emacs-lock-default-locking-mode' (which see);
afterwards, the locking mode most recently set on the buffer is
used instead.
When called from Elisp code, ARG can be any locking mode:
exit -- Emacs cannot exit while the buffer is locked
kill -- the buffer cannot be killed, but Emacs can exit as usual
all -- the buffer is locked against both actions
Other values are interpreted as usual.
See also `emacs-lock-unlockable-modes', which exempts buffers under
some major modes from being locked under some circumstances."
:init-value nil
:lighter (""
(emacs-lock--try-unlocking " locked:" " Locked:")
(:eval (symbol-name emacs-lock-mode)))
:group 'emacs-lock
:variable (emacs-lock-mode .
(lambda (mode)
(emacs-lock--set-mode mode arg)))
(when emacs-lock-mode
(setq emacs-lock--old-mode emacs-lock-mode)
(setq emacs-lock--try-unlocking
(and (if (eq emacs-lock-unlockable-modes t)
(emacs-lock-live-process-p (current-buffer))
(assq major-mode emacs-lock-unlockable-modes))
t))))
(unless noninteractive
(add-hook 'kill-buffer-query-functions 'emacs-lock--kill-buffer-query-functions)
;; We set a hook in both kill-emacs-hook and kill-emacs-query-functions because
;; we really want to use k-e-q-f to stop as soon as possible, but don't want to
;; be caught by surprise if someone calls `kill-emacs' instead.
(add-hook 'kill-emacs-hook 'emacs-lock--kill-emacs-hook)
(add-hook 'kill-emacs-query-functions 'emacs-lock--kill-emacs-query-functions))
(defun emacs-lock-unload-function ()
"Unload the Emacs Lock library."
(catch :continue
(dolist (buffer (buffer-list))
(set-buffer buffer)
(when emacs-lock-mode
(if (y-or-n-p (format "Buffer %S is locked, unlock it? " (buffer-name)))
(emacs-lock-mode -1)
(message "Unloading of feature `emacs-lock' aborted.")
(throw :continue t))))
;; continue standard unloading
nil))
;;; Compatibility
(defun toggle-emacs-lock ()
"Toggle `emacs-lock-from-exiting' for the current buffer."
(declare (obsolete emacs-lock-mode "24.1"))
(interactive)
(call-interactively 'emacs-lock-mode))
(provide 'emacs-lock)
;;; emacs-lock.el ends here