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Desktop: protect users against inadvertant upgrading of desktop file.

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An upgraded (version 208) desktop file cannot be read in Emacs < 25.

* etc/NEWS: Add an entry about upgrading a desktop file.

* lisp/desktop.el (desktop-file-version): Amend doc string.
(desktop-native-file-version, desktop-io-file-version): new variables.
(desktop-clear): Set desktop-io-file-version to nil.
(desktop-buffer-info): make the presence of the last item on the list
conditional on (>= desktop-io-file-version 208).
(desktop-save): Add extra parameter VERSION to take user's C-u or C-u C-u.
Amend the doc string.  Add code to determine the output file version.
(desktop-create-buffer): Set desktop-io-file-version to the input file's
version.
This commit is contained in:
Alan Mackenzie 2016-01-18 13:32:22 +00:00
parent 130d512045
commit 20defc5538
2 changed files with 114 additions and 48 deletions
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11
etc/NEWS
View file

@ -315,6 +315,17 @@ current package keywords are recognized. Set the new option
It's meant for use together with `compile':
emacs -batch --eval "(checkdoc-file \"subr.el\")"
** Desktop
---
*** The desktop format version has been upgraded from 206 to 208.
Although Emacs 25.1 can read a version 206 desktop, earlier Emacsen
cannot read a version 208 desktop. To upgrade your desktop file, you
must explicitly request the upgrade, by C-u M-x desktop-save. You are
recommended to do this as soon as you have firmly upgraded to Emacs
25.1 (or later). Should you ever need to downgrade your desktop file
to version 206, you can do this with C-u C-u M-x desktop-save.
+++
** New function `bookmark-set-no-overwrite' bound to C-x r M.
It raises an error if a bookmark of that name already exists,

151
lisp/desktop.el
View file

@ -140,8 +140,15 @@
(defvar desktop-file-version "208"
"Version number of desktop file format.
Written into the desktop file and used at desktop read to provide
backward compatibility.")
Used at desktop read to provide backward compatibility.")
(defconst desktop-native-file-version 208
"Format version of the current desktop package, an integer.")
(defvar desktop-io-file-version nil
"The format version of the current desktop file (an integer) or nil.")
;; Note: Historically, the version number is embedded in the entry for
;; each buffer. It is highly inadvisable for different buffer entries
;; to have different format versions.
;; ----------------------------------------------------------------------------
;; USER OPTIONS -- settings you might want to play with.
@ -693,6 +700,7 @@ deletes all frames except the selected one (and its minibuffer frame,
if different)."
(interactive)
(desktop-lazy-abort)
(setq desktop-io-file-version nil)
(dolist (var desktop-globals-to-clear)
(if (symbolp var)
(eval `(setq-default ,var nil))
@ -781,44 +789,46 @@ buffer, which is (in order):
local variables;
auxiliary information given by `desktop-var-serdes-funs'."
(set-buffer buffer)
(list
;; base name of the buffer; replaces the buffer name if managed by uniquify
(and (fboundp 'uniquify-buffer-base-name) (uniquify-buffer-base-name))
;; basic information
(desktop-file-name (buffer-file-name) desktop-dirname)
(buffer-name)
major-mode
;; minor modes
(let (ret)
(dolist (minor-mode (mapcar #'car minor-mode-alist) ret)
(and (boundp minor-mode)
(symbol-value minor-mode)
(let* ((special (assq minor-mode desktop-minor-mode-table))
(value (cond (special (cadr special))
((functionp minor-mode) minor-mode))))
(when value (cl-pushnew value ret))))))
;; point and mark, and read-only status
(point)
(list (mark t) mark-active)
buffer-read-only
;; auxiliary information
(when (functionp desktop-save-buffer)
(funcall desktop-save-buffer desktop-dirname))
;; local variables
(let ((loclist (buffer-local-variables))
(ll nil))
(dolist (local desktop-locals-to-save)
(let ((here (assq local loclist)))
(cond (here
(push here ll))
((member local loclist)
(push local ll)))))
ll)
(mapcar (lambda (record)
(let ((var (car record)))
(list var
(funcall (cadr record) (symbol-value var)))))
desktop-var-serdes-funs)))
`(
;; base name of the buffer; replaces the buffer name if managed by uniquify
,(and (fboundp 'uniquify-buffer-base-name) (uniquify-buffer-base-name))
;; basic information
,(desktop-file-name (buffer-file-name) desktop-dirname)
,(buffer-name)
,major-mode
;; minor modes
,(let (ret)
(dolist (minor-mode (mapcar #'car minor-mode-alist) ret)
(and (boundp minor-mode)
(symbol-value minor-mode)
(let* ((special (assq minor-mode desktop-minor-mode-table))
(value (cond (special (cadr special))
((functionp minor-mode) minor-mode))))
(when value (cl-pushnew value ret))))))
;; point and mark, and read-only status
,(point)
,(list (mark t) mark-active)
,buffer-read-only
;; auxiliary information
,(when (functionp desktop-save-buffer)
(funcall desktop-save-buffer desktop-dirname))
;; local variables
,(let ((loclist (buffer-local-variables))
(ll nil))
(dolist (local desktop-locals-to-save)
(let ((here (assq local loclist)))
(cond (here
(push here ll))
((member local loclist)
(push local ll)))))
ll)
,@(when (>= desktop-io-file-version 208)
(list
(mapcar (lambda (record)
(let ((var (car record)))
(list var
(funcall (cadr record) (symbol-value var)))))
desktop-var-serdes-funs)))))
;; ----------------------------------------------------------------------------
(defun desktop--v2s (value)
@ -983,20 +993,41 @@ Frames with a non-nil `desktop-dont-save' parameter are not saved."
:predicate #'desktop--check-dont-save))))
;;;###autoload
(defun desktop-save (dirname &optional release only-if-changed)
(defun desktop-save (dirname &optional release only-if-changed version)
"Save the desktop in a desktop file.
Parameter DIRNAME specifies where to save the desktop file.
Optional parameter RELEASE says whether we're done with this desktop.
If ONLY-IF-CHANGED is non-nil, compare the current desktop information
to that in the desktop file, and if the desktop information has not
changed since it was last saved then do not rewrite the file."
Optional parameter RELEASE says whether we're done with this
desktop. If ONLY-IF-CHANGED is non-nil, compare the current
desktop information to that in the desktop file, and if the
desktop information has not changed since it was last saved then
do not rewrite the file.
This function can save the desktop in either format version
208 (which only Emacs 25.1 and later can read) or version
206 (which is readable by any Emacs from version 22.1 onwards).
By default, it will use the same format the desktop file had when
it was last saved, or version 208 when writing a fresh desktop
file.
To upgrade a version 206 file to version 208, call this command
explicitly with a bare prefix argument: C-u M-x desktop-save.
You are recommended to do this once you have firmly upgraded to
Emacs 25.1 (or later). To downgrade a version 208 file to version
206, use a double command prefix: C-u C-u M-x desktop-save.
Confirmation will be requested in either case. In a non-interactive
call, VERSION can be given as an integer, either 206 or 208, which
will be accepted as the format version in which to save the file
without further confirmation."
(interactive (list
;; Or should we just use (car desktop-path)?
(let ((default (if (member "." desktop-path)
default-directory
user-emacs-directory)))
(read-directory-name "Directory to save desktop file in: "
default default t))))
default default t))
nil
nil
current-prefix-arg))
(setq desktop-dirname (file-name-as-directory (expand-file-name dirname)))
(save-excursion
(let ((eager desktop-restore-eager)
@ -1017,12 +1048,34 @@ changed since it was last saved then do not rewrite the file."
(desktop-release-lock)
(unless (and new-modtime (desktop-owner)) (desktop-claim-lock)))
;; What format are we going to write the file in?
(setq desktop-io-file-version
(cond
((equal version '(4))
(if (or (eq desktop-io-file-version 208)
(yes-or-no-p "Save desktop file in format 208 \
\(Readable by Emacs 25.1 and later only)? "))
208
(or desktop-io-file-version desktop-native-file-version)))
((equal version '(16))
(if (or (eq desktop-io-file-version 206)
(yes-or-no-p "Save desktop file in format 206 \
\(Readable by all Emacs versions since 22.1)? "))
206
(or desktop-io-file-version desktop-native-file-version)))
((memq version '(206 208))
version)
((null desktop-io-file-version) ; As yet, no desktop file exists.
desktop-native-file-version)
(t
desktop-io-file-version)))
(with-temp-buffer
(insert
";; -*- mode: emacs-lisp; coding: emacs-mule; -*-\n"
desktop-header
";; Created " (current-time-string) "\n"
";; Desktop file format version " desktop-file-version "\n"
";; Desktop file format version " (format "%d" desktop-io-file-version) "\n"
";; Emacs version " emacs-version "\n")
(save-excursion (run-hooks 'desktop-save-hook))
(goto-char (point-max))
@ -1052,7 +1105,7 @@ changed since it was last saved then do not rewrite the file."
"desktop-create-buffer"
"desktop-append-buffer-args")
" "
desktop-file-version)
(format "%d" desktop-io-file-version))
;; If there's a non-empty base name, we save it instead of the buffer name
(when (and base (not (string= base "")))
(setcar (nthcdr 1 l) base))
@ -1390,6 +1443,8 @@ and try to load that."
compacted-vars
&rest _unsupported)
(setq desktop-io-file-version file-version)
(let ((desktop-file-version file-version)
(desktop-buffer-file-name buffer-filename)
(desktop-buffer-name buffer-name)