suggestion: reverting/notifying of files that no longer exist

suggestion: reverting/notifying of files that no longer exist

[Karl Chen]

I think Emacs (maybe as part of auto-revert-mode) should notify
you when you edit files that no longer exist.  Sometimes I rename
or move a file in shell, but still have the old file open and
accidentally edit buffer for the old file.

It would be very useful if Emacs tells you when a file that used
to exist vanishes:
    (1) when you edit its buffer
    (2) if (global-)auto-revert-mode or some customizable variable
        is enabled, as soon as the file vanishes



-- 
Karl 2004-07-09 08:41

Re: suggestion: reverting/notifying of files that no longer exist

[Juri Linkov]

Karl Chen <quarl@hkn.eecs.berkeley.edu> writes:
> I think Emacs (maybe as part of auto-revert-mode) should notify
> you when you edit files that no longer exist.  Sometimes I rename
> or move a file in shell, but still have the old file open and
> accidentally edit buffer for the old file.
>
> It would be very useful if Emacs tells you when a file that used
> to exist vanishes:
>     (1) when you edit its buffer
>     (2) if (global-)auto-revert-mode or some customizable variable
>         is enabled, as soon as the file vanishes

This is the kind of situation Emacs should warn the user about.
It's no fun having an unintentionally forked version which needs
to be merged later with the original version when the fact of forking
is discovered by the user.

One place where the warning could be added is `basic-save-buffer'.  It
could ask if the user tries to save the buffer which was at least once
saved to the file and was renamed or moved afterwards.  The complete
condition to check this situation is:

(and (not (verify-visited-file-modtime (current-buffer)))
     (not (file-exists-p buffer-file-name))
     (> buffer-saved-size 0))

It works in all cases with the exception of the case when a
0-sized file is moved or renamed.  However, this case is not
noteworthy.

Index: lisp/files.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/files.el,v
retrieving revision 1.707
diff -c -r1.707 files.el
*** lisp/files.el	26 Jun 2004 14:41:13 -0000	1.707
--- lisp/files.el	12 Jul 2004 14:05:51 -0000
***************
*** 3082,3090 ****
  		(set-visited-file-name filename)))
  	  (or (verify-visited-file-modtime (current-buffer))
! 	      (not (file-exists-p buffer-file-name))
  	      (yes-or-no-p
! 	       (format "%s has changed since visited or saved.  Save anyway? "
! 		       (file-name-nondirectory buffer-file-name)))
  	      (error "Save not confirmed"))
  	  (save-restriction
  	    (widen)
--- 3082,3093 ----
  		(set-visited-file-name filename)))
  	  (or (verify-visited-file-modtime (current-buffer))
! 	      (not (or (file-exists-p buffer-file-name)
! 		       (> buffer-saved-size 0)))
  	      (yes-or-no-p
! 	       (format "%s was %s since visited or saved.  Save anyway? "
! 		       (file-name-nondirectory buffer-file-name)
! 		       (if (file-exists-p buffer-file-name)
! 			   "changed" "renamed or deleted")))
  	      (error "Save not confirmed"))
  	  (save-restriction
  	    (widen)

-- 
Juri Linkov
http://www.jurta.org/emacs/

default file name to buffer name (was: reverting/notifying of files that no longer exist)

[Juri Linkov]

BTW, I'd like to suggest other improvements in `basic-save-buffer':

1. Add a default value to the minibuffer asking for the file name of
   the buffer not visiting any file.  It makes sense to use the buffer
   name as the default value of the file name.

2. Currently, if the user specifies the directory name in the minibuffer
   asking for the file name, then the user is asked later about
   overwriting the existing directory with a new file.  Since overwriting
   a directory with a file is too dangerous (or not possible at all
   on some systems), it is better to treat directory names specially
   and to ask the user about saving the file with the name composed
   from the specified directory name and the current buffer name.

Index: lisp/files.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/files.el,v
retrieving revision 1.707
diff -c -r1.707 files.el
*** lisp/files.el	26 Jun 2004 14:41:13 -0000	1.707
--- lisp/files.el	12 Jul 2004 15:17:43 -0000
***************
*** 3074,3084 ****
  	  (or buffer-file-name
  	      (let ((filename
  		     (expand-file-name
! 		      (read-file-name "File to save in: ") nil)))
! 		(and (file-exists-p filename)
! 		     (or (y-or-n-p (format "File `%s' exists; overwrite? "
! 					   filename))
! 			 (error "Canceled")))
  		(set-visited-file-name filename)))
  	  (or (verify-visited-file-modtime (current-buffer))
--- 3074,3092 ----
  	  (or buffer-file-name
  	      (let ((filename
  		     (expand-file-name
! 		      (read-file-name
! 		       (format "File to save in (default %s): " (buffer-name))
! 		       nil (expand-file-name (buffer-name))))))
! 		(if (file-exists-p filename)
! 		    (if (file-directory-p filename)
! 			(let ((new-name (concat (file-name-as-directory filename)
! 						(buffer-name))))
! 			  (if (y-or-n-p (format "Save as %s? " new-name))
! 			      (setq filename new-name)
! 			    (error "Canceled")))
! 		      (or (y-or-n-p (format "File %s exists; overwrite? "
! 					    filename))
! 			  (error "Canceled"))))
  		(set-visited-file-name filename)))
  	  (or (verify-visited-file-modtime (current-buffer))

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: default file name to buffer name (was: reverting/notifying of files that no longer exist)

[Richard Stallman]

These changes seem useful.

Re: suggestion: reverting/notifying of files that no longer exist

[Karl Chen]

>>>>> "Juri" == Juri Linkov <juri@jurta.org> writes:
    Juri> One place where the warning could be added is
    Juri> `basic-save-buffer'.

That would be good; I think it'd be even better however if it
notified you the second you start editing.  Because otherwise if
you work on it for 20 minutes before saving, you've already
"forked."

-- 
Karl 2004-07-12 11:59

Re: suggestion: reverting/notifying of files that no longer exist

[Juri Linkov]

Karl Chen <quarl@hkn.eecs.berkeley.edu> writes:
>> One place where the warning could be added is `basic-save-buffer'.
>
> That would be good; I think it'd be even better however if it
> notified you the second you start editing.  Because otherwise if
> you work on it for 20 minutes before saving, you've already
> "forked."

Notifying at the moment you start editing would be good too.
Perhaps instead of creating a new function, that could be done
in the existing function `ask-user-about-supersession-threat'
which is already used for a similar purpose, and which could be
called from `prepare_to_modify_buffer' when a previously saved
file was deleted or renamed.

Index: src/insdel.c
===================================================================
RCS file: /cvsroot/emacs/emacs/src/insdel.c,v
retrieving revision 1.178
diff -u -r1.178 insdel.c
--- src/insdel.c	22 May 2004 22:15:37 -0000	1.178
+++ src/insdel.c	14 Jul 2004 14:05:07 -0000
@@ -1931,7 +1931,14 @@
       /* Make binding buffer-file-name to nil effective.  */
       && !NILP (current_buffer->filename)
       && SAVE_MODIFF >= MODIFF)
-    lock_file (current_buffer->file_truename);
+    {
+      lock_file (current_buffer->file_truename);
+      if (NILP (Fverify_visited_file_modtime (Fcurrent_buffer ()))
+          && current_buffer->save_length > 0
+          && NILP (Ffile_exists_p (current_buffer->filename)))
+        call1 (intern ("ask-user-about-supersession-threat"),
+               current_buffer->filename);
+    }
 #else
   /* At least warn if this file has changed on disk since it was visited.  */
   if (!NILP (current_buffer->filename)

Index: lisp/userlock.el
===================================================================
RCS file: /cvsroot/emacs/emacs/lisp/userlock.el,v
retrieving revision 1.14
diff -u -r1.14 userlock.el
--- lisp/userlock.el	1 Sep 2003 15:45:17 -0000	1.14
+++ lisp/userlock.el	14 Jul 2004 14:05:34 -0000
@@ -112,8 +112,10 @@
   (save-window-excursion
     (let (answer)
       (while (null answer)
-	(message "%s changed on disk; really edit the buffer? (y, n, r or C-h) "
-		 (file-name-nondirectory fn))
+	(message "%s %s on disk; really edit the buffer? (y, n, r or C-h) "
+		 (file-name-nondirectory fn)
+                 (if (file-exists-p buffer-file-name)
+                     "changed" "renamed or deleted"))
 	(let ((tem (downcase (let ((cursor-in-echo-area t))
 			       (read-char-exclusive)))))
 	  (setq answer
@@ -137,8 +139,11 @@
 		 (signal 'file-supersession
 			 (list "File reverted" fn)))
 		((eq answer 'yield)
-		 (signal 'file-supersession
-			 (list "File changed on disk" fn))))))
+                 (if (file-exists-p buffer-file-name)
+                     (signal 'file-supersession
+                             (list "File changed on disk" fn))
+                   (signal 'file-supersession
+                           (list "File renamed or deleted on disk" fn)))))))
       (message
         "File on disk now will become a backup file if you save these changes.")
       (setq buffer-backed-up nil))))

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: suggestion: reverting/notifying of files that no longer exist

[Karl Chen]

Looks good (haven't tested it).  Thanks for working on this!

>>>>> "Juri" == Juri Linkov <juri@jurta.org> writes:
    Juri> + (message "%s %s on disk; really edit the buffer? (y,
    Juri>  	n, r or C-h) "
    Juri> + (file-name-nondirectory fn)
    Juri> + (if (file-exists-p buffer-file-name)
    Juri> + "changed" "renamed or deleted"))

BTW, I don't know if Emacs coding standards say much regarding
internationalization, but in general it's better to write out
   (message "%s changed on disk...")
and
   (message "%s renamed or deleted on disk...")
for translation. 
(http://www.gnu.org/software/gettext/manual/html_node/gettext_15.html)

-- 
Karl 2004-07-14 10:24

i18n (was: reverting/notifying of files that no longer exist)

[Juri Linkov]

Karl Chen <quarl@hkn.eecs.berkeley.edu> writes:
> BTW, I don't know if Emacs coding standards say much regarding
> internationalization, but in general it's better to write out
>    (message "%s changed on disk...")
> and
>    (message "%s renamed or deleted on disk...")
> for translation. 
> (http://www.gnu.org/software/gettext/manual/html_node/gettext_15.html)

According to those guidelines the right way to translate messages is
to call the `gettext' function on messages before placeholders in them
get expanded with arguments, i.e. to write:

(message (gettext "File %s renamed") filename)

However, this might not be the best solution for Emacs, since it has
several powerful mechanisms like regexps to avoid the need to add
`gettext' functions to every `message' call.  So after the call to
(message "File %s renamed" filename) the function `message' receives
a string like "File /some/path/somefile renamed" and could use a
variable with translation mappings to performs regexp replacements
before messages get displayed in the echo area, e.g.:

(defvar message-translations
 '(("some_language_name" "^File \\(.?+\\) renamed$" "Elif \1 demaner")
   (... ... ...)))

Anyway, I believe this feature is for Emacs 22, and etc/TODO already
has an entry for that.

-- 
Juri Linkov
http://www.jurta.org/emacs/

Re: suggestion: reverting/notifying of files that no longer exist

[Richard Stallman]

Thanks for thining of this.  Please install your change.