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Re: Don't complain about changed file when it hasn't changed
From: |
Stefan Monnier |
Subject: |
Re: Don't complain about changed file when it hasn't changed |
Date: |
Mon, 29 Aug 2016 09:17:06 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
>> The patch below is supposed to change Emacs such that if the file's
>> timestamp has changed, but the contents is still the same, it doesn't
>> prompt the user about a supersession-threat.
>> Any objection?
> This sounds like a neat feature! Are you sure you want (point-min) and
> (point-max) rather than 1 and (buffer-size), though?
I hate this assumption that point-min is 1 (so much so that my own
local Emacs has point-min set to 12345678). I dreamed of changing this
long-standing wart so that point-min starts at 0 but it would require
changes in the redisplay code which I was not able to figure out.
[ For the curious, the error of using 1 became blindly obvious when
I did some work on src/intervals.c where we have things like
interval_start_pos (that's right: 15 lines to decide if it starts
with 0 or with 1). ]
> Also, maybe this should be predicated on a test for small-enough files?
> For large-ish files, it could make things slow.
Presumably, this code is not run often and is normally followed by
a prompt to the user, so its acceptable time scale is fairly large.
If we want to speed it up, I think a more promising approach would be
for "visited-modtime" to keep not just the modtime but also the file
size, so we would only perform the (potentially slow)
insert-file-contents with the new file has the same size as the old.
Michael added:
> Same concern here, for remote files. For large remote files I would
> prefer a cksum call, if possible. But maybe we shall profile this, first.
Of course we can't cksum the buffer without first encoding it. Also,
this would require a cksum on files. Is there a reliably-available
cksum operation we could run on files?
Stefan
PS: I just noticed a problem with the patch. I need to set
coding-system-for-read around the insert-file-contents call, otherwise
we might fail to notice when the only change to the file is that it uses
another coding system.
>> diff --git a/lisp/userlock.el b/lisp/userlock.el
>> index a0c55fd..9b45ef4 100644
>> --- a/lisp/userlock.el
>> +++ b/lisp/userlock.el
>> @@ -97,6 +97,20 @@ ask-user-about-lock-help
>>
>> (define-error 'file-supersession nil 'file-error)
>>
>> +(defun userlock--check-content-unchanged (fn)
>> + (save-restriction
>> + (widen)
>> + (let ((buf (current-buffer))
>> + (start (point-min))
>> + (end (point-max)))
>> + (when (with-temp-buffer
>> + (insert-file-contents fn)
>> + (= 0 (compare-buffer-substrings
>> + buf start end
>> + (current-buffer) (point-min) (point-max))))
>> + (set-visited-file-modtime)
>> + 'unchanged))))
>> +
>> ;;;###autoload
>> (defun ask-user-about-supersession-threat (fn)
>> "Ask a user who is about to modify an obsolete buffer what to do.
>> @@ -106,30 +120,30 @@ ask-user-about-supersession-threat
>>
>> You can rewrite this to use any criterion you like to choose which one to do.
>> The buffer in question is current when this function is called."
>> - (discard-input)
>> - (save-window-excursion
>> - (let ((prompt
>> - (format "%s changed on disk; \
>> + (unless (userlock--check-content-unchanged fn)
>> + (discard-input)
>> + (save-window-excursion
>> + (let ((prompt
>> + (format "%s changed on disk; \
>> really edit the buffer? (y, n, r or C-h) "
>> - (file-name-nondirectory fn)))
>> - (choices '(?y ?n ?r ?? ?\C-h))
>> - answer)
>> - (while (null answer)
>> - (setq answer (read-char-choice prompt choices))
>> - (cond ((memq answer '(?? ?\C-h))
>> - (ask-user-about-supersession-help)
>> - (setq answer nil))
>> - ((eq answer ?r)
>> - ;; Ask for confirmation if buffer modified
>> - (revert-buffer nil (not (buffer-modified-p)))
>> - (signal 'file-supersession
>> - (list "File reverted" fn)))
>> - ((eq answer ?n)
>> - (signal 'file-supersession
>> - (list "File changed on disk" fn)))))
>> - (message
>> - "File on disk now will become a backup file if you save these
>> changes.")
>> - (setq buffer-backed-up nil))))
>> + (file-name-nondirectory fn))))
>> + (while
>> + (let ((answer (read-char-choice prompt '(?y ?n ?r ?? ?\C-h))))
>> + (cond ((memq answer '(?? ?\C-h))
>> + (ask-user-about-supersession-help)
>> + 'repeat)
>> + ((eq answer ?r)
>> + ;; Ask for confirmation if buffer modified
>> + (revert-buffer nil (not (buffer-modified-p)))
>> + (signal 'file-supersession
>> + (list "File reverted" fn)))
>> + ((eq answer ?n)
>> + (signal 'file-supersession
>> + (list "File changed on disk" fn)))
>> + (t (null answer)))))
>> + (message
>> + "File on disk now will become a backup file if you save these
>> changes.")
>> + (setq buffer-backed-up nil)))))
>>
>> (defun ask-user-about-supersession-help ()
>> (with-output-to-temp-buffer "*Help*"
>>
>>
Re: Don't complain about changed file when it hasn't changed,
Stefan Monnier <=
Re: Don't complain about changed file when it hasn't changed, Clément Pit--Claudel, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Stefan Monnier, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Clément Pit--Claudel, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Eli Zaretskii, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Clément Pit--Claudel, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Stefan Monnier, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Eli Zaretskii, 2016/08/30
Re: Don't complain about changed file when it hasn't changed, Eli Zaretskii, 2016/08/29