GNU bug report logs - #52543
Add option to eliminate all duplications from the kill ring

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: ndame <laszlomail <at> protonmail.com>
To: "Bug reports for GNU Emacs,
 the Swiss army knife of text editors" <bug-gnu-emacs <at> gnu.org>
Subject: Add option to eliminate all duplications from the kill ring
Date: Thu, 16 Dec 2021 09:49:45 +0000

There is  kill-do-not-save-duplicates, but it deletes
only subsequent duplicates.

There should be an other variable which prevents any duplicates
even if there are, say,  10 or 20 items between them.

I expected kill-do-not-save-duplicates to do that, that variable
seems misnamed. It should be kill-do-not-save-subsequent-duplicates
instead.

Message #8 received at 52543 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: ndame <laszlomail <at> protonmail.com>
Cc: 52543 <at> debbugs.gnu.org
Subject: Re: bug#52543: Add option to eliminate all duplications from the
 kill ring
Date: Sun, 19 Dec 2021 13:04:42 +0100

ndame <laszlomail <at> protonmail.com> writes:

> There is  kill-do-not-save-duplicates, but it deletes
> only subsequent duplicates.
>
> There should be an other variable which prevents any duplicates
> even if there are, say,  10 or 20 items between them.
>
> I expected kill-do-not-save-duplicates to do that, that variable
> seems misnamed. It should be kill-do-not-save-subsequent-duplicates
> instead.

This has previously been discussed, and we decided to not alter how this
works, because it'd be too surprising.  (And there are options to filter
the kill ring that users that want that can use.)  So I'm closing this
bug report.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #15 received at 52543 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: ndame <laszlomail <at> protonmail.com>, 52543 <at> debbugs.gnu.org
Subject: Re: bug#52543: Add option to eliminate all duplications from the
 kill ring
Date: Sun, 19 Dec 2021 19:03:49 +0200

>> There is  kill-do-not-save-duplicates, but it deletes
>> only subsequent duplicates.
>>
>> There should be an other variable which prevents any duplicates
>> even if there are, say,  10 or 20 items between them.
>>
>> I expected kill-do-not-save-duplicates to do that, that variable
>> seems misnamed. It should be kill-do-not-save-subsequent-duplicates
>> instead.
>
> This has previously been discussed, and we decided to not alter how this
> works, because it'd be too surprising.  (And there are options to filter
> the kill ring that users that want that can use.)  So I'm closing this
> bug report.

Indeed:

  (setq kill-transform-function (lambda (s) (unless (member s kill-ring) s)))

Message #18 received at 52543 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: ndame <laszlomail <at> protonmail.com>, 52543 <at> debbugs.gnu.org
Subject: Re: bug#52543: Add option to eliminate all duplications from the
 kill ring
Date: Sun, 19 Dec 2021 20:05:00 +0200

>>> There is  kill-do-not-save-duplicates, but it deletes
>>> only subsequent duplicates.
>>>
>>> There should be an other variable which prevents any duplicates
>>> even if there are, say,  10 or 20 items between them.
>>>
>>> I expected kill-do-not-save-duplicates to do that, that variable
>>> seems misnamed. It should be kill-do-not-save-subsequent-duplicates
>>> instead.
>>
>> This has previously been discussed, and we decided to not alter how this
>> works, because it'd be too surprising.  (And there are options to filter
>> the kill ring that users that want that can use.)  So I'm closing this
>> bug report.
>
> Indeed:
>
>   (setq kill-transform-function (lambda (s) (unless (member s kill-ring) s)))

Here is the same as a choice to make it easier for everyone
to satisfy this frequent need - like history-delete-duplicates
and comint-input-ignoredups in Emacs, and ignoredups in shell.
If this is ok, more documentation could be added:

diff --git a/lisp/simple.el b/lisp/simple.el
index 959e7ea94c..466bc9c12d 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -5118,6 +5118,8 @@ kill-transform-function
 be put on the kill ring).  It should return a string or nil.  If
 the latter, the string is not put on the kill ring."
   :type '(choice (const :tag "No transform" nil)
+                 (const :tag "Ignore duplicates"
+                        (lambda (s) (unless (member s kill-ring) s)))
                  function)
   :group 'killing
   :version "28.1")
-- 

Message #21 received at 52543 <at> debbugs.gnu.org (full text, mbox):

From: Juri Linkov <juri <at> linkov.net>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: ndame <laszlomail <at> protonmail.com>, 52543 <at> debbugs.gnu.org
Subject: Re: bug#52543: Add option to eliminate all duplications from the
 kill ring
Date: Sun, 19 Dec 2021 21:44:09 +0200

>>> There is  kill-do-not-save-duplicates, but it deletes
>>> only subsequent duplicates.
>>>
>>> There should be an other variable which prevents any duplicates
>>> even if there are, say,  10 or 20 items between them.
>>>
>>> I expected kill-do-not-save-duplicates to do that, that variable
>>> seems misnamed. It should be kill-do-not-save-subsequent-duplicates
>>> instead.
>>
>> This has previously been discussed, and we decided to not alter how this
>> works, because it'd be too surprising.  (And there are options to filter
>> the kill ring that users that want that can use.)  So I'm closing this
>> bug report.
>
> Indeed:
>
>   (setq kill-transform-function (lambda (s) (unless (member s kill-ring) s)))

Sorry, this was wrong.  It should delete all previous strings,
and add a new to the top of the kill-ring:

  (setq kill-transform-function (lambda (s) (setq kill-ring (delete s kill-ring)) s))

But it would be strange to modify kill-ring in the transform function.
So maybe kill-do-not-save-duplicates should support a special choice
'delete-duplicates' after all.

Message #24 received at 52543 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: Juri Linkov <juri <at> linkov.net>
Cc: ndame <laszlomail <at> protonmail.com>, 52543 <at> debbugs.gnu.org
Subject: Re: bug#52543: Add option to eliminate all duplications from the
 kill ring
Date: Mon, 20 Dec 2021 11:01:04 +0100

Juri Linkov <juri <at> linkov.net> writes:

> But it would be strange to modify kill-ring in the transform function.
> So maybe kill-do-not-save-duplicates should support a special choice
> 'delete-duplicates' after all.

I think some people wouldn't want to remove the duplicates (and add to
the front), and some wouldn't want to add at all (I think that was the
request in the other bug report?), and some want to take text properties
into account, and some don't, so I think leaving this to the user and
the transform function is the right solution.  But we don't have to make
any pre-made functions for this.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

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