GNU bug report logs - #64104
Subject: 30.0.50; uncomment-region-default-1

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

From: Andreas Röhler <andreas.roehler <at> easy-emacs.de>
To: bug-gnu-emacs <at> gnu.org
Subject: Subject: 30.0.50; uncomment-region-default-1
Date: Fri, 16 Jun 2023 10:51:24 +0200

Hi,

C-u comment-dwim RET with an active region of the following Python code:

---
# for i in text:
#     print("(i): {}".format(str(i)))
---

results in error saying

uncomment-region-default-1: Beginning of buffer

AFAIU the culprit is in newcomment.el, line 933:

(numarg (prefix-numeric-value arg))

and later in line 978

it tries

(delete-char (- numarg))

which at the beginning of buffer causes that error.

comment-dwin says:

if a prefix ARG is specified, call ‘comment-kill’

which is my intended use-case.

Thanks,

Andreas Röhler

In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.33, cairo version 1.16.0) of 2023-06-16 built on kanu
Repository revision: f2aae8b879baa4986b69af7ee54fe4eb987b99d6
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101004
System Description: Ubuntu 22.04.2 LTS

Configured using:
 'configure --with-tree-sitter --with-modules --with-mailutils'

Configured features:
ACL CAIRO DBUS FREETYPE GIF GLIB GMP GNUTLS GSETTINGS HARFBUZZ JPEG
LIBOTF LIBSELINUX LIBSYSTEMD LIBXML2 MODULES NOTIFY INOTIFY PDUMPER PNG
RSVG SECCOMP SOUND THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER X11 XDBE
XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
  value of $LANG: de_DE.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix

Major mode: Python

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny rfc822
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treesit cl-seq comint ansi-osc ring ansi-color dired-aux dired
dired-loaddefs time-date subr-x wheatgrass-theme cus-theme cus-edit pp
cus-start cus-load icons wid-edit cl-loaddefs cl-lib rmc iso-transl
tooltip cconv eldoc paren electric uniquify ediff-hook vc-hooks
lisp-float-type elisp-mode mwheel term/x-win x-win term/common-win x-dnd
tool-bar dnd fontset image regexp-opt fringe tabulated-list replace
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cyrillic chinese composite emoji-zwj charscript charprop case-table
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emacs)

Memory information:
((conses 16 135452 11240)
 (symbols 48 20124 0)
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Message #8 received at 64104 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Andreas Röhler <andreas.roehler <at> easy-emacs.de>,
 Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 64104 <at> debbugs.gnu.org
Subject: Re: bug#64104: Subject: 30.0.50; uncomment-region-default-1
Date: Sat, 17 Jun 2023 11:38:24 +0300

> Date: Fri, 16 Jun 2023 10:51:24 +0200
> From: Andreas Röhler <andreas.roehler <at> easy-emacs.de>
> 
> C-u comment-dwim RET with an active region of the following Python code:
> 
> ---
> # for i in text:
> #     print("(i): {}".format(str(i)))
> ---
> 
> results in error saying
> 
> uncomment-region-default-1: Beginning of buffer

AFAICT, that's because invoking comment-dwim with C-u in this case
makes no sense: the comment delimiters have just 1 character in this
case.  Try "C-u 1 M-x comment-dwim" instead.

> comment-dwin says:
> 
> if a prefix ARG is specified, call ‘comment-kill’
> 
> which is my intended use-case.

If this is what you wanted, then you should invoke "C-u comment-dwin"
without having an active region.  The doc string says that if the
region is active, it will call comment-region or uncomment-region, and
will call comment-kill only "otherwise" (i.e. if there's no active
region).  I suggest to read the node "Comment Commands" in the Emacs
manual, it describes this in more detail.

I've now made the doc string slightly more detailed, especially wrt
how the prefix argument is used in the various use cases, but other
than that, I don't think there's a bug here.

Stefan, any comments?

Message #11 received at 64104 <at> debbugs.gnu.org (full text, mbox):

From: Stefan Monnier <monnier <at> iro.umontreal.ca>
To: Eli Zaretskii <eliz <at> gnu.org>
Cc: 64104 <at> debbugs.gnu.org,
 Andreas Röhler <andreas.roehler <at> easy-emacs.de>
Subject: Re: bug#64104: Subject: 30.0.50; uncomment-region-default-1
Date: Sat, 17 Jun 2023 14:39:08 -0400

>> C-u comment-dwim RET with an active region of the following Python code:
>> 
>> ---
>> # for i in text:
>> #     print("(i): {}".format(str(i)))
>> ---
>> 
>> results in error saying
>> 
>> uncomment-region-default-1: Beginning of buffer

> Stefan, any comments?

- The error we give is not very user-friendly, so it might be good to
  catch it and re-raise it as something more meaning ful the specific
  operation performed.

- I have the vague impression that in some earlier version of that code we
  would not signal an error but just remove as many comment markers as
  possible (but no more than requested).
  That could be a more friendly behavior.


        Stefan

Message #14 received at 64104 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 64104 <at> debbugs.gnu.org, andreas.roehler <at> easy-emacs.de
Subject: Re: bug#64104: Subject: 30.0.50; uncomment-region-default-1
Date: Sun, 18 Jun 2023 08:53:03 +0300

> From: Stefan Monnier <monnier <at> iro.umontreal.ca>
> Cc: Andreas Röhler <andreas.roehler <at> easy-emacs.de>,
>   64104 <at> debbugs.gnu.org
> Date: Sat, 17 Jun 2023 14:39:08 -0400
> 
> >> C-u comment-dwim RET with an active region of the following Python code:
> >> 
> >> ---
> >> # for i in text:
> >> #     print("(i): {}".format(str(i)))
> >> ---
> >> 
> >> results in error saying
> >> 
> >> uncomment-region-default-1: Beginning of buffer
> 
> > Stefan, any comments?
> 
> - The error we give is not very user-friendly, so it might be good to
>   catch it and re-raise it as something more meaning ful the specific
>   operation performed.
> 
> - I have the vague impression that in some earlier version of that code we
>   would not signal an error but just remove as many comment markers as
>   possible (but no more than requested).
>   That could be a more friendly behavior.

I'll leave the bug open, then.  Patches to improve this command are
welcome.

Message #17 received at 64104 <at> debbugs.gnu.org (full text, mbox):

From: Andreas Röhler <andreas.roehler <at> easy-emacs.de>
To: Eli Zaretskii <eliz <at> gnu.org>, Stefan Monnier <monnier <at> iro.umontreal.ca>
Cc: 64104 <at> debbugs.gnu.org
Subject: Re: bug#64104: Subject: 30.0.50; uncomment-region-default-1
Date: Sun, 18 Jun 2023 15:00:19 +0200

Am 18.06.23 um 07:53 schrieb Eli Zaretskii:
>> From: Stefan Monnier <monnier <at> iro.umontreal.ca>
>> Cc: Andreas Röhler <andreas.roehler <at> easy-emacs.de>,
>>    64104 <at> debbugs.gnu.org
>> Date: Sat, 17 Jun 2023 14:39:08 -0400
>>
>>>> C-u comment-dwim RET with an active region of the following Python code:
>>>>
>>>> ---
>>>> # for i in text:
>>>> #     print("(i): {}".format(str(i)))
>>>> ---
>>>>
>>>> results in error saying
>>>>
>>>> uncomment-region-default-1: Beginning of buffer
>>> Stefan, any comments?
>> - The error we give is not very user-friendly, so it might be good to
>>    catch it and re-raise it as something more meaning ful the specific
>>    operation performed.
>>
>> - I have the vague impression that in some earlier version of that code we
>>    would not signal an error but just remove as many comment markers as
>>    possible (but no more than requested).
>>    That could be a more friendly behavior.
> I'll leave the bug open, then.  Patches to improve this command are
> welcome.


Unfortunately don't have a trivial fix.

Suggest a simplified caller:

(defun comment-dwim (arg)
  "Call the comment command you want (Do What I Mean).

Comment or uncomment the current line, or, if active, the region.

With \\[universal-argument] copy line or region before changing it.

You can configure `comment-style' to change the way regions are commented."
  (interactive "*P")
  (comment-normalize-vars)
  (when (eq 4 (prefix-numeric-value))
    (copy-region-as-kill (or (region-beginning) 
(line-beginning-position)) (or (region-end) (line-end-position))))
  (comment-or-uncomment-region (or (region-beginning) 
(line-beginning-position)) (or (region-end)) (line-end-position)))

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