GNU bug report logs - #55702
29.0.50; python-mark-defun does not handle backslash escaped newline

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

From: kobarity <kobarity <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: 29.0.50; python-mark-defun does not handle backslash escaped newline
Date: Sun, 29 May 2022 21:22:18 +0900

When the following steps are performed, the first line "def \" will
not be included in the region.

1. emacs -Q
2. Load the following Python file using M-x find-file

#+begin_src python
def \
        foo(x):
    return x
#+end_src

3. M-x forward-line (Move point to the line "foo(x):".)
4. M-x python-mark-defun

In GNU Emacs 29.0.50 (build 4, x86_64-pc-linux-gnu)
 of 2022-05-21 built on ubuntu
Repository revision: 208102fa470e3417320062cdb48a9967d80bf092
Repository branch: master
System Description: Ubuntu 22.04 LTS

Configured using:
 'configure --without-x --with-gnutls=ifavailable'

Configured features:
ACL LIBXML2 MODULES NOTIFY INOTIFY PDUMPER SECCOMP SOUND SQLITE3 THREADS
XIM ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Lisp Interaction

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-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
  indent-tabs-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 regexp-opt sort mail-extr face-remap help-mode tool-bar emacsbug
message mailcap yank-media rmc puny dired dired-loaddefs rfc822 mml
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text-property-search time-date seq mm-decode mm-bodies mm-encode
mail-parse rfc2231 mailabbrev gmm-utils mailheader cl-loaddefs cl-lib
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text-properties overlay sha1 md5 base64 format env code-pages mule
custom widget keymap hashtable-print-readable backquote threads inotify
multi-tty make-network-process emacs)

Memory information:
((conses 16 48401 6401)
 (symbols 48 5803 1)
 (strings 32 16090 1890)
 (string-bytes 1 510153)
 (vectors 16 9643)
 (vector-slots 8 112266 9121)
 (floats 8 25 264)
 (intervals 56 385 66)
 (buffers 992 12))

Message #8 received at 55702 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: 55702 <at> debbugs.gnu.org
Subject: 29.0.50; python-mark-defun does not handle backslash escaped newline
Date: Sun, 29 May 2022 21:27:47 +0900

[Message part 1 (text/plain, inline)]

python-mark-defun and python-info-looking-at-beginning-of-defun do not
consider the presence of backslash escaped newline in defuns.
Attached is a patch to fix this issue.

[fix-55702.patch (application/octet-stream, attachment)]

Message #11 received at 55702 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: 55702 <at> debbugs.gnu.org
Subject: 29.0.50; python-mark-defun does not handle backslash escaped newline
Date: Sun, 29 May 2022 22:11:41 +0900

Sorry, it may not be good to change the behavior of
python-info-looking-at-beginning-of-defun.  I will reconsider the fix.

Message #14 received at 55702 <at> debbugs.gnu.org (full text, mbox):

From: kobarity <kobarity <at> gmail.com>
To: 55702 <at> debbugs.gnu.org
Subject: 29.0.50; python-mark-defun does not handle backslash escaped newline
Date: Sun, 3 Jul 2022 17:56:56 +0900

[Message part 1 (text/plain, inline)]

Hello,

I wrote:
> When the following steps are performed, the first line "def \" will
> not be included in the region.
>
> 1. emacs -Q
> 2. Load the following Python file using M-x find-file
>
> #+begin_src python
> def \
>         foo(x):
>     return x
> #+end_src
>
> 3. M-x forward-line (Move point to the line "foo(x):".)
> 4. M-x python-mark-defun

In fact, this is not only the issue in python-mark-defun, but also the
issue in python-nav-beginning-of-defun. In the example above,
python-nav-beginning-of-defun does not move the point if the point is
located at the beginning of the line "foo(x):". My previous patch was
not sufficient to solve the issue in python-nav-beginning-of-defun. So
I attach the revised patch.

On the other hand, I'm wondering if it is worth supporting such rarely
used forms, as there seems to be some more issues regarding the line
continuation using backslash. Is it better to leave such rarely used
forms unsupported and keep the code simple?

Below is the explanation of my patch:

> Sorry, it may not be good to change the behavior of
> python-info-looking-at-beginning-of-defun.  I will reconsider the fix.

Instead of changing the default behavior of
python-info-looking-at-beginning-of-defun, I added an argument to
change the behavior. When CHECK-STATEMENT is non-nil, the current
statement is checked instead of the current physical line.

This argument is used in python-nav--beginning-of-defun to be able
to recognize the defun with line continuation using backslash. When
ARG is positive, the point is moved to the end of the statement if the
point is located at the continuation line. This is necessary for
re-search-backward to find the defun regexp.

If the defun is found when ARG is negative, it is necessary to move
point to the beginning of the statement, because the point is at the
end of the defun regexp which may be in the different line from the
beginning of the statement.

Best Regards,

[fix-55702.patch (application/octet-stream, attachment)]

Message #17 received at 55702 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: kobarity <kobarity <at> gmail.com>
Cc: 55702 <at> debbugs.gnu.org
Subject: Re: bug#55702: 29.0.50; python-mark-defun does not handle backslash
 escaped newline
Date: Sun, 03 Jul 2022 14:23:02 +0200

kobarity <kobarity <at> gmail.com> writes:

> On the other hand, I'm wondering if it is worth supporting such rarely
> used forms, as there seems to be some more issues regarding the line
> continuation using backslash. Is it better to leave such rarely used
> forms unsupported and keep the code simple?

It does seem slightly obscure, but the patch seems to make sense to me,
so I've pushed it to Emacs 29.

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

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