bug#65870: 30.0.50; Error in python-mode when try to delete a character in badly-indented code

bug#65870: 30.0.50; Error in python-mode when try to delete a character in badly-indented code

[Daniel Lopez]

To reproduce from emacs -Q:
  C-x b hello.py RET
  M-x python-mode
  On the first line, type the word "return", then press the Return key.
  On the second line, type one or more spaces.
  Press Backspace. This triggers the error message:
      python-indent-line: Wrong type argument: wholenump, -4
  and, the last-typed space is not deleted.

Backtrace of the error:
  Debugger entered--Lisp error: (wrong-type-argument wholenump -4)
    indent-line-to(-4)
    python-indent-line(t)
    python-indent-dedent-line()
    python-indent-dedent-line-backspace(1)
    funcall-interactively(python-indent-dedent-line-backspace 1)
    command-execute(python-indent-dedent-line-backspace)

This can also happen with Python keywords/statements that tend to end a
scope, eg. "break" or "raise", as well as "return".

I guess the smart dedenting sees the "return" (or similar statement) at
top-level scope and then tries to move the cursor to a parent scope /
negative column that doesn't exist. Perhaps one of those indent
functions could clamp itself somehow to not do that but I'm not sure
where the best place for that would be.

Daniel



In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
  3.24.36, cairo version 1.17.8) of 2023-02-21 built on ENO
Repository revision: 098add06eb7d742ff0e6ee0e294931a93a60c71c
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12101008
System Description: Arch Linux

Configured using:
  'configure --prefix=/usr --sysconfdir=/etc --libexecdir=/usr/lib
  --localstatedir=/var --mandir=/usr/share/man --with-gameuser=:games
  --with-modules --without-libotf --without-m17n-flt --without-gconf
  --with-native-compilation=yes --with-xinput2 --with-x-toolkit=gtk3
  --without-xaw3d --with-sound=no --with-tree-sitter --without-gpm
  --without-compress-install
  '--program-transform-name=s/\([ec]tags\)/\1.emacs/'
  'CFLAGS=-march=x86-64 -mtune=generic -O2 -pipe -fno-plt -fexceptions
  -Wp,-D_FORTIFY_SOURCE=2 -Wformat -fstack-clash-protection
  -fcf-protection'
  LDFLAGS=-Wl,-O1,--sort-common,--as-needed,-z,relro,-z,now'

Configured features:
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LCMS2 LIBSYSTEMD LIBXML2 MODULES NATIVE_COMP NOTIFY INOTIFY PDUMPER PNG
RSVG SECCOMP SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER WEBP
X11 XDBE XIM XINPUT2 XPM GTK3 ZLIB

Important settings:
   value of $LANG: en_GB.UTF-8
   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
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   auto-compression-mode: t

Load-path shadows:
None found.

Features:
(shadow sort mail-extr emacsbug message mailcap yank-media puny dired
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native-compile emacs)

Memory information:
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bug#65870: 30.0.50; Error in python-mode when try to delete a character in badly-indented code

[Eli Zaretskii]

> Date: Mon, 11 Sep 2023 17:36:59 +0100
> From: Daniel Lopez <daniel.lopez999@gmail.com>
> 
> To reproduce from emacs -Q:
>   C-x b hello.py RET
>   M-x python-mode
>   On the first line, type the word "return", then press the Return key.
>   On the second line, type one or more spaces.
>   Press Backspace. This triggers the error message:
>       python-indent-line: Wrong type argument: wholenump, -4
>   and, the last-typed space is not deleted.
> 
> Backtrace of the error:
>   Debugger entered--Lisp error: (wrong-type-argument wholenump -4)
>     indent-line-to(-4)
>     python-indent-line(t)
>     python-indent-dedent-line()
>     python-indent-dedent-line-backspace(1)
>     funcall-interactively(python-indent-dedent-line-backspace 1)
>     command-execute(python-indent-dedent-line-backspace)
> 
> This can also happen with Python keywords/statements that tend to end a
> scope, eg. "break" or "raise", as well as "return".
> 
> I guess the smart dedenting sees the "return" (or similar statement) at
> top-level scope and then tries to move the cursor to a parent scope /
> negative column that doesn't exist. Perhaps one of those indent
> functions could clamp itself somehow to not do that but I'm not sure
> where the best place for that would be.

Thanks.

kobarity, any suggestions or comments?

bug#65870: 30.0.50; Error in python-mode when try to delete a character in badly-indented code

[kobarity]

[-- Attachment #1: Type: text/plain, Size: 1465 bytes --]


Eli Zaretskii wrote:
> > Date: Mon, 11 Sep 2023 17:36:59 +0100
> > From: Daniel Lopez <daniel.lopez999@gmail.com>
> > 
> > To reproduce from emacs -Q:
> >   C-x b hello.py RET
> >   M-x python-mode
> >   On the first line, type the word "return", then press the Return key.
> >   On the second line, type one or more spaces.
> >   Press Backspace. This triggers the error message:
> >       python-indent-line: Wrong type argument: wholenump, -4
> >   and, the last-typed space is not deleted.
> > 
> > Backtrace of the error:
> >   Debugger entered--Lisp error: (wrong-type-argument wholenump -4)
> >     indent-line-to(-4)
> >     python-indent-line(t)
> >     python-indent-dedent-line()
> >     python-indent-dedent-line-backspace(1)
> >     funcall-interactively(python-indent-dedent-line-backspace 1)
> >     command-execute(python-indent-dedent-line-backspace)
> > 
> > This can also happen with Python keywords/statements that tend to end a
> > scope, eg. "break" or "raise", as well as "return".
> > 
> > I guess the smart dedenting sees the "return" (or similar statement) at
> > top-level scope and then tries to move the cursor to a parent scope /
> > negative column that doesn't exist. Perhaps one of those indent
> > functions could clamp itself somehow to not do that but I'm not sure
> > where the best place for that would be.
> 
> Thanks.
> 
> kobarity, any suggestions or comments?

Thank you for the report.  The attached is the proposed fix.

[-- Attachment #2: 0001-Fix-Python-mode-error-caused-by-incorrect-indentatio.patch --]
[-- Type: application/octet-stream, Size: 1810 bytes --]

From 32f0dbe5f942ffa60f0945d2ffb771db82db5832 Mon Sep 17 00:00:00 2001
From: kobarity <kobarity@gmail.com>
Date: Sat, 16 Sep 2023 23:14:45 +0900
Subject: [PATCH] Fix Python mode error caused by incorrect indentation

* lisp/progmodes/python.el (python-indent--calculate-indentation):
Guard against negative indentation.  (Bug #65870)

* test/lisp/progmodes/python-tests.el
(python-indent-badly-indented-block-end): New test.
---
 lisp/progmodes/python.el            | 2 +-
 test/lisp/progmodes/python-tests.el | 9 +++++++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/lisp/progmodes/python.el b/lisp/progmodes/python.el
index 4b940b3f13b..d7e49e225d8 100644
--- a/lisp/progmodes/python.el
+++ b/lisp/progmodes/python.el
@@ -1660,7 +1660,7 @@ python-indent--calculate-indentation
         (`(:after-block-end . ,start)
          ;; Subtract one indentation level.
          (goto-char start)
-         (- (current-indentation) python-indent-offset))
+         (max 0 (- (current-indentation) python-indent-offset)))
         (`(:at-dedenter-block-start . ,_)
          ;; List all possible indentation levels from opening blocks.
          (let ((opening-block-start-points
diff --git a/test/lisp/progmodes/python-tests.el b/test/lisp/progmodes/python-tests.el
index a44a11896f0..f3456030975 100644
--- a/test/lisp/progmodes/python-tests.el
+++ b/test/lisp/progmodes/python-tests.el
@@ -2081,6 +2081,15 @@ python-indent-after-bare-match
    (python-tests-look-at "else:")
    (should (= (python-indent-calculate-indentation) 4))))
 
+(ert-deftest python-indent-badly-indented-block-end ()
+  "Test BUG 65870 regression."
+  (python-tests-with-temp-buffer
+   "
+return
+"
+   (goto-char (point-max))
+   (should (= (python-indent-calculate-indentation) 0))))
+
 \f
 ;;; Filling
 
-- 
2.34.1

bug#65870: 30.0.50; Error in python-mode when try to delete a character in badly-indented code

[Daniel Lopez]

On 16/09/2023 16:06, kobarity wrote:
> 
> Eli Zaretskii wrote:
>>> Date: Mon, 11 Sep 2023 17:36:59 +0100
>>> From: Daniel Lopez <daniel.lopez999@gmail.com>
>>>
>>> To reproduce from emacs -Q:
>>>    C-x b hello.py RET
>>>    M-x python-mode
>>>    On the first line, type the word "return", then press the Return key.
>>>    On the second line, type one or more spaces.
>>>    Press Backspace. This triggers the error message:
>>>        python-indent-line: Wrong type argument: wholenump, -4
>>>    and, the last-typed space is not deleted.
>>>
>>> Backtrace of the error:
>>>    Debugger entered--Lisp error: (wrong-type-argument wholenump -4)
>>>      indent-line-to(-4)
>>>      python-indent-line(t)
>>>      python-indent-dedent-line()
>>>      python-indent-dedent-line-backspace(1)
>>>      funcall-interactively(python-indent-dedent-line-backspace 1)
>>>      command-execute(python-indent-dedent-line-backspace)
>>>
>>> This can also happen with Python keywords/statements that tend to end a
>>> scope, eg. "break" or "raise", as well as "return".
>>>
>>> I guess the smart dedenting sees the "return" (or similar statement) at
>>> top-level scope and then tries to move the cursor to a parent scope /
>>> negative column that doesn't exist. Perhaps one of those indent
>>> functions could clamp itself somehow to not do that but I'm not sure
>>> where the best place for that would be.
>>
>> Thanks.
>>
>> kobarity, any suggestions or comments?
> 
> Thank you for the report.  The attached is the proposed fix.

On applying the fix to my own installation, I can confirm that it works 
for me. Thanks. :)