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

From: kobarity <[email-masked]>
Date: Sun, 17 Sep 2023 00:06:58 +0900

Eli Zaretskii wrote:
> > Date: Mon, 11 Sep 2023 17:36:59 +0100
> > From: Daniel Lopez <[email-masked]>
> > 
> > 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.