bug#70617: 30.0.50; python-indent-shift-right indents left when line is whitespace

[Patrick Poitras <patrick.f.poitras@gmail.com>]

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Hi all.

I've noticed this weird behavior of python-indent-shift-right.

Let's say I have a block of code. The "|" character represents my cursor

In a python file, I write

if True:
|

(... file contents continue)

and then call python-indent-shift-right on an empty line. It does nothing.
If the second line has any amount of spaces, the whitespace is entirely
deleted.

Given that Python's whitespace is syntactically significant, the expected
behavior should be to add an indent to an empty line, or to prepend 4
characters (or 8, given user choice) to the empty line if it has
whitespace. From a cursory glance, I think we're running into some behavior
of indent-rigidly that tries to prevent the addition of superfluous white
space following an indented block of code. I assume this would be
potentially desirable for languages with non-significant whitespace, but in
the case of the python-specific function, the resulting behavior defies
both the function name and description.

----- System information -----
In GNU Emacs 30.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version
 3.24.41, cairo version 1.18.0) of 2024-04-27 built on
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Windowing system distributor 'The X.Org Foundation', version 11.0.12101012
System Description: openSUSE Tumbleweed

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Load-path shadows:
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