bug#57686: 28.1.91; Python-mode C-M-a and C-M-e not always symmetrical

[Fabrice Bauzac-Stehly]

Hello,

In python-mode, with a class that has methods, if I do end-of-defun
then beginning-of-defun, I do not necessarily come back to the
original location.

================

Example:

In a python-mode buffer, put:
----
def fun1():
    pass

class MyClass:
    def meth1(self):
        pass

    def meth2(self):
        pass

    def meth3(self):
        pass

def fun2():
    pass

def fun3():
    pass
----

Place the point at the beginning of the "class MyClass" line.

Hit C-M-e to go to the end of the MyClass defun.

Hit C-M-a.  Point goes to the first line of meth3, but I would expect
to go back to the beginning of the MyClass defun.

This is especially annoying when I have a class with dozens of methods,
in which case I have to hit C-M-a a number of times to go back to the
first line of the class, even though I have left it with only one
keystroke C-M-e.

================

By doing various C-M-e and C-M-a, it feels like python-mode defun
motion sometimes considers that a method inside a class is a defun,
however if I understood correctly[1], a defun is a top-level
statement, so methods should never be considered as defuns.  Is it the
root cause of my problem?

[1] https://lists.gnu.org/archive/html/emacs-devel/2022-08/msg00200.html

================

Note: I have put this workaround in my configuration, which seems to
work reasonably well for the moment:

----
;; Somehow fix C-M-a (backward-defun) by removing "(* space)" in python.el:
(require 'python)
(defvar python-nav-beginning-of-defun-regexp
  (python-rx line-start defun (+ space) (group symbol-name))
  "Regexp matching class or function definition.
The name of the defun should be grouped so it can be retrieved
via `match-string'.")
----

Thanks!

In GNU Emacs 28.1.91 (build 1, x86_64-pc-linux-gnu, cairo version 1.17.6)
 of 2022-09-02 built on fedora.home
Repository revision: e6af4968f947a3e536fbd80e74fea44ca18e22ac
Repository branch: HEAD
Windowing system distributor 'The X.Org Foundation', version 11.0.12201003
System Description: Fedora Linux 36 (Workstation Edition)

Configured using:
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Best regards

-- 
Fabrice Bauzac-Stehly
PGP 01EEACF8244E9C14B551C5256ADA5F189BD322B6