readline error when saving interactive command history when history file path is a symlink to a relative path

Bug report

Bug description:

To reproduce the issue

1. Set up home directory like following:

$HOME/
  .python_history --> foo/history_file
  foo/
    history_file

2. Launch a Python interactive session with CWD different from $HOME
3. Execute the following

import readline
import os
history_path=os.path.expanduser("~/.python_history")
assert os.path.exists(history_path)
readline.write_history_file(history_path)

4. Observe the following error

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
FileNotFoundError: [Errno 2] No such file or directory

Possible cause

This is likely due to how GNU readline commits history information to file. As of GNU readline v8.2 (used in Python 3.10 and 3.12 among others), it creates a temporary file in the parent directory of the history file, write to that temporary file, and then rename the temporary file to the history file. See history_tempfile in histfile.c of GNU readline.

GNU readline determines the parent directory from the readlink output of the user-supplied history file path. In this case, since the history file is a symlink with a relative path, the parent directory is resolved to the relative path foo/. If foo/ doesn't exist in the CWD, history saving fails.

CPython versions tested on:

3.10, 3.12

Operating systems tested on:

Linux

Beginne mit der Reproduktion unter Verwendung eines Symlinks mit relativem Ziel und einem Arbeitsverzeichnis, das sich von $HOME unterscheidet. Lies die Logik von GNU readline für history_tempfile in histfile.c und verfolge, wie CPython's readline.write_history_file dorthin gelangt. Erledigt ist die Aufgabe, wenn das Speichern des Verlaufs für das beschriebene Symlink-Layout auf den getesteten Linux-Konfigurationen erfolgreich ist und eine Regressionstestabdeckung für diesen Fall vorhanden ist.