From e5cb5dbbf9d916cc25f6d9585ee66b77efbf25f4 Mon Sep 17 00:00:00 2001
From: jdunter <2ve@mailbox.org>
Date: Sat, 19 Jul 2025 16:08:19 +0200
Subject: [PATCH] gh-54732: Make argparse error caused by empty rows in option
 files explicit (GH-136795) (cherry picked from commit
 8ffc3ef01e83ffe629c6107082677de4d23974d5)

Co-authored-by: jdunter <2ve@mailbox.org>
Co-authored-by: Adam Turner <9087854+AA-Turner@users.noreply.github.com>
---
 Doc/library/argparse.rst | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/Doc/library/argparse.rst b/Doc/library/argparse.rst
index f189f6b8fa8953..a08f713ab56ba3 100644
--- a/Doc/library/argparse.rst
+++ b/Doc/library/argparse.rst
@@ -434,12 +434,18 @@ arguments they contain.  For example::
    >>> parser.parse_args(['-f', 'foo', '@args.txt'])
    Namespace(f='bar')
 
-Arguments read from a file must by default be one per line (but see also
+Arguments read from a file must be one per line by default (but see also
 :meth:`~ArgumentParser.convert_arg_line_to_args`) and are treated as if they
 were in the same place as the original file referencing argument on the command
 line.  So in the example above, the expression ``['-f', 'foo', '@args.txt']``
 is considered equivalent to the expression ``['-f', 'foo', '-f', 'bar']``.
 
+.. note::
+
+   Empty lines are treated as empty strings (``''``), which are allowed as values but
+   not as arguments. Empty lines that are read as arguments will result in an
+   "unrecognized arguments" error.
+
 :class:`ArgumentParser` uses :term:`filesystem encoding and error handler`
 to read the file containing arguments.