gh-54732: Fix argparse arg file parsing

Lib/argparse.py

@@ -2363,6 +2363,8 @@ def _read_args_from_files(self, arg_strings):
                               errors=_sys.getfilesystemencodeerrors()) as args_file:
                         arg_strings = []
                         for arg_line in args_file.read().splitlines():
+                            if not arg_line.strip():
+                                continue
                             for arg in self.convert_arg_line_to_args(arg_line):
                                 arg_strings.append(arg)
                         arg_strings = self._read_args_from_files(arg_strings)

Lib/test/test_argparse.py

@@ -1715,6 +1715,7 @@ def setUp(self):
                           b'@hello'),
             ('invalid', b'@no-such-path\n'),
             ('undecodable', self.undecodable + b'\n'),
+            ('blanklines', b'spam\n\nham\n')
         ]
         for path, text in file_texts:
             with open(path, 'wb') as file:
@@ -1736,6 +1737,7 @@ def setUp(self):
         ('-a B @recursive Y Z', NS(a='A', x=hello, y=['Y', 'Z'])),
         ('X @recursive Z -a B', NS(a='B', x='X', y=[hello, 'Z'])),
         (["-a", "", "X", "Y"], NS(a='', x='X', y=['Y'])),
+        ('@blanklines', NS(a=None, x='spam', y=['ham'])),
     ]
     if os_helper.TESTFN_UNDECODABLE:
         undecodable = os_helper.TESTFN_UNDECODABLE.lstrip(b'@')

Misc/NEWS.d/next/Library/2025-05-16-21-54-00.gh-issue-54732.asfjdf.rst

@@ -0,0 +1 @@
+Fix issue in :mod:`argparse` where an args file with blank lines could not be parsed.