From 6a0f7051e830ba00735161b822c5554fb36de674 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Wed, 31 Jan 2024 20:07:18 +0200
Subject: [PATCH] gh-109475: Fix support of explicit option value "--" in
 argparse

For example "--option=--".
---
 Lib/argparse.py                                  |  2 +-
 Lib/test/test_argparse.py                        | 16 ++++++++++++++++
 ...024-01-31-20-07-11.gh-issue-109475.lmTb9S.rst |  2 ++
 3 files changed, 19 insertions(+), 1 deletion(-)
 create mode 100644 Misc/NEWS.d/next/Library/2024-01-31-20-07-11.gh-issue-109475.lmTb9S.rst

diff --git a/Lib/argparse.py b/Lib/argparse.py
index a32884db80d1ea..b8eeb20ccb6c24 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -2489,7 +2489,7 @@ def parse_known_intermixed_args(self, args=None, namespace=None):
     # ========================
     def _get_values(self, action, arg_strings):
         # for everything but PARSER, REMAINDER args, strip out first '--'
-        if action.nargs not in [PARSER, REMAINDER]:
+        if not action.option_strings and action.nargs not in [PARSER, REMAINDER]:
             try:
                 arg_strings.remove('--')
             except ValueError:
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 7c1f5d36999a3d..112ed586b5bc3b 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -5405,6 +5405,22 @@ def test_zero_or_more_optional(self):
         args = parser.parse_args([])
         self.assertEqual(NS(x=[]), args)
 
+    def test_double_dash(self):
+        parser = argparse.ArgumentParser()
+        parser.add_argument('-f', '--foo', nargs='*')
+        parser.add_argument('bar', nargs='*')
+
+        args = parser.parse_args(['--foo=--'])
+        self.assertEqual(NS(foo=['--'], bar=[]), args)
+        args = parser.parse_args(['--foo', '--'])
+        self.assertEqual(NS(foo=[], bar=[]), args)
+        args = parser.parse_args(['-f--'])
+        self.assertEqual(NS(foo=['--'], bar=[]), args)
+        args = parser.parse_args(['-f', '--'])
+        self.assertEqual(NS(foo=[], bar=[]), args)
+        args = parser.parse_args(['--foo', 'a', 'b', '--', 'c', 'd'])
+        self.assertEqual(NS(foo=['a', 'b'], bar=['c', 'd']), args)
+
 
 # ===========================
 # parse_intermixed_args tests
diff --git a/Misc/NEWS.d/next/Library/2024-01-31-20-07-11.gh-issue-109475.lmTb9S.rst b/Misc/NEWS.d/next/Library/2024-01-31-20-07-11.gh-issue-109475.lmTb9S.rst
new file mode 100644
index 00000000000000..7582cb2bcd7629
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2024-01-31-20-07-11.gh-issue-109475.lmTb9S.rst
@@ -0,0 +1,2 @@
+Fix support of explicit option value "--" in :mod:`argparse` (e.g.
+``--option=--``).