From b1c0c60a4b7e11abed82bdbb060faad65dcff218 Mon Sep 17 00:00:00 2001
From: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Date: Thu, 8 May 2025 16:28:16 +0300
Subject: [PATCH 1/3] Fix subclassing HelpFormatter

---
 Lib/argparse.py                               |  6 ++---
 Lib/test/test_argparse.py                     | 24 +++++++++++++++++++
 ...-05-08-16-28-05.gh-issue-133653.7cxHXN.rst |  1 +
 3 files changed, 27 insertions(+), 4 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst

diff --git a/Lib/argparse.py b/Lib/argparse.py
index f13ac82dbc50b3..aa15cc6d0525d9 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -2723,15 +2723,13 @@ def format_help(self):
         return formatter.format_help()
 
     def _get_formatter(self):
-        if isinstance(self.formatter_class, type) and issubclass(
-            self.formatter_class, HelpFormatter
-        ):
+        try:
             return self.formatter_class(
                 prog=self.prog,
                 prefix_chars=self.prefix_chars,
                 color=self.color,
             )
-        else:
+        except TypeError:
             return self.formatter_class(prog=self.prog)
 
     # =====================
diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py
index 5a6be1180c1a3e..d9bb58c1c8f322 100644
--- a/Lib/test/test_argparse.py
+++ b/Lib/test/test_argparse.py
@@ -5176,6 +5176,30 @@ class TestHelpTupleMetavarPositional(HelpTestCase):
     version = ''
 
 
+class TestHelpFormatter(HelpTestCase):
+    """Test the HelpFormatter"""
+
+    # Test subclassing the help formatter
+    class MyFormatter(argparse.HelpFormatter):
+        def __init__(self, prog) -> None:
+            super().__init__(prog)
+
+    parser_signature = Sig(
+        prog="PROG",
+        formatter_class=MyFormatter,
+        description="Test with subclassing the help formatter",
+    )
+    usage = '''\
+        usage: PROG [-h]
+        '''
+    help = usage + '''\
+
+        Test with subclassing the help formatter
+
+        options:
+          -h, --help  show this help message and exit
+        '''
+
 class TestHelpRawText(HelpTestCase):
     """Test the RawTextHelpFormatter"""
 
diff --git a/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst b/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst
new file mode 100644
index 00000000000000..0883c9448b5102
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst
@@ -0,0 +1 @@
+Fix subclassing :meth:`argparse.HelpFormatter`. Patch by Hugo van Kemenade.

From fa4d044195bb9be4d7a51282926dbdfaa6367833 Mon Sep 17 00:00:00 2001
From: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Date: Thu, 8 May 2025 16:51:43 +0300
Subject: [PATCH 2/3] Fix Sphinx warning

---
 .../next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst b/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst
index 0883c9448b5102..d49de56cee719d 100644
--- a/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst
+++ b/Misc/NEWS.d/next/Library/2025-05-08-16-28-05.gh-issue-133653.7cxHXN.rst
@@ -1 +1 @@
-Fix subclassing :meth:`argparse.HelpFormatter`. Patch by Hugo van Kemenade.
+Fix subclassing :meth:`!argparse.HelpFormatter`. Patch by Hugo van Kemenade.

From 91c1f4fe19dc69075b28f2ea2e8e4a662e5e5370 Mon Sep 17 00:00:00 2001
From: Hugo van Kemenade <1324225+hugovk@users.noreply.github.com>
Date: Thu, 8 May 2025 18:33:35 +0300
Subject: [PATCH 3/3] Big if

---
 Lib/argparse.py | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/Lib/argparse.py b/Lib/argparse.py
index aa15cc6d0525d9..06d8e6cc1f1ca2 100644
--- a/Lib/argparse.py
+++ b/Lib/argparse.py
@@ -2723,13 +2723,23 @@ def format_help(self):
         return formatter.format_help()
 
     def _get_formatter(self):
-        try:
+        import inspect
+        if len(
+            [v.kind for (k, v) in
+             inspect.signature(self.formatter_class).parameters.items()
+             if k in ('prefix_chars', 'color')
+                and v.kind in (
+                        inspect._ParameterKind.POSITIONAL_OR_KEYWORD,
+                        inspect._ParameterKind.KEYWORD_ONLY,
+                )
+             ]
+        ) == 2:
             return self.formatter_class(
                 prog=self.prog,
                 prefix_chars=self.prefix_chars,
                 color=self.color,
             )
-        except TypeError:
+        else:
             return self.formatter_class(prog=self.prog)
 
     # =====================