Support Python 3.14.0b1

3524.patch

@@ -0,0 +1,40 @@
+From 3c5d56bf8bb8405d0eceef912ba4cad7d077448c Mon Sep 17 00:00:00 2001
+From: Florian Bruhin <me@the-compiler.org>
+Date: Thu, 8 May 2025 10:47:22 +0200
+Subject: [PATCH] Fix custom HelpFormatter for Python 3.14
+
+https://github.com/python/cpython/pull/132323 passes prefix_chars=
+(and other arguments) to the formatter_class, but the custom HelpFormatter only
+accepted prog=.
+
+Accept any keyword arguments and pass them on to the parent class.
+
+Fixes #3523
+---
+ docs/changelog/3523.bugfix.rst | 1 +
+ src/tox/config/cli/parser.py   | 4 ++--
+ 2 files changed, 3 insertions(+), 2 deletions(-)
+ create mode 100644 docs/changelog/3523.bugfix.rst
+
+diff --git a/docs/changelog/3523.bugfix.rst b/docs/changelog/3523.bugfix.rst
+new file mode 100644
+index 000000000..3052d877e
+--- /dev/null
++++ b/docs/changelog/3523.bugfix.rst
+@@ -0,0 +1 @@
++Fix ``TypeError`` for ``HelpFormatter`` with Python 3.14
+diff --git a/src/tox/config/cli/parser.py b/src/tox/config/cli/parser.py
+index 87629ae49..904ff7aad 100644
+--- a/src/tox/config/cli/parser.py
++++ b/src/tox/config/cli/parser.py
+@@ -95,8 +95,8 @@ def parse_args(  # type: ignore[override] # avoid defining all overloads
+ class HelpFormatter(ArgumentDefaultsHelpFormatter):
+     """A help formatter that provides the default value and the source it comes from."""
+ 
+-    def __init__(self, prog: str) -> None:
+-        super().__init__(prog, max_help_position=30, width=240)
++    def __init__(self, prog: str, **kwargs: Any) -> None:
++        super().__init__(prog, max_help_position=30, width=240, **kwargs)
+ 
+     def _get_help_string(self, action: Action) -> str | None:
+         text: str = super()._get_help_string(action) or ""

python-tox.spec

@@ -28,6 +28,9 @@ License:        MIT
 URL:            https://tox.readthedocs.io/
 Source:         %{pypi_source tox}
 
+# Support Python 3.14.0b1
+Patch:          https://github.com/tox-dev/tox/pull/3524.patch
+
 # Remove dependency on devpi-process.
 # Remove dependency on detect-test-pollution.
 # Remove coverage-related dependencies.