New `SyntaxWarning` in Python 3.14 causing the CI to fail

[Avasam]

Heads up, the latest Python 3.14 alpha is causing SyntaxWarnings in the mypy-pytest plugin because of pluggy. I opened pytest-dev/pluggy#573 . But in the mean time you may want to not treat SyntaxWarnings as errors if this isn't solved quickly.

(I'm opening this in Skeleton since this affects all downstream projects)

[jaraco]

Thanks for the report. Currently, the 3.14 tests are allowed to fail (don't block builds), so as long as the issue is fixed in pluggy before the RC phase of 3.14, it shouldn't be a problem. Hopefully we can close this as obsolete in a few weeks.

[Avasam]

Pluggy 1.6.0 has been released an is included in the current versions pin range with pytest. So this fixes itself whenever a pip cache a busted.

[Avasam]

There's still some failure with Python 3.14, but I think it's just python/cpython#133941 .

.tox/py/lib/python3.14/site-packages/mypy/main.py:1055: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
self = CapturableArgumentParser(prog='mypy', usage='%(prog)s [-h] [-v] [-V] [more options; see below]\n            [-m MODULE...fig_file.html\n', formatter_class=<class 'mypy.main.AugmentedHelpFormatter'>, conflict_handler='error', add_help=False)
args = ('--enable-incomplete-feature',)
kwargs = {'dest': 'enable_incomplete_feature', 'help': 'Enable support of incomplete/experimental features for early preview', 'metavar': '{InlineTypedDict,PreciseTupleTypes}', 'option_strings': ['--enable-incomplete-feature']}
chars = '-', dest = 'enable_incomplete_feature', action_name = 'append'
action_class = <class 'argparse._AppendAction'>
action = _AppendAction(option_strings=['--enable-incomplete-feature'], dest='enable_incomplete_feature', nargs=None, const=None...f incomplete/experimental features for early preview', metavar='{InlineTypedDict,PreciseTupleTypes}', deprecated=False)
type_func = <function ArgumentParser.__init__.<locals>.identity at 0x7f175861eae0>
    def add_argument(self, *args, **kwargs):
        """
        add_argument(dest, ..., name=value, ...)
        add_argument(option_string, option_string, ..., name=value, ...)
        """
    
        # if no positional args are supplied or only one is supplied and
        # it doesn't look like an option string, parse a positional
        # argument
        chars = self.prefix_chars
        if not args or len(args) == 1 and args[0][0] not in chars:
            if args and 'dest' in kwargs:
                raise TypeError('dest supplied twice for positional argument,'
                                ' did you mean metavar?')
            kwargs = self._get_positional_kwargs(*args, **kwargs)
    
        # otherwise, we're adding an optional argument
        else:
            kwargs = self._get_optional_kwargs(*args, **kwargs)
    
        # if no default was supplied, use the parser-level default
        if 'default' not in kwargs:
            dest = kwargs['dest']
            if dest in self._defaults:
                kwargs['default'] = self._defaults[dest]
            elif self.argument_default is not None:
                kwargs['default'] = self.argument_default
    
        # create the action object, and add it to the parser
        action_name = kwargs.get('action')
        action_class = self._pop_action_class(kwargs)
        if not callable(action_class):
            raise ValueError('unknown action {action_class!r}')
        action = action_class(**kwargs)
    
        # raise an error if action for positional argument does not
        # consume arguments
        if not action.option_strings and action.nargs == 0:
            raise ValueError(f'action {action_name!r} is not valid for positional arguments')
    
        # raise an error if the action type is not callable
        type_func = self._registry_get('type', action.type, action.type)
        if not callable(type_func):
            raise TypeError(f'{type_func!r} is not callable')
    
        if type_func is FileType:
            raise TypeError(f'{type_func!r} is a FileType class object, '
                            f'instance of it must be passed')
    
        # raise an error if the metavar does not match the type
        if hasattr(self, "_get_formatter"):
>           formatter = self._get_formatter()
/opt/hostedtoolcache/Python/3.14.0-beta.1/x64/lib/python3.14/argparse.py:1562: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
self = CapturableArgumentParser(prog='mypy', usage='%(prog)s [-h] [-v] [-V] [more options; see below]\n            [-m MODULE...fig_file.html\n', formatter_class=<class 'mypy.main.AugmentedHelpFormatter'>, conflict_handler='error', add_help=False)
    def _get_formatter(self):
        if isinstance(self.formatter_class, type) and issubclass(
            self.formatter_class, HelpFormatter
        ):
>           return self.formatter_class(
                prog=self.prog,
                prefix_chars=self.prefix_chars,
                color=self.color,
            )
E           TypeError: AugmentedHelpFormatter.__init__() got an unexpected keyword argument 'prefix_chars'
/opt/hostedtoolcache/Python/3.14.0-beta.1/x64/lib/python3.14/argparse.py:2729: TypeError