diff --git a/Lib/argparse.py b/Lib/argparse.py index cbecb3b753c..550415dc934 100644 --- a/Lib/argparse.py +++ b/Lib/argparse.py @@ -1441,11 +1441,17 @@ class _ActionsContainer(object): 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 "%s"' % (action_class,)) 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): @@ -1554,7 +1560,9 @@ class _ActionsContainer(object): # mark positional arguments as required if at least one is # always required nargs = kwargs.get('nargs') - if nargs not in [OPTIONAL, ZERO_OR_MORE, REMAINDER, SUPPRESS, 0]: + if nargs == 0: + raise ValueError('nargs for positionals must be != 0') + if nargs not in [OPTIONAL, ZERO_OR_MORE, REMAINDER, SUPPRESS]: kwargs['required'] = True # return the keyword arguments with no option strings diff --git a/Lib/test/test_argparse.py b/Lib/test/test_argparse.py index 1fc97de78f7..f52a4b6bdd8 100644 --- a/Lib/test/test_argparse.py +++ b/Lib/test/test_argparse.py @@ -5424,8 +5424,11 @@ class TestInvalidArgumentConstructors(TestCase): with self.subTest(attrs=attrs): self.assertTypeError('-x', action=action, **attrs) self.assertTypeError('x', action=action, **attrs) + self.assertValueError('x', action=action, + errmsg=f"action '{action}' is not valid for positional arguments") self.assertTypeError('-x', action=action, nargs=0) - self.assertTypeError('x', action=action, nargs=0) + self.assertValueError('x', action=action, nargs=0, + errmsg='nargs for positionals must be != 0') def test_no_argument_no_const_actions(self): # options with zero arguments @@ -5445,7 +5448,7 @@ class TestInvalidArgumentConstructors(TestCase): self.assertValueError('-x', nargs=0, action=action, errmsg=f'nargs for {action_name} actions must be != 0') self.assertValueError('spam', nargs=0, action=action, - errmsg=f'nargs for {action_name} actions must be != 0') + errmsg='nargs for positionals must be != 0') # const is disallowed with non-optional arguments for nargs in [1, '*', '+']: diff --git a/Misc/NEWS.d/next/Library/2024-10-01-13-11-53.gh-issue-85935.CTwJUy.rst b/Misc/NEWS.d/next/Library/2024-10-01-13-11-53.gh-issue-85935.CTwJUy.rst new file mode 100644 index 00000000000..553f206bf26 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2024-10-01-13-11-53.gh-issue-85935.CTwJUy.rst @@ -0,0 +1,4 @@ +:meth:`argparse.ArgumentParser.add_argument` now raises an exception if +an :ref:`action` that does not consume arguments (like 'store_const' or +'store_true') or explicit ``nargs=0`` are specified for positional +arguments.