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gh-85935: Check for nargs=0 for positional arguments in argparse (GH-124839)

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Raise ValueError in add_argument() if either explicit nargs=0 or action
that does not consume arguments (like 'store_const' or 'store_true') is
specified for positional argument.
This commit is contained in:
Serhiy Storchaka 2024-10-12 16:04:17 +03:00 committed by GitHub
parent 63cf4e914f
commit 9944ad388c
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GPG Key ID: B5690EEEBB952194
3 changed files with 18 additions and 3 deletions
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10
Lib/argparse.py
View File

@ -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

7
Lib/test/test_argparse.py
View File

@ -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, '*', '+']:

4
Misc/NEWS.d/next/Library/2024-10-01-13-11-53.gh-issue-85935.CTwJUy.rst Normal file
View File

@ -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.