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gh-97848: argparse: Disallow misbehaving actions for positional arguments #98367

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gh-97848: argparse: Disallow misbehaving actions for positional arguments #98367

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a6da57d
Disallow 'store_true' action for positional arguments
kkarbowiak Oct 17, 2022
d8be724
Disallow 'store_false' action for positional arguments
kkarbowiak Oct 17, 2022
3772f00
Disallow 'store_const' action for positional arguments
kkarbowiak Oct 17, 2022
b43e81c
Refactor code
kkarbowiak Oct 17, 2022
6644aab
Add tests
kkarbowiak Oct 17, 2022
a0e7b90
📜🤖 Added by blurb_it.
blurb-it[bot] Oct 17, 2022
f07104c
Refactor code
kkarbowiak Oct 18, 2022
b26fdb4
Update Misc/NEWS.d/next/Library/2022-10-17-20-20-18.gh-issue-97848.Rn…
kkarbowiak Oct 18, 2022
a4597b1
Avoid double search
kkarbowiak Oct 21, 2022
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8 changes: 8 additions & 0 deletions Lib/argparse.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1540,6 +1540,14 @@ def _get_positional_kwargs(self, dest, **kwargs):
msg = _("'required' is an invalid argument for positionals")
raise TypeError(msg)

# make sure 'store_true', 'store_false', or 'store_const' action
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This feels inelegant because we're hardcoding the names of individual actions. I'm not familiar enough with argparse to propose an alternative implementation though.

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@JelleZijlstra thank you for the review.

You say the change feels inelegant, because the names of individual actions are hardcoded. Do I understand correctly that you would prefer some named values or enumeration? Or did you mean something else?

I also am not a huge fan of using these strings directly, but this is the interface exposed by the ArgumentParser class and as such I think the names are committed to and won't change.

Anyway, I am open to all suggestions on how to improve this PR.

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I think that more elegant and general solution would be

  • either add an optional boolean parameter for registry()
  • or add an optional class attribute in _StoreTrueAction etc.

It can be tested in add_argument(), after testing that the action is a callable.

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Actually, such flag already exists. You can check if nargs is 0 to detect actions that do not consume arguments.

# is not specified
if 'action' in kwargs:
action = kwargs.get('action')
if action in ('store_true', 'store_false', 'store_const'):
msg = _("{action} is an invalid action for positionals", {'action': action})
raise TypeError(msg)

# mark positional arguments as required if at least one is
# always required
if kwargs.get('nargs') not in [OPTIONAL, ZERO_OR_MORE]:
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9 changes: 9 additions & 0 deletions Lib/test/test_argparse.py
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Expand Up @@ -4714,6 +4714,15 @@ def test_parsers_action_missing_params(self):
def test_required_positional(self):
self.assertTypeError('foo', required=True)

def test_positionals_with_store_true_action(self):
self.assertTypeError('foo', action='store_true')

def test_positionals_with_store_false_action(self):
self.assertTypeError('foo', action='store_false')

def test_positionals_with_store_const_action(self):
self.assertTypeError('foo', action='store_const', const='bar')

def test_user_defined_action(self):

class Success(Exception):
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1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Library/2022-10-17-20-20-18.gh-issue-97848.RnkhKZ.rst
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@@ -0,0 +1 @@
Disallow ``store_true``, ``store_false``, and ``store_const`` actions for positional arguments in :mod:`argparse` module.