paul j3 <[email protected]> added the comment:
By defining a custom 'type' function:
def foo(astr):
if astr is argparse.SUPPRESS:
raise KeyError
return astr
I get the full traceback
1831 def take_action(action, argument_strings, option_string=None):
1832 seen_actions.add(action)
-> 1833 argument_values = self._get_values(action, argument_strings)
and in '_get_values' the error is produced when it calls '_get_value' (which
runs the 'type' function):
# optional argument produces a default when not present
if not arg_strings and action.nargs == OPTIONAL:
if action.option_strings:
value = action.const
else:
value = action.default
if isinstance(value, str):
--> value = self._get_value(action, value)
self._check_value(action, value)
It identifies this as an OPTIONAL action that has received an empty argument
list, and assigns it the action.default.
ZERO_OR_MORE * also gets the action.default, but without a _get_value() call.
That default can be SUPPRESSed by the test at the end of take_action.
A couple of fixes come to mind:
- add a SUPPRESS test at the start of take_action
- add a SUPPRESS test to _get_values block I quote above, maybe bypassing the
`_get_value` call
There is a unittest case of a suppressed optional positional; it just doesn't
also test for a failed type.
class TestDefaultSuppress(ParserTestCase):
"""Test actions with suppressed defaults"""
argument_signatures = [
Sig('foo', nargs='?', default=argparse.SUPPRESS)
I'm inclined go with the second choice, but the alternatives need to be
throughly tested.
In the mean time, an 'int' type could be replaced with one that is SUPPRESS
knowledgeable:
def bar(astr):
if astr is argparse.SUPPRESS:
return astr
else:
return int(astr)
Note that this use of action.default is different from the normal default
handling at the start of parse_known_args (and the end of _parse_known_args).
It's specifically for positionals that will always be 'seen' (because an empty
argument strings list satisfies their nargs).
----------
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Python tracker <[email protected]>
<https://bugs.python.org/issue36078>
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