Josh Meranda added the comment:
I agree with Bigbird and paul.j3.
> But I think this is a real bug in argparse, not a documentation problem.
> Off hand I can't think of clean way of refining the description without
> getting overly technical about the error handling.
It seems like a reasonable conclusion to make that, "If the user would like to
catch errors manually, the feature can be enabled by setting exit_on_error to
False" indicates that wrapping any call to parser.parse_args() or
parser.parse_known_args() will catch any known error that may raised. So
outside of adding the workaround of subclassing ArgumentParser to the
documentation, this probably needs a patch to the code.
Any solution will probably also need to implement a new error type to be able
to handle these cases since they can be caused by multiple arguments being
included / excluded, which is not something that ArgumentError can adequately
describe by referencing only a single argument. Something like:
class MultipleArgumentError(ArgumentError):
def __init__(self, arguments, message):
self.argument_names = filter([_get_action_name(arg) for arg in
arguments], lambda name: name)
self.message = message
def __str__(self):
if self.argument_names is None:
format = '%(message)s'
else:
format = 'argument %(argument_names): %(message)s'
return format % dict(message=self.message,
argument_names=', '.join(self.argument_name))
I'm not sure I like the idea of changing the exit or error methods since they
have a a clear purpose and don't need to be repurposed to also include error
handling. It seems to me that adding checks to self.exit_on_error in
_parse_known_args to handle the missing required arguments and in parse_args to
handle unknown arguments is probably a quick and clean solution.
--
nosy: +joshmeranda
versions: +Python 3.9 -Python 3.10
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