[issue14191] argparse doesn't allow optionals within positionals
paul j3
report at bugs.python.org
Tue Apr 16 09:09:45 CEST 2013
paul j3 added the comment:
This patch permits the mixing of optionals with positionals, with the caveat that a particular positional cannot be split up.
If:
parser = ArgumentParser()
parser.add_argument('-f','--foo')
parser.add_argument('cmd')
parser.add_argument('rest', nargs='*')
'-f1 cmd 1 2 3',
'cmd -f1 1 2 3',
'cmd 1 2 3 -f1'
all give {cmd='cmd', rest=['1','2','3'], foo='1'}.
But 'cmd 1 -f1 2 3', does not recognize ['2','3'].
Previously 'cmd -f1 1 2 3' would return rest=[], and not recognize ['1','2','3']. With this change the nargs='*' behaves more like nargs='+', surviving to parse the 2nd group of positional strings.
The trick is to modify arg_counts in consume_positionals(), removing matches that don't do anything (don't consume argument strings).
if 'O' in arg_strings_pattern[start_index:]:
# if there is an optional after this, remove
# 'empty' positionals from the current match
while len(arg_counts)>1 and arg_counts[-1]==0:
arg_counts = arg_counts[:-1]
This change passes all of the existing test_argparse.py tests. It also passes the optparse tests that I added in http://bugs.python.org/issue9334#msg184987
I added 4 cases to illustrate this change.
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Added file: http://bugs.python.org/file29880/mixed.patch
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