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I have a web server written in python which takes an optional argument telling it what IP and port to bind to. Here's the definition:
parser.add_argument(
 '-b', '--bind',
 metavar="[ip]:port",
 type=unicode,
 help="IP and port to bind to."
)
There are several other arguments as well. When the usage is printed (due to parse failures or -h), if the command line is longer than terminal width, it is wrapped. Here is the (relevant) code in argparse.py:311 which deals with this scenario:
# wrap the usage parts if it's too long
text_width = self._width - self._current_indent 
if len(prefix) + len(usage) > text_width: 
 
 # break usage into wrappable parts 
 part_regexp = r'\(.*?\)+|\[.*?\]+|\S+' 
 opt_usage = format(optionals, groups) 
 pos_usage = format(positionals, groups) 
 opt_parts = _re.findall(part_regexp, opt_usage) 
 pos_parts = _re.findall(part_regexp, pos_usage) 
 assert ' '.join(opt_parts) == opt_usage
 assert ' '.join(pos_parts) == pos_usage
Note how part_regexp extracts words, and text surrounded with round/square brackets. Now the argument I defined above, when displayed in usage text, looks like this: [-b [ip]:port]
part_regexp however, will cut it into "[-b [ip]" and ":port]" and concatenated later with " ", it will have an extra space which causes the first assertion to fail.
I fiddled with part_regexp but that proved unreliable at best. I think the opt_parts should be obtained, not from the final formatted text, but from actual argument objects.
For a demonstration, see the attachment.