Issue 25297: max_help_position is not works in argparse library (original) (raw)

Hi colleagues I have the code (max_help_position is 2000):

formatter_class=lambda prog: argparse.HelpFormatter(prog, max_help_position=2000) parser = argparse.ArgumentParser(formatter_class=formatter_class)

subparsers = parser.add_subparsers(title="Commands", metavar="")

cmd_parser = subparsers.add_parser('long_long_long_long_long_long_long', help='- jksljdalkjda', formatter_class=formatter_class)

args = parser.parse_args(['-h']) print args

Result:

we have

optional arguments: -h, --help show this help message and exit

Commands: long_long_long_long_long_long_long - jksljdalkjda small - descr

instead

optional arguments: -h, --help show this help message and exit

Commands: long_long_long_long_long_long_long - jksljdalkjda small - descr

The code:

class MyFormatter(argparse.HelpFormatter): def init(self, prog): super(MyFormatter, self).init(prog, max_help_position=2000, width=2000) self._max_help_position = 2000 self._action_max_length += 4

got same result.

The strings like:

formatter_class = lambda prog: argparse.HelpFormatter(prog, max_help_position=2000, width=2000)

formatter_class = lambda prog: argparse.HelpFormatter(prog, max_help_position=1000, width=2000)

formatter_class = lambda prog: argparse.HelpFormatter(prog, max_help_position=2000, width=1000)

got same result: we always have new line after command.

There's a bug in the HelpFormatter.add_argument method. It does not take into account the extra indentation of subactions (sub parsers) when calculating self._action_max_length.

The corrected method and a test case is in the attached file.

class MyFormatter(argparse.HelpFormatter): """ Corrected _max_action_length for the indenting of subactions """ def add_argument(self, action): if action.help is not argparse.SUPPRESS:

        # find all invocations
        get_invocation = self._format_action_invocation
        invocations = [get_invocation(action)]
        current_indent = self._current_indent
        for subaction in self._iter_indented_subactions(action):
            # compensate for the indent that will be added
            indent_chg = self._current_indent - current_indent
            added_indent = 'x'*indent_chg
            invocations.append(added_indent + get_invocation( subaction) )
        # print('inv', invocations)

        # update the maximum item length
        invocation_length = max([len(s) for s in invocations])
        action_length = invocation_length + self._current_indent
        self._action_max_length = max(self._action_max_length,
                                      action_length)

        # add the item to the list
        self._add_item(self._format_action, [action])

Without this correction self._action_max_length is off by 2 if a subparser has the longest invocation. Normally that wouldn't be an issue since normally subparser names are short and easy to use. But with the 'aliases' that newer argparse allows, the invocation could be longer, and possibly longer than regular arguments.

I haven't passed this correction through test_argparse.py. It also would need a test case or two. I don't think it need a documentation change.

I don't know if this correction will work with the subparser grouping proposed in http://bugs.python.org/issue9341.