argparse_utils.py - mozsearch

Enable keyboard shortcuts

# Copyright 2015 The Chromium Authors. All rights reserved.

# Use of this source code is governed by a BSD-style license that can be

# found in the LICENSE file.

import argparse

class CustomHelpAction(argparse.Action):

  '''Allows defining custom help actions.

  Help actions can run even when the parser would otherwise fail on missing

  arguments. The first help or custom help command mentioned on the command

  line will have its help text displayed.

  Usage:

      parser = argparse.ArgumentParser(...)

      CustomHelpAction.EnableFor(parser)

      parser.add_argument('--foo-help',

                          action='custom_help',

                          custom_help_text='this is the help message',

                          help='What this helps with')

'''

  # Derived from argparse._HelpAction from

  # https://github.com/python/cpython/blob/master/Lib/argparse.py

  # pylint: disable=redefined-builtin

  # (complains about 'help' being redefined)

  def __init__(self,

               option_strings,

               dest=argparse.SUPPRESS,

               default=argparse.SUPPRESS,

               custom_help_text=None,

               help=None):

    super(CustomHelpAction, self).__init__(option_strings=option_strings,

                                           dest=dest,

                                           default=default,

                                           nargs=0,

                                           help=help)

    if not custom_help_text:

      raise ValueError('custom_help_text is required')

    self._help_text = custom_help_text

  def __call__(self, parser, namespace, values, option_string=None):

    print(self._help_text)

    parser.exit()

  @staticmethod

  def EnableFor(parser):

    parser.register('action', 'custom_help', CustomHelpAction)