closes #848 - allows custom formatters for arguments

[jsoma]

Issue is here. For the second crazy example, I used the following mapshaper command which could not previously be reproduced with Gooey:

mapshaper -i 'cb_2020_us_county_500k.shp' \
    -each 'JOIN_FIPS="USA-" + GEOID' \
    --join 'us-counties-recent.csv' keys=JOIN_FIPS,geoid \
    -classify field=cases_avg_per_100k save-as=fill \
    colors=Magma invert breaks=10,30,50,70,100,250 \
    -proj 'albersusa' \
    -simplify '2%' \
    -o 'out.svg'

With this PR, you can now use cli_formatter with gooey_options to make it happen:

@Gooey(target="mapshaper", suppress_gooey_flag=True) 
def main():
  parser = GooeyParser(description="Input data")

  inputs = parser.add_argument_group('Joining util')
  inputs.add_argument('-i',
                      metavar='Input Shapefile',
                      default='cb_2020_us_county_500k.shp',
                      widget='FileChooser')

  inputs.add_argument('-each',
                      default='JOIN_FIPS="USA-" + GEOID',
                      metavar='Do a thing for each row')

  inputs.add_argument('--join',
                      metavar='Input CSV',
                      default='us-counties-recent.csv')

  inputs.add_argument('--keys',
                      default='JOIN_FIPS,geoid',
                      metavar='Join key',
                      gooey_options={ 'cli_formatter': '{dest}={value}'})
  
  colors = parser.add_argument_group('Coloring')

  colors.add_argument('-classify', gooey_options= {'visible': False, 'cli_formatter': '{id}'})
  colors.add_argument('--field', default='cases_avg_per_100k', gooey_options= {'cli_formatter': '{dest}={value}'})
  colors.add_argument('--save-as', default='fill', gooey_options= {'cli_formatter': 'save-as={value}'})
  colors.add_argument('--colors', default='Magma', gooey_options= {'cli_formatter': '{dest}={value}'})
  colors.add_argument('--invert', default=True, action='store_true', gooey_options={ 'cli_formatter': '{dest}'})
  colors.add_argument('--breaks', default='10,30,50,70,100,250', gooey_options= {'cli_formatter': '{dest}={value}'})

  viz = parser.add_argument_group('Visualization')

  viz.add_argument('-proj',
                      metavar='Projection',
                      default='albersusa',
                      choices=['albersusa', 'merc','lcc','aea'])

  viz.add_argument('-simplify',
                      metavar='Simplify',
                      default='2%')

  output = parser.add_argument_group('Output')
  output.add_argument('-o',
                      metavar='Output file',
                      default='out.svg',
                      widget='FileChooser')

  args = parser.parse_args()

if __name__ == '__main__':
  main()

Beyond the basics of formatting as key=value or adding percentages/etc, you can use fun tricks like forcing optional parameters to be positional, in case -- is not supported, as it can sidestep the "is this positional?" check. Lots of new flexibility!

Checklist:

• You're opening this PR against the current release branch
• Works on both Python 2.7 & Python 3.x
  • Tested on 3, but not 2. Nothing crazy or especially modern in there so it should be fine, though.
• Commits have been squashed and includes the relevant issue number
• Pull request description contains link to relevant issue or detailed notes on changes
• This must include example code demonstrating your feature or the bug being fixed
• All existing tests pass
• Your bug fix / feature has associated test coverage
• README.md is updated (if relevant)
  • Didn't want to write up the gooey_options until confirmed that it gets a thumbs up