How do I return a value when @click.option is used to pass a command line argument to a function?

Question

I am trying to use click python package to pass a command line argument to a function. The example from official documentation works as explained. But nowhere in the documentati

Answer 1

After looking through click's source code/reference I stumbled across the main() method of BaseCommand which takes the parameter, standalone_mode, that allows you to return values if disabled (it is True by default). Hope this helps someone in the future.

Setup code:

import sys
import click

@click.group(invoke_without_command=True)
@click.option('--option1')
@click.argument('arg1')
def main(option1, arg1):
    class SpecialObject():
        def __init__(self, option, arg):
            self.option = option
            self.arg = arg
        def __repr__(self):
            return str(self.option)+str(self.arg)

    return SpecialObject(option1, arg1)

@main.command()
def subcmd():
    return [4,5,6]

Test code:

if __name__ == "__main__":
    commands = (
        ["--help"], 
        ["arg_val",],
        ["--option1","option1_val","arg1_val"],
        ["arg_val","subcmd"],
        ["arg_val","subcmd", "--help",], 
    )
    print(f'Click Version: {click.__version__}')
    print(f'Python Version: {sys.version}')
    for cmd in commands:
        print('-----------')
        print(f'Starting cmd:{cmd}')
        ret_val = main.main(cmd, standalone_mode=False)
        print(f"Returned: {type(ret_val)}, {ret_val}\n"

Output:

$ python __main__.py
Click Version: 7.1.2
Python Version: 3.9.1 (default, Dec 11 2020, 09:29:25) [MSC v.1916 64 bit (AMD64)]
-----------
Starting cmd:['--help']
Usage: __main__.py [OPTIONS] ARG1 COMMAND [ARGS]...

Options:
  --option1 TEXT
  --help          Show this message and exit.

Commands:
  subcmd
Returned: , 0

-----------
Starting cmd:['arg_val']
Returned: .SpecialObject'>, Nonearg_val

-----------
Starting cmd:['--option1', 'option1_val', 'arg1_val']
Returned: .SpecialObject'>, option1_valarg1_val

-----------
Starting cmd:['arg_val', 'subcmd']
Returned: , [4, 5, 6]

-----------
Starting cmd:['arg_val', 'subcmd', '--help']
Usage: __main__.py subcmd [OPTIONS]

Options:
  --help  Show this message and exit.
Returned: , 0