3

I recently have been using the click package to build command line interfaces which has worked perfectly, so far.

Now I got into some trouble when using chained commands in combination with the context object. The problem is that I somehow get an error when I want to call the function of another command from within another command.

It is probably somehow related to the usage of decorators within click but I don't see the error right now.

This is a minimal example of my code:

import click


@click.group(chain=True)
@click.option('--some_common_option', type=float, default=1e-10)
@click.pass_context
def cli(ctx, some_common_option):
    # save shared params within context object for different commands
    for k, v in locals().items():
        if 'ctx' not in k:
            ctx.obj[k] = v

    return True


@cli.command()
@click.argument('some_argument', type=str)
@click.pass_context
def say_something(ctx, some_argument):
    print(some_argument)

    return True


@cli.command()
@click.argument('some_other_argument', type=str)
@click.pass_context
def say_more(ctx, some_other_argument):
    ctx.obj['text'] = some_other_argument
    say_something(ctx, ctx.obj['text'])

    return True


if __name__ == '__main__':
    cli(obj={})

And this is the error that is provided on the terminal:

$ python test.py say_something 'Hello!'
Hello!
$ python test.py say_more 'How are you?'
Traceback (most recent call last):
  File "test.py", line 36, in <module>
    cli(obj={})
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 1092, in invoke
    rv.append(sub_ctx.command.invoke(sub_ctx))
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "test.py", line 30, in say_more
    say_something(ctx, ctx.obj['text'])
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/user/.anaconda3/lib/python3.6/site-packages/click/core.py", line 683, in main
    args = list(args)
TypeError: 'Context' object is not iterable
$

I am wondering why and where the iteration over the context object takes place.

Any hints how I can fix this and use the function from within another command?

Stephen Rauch
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Cord Kaldemeyer
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1 Answers1

7

If you can edit your click command functions, you can organize them like this:

@cli.command()
@click.argument('some_argument', type=str)
@click.pass_context
def say_something(ctx, some_argument):
    return _say_something(ctx, some_argument):

def _say_something(ctx, some_argument):
    print(some_argument)

If built like this, then you can call _say_something() function as an undecorated (normal) Python function.

If you can not edit your commands

Building on this answer you can pass the context to another click command using this function:

Code:

def call_click_command_with_ctx(cmd, ctx, *args, **kwargs):
    """ Wrapper to call a click command with a Context object

    :param cmd: click cli command function to call
    :param ctx: click context
    :param args: arguments to pass to the function
    :param kwargs: keyword arguments to pass to the function
    :return: None
    """

    # monkey patch make_context
    def make_context(*some_args, **some_kwargs):
        child_ctx = click.Context(cmd, parent=ctx)
        with child_ctx.scope(cleanup=False):
            cmd.parse_args(child_ctx, list(args))
        return child_ctx

    cmd.make_context = make_context
    prev_make_context = cmd.make_context

    # call the command
    call_click_command(cmd, *args, **kwargs)

    # restore make_context
    cmd.make_context = prev_make_context

How does this work?

This works because click is a well designed OO framework. The @click.Command object can be introspected to determine what parameters it is expecting. Then a command line can be constructed that will look like the command line that click is expecting. In addition, the make_context method of the command can be overridden to allow the command context to used by the command.

Code from Previous Answer:

def call_click_command(cmd, *args, **kwargs):
    """ Wrapper to call a click command

    :param cmd: click cli command function to call
    :param args: arguments to pass to the function
    :param kwargs: keywrod arguments to pass to the function
    :return: None
    """

    # Get positional arguments from args
    arg_values = {c.name: a for a, c in zip(args, cmd.params)}
    args_needed = {c.name: c for c in cmd.params
                   if c.name not in arg_values}

    # build and check opts list from kwargs
    opts = {a.name: a for a in cmd.params if isinstance(a, click.Option)}
    for name in kwargs:
        if name in opts:
            arg_values[name] = kwargs[name]
        else:
            if name in args_needed:
                arg_values[name] = kwargs[name]
                del args_needed[name]
            else:
                raise click.BadParameter(
                    "Unknown keyword argument '{}'".format(name))


    # check positional arguments list
    for arg in (a for a in cmd.params if isinstance(a, click.Argument)):
        if arg.name not in arg_values:
            raise click.BadParameter("Missing required positional"
                                     "parameter '{}'".format(arg.name))

    # build parameter lists
    opts_list = sum(
        [[o.opts[0], str(arg_values[n])] for n, o in opts.items()], [])
    args_list = [str(v) for n, v in arg_values.items() if n not in opts]

    # call the command
    cmd(opts_list + args_list)

Test Code:

import click

@click.group(chain=True)
@click.option('--some_common_option', type=float, default=1e-10)
@click.pass_context
def cli(ctx, some_common_option):
    # save shared params within context object for different commands
    for k, v in locals().items():
        if 'ctx' not in k:
            ctx.obj[k] = v


@cli.command()
@click.argument('some_argument', type=str)
@click.pass_context
def say_something(ctx, some_argument):
    print(some_argument)


@cli.command()
@click.argument('some_other_argument', type=str)
@click.pass_context
def say_more(ctx, some_other_argument):
    ctx.obj['text'] = some_other_argument
    call_click_command_with_ctx(say_something, ctx, ctx.obj['text'])


if __name__ == "__main__":
    commands = (
        'say_something something',
        'say_more more',
        '--help',
    )

    import sys, time

    time.sleep(1)
    print('Click Version: {}'.format(click.__version__))
    print('Python Version: {}'.format(sys.version))
    for cmd in commands:
        try:
            time.sleep(0.1)
            print('-----------')
            print('> ' + cmd)
            time.sleep(0.1)
            cli(cmd.split(), obj={})

        except BaseException as exc:
            if str(exc) != '0' and \
                    not isinstance(exc, (click.ClickException, SystemExit)):
                raise

Results:

Click Version: 6.7
Python Version: 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)]
-----------
> say_something something
something
-----------
> say_more more
more
-----------
> --help
Usage: test.py [OPTIONS] COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]...

Options:
  --some_common_option FLOAT
  --help                      Show this message and exit.

Commands:
  say_more
  say_something
Stephen Rauch
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