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https://github.com/click-contrib/click-plugins

Register CLI commands via setuptools entry-points.
https://github.com/click-contrib/click-plugins

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Register CLI commands via setuptools entry-points.

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README 

        
=============

click-plugins

=============



.. image:: https://travis-ci.org/click-contrib/click-plugins.svg?branch=master

    :target: https://travis-ci.org/click-contrib/click-plugins?branch=master



.. image:: https://coveralls.io/repos/click-contrib/click-plugins/badge.svg?branch=master&service=github

    :target: https://coveralls.io/github/click-contrib/click-plugins?branch=master



An extension module for `click `_ to register

external CLI commands via setuptools entry-points.



Why?

----



Lets say you develop a commandline interface and someone requests a new feature

that is absolutely related to your project but would have negative consequences

like additional dependencies, major refactoring, or maybe its just too domain

specific to be supported directly.  Rather than developing a separate standalone

utility you could offer up a `setuptools entry point `_

that allows others to use your commandline utility as a home for their related

sub-commands.  You get to choose where these sub-commands or sub-groups CAN be

registered but the plugin developer gets to choose they ARE registered.  You

could have all plugins register alongside the core commands, in a special

sub-group, across multiple sub-groups, or some combination.



Enabling Plugins

----------------



For a more detailed example see the `examples `_ section.



The only requirement is decorating ``click.group()`` with ``click_plugins.with_plugins()``

which handles attaching external commands and groups.  In this case the core CLI developer

registers CLI plugins from ``core_package.cli_plugins``.



.. code-block:: python



    from pkg_resources import iter_entry_points



    import click

    from click_plugins import with_plugins



    @with_plugins(iter_entry_points('core_package.cli_plugins'))

    @click.group()

    def cli():

        """Commandline interface for yourpackage."""



    @cli.command()

    def subcommand():

        """Subcommand that does something."""



Developing Plugins

------------------



Plugin developers need to register their sub-commands or sub-groups to an

entry-point in their ``setup.py`` that is loaded by the core package.



.. code-block:: python



    from setuptools import setup



    setup(

        name='yourscript',

        version='0.1',

        py_modules=['yourscript'],

        install_requires=[

            'click',

        ],

        entry_points='''

            [core_package.cli_plugins]

            cool_subcommand=yourscript.cli:cool_subcommand

            another_subcommand=yourscript.cli:another_subcommand

        ''',

    )



Broken and Incompatible Plugins

-------------------------------



Any sub-command or sub-group that cannot be loaded is caught and converted to

a ``click_plugins.core.BrokenCommand()`` rather than just crashing the entire

CLI.  The short-help is converted to a warning message like:



.. code-block:: console



    Warning: could not load plugin. See ``  --help``.



and if the sub-command or group is executed the entire traceback is printed.



Best Practices and Extra Credit

-------------------------------



Opening a CLI to plugins encourages other developers to independently extend

functionality independently but there is no guarantee these new features will

be "on brand".  Plugin developers are almost certainly already using features

in the core package the CLI belongs to so defining commonly used arguments and

options in one place lets plugin developers reuse these flags to produce a more

cohesive CLI.  If the CLI is simple maybe just define them at the top of

``yourpackage/cli.py`` or for more complex packages something like

``yourpackage/cli/options.py``.  These common options need to be easy to find

and be well documented so that plugin developers know what variable to give to

their sub-command's function and what object they can expect to receive.  Don't

forget to document non-obvious callbacks.



Keep in mind that plugin developers also have access to the parent group's

``ctx.obj``, which is very useful for passing things like verbosity levels or

config values around to sub-commands.



Here's some code that sub-commands could re-use:



.. code-block:: python



    from multiprocessing import cpu_count



    import click



    jobs_opt = click.option(

        '-j', '--jobs', metavar='CORES', type=click.IntRange(min=1, max=cpu_count()), default=1,

        show_default=True, help="Process data across N cores."

    )



Plugin developers can access this with:



.. code-block:: python



    import click

    import parent_cli_package.cli.options



    @click.command()

    @parent_cli_package.cli.options.jobs_opt

    def subcommand(jobs):

        """I do something domain specific."""



Installation

------------



With ``pip``:



.. code-block:: console



    $ pip install click-plugins



From source:



.. code-block:: console



    $ git clone https://github.com/click-contrib/click-plugins.git

    $ cd click-plugins

    $ python setup.py install



Developing

----------



.. code-block:: console



    $ git clone https://github.com/click-contrib/click-plugins.git

    $ cd click-plugins

    $ pip install -e .\[dev\]

    $ pytest tests --cov click_plugins --cov-report term-missing



Changelog

---------



See ``CHANGES.txt``



Authors

-------



See ``AUTHORS.txt``



License

-------



See ``LICENSE.txt``