flake8/docs/source/dev/registering_plugins.rst
2016-02-06 14:36:44 -06:00

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==================================
Registering a Plugin with Flake8
==================================
To register any kind of plugin with Flake8, you need a few things:
#. You need a way to install the plugin (whether it is packaged on its own or
as part of something else). In this section, we will use a ``setup.py``
written for an example plugin.
#. A name for your plugin that will (ideally) be unique.
#. A somewhat recent version of setuptools (newer than 0.7.0 but preferably as
recent as you can attain).
Flake8 presently relies on a functionality provided by setuptools called
`Entry Points`_. These allow any package to register a plugin with Flake8 via
that package's ``setup.py`` file.
Let's presume that we already have our plugin written and it's in a module
called ``flake8_example``. We might have a ``setup.py`` that looks something
like:
.. code-block:: python
from __future__ import with_statement
import setuptools
requires = [
"flake8 > 3.0.0",
]
flake8_entry_point = # ...
setuptools.setup(
name="flake8_example",
license="MIT",
version="0.1.0",
description="our extension to flake8",
author="Me",
author_email="example@example.com",
url="https://gitlab.com/me/flake8_example",
packages=[
"flake8_example",
],
install_requires=requires,
entry_points={
flake8_entry_point: [
'X = flake8_example.ExamplePlugin',
],
},
classifiers=[
"Environment :: Console",
"Intended Audience :: Developers",
"License :: OSI Approved :: MIT License",
"Programming Language :: Python",
"Programming Language :: Python :: 2",
"Programming Language :: Python :: 3",
"Topic :: Software Development :: Libraries :: Python Modules",
"Topic :: Software Development :: Quality Assurance",
],
)
Note specifically these lines:
.. code-block:: python
flake8_entry_point = # ...
setuptools.setup(
# snip ...
entry_points={
flake8_entry_point: [
'X = flake8_example.ExamplePlugin',
],
},
# snip ...
)
We tell setuptools to register our entry point "X" inside the specific
grouping of entry-points that flake8 should look in.
Flake8 presently looks at three groups:
- ``flake8.extension``
- ``flake8.format``
- ``flake8.report``
If your plugin is one that adds checks to Flake8, you will use
``flake8.extension``. If your plugin formats the output and provides that to
the user, you will use ``flake8.format``. Finally, if your plugin performs
extra report handling (filtering, etc.) it will use ``flake8.report``.
If our ``ExamplePlugin`` is something that adds checks, our code would look
like:
.. code-block:: python
setuptools.setup(
# snip ...
entry_points={
'flake8.extension': [
'X = flake8_example.ExamplePlugin',
],
},
# snip ...
)
.. _Entry Points:
https://pythonhosted.org/setuptools/pkg_resources.html#entry-points