flake8-polyfill is a package that provides some compatibility helpers for Flake8 plugins that intend to support Flake8 2.x and 3.x simultaneously.

pip install flake8-polyfill

One problem area with compatibility with Flake8 2.x and 3.x is the registering options and receiving the parsed values.

Flake8 3.0 added extra parameters to the add_option method which don't have the same effect on Flake8 2.x. To accomodate the change, this polyfill module allows you to do:

from flake8_polyfill import options

class MyFlake8Plugin(object):
    @classmethod
    def add_options(cls, parser):
        options.register(parser, '--my-long-option-name',
                         parse_from_config=True,
                         comma_separated_list=True,
                         default='...',
                         help='...')
        options.register(parser, '-m', '--my-other-long-option-name',
                         parse_from_config=True,
                         normalize_paths=True,
                         default='...',
                         help='...')

    @classmethod
    def parse_options(cls, values):
        cls.my_long_option_name = values.my_long_option_name
        cls.my_other_long_option_name = values.my_other_long_option_name

And have the code work the same way on both versions.

Until Flake8 2.6, getting the code on standard in from a plugin has been simple:

import pep8

stdin = pep8.get_stdin_value()

In 2.6 you now have to know whether to use pep8 or pycodestyle since Flake8 2.6 made a hard change to pycodestyle.

The reason you need to know which module to use is because standard in can be exhausted and Flake8 does some work to cache the value so that call always returns the desired data.

In 3.0, Flake8 no longer monkey-patches those modules.

To accommodate this, this package provides:

from flake8_polyfill import stdin

stdin.monkey_patch('all')
stdin.monkey_patch('pep8')
stdin.monkey_patch('pycodestyle')

This allows you to have the polyfill module monkey-patch what you want so it is always monkey-patched. It will also do so in an intelligent way.

Flake8 2.x did not include an object that would allow for easy version comparison. Flake8 3.0, however, added a __version_info__ attribute. For consistency, Flake8 Polyfill will turn 2.x's version string into a tuple suitable for comparison.

from flake8_polyfill import version

if (2, 4) <= version.version_info < (2, 6):
    # ...
elif (2, 6) <= version.version_info < (3, 0):
    # ...
elif (3, 0) <= version.version_info < (4, 0):
    # ...

MIT

Ian Cordasco