Hacking Checks

The neutron_lib.hacking package implements a number of public flake8 checks intended to help adopters validate their compliance with the latest hacking standards.

To adopt neutron-lib’s hacking checks:

  1. Update your project’s tox.ini to include hacking checks from neutron-lib. More specifically, copy hacking checks under “Checks for neutron and related projects” in [flake8.local-plugin] extension in neutron-lib tox.ini to [flake8.local-plugin] extension in your project’s tox.ini.

    For example in your tox.ini:

    extension =
      # Checks from neutron-lib
      N521 = neutron_lib.hacking.checks:use_jsonutils
      N524 = neutron_lib.hacking.checks:check_no_contextlib_nested
      N529 = neutron_lib.hacking.checks:no_mutable_default_args
      N530 = neutron_lib.hacking.checks:check_neutron_namespace_imports
      N532 = neutron_lib.hacking.translation_checks:check_log_warn_deprecated
      N534 = neutron_lib.hacking.translation_checks:check_raised_localized_exceptions
      N536 = neutron_lib.hacking.checks:assert_equal_none
      N537 = neutron_lib.hacking.translation_checks:no_translate_logs

    Under certain circumstances, adopters may need to ignore specific neutron-lib hacking checks temporarily. You can ignore such checks just by commenting out them (hopefully with a proper reason).

    If your project has its own hacking checks, you can add more rules to [flake8.local-plugin] extension along with hacking checks from neutron-lib.


    The above configuration assumes hacking 2.x. If your project uses hacking 1.x, see Hacking 1.x support below.

  2. Update your project’s tox.ini enable any flake8 extensions neutron-lib’s tox.ini does. These are hacking checks otherwise disabled by default that neutron-lib expects to run.

    For example in neutron-lib’s tox.ini:

    # H904: Delay string interpolations at logging calls

    In the example above, adopters should also add H904 to the enable-extensions in their tox.ini.

  3. Actively adopt neutron-lib hacking checks by running and monitoring the neutron-lib periodic job (as per stadium guidelines and watching for announcements. Announcements regarding neutron-lib adopter hacking checks will be communicated via openstack-discuss email list and neutron meetings.

Hacking 1.x support

If your project uses hacking 1.x, you need a different way to consume hacking checks from neutron-lib.


hacking 1.x support is deprecated and will be dropped once all neutron related projects migrate to hacking 2.x.

Update your project’s tox.ini to use neutron_lib.hacking.checks.factory for its local-check-factory.

For example in your tox.ini:

local-check-factory = neutron_lib.hacking.checks.factory

If your project needs to register additional project specific hacking checks, you can define your own factory function that calls neutron-lib’s factory function.

For example in your project’s python source:

def my_factory(register):
    # register neutron-lib checks
    # register project specific checks

And use your project’s own factory in tox.ini:

local-check-factory = myproject.mypkg.my_factory