Package: hacking
Introductionhacking is a set of flake8 plugins that test and enforce theOpenStack StyleGuideHacking pins its dependencies, as a new release of some dependency can break
hacking based gating jobs. This is because new versions of dependencies can
introduce new rules, or make existing rules stricter.Installationhacking is available from pypi, so just run:pip install hackingThis will install specific versions offlake8with thehacking,pep8,mccabeandpyflakesplugins.OriginHacking started its life out as a text file in Nova’s first commit. It was
initially based on theGoogle Python Style Guide, and over time more
OpenStack specific rules were added. Hacking serves several purposes:Agree on a common style guide so reviews don’t get bogged down on style
nit picks. (example: docstring guidelines)Make code written by many different authors easier to read by making the
style more uniform. (example: unix vs windows newlines)Call out dangerous patterns and avoid them. (example: shadowing built-in
or reserved words)Initially the hacking style guide was enforced manually by reviewers, but this
was a big waste of time so hacking, the tool, was born to automate
the process and remove the extra burden from human reviewers.Versioninghacking uses themajor.minor.maintenancerelease notation, where maintenance
releases cannot contain new checks.  This way projects can gate on hacking
by pinning on themajor.minornumber while accepting maintenance updates
without being concerned that a new version will break the gate with a new
check.For example a project can depend onhacking>=0.10.0,<0.11.0, and can know
that0.10.1will not fail in places where0.10.0passed.Adding additional checksEach check is a pep8 plugin so readhttps://github.com/jcrocholl/pep8/blob/master/docs/developer.rst#contributeThe focus of new or changed rules should be to do one of the followingSubstantially increase the reviewability of the code (eg: H301, H303)
as they make it easy to understand where symbols come from)Catch a common programming error that may arise in the future (H201)Prevent a situation that would 100% of the time be -1ed by
developers (H903)But, as always, remember that these are Guidelines. Treat them as
such. There are always times for exceptions. All new rules should
support noqa.If a check needs to be staged in, or it does not apply to every project or its
branch, it can be added as off by default.RequirementsThe check must already have community support. We do not want to dictate
style, only enforce it.The canonical source of the OpenStack Style Guidelines isStyleGuide,
and hacking just enforces
them; so when adding a new check, it must be inHACKING.rstFalse negatives are ok, but false positives are notCannot be project specific, project specific checks should beLocal ChecksInclude extensive testsRegistered as entry_points insetup.cfgError code must be in the relevantHxxxgroupThe check should not attempt to import modules from the code being checked.
Importing random modules, has caused all kinds of trouble for us in the past.Enabling off-by-default checksSome of the available checks are disabled by default. These checks are:[H106] Don’t put vim configuration in source files.[H203] Use assertIs(Not)None to check for None.[H204] Use assert(Not)Equal to check for equality.[H205] Use assert(Greater|Less)(Equal) for comparison.[H210] Require ‘autospec’, ‘spec’, or ‘spec_set’ in
mock.patch/mock.patch.object calls[H904] Delay string interpolations at logging calls.To enable these checks, edit theflake8section of thetox.inifile.
For example to enable H106 and H203:[flake8]enable-extensions=H106,H203Local Checkshacking supports having local changes in a source tree. They need to
be registered individually in tox.ini:Add to tox.ini a new sectionflake8:local-pluginsand list each plugin with
its entry-point. Additionally, you can add the path to the files
containing the plugins so that the repository does not need to be
installed with thepathsdirective.[flake8:local-plugins]extension=N307=checks:import_no_db_in_virtN325=checks:CheckForStrUnicodeExcpaths=./nova/hackingThe plugins, in the example above they live innova/hacking/checks.py, need to annotate all functions with@core.flake8extfromhackingimportcore...@core.flake8extdefimport_no_db_in_virt(logical_line,filename):...classCheckForStrUnicodeExc(BaseASTChecker):name="check_for_str_unicode_exc"version="1.0"...Further details are part of theflake8 documentation.