Hi everyone, Just wanted to let you know of a few upcoming changes to our flake8 linter that I'm planning:
*1. Upgrading flake8, pycodestyle and pyflakes* It's been awhile since we've bumped these tools. The upgrades will be: flake8: 3.5.0 -> 3.7.4 pycodestyle: 2.3.1 -> 2.5.0 pyflakes: 1.5.0 -> 2.1.0 These updates add the following new error codes: F632, F633, F723, F811, E117, W504, W605, W606 For their meanings see: http://flake8.pycqa.org/en/latest/user/error-codes.html http://pep8.readthedocs.io/en/latest/intro.html#configuration I plan to disable these new rules at first. They'll be separated via comment from the other intentionally disabled rules in the config. *2. Deprecating subdirectory .flake8 files (bug 1515746 <https://bugzilla.mozilla.org/show_bug.cgi?id=1515746>)* There will be a single canonical .flake8 file in the root of the repository. The main motivation for this is an implementation detail where this feature is preventing us from switching to a blacklist. But this will also simplify our configs and code, keep editor integrations in-line with |mach lint|, and improve perf. This is now possible because of flake8 3.7's new per-file-ignores <http://flake8.pycqa.org/en/latest/user/options.html#cmdoption-flake8-per-file-ignores> feature. This can be implemented without any change to how our current files are linted, i.e no source code will be modified as part of this change. *3. Switching to a blacklist (bug 1367092 <https://bugzilla.mozilla.org/show_bug.cgi?id=1367092>)* Currently we register <https://searchfox.org/mozilla-central/source/tools/lint/flake8.yml#4> which files and directories should be linted. This is not ideal because any new code added outside of those directories will not be linted by default. Instead, we will define which paths *shouldn't* be linted. This will be possible thanks to the deprecation of subdirectory configs (it's a long story). As part of this process I intend to only exclude what is absolutely necessary (within reason). This means some .py files which had no issues but weren't being linted will start being linted. It also means new modules will automatically be linted. *4. Enabling flake8-isort (bug 1492495 <https://bugzilla.mozilla.org/show_bug.cgi?id=1492495>)* Isort is a tool to format python imports, and flake8-isort is a shim to use it as a linter. I'm proposing flake8-isort over the more popular flake8-import-order because we'll get automatic fixing for free. Manually re-ordering imports is not something I think anyone should be subjected to. Isort is configurable, but the default is pretty close to what we unofficially tend to use anyway, namely: # stdlib imports import os import sys from collections import OrderedDict, defaultdict # external dependency imports import requests from mozprocess import ProcessHandler # internal imports import mymodule from . import name I think I'd like to enable this at the 'warning' level to start (so it doesn't cause backouts or show up without --warnings). This will give people a feel for the new syntax and allow us to start using --fix to re-order imports before making it a hard requirement. This item item is potentially controversial, so let me know if you have any objections to enabling this. *5. Mass enabling of rules* With flake8 + dependencies upgraded and flake8-isort installed, we'll have many new rules (which were all turned off by default) to triage and enable. Ideally this would all happen in a single massive commit similar to our format efforts in other languages. We would use the magic commit string to keep it out of git/hg blame. Not everything will happen all at once, the items at the top of the list will land before the items near the bottom. Let me know if you have any questions or objections! Cheers, Andrew
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