Feature Switches With Waffle

Feature Switch with Waffle

Purpose of this task is to allow people managing the system to quickly revert new functionality in case a bug or any other side effects are discovered or even if they want to delay the release of a feature using a lite Circuit Breaker pattern.

Install

Make sure that library is installed and present.

Install with uv with:

uv add django-waffle

Install with pip:

pip install django-waffle

Setup

Check project's settings.py. There are many settings in <https://waffle.readthedocs.io/en/stable/starting/configuring.html>. Inform user and ask to discuss every one if requested.

Check if at least one WAFFLE_ parameter is set, if so assume user has setup Waffle for their project and do not suggest to setup again, notify though about it:

"It seems that Waffle has been setup from reading your setting file."

Definitely discuss the following:

WAFFLE_SWITCH_DEFAULT

When a Switch is undefined in the database, Waffle considers it False. Set this to True to make Waffle consider undefined switches True. Defaults to False.

Suggest to make it True for non deployed environments.

Suggestion: WAFFLE_SWITCH_DEFAULT = DEBUG

WAFFLE_CREATE_MISSING_SWITCHES

Suggest to set to True so that it will be more obvious what is going on in the database.

Decorate Code

For switches check with waffle.switch_is_active('switch_name'), Waffle should be present in the file import waffle.

Code should be like:

import waffle

if waffle.switch_is_active("switch_name"):
    # implement "new" untested functionality
else:
    # Current, established functionality

Decorate Views

Function Based

from waffle.decorators import waffle_switch

@waffle_switch("switch_name")
def my_view(request):
    pass

or

@waffle_switch("switch_name", "url_name_to_redirect_to")
def my_other_view(request):
    pass

Class Based

from waffle.mixins import WaffleSwitchMixin

class MyClass(WaffleSwitchMixin, View):
    waffle_switch = "my_switch"

Decorate Templates

Waffle tags library needs to be present:

{% load waffle_tags %}

Then to wrap functionality:

{% switch "switch_name" %}
    switch_name is active!
{% else %}
    switch_name is inactive
{% endswitch %}

Decorate Javascript

Decided not to add it at this version of this skill.

Unit Tests

Initially

from waffle.testutils import override_switch

Then either

with override_switch("switch_name", active=True):
    # Only "switch_name" is affected, other ones behave normally.
    assert waffle.switch_is_active("switch_name")

... for a specific assertion, or

@override_switch("switch_name", active=True)
def test_with_switch_active():
    assert waffle.switch_is_active("switch_name")

and setting active=False for regression

@override_switch("switch_name", active=False)
def test_with_switch_not_active():
    assert not waffle.switch_is_active("switch_name")

for whole tests very dependent on a switch.

Instructions to Manage Switches

Always after applying this skill, inform for the following command line commands:

Switches Use manage.py to change the values of your switches:

To set off:

uv run python manage.py waffle_switch switch_name off

or

uv run python manage.py waffle_switch switch_name off --create

... if not present

To set on:

uv run python manage.py waffle_switch switch_name on

or

uv run python manage.py waffle_switch switch_name on --create

... if not present

and to list all existing switches:

uv run python manage.py waffle_switch -l