plain.flags

Local feature flags via database models.

Custom flags are written as subclasses of Flag. You define the flag's "key" and initial value, and the results will be stored in the database for future reference.

# app/flags.py
from plain.flags import Flag


class FooEnabled(Flag):
    def __init__(self, user):
        self.user = user

    def get_key(self):
        return self.user

    def get_value(self):
        # Initially all users will have this feature disabled
        # and we'll enable them manually in the admin
        return False

Use flags in HTML templates:

{% if flags.FooEnabled(request.user) %}
    <p>Foo is enabled for you!</p>
{% else %}
    <p>Foo is disabled for you.</p>
{% endif %}

Or in Python:

import flags


print(flags.FooEnabled(user).value)

Installation

INSTALLED_PACKAGES = [
    ...
    "plain.flags",
]

Create a flags.py at the top of your app (or point settings.FLAGS_MODULE to a different location).

Advanced usage

Ultimately you can do whatever you want inside of get_key and get_value.

class OrganizationFeature(Flag):
    url_param_name = ""

    def __init__(self, request=None, organization=None):
        # Both of these are optional, but will usually both be given
        self.request = request
        self.organization = organization

    def get_key(self):
        if (
            self.url_param_name
            and self.request
            and self.url_param_name in self.request.GET
        ):
            return None

        if not self.organization:
            # Don't save the flag result for PRs without an organization
            return None

        return self.organization

    def get_value(self):
        if self.url_param_name and self.request:
            if self.request.GET.get(self.url_param_name) == "1":
                return True

            if self.request.GET.get(self.url_param_name) == "0":
                return False

        if not self.organization:
            return False

        # All organizations will start with False,
        # and I'll override in the DB for the ones that should be True
        return False


class AIEnabled(OrganizationFeature):
    pass

Source

plain-flags

plain

flags

bridge.py

 1from plain.runtime import settings
 2
 3from . import exceptions
 4from .flags import Flag
 5
 6
 7def get_flags_module():
 8    flags_module = settings.FLAGS_MODULE
 9
10    try:
11        return __import__(flags_module)
12    except ImportError as e:
13        raise exceptions.FlagImportError(
14            f"Could not import {flags_module} module"
15        ) from e
16
17
18def get_flag_class(flag_name: str) -> Flag:
19    flags_module = get_flags_module()
20
21    try:
22        flag_class = getattr(flags_module, flag_name)
23    except AttributeError as e:
24        raise exceptions.FlagImportError(
25            f"Could not find {flag_name} in {flags_module} module"
26        ) from e
27
28    return flag_class