Callable Defaults

default may also be a callable that is invoked at read time. The returned value is normalised, validated against the schema and used as the default for that lookup.

from django.conf import settings
from habarico.contrib.preferences import register_preference
from habarico.contrib.preferences.schemas import ThemePreference

register_preference(
    "theme",
    schema=ThemePreference,
    default=lambda: getattr(settings, "DEFAULT_THEME", "light"),
)

Use this when the default depends on runtime state (settings, feature flags, current tenant). Return the EMPTY sentinel from habarico.contrib.preferences.registry to signal "no default available right now"; if the callable returns a value that fails schema validation, the lookup also resolves to "no default" (no exception is raised — the caller gets None).