Sample admin filter hack to customize choices

admin.py

from django.contrib import admin
from django.utils.translation import gettext_lazy as _

from ..choices import get_language_choices, get_language_default


class DeprecatedLanguageListFilter(admin.SimpleListFilter):
    """
    Add Human-readable language title as defined in LANGUAGES setting.

    The behavior of this filter have been largely tested and was feeling awful, default
    listing on default language is not very obvious.

    It is keeped for now as it implement a way to hack the choices.
    """
    title = _("language")

    # Parameter for the filter that will be used in the URL query.
    parameter_name = "lang"

    def choices(self, changelist):
        """
        Hack the filter list to change the default name to match this specific filter
        behavior.
        """
        choices = list(super().choices(changelist))
        choices[0]["display"] = _("Default language")

        return choices

    def lookups(self, request, model_admin):
        """
        Add again the "All" entry but with a special keyword "all" to use to select the
        right queryset.
        """
        base_choices = list(get_language_choices())

        return [('all', _('All'))] + base_choices

    def queryset(self, request, queryset):
        """
        Use the default language for default queryset (with no URL argument) or
        return article queryset for all language (if ``all`` argument is given) or
        return article queryset filtered on given language code (from given argument).
        """
        if self.value() and self.value() == "all":
            return queryset.filter()
        elif self.value():
            return queryset.filter(language=self.value())
        else:
            return queryset.filter(language=get_language_default())