django/contrib/admin/decorators.py

def action(function=None, *, permissions=None, description=None):
    """
    Conveniently add attributes to an action function::

        @admin.action(
            permissions=['publish'],
            description='Mark selected stories as published',
        )
        def make_published(self, request, queryset):
            queryset.update(status='p')

    This is equivalent to setting some attributes (with the original, longer
    names) on the function directly::

        def make_published(self, request, queryset):
            queryset.update(status='p')
        make_published.allowed_permissions = ['publish']
        make_published.short_description = 'Mark selected stories as published'
    """

    def decorator(func):
        if permissions is not None:
            func.allowed_permissions = permissions
        if description is not None:
            func.short_description = description
        return func

    if function is None:
        return decorator
    else:
        return decorator(function)


def display(
    function=None, *, boolean=None, ordering=None, description=None, empty_value=None
):
    """
    Conveniently add attributes to a display function::

        @admin.display(
            boolean=True,
            ordering='-publish_date',
            description='Is Published?',
        )
        def is_published(self, obj):
            return obj.publish_date is not None

    This is equivalent to setting some attributes (with the original, longer
    names) on the function directly::

        def is_published(self, obj):
            return obj.publish_date is not None
        is_published.boolean = True
        is_published.admin_order_field = '-publish_date'
        is_published.short_description = 'Is Published?'
    """

    def decorator(func):
        if boolean is not None and empty_value is not None:
            raise ValueError(
                "The boolean and empty_value arguments to the @display "
                "decorator are mutually exclusive."
            )
        if boolean is not None:
            func.boolean = boolean
        if ordering is not None:
            func.admin_order_field = ordering
        if description is not None:
            func.short_description = description
        if empty_value is not None:
            func.empty_value_display = empty_value
        return func

    if function is None:
        return decorator
    else:
        return decorator(function)


def register(*models, site=None):
    """
    Register the given model(s) classes and wrapped ModelAdmin class with
    admin site:

    @register(Author)
    class AuthorAdmin(admin.ModelAdmin):
        pass

    The `site` kwarg is an admin site to use instead of the default admin site.
    """
    from django.contrib.admin import ModelAdmin
    from django.contrib.admin.sites import AdminSite
    from django.contrib.admin.sites import site as default_site

    def _model_admin_wrapper(admin_class):
        if not models:
            raise ValueError("At least one model must be passed to register.")

        admin_site = site or default_site

        if not isinstance(admin_site, AdminSite):
            raise ValueError("site must subclass AdminSite")

        if not issubclass(admin_class, ModelAdmin):
            raise ValueError("Wrapped class must subclass ModelAdmin.")

        admin_site.register(models, admin_class=admin_class)

        return admin_class

    return _model_admin_wrapper