# Django 2.2.9.dev20191202104323 文档

# django.contrib.messages.api 源代码

    from django.contrib.messages import constants
    from django.contrib.messages.storage import default_storage

    __all__ = (
        'add_message', 'get_messages',
        'get_level', 'set_level',
        'debug', 'info', 'success', 'warning', 'error',
        'MessageFailure',
    )

    class MessageFailure(Exception):
        pass

    def add_message(request, level, message, extra_tags='', fail_silently=False):
        """
        Attempt to add a message to the request using the 'messages' app.
        """
        try:
            messages = request._messages
        except AttributeError:
            if not hasattr(request, 'META'):
                raise TypeError(
                    "add_message() argument must be an HttpRequest object, not "
                    "'%s'." % request.__class__.__name__
                )
            if not fail_silently:
                raise MessageFailure(
                    'You cannot add messages without installing '
                    'django.contrib.messages.middleware.MessageMiddleware'
                )
        else:
            return messages.add(level, message, extra_tags)

    def get_messages(request):
        """
        Return the message storage on the request if it exists, otherwise return
        an empty list.
        """
        return getattr(request, '_messages', [])

    def get_level(request):
        """
        Return the minimum level of messages to be recorded.

        The default level is the ``MESSAGE_LEVEL`` setting. If this is not found,
        use the ``INFO`` level.
        """
        storage = getattr(request, '_messages', default_storage(request))
        return storage.level

    def set_level(request, level):
        """
        Set the minimum level of messages to be recorded, and return ``True`` if
        the level was recorded successfully.

        If set to ``None``, use the default level (see the get_level() function).
        """
        if not hasattr(request, '_messages'):
            return False
        request._messages.level = level
        return True

    def debug(request, message, extra_tags='', fail_silently=False):
        """Add a message with the ``DEBUG`` level."""
        add_message(request, constants.DEBUG, message, extra_tags=extra_tags,
                    fail_silently=fail_silently)

    def info(request, message, extra_tags='', fail_silently=False):
        """Add a message with the ``INFO`` level."""
        add_message(request, constants.INFO, message, extra_tags=extra_tags,
                    fail_silently=fail_silently)

    def success(request, message, extra_tags='', fail_silently=False):
        """Add a message with the ``SUCCESS`` level."""
        add_message(request, constants.SUCCESS, message, extra_tags=extra_tags,
                    fail_silently=fail_silently)

    def warning(request, message, extra_tags='', fail_silently=False):
        """Add a message with the ``WARNING`` level."""
        add_message(request, constants.WARNING, message, extra_tags=extra_tags,
                    fail_silently=fail_silently)

    def error(request, message, extra_tags='', fail_silently=False):
        """Add a message with the ``ERROR`` level."""
        add_message(request, constants.ERROR, message, extra_tags=extra_tags,
                    fail_silently=fail_silently)