Ticket #17419: jsonfilter.py

# -*- coding: utf-8 -*-
from __future__ import unicode_literals
import json
from django import template
from django.core.serializers.json import DjangoJSONEncoder
from django.utils.html import conditional_escape
from django.utils.safestring import mark_safe

register = template.Library()


class SafeJSONEncoder(DjangoJSONEncoder):
    def _recursive_escape(self, o, esc=conditional_escape):
        if isinstance(o, dict):
            return type(o)((esc(k), self._recursive_escape(v)) for (k, v) in o.iteritems())
        if isinstance(o, (list, tuple)):
            return type(o)(self._recursive_escape(v) for v in o)
        try:
            return type(o)(esc(o))
        except ValueError:
            return esc(o)

    def encode(self, o):
        value = self._recursive_escape(o)
        return super(SafeJSONEncoder, self).encode(value)


@register.filter('json')
def json_filter(value):
    """
    Returns the JSON representation of ``value`` in a safe manner.
    """
    return mark_safe(json.dumps(value, cls=SafeJSONEncoder))