Source code for django_extensions.db.fields.json

# -*- coding: utf-8 -*-
"""
JSONField automatically serializes most Python terms to JSON data.
Creates a TEXT field with a default value of "{}".  See test_json.py for
more information.

 from django.db import models
 from django_extensions.db.fields import json

 class LOL(models.Model):
     extra = json.JSONField()
"""
from __future__ import absolute_import

import json
import six

from django.conf import settings
from django.core.serializers.json import DjangoJSONEncoder
from django.db import models


def dumps(value):
    return DjangoJSONEncoder().encode(value)


def loads(txt):
    value = json.loads(
        txt,
        encoding=settings.DEFAULT_CHARSET
    )
    return value


class JSONDict(dict):
    """
    Hack so repr() called by dumpdata will output JSON instead of
    Python formatted data.  This way fixtures will work!
    """
    def __repr__(self):
        return dumps(self)


class JSONList(list):
    """
    As above
    """
    def __repr__(self):
        return dumps(self)


class JSONField(models.TextField):
    """JSONField is a generic textfield that neatly serializes/unserializes
    JSON objects seamlessly.  Main thingy must be a dict object."""

    def __init__(self, *args, **kwargs):
        kwargs['default'] = kwargs.get('default', dict)
        models.TextField.__init__(self, *args, **kwargs)

    def get_default(self):
        if self.has_default():
            default = self.default

            if callable(default):
                default = default()

            return self.to_python(default)
        return super(JSONField, self).get_default()

    def to_python(self, value):
        """Convert our string value to JSON after we load it from the DB"""
        if value is None or value == '':
            return {}

        if isinstance(value, six.string_types):
            res = loads(value)
        else:
            res = value

        if isinstance(res, dict):
            return JSONDict(**res)
        elif isinstance(res, list):
            return JSONList(res)

        return res

    def get_prep_value(self, value):
        if not isinstance(value, six.string_types):
            return dumps(value)
        return super(models.TextField, self).get_prep_value(value)

    def from_db_value(self, value, expression, connection, context):
        return self.to_python(value)

    def get_db_prep_save(self, value, connection, **kwargs):
        """Convert our JSON object to a string before we save"""
        if value is None and self.null:
            return None
        # default values come in as strings; only non-strings should be
        # run through `dumps`
        if not isinstance(value, six.string_types):
            value = dumps(value)

        return value

    def deconstruct(self):
        name, path, args, kwargs = super(JSONField, self).deconstruct()
        if self.default == '{}':
            del kwargs['default']
        return name, path, args, kwargs