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import json
from psycopg2.extras import Json
from django.contrib.postgres import forms, lookups
from django.core import exceptions
from django.db.models import Field, Transform
from django.utils.translation import ugettext_lazy as _
__all__ = ['JSONField']
class JSONField(Field):
empty_strings_allowed = False
description = _('A JSON object')
default_error_messages = {
'invalid': _("Value must be valid JSON."),
}
def db_type(self, connection):
return 'jsonb'
def get_transform(self, name):
transform = super(JSONField, self).get_transform(name)
if transform:
return transform
return KeyTransformFactory(name)
def get_prep_value(self, value):
if value is not None:
return Json(value)
return value
def validate(self, value, model_instance):
super(JSONField, self).validate(value, model_instance)
try:
json.dumps(value)
except TypeError:
raise exceptions.ValidationError(
self.error_messages['invalid'],
code='invalid',
params={'value': value},
)
def value_to_string(self, obj):
value = self.value_from_object(obj)
return value
def formfield(self, **kwargs):
defaults = {'form_class': forms.JSONField}
defaults.update(kwargs)
return super(JSONField, self).formfield(**defaults)
JSONField.register_lookup(lookups.DataContains)
JSONField.register_lookup(lookups.ContainedBy)
JSONField.register_lookup(lookups.HasKey)
JSONField.register_lookup(lookups.HasKeys)
JSONField.register_lookup(lookups.HasAnyKeys)
class KeyTransform(Transform):
def __init__(self, key_name, *args, **kwargs):
super(KeyTransform, self).__init__(*args, **kwargs)
self.key_name = key_name
def as_sql(self, compiler, connection):
key_transforms = [self.key_name]
previous = self.lhs
while isinstance(previous, KeyTransform):
key_transforms.insert(0, previous.key_name)
previous = previous.lhs
lhs, params = compiler.compile(previous)
if len(key_transforms) > 1:
return "{} #> %s".format(lhs), [key_transforms] + params
try:
lookup = int(self.key_name)
except ValueError:
lookup = self.key_name
return '(%s %s %%s)' % (lhs, self.operator), [lookup] + params
class KeyTransformFactory(object):
def __init__(self, key_name):
self.key_name = key_name
def __call__(self, *args, **kwargs):
return KeyTransform(self.key_name, *args, **kwargs)
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