"""
YAML serializer.
Requires PyYaml (https://pyyaml.org/), but that's checked for in __init__.
"""
import collections
import decimal
from io import StringIO
import yaml
from django.core.serializers.base import DeserializationError
from django.core.serializers.python import Deserializer as PythonDeserializer
from django.core.serializers.python import Serializer as PythonSerializer
from django.db import models
# Use the C (faster) implementation if possible
try:
from yaml import CSafeDumper as SafeDumper
from yaml import CSafeLoader as SafeLoader
except ImportError:
from yaml import SafeDumper, SafeLoader
class DjangoSafeDumper(SafeDumper):
def represent_decimal(self, data):
return self.represent_scalar("tag:yaml.org,2002:str", str(data))
def represent_ordered_dict(self, data):
return self.represent_mapping("tag:yaml.org,2002:map", data.items())
DjangoSafeDumper.add_representer(decimal.Decimal, DjangoSafeDumper.represent_decimal)
DjangoSafeDumper.add_representer(
collections.OrderedDict, DjangoSafeDumper.represent_ordered_dict
)
# Workaround to represent dictionaries in insertion order.
# See https://github.com/yaml/pyyaml/pull/143.
DjangoSafeDumper.add_representer(dict, DjangoSafeDumper.represent_ordered_dict)
class Serializer(PythonSerializer):
"""Convert a queryset to YAML."""
internal_use_only = False
def handle_field(self, obj, field):
# A nasty special case: base YAML doesn't support serialization of time
# types (as opposed to dates or datetimes, which it does support). Since
# we want to use the "safe" serializer for better interoperability, we
# need to do something with those pesky times. Converting 'em to strings
# isn't perfect, but it's better than a "!!python/time" type which would
# halt deserialization under any other language.
if isinstance(field, models.TimeField) and getattr(obj, field.name) is not None:
self._current[field.name] = str(getattr(obj, field.name))
else:
super().handle_field(obj, field)
def end_serialization(self):
self.options.setdefault("allow_unicode", True)
yaml.dump(self.objects, self.stream, Dumper=DjangoSafeDumper, **self.options)
def getvalue(self):
# Grandparent super
return super(PythonSerializer, self).getvalue()
def Deserializer(stream_or_string, **options):
"""Deserialize a stream or string of YAML data."""
if isinstance(stream_or_string, bytes):
stream_or_string = stream_or_string.decode()
if isinstance(stream_or_string, str):
stream = StringIO(stream_or_string)
else:
stream = stream_or_string
try:
yield from PythonDeserializer(yaml.load(stream, Loader=SafeLoader), **options)
except (GeneratorExit, DeserializationError):
raise
except Exception as exc:
raise DeserializationError() from exc