"""
A Python "serializer". Doesn't do much serializing per se -- just converts to
and from basic Python data types (lists, dicts, strings, etc.). Useful as a basis for
other serializers.
"""
from django.apps import apps
from django.core.serializers import base
from django.db import DEFAULT_DB_ALIAS, models
from django.utils.encoding import is_protected_type
class Serializer(base.Serializer):
"""
Serialize a QuerySet to basic Python objects.
"""
internal_use_only = True
def start_serialization(self):
self._current = None
self.objects = []
def end_serialization(self):
pass
def start_object(self, obj):
self._current = {}
def end_object(self, obj):
self.objects.append(self.get_dump_object(obj))
self._current = None
def get_dump_object(self, obj):
data = {"model": str(obj._meta)}
if not self.use_natural_primary_keys or not hasattr(obj, "natural_key"):
data["pk"] = self._value_from_field(obj, obj._meta.pk)
data["fields"] = self._current
return data
def _value_from_field(self, obj, field):
value = field.value_from_object(obj)
# Protected types (i.e., primitives like None, numbers, dates,
# and Decimals) are passed through as is. All other values are
# converted to string first.
return value if is_protected_type(value) else field.value_to_string(obj)
def handle_field(self, obj, field):
self._current[field.name] = self._value_from_field(obj, field)
def handle_fk_field(self, obj, field):
if self.use_natural_foreign_keys and hasattr(
field.remote_field.model, "natural_key"
):
related = getattr(obj, field.name)
if related:
value = related.natural_key()
else:
value = None
else:
value = self._value_from_field(obj, field)
self._current[field.name] = value
def handle_m2m_field(self, obj, field):
if field.remote_field.through._meta.auto_created:
if self.use_natural_foreign_keys and hasattr(
field.remote_field.model, "natural_key"
):
def m2m_value(value):
return value.natural_key()
def queryset_iterator(obj, field):
return getattr(obj, field.name).iterator()
else:
def m2m_value(value):
return self._value_from_field(value, value._meta.pk)
def queryset_iterator(obj, field):
return (
getattr(obj, field.name)
.select_related(None)
.only("pk")
.iterator()
)
m2m_iter = getattr(obj, "_prefetched_objects_cache", {}).get(
field.name,
queryset_iterator(obj, field),
)
self._current[field.name] = [m2m_value(related) for related in m2m_iter]
def getvalue(self):
return self.objects
def Deserializer(
object_list, *, using=DEFAULT_DB_ALIAS, ignorenonexistent=False, **options
):
"""
Deserialize simple Python objects back into Django ORM instances.
It's expected that you pass the Python objects themselves (instead of a
stream or a string) to the constructor
"""
handle_forward_references = options.pop("handle_forward_references", False)
field_names_cache = {} # Model: <list of field_names>
for d in object_list:
# Look up the model and starting build a dict of data for it.
try:
Model = _get_model(d["model"])
except base.DeserializationError:
if ignorenonexistent:
continue
else:
raise
data = {}
if "pk" in d:
try:
data[Model._meta.pk.attname] = Model._meta.pk.to_python(d.get("pk"))
except Exception as e:
raise base.DeserializationError.WithData(
e, d["model"], d.get("pk"), None
)
m2m_data = {}
deferred_fields = {}
if Model not in field_names_cache:
field_names_cache[Model] = {f.name for f in Model._meta.get_fields()}
field_names = field_names_cache[Model]
# Handle each field
for field_name, field_value in d["fields"].items():
if ignorenonexistent and field_name not in field_names:
# skip fields no longer on model
continue
field = Model._meta.get_field(field_name)
# Handle M2M relations
if field.remote_field and isinstance(
field.remote_field, models.ManyToManyRel
):
try:
values = base.deserialize_m2m_values(
field, field_value, using, handle_forward_references
)
except base.M2MDeserializationError as e:
raise base.DeserializationError.WithData(
e.original_exc, d["model"], d.get("pk"), e.pk
)
if values == base.DEFER_FIELD:
deferred_fields[field] = field_value
else:
m2m_data[field.name] = values
# Handle FK fields
elif field.remote_field and isinstance(
field.remote_field, models.ManyToOneRel
):
try:
value = base.deserialize_fk_value(
field, field_value, using, handle_forward_references
)
except Exception as e:
raise base.DeserializationError.WithData(
e, d["model"], d.get("pk"), field_value
)
if value == base.DEFER_FIELD:
deferred_fields[field] = field_value
else:
data[field.attname] = value
# Handle all other fields
else:
try:
data[field.name] = field.to_python(field_value)
except Exception as e:
raise base.DeserializationError.WithData(
e, d["model"], d.get("pk"), field_value
)
obj = base.build_instance(Model, data, using)
yield base.DeserializedObject(obj, m2m_data, deferred_fields)
def _get_model(model_identifier):
"""Look up a model from an "app_label.model_name" string."""
try:
return apps.get_model(model_identifier)
except (LookupError, TypeError):
raise base.DeserializationError(
"Invalid model identifier: '%s'" % model_identifier
)