class Union(marshmallow.fields.Field):
"""Field that accepts any one of multiple fields.
Source: https://github.com/adamboche/python-marshmallow-union
Each argument will be tried until one succeeds.
Args:
fields: The list of candidate fields to try.
reverse_serialize_candidates: Whether to try the candidates in reverse order when serializing.
"""
def __init__(
self,
fields: list[marshmallow.fields.Field],
*,
reverse_serialize_candidates: bool = False,
**kwargs: Any,
) -> None:
self._candidate_fields = fields
self._reverse_serialize_candidates = reverse_serialize_candidates
super().__init__(**kwargs)
def _serialize(self, value: Any, attr: str | None, obj: str, **kwargs: Any) -> Any:
"""Pulls the value for the given key from the object, applies the field's formatting and returns the result.
Args:
value: The value to be serialized.
attr: The attribute or key to get from the object.
obj: The object to pull the key from.
kwargs: Field-specific keyword arguments.
Raises:
marshmallow.exceptions.ValidationError: In case of formatting problem
"""
error_store = kwargs.pop("error_store", marshmallow.error_store.ErrorStore())
fields = (
list(reversed(self._candidate_fields)) if self._reverse_serialize_candidates else self._candidate_fields
)
for candidate_field in fields:
try:
# pylint: disable=protected-access
return candidate_field._serialize(value, attr, obj, error_store=error_store, **kwargs)
except (TypeError, ValueError) as e:
error_store.store_error({attr: str(e)})
raise ExceptionGroupError("All serializers raised exceptions.", error_store.errors)
def _deserialize(self, value: Any, attr: str | None = None, data: Any = None, **kwargs: Any) -> Any:
"""Deserialize ``value``.
Args:
value: The value to be deserialized.
attr: The attribute/key in `data` to be deserialized.
data: The raw input data passed to the `Schema.load`.
kwargs: Field-specific keyword arguments.
Raises:
ValidationError: If an invalid value is passed or if a required value is missing.
"""
errors = []
for candidate_field in self._candidate_fields:
try:
return candidate_field.deserialize(value, attr, data, **kwargs)
except marshmallow.exceptions.ValidationError as exc:
errors.append(exc.messages)
raise marshmallow.exceptions.ValidationError(message=errors, field_name=attr or "")