Source code for cattrs.preconf.json

"""Preconfigured converters for the stdlib json."""

from base64 import b85decode, b85encode
from datetime import date, datetime
from json import dumps, loads
from typing import Any, Type, TypeVar, Union

from .._compat import AbstractSet, Counter
from ..converters import BaseConverter, Converter
from ..strategies import configure_union_passthrough
from . import wrap

T = TypeVar("T")


class JsonConverter(Converter):
    def dumps(self, obj: Any, unstructure_as: Any = None, **kwargs: Any) -> str:
        return dumps(self.unstructure(obj, unstructure_as=unstructure_as), **kwargs)

    def loads(self, data: Union[bytes, str], cl: Type[T], **kwargs: Any) -> T:
        return self.structure(loads(data, **kwargs), cl)


def configure_converter(converter: BaseConverter):
    """
    Configure the converter for use with the stdlib json module.

    * bytes are serialized as base85 strings
    * datetimes are serialized as ISO 8601
    * counters are serialized as dicts
    * sets are serialized as lists
    * union passthrough is configured for unions of strings, bools, ints,
      floats and None
    """
    converter.register_unstructure_hook(
        bytes, lambda v: (b85encode(v) if v else b"").decode("utf8")
    )
    converter.register_structure_hook(bytes, lambda v, _: b85decode(v))
    converter.register_unstructure_hook(datetime, lambda v: v.isoformat())
    converter.register_structure_hook(datetime, lambda v, _: datetime.fromisoformat(v))
    converter.register_unstructure_hook(date, lambda v: v.isoformat())
    converter.register_structure_hook(date, lambda v, _: date.fromisoformat(v))
    configure_union_passthrough(Union[str, bool, int, float, None], converter)


@wrap(JsonConverter)
def make_converter(*args: Any, **kwargs: Any) -> JsonConverter:
    kwargs["unstruct_collection_overrides"] = {
        AbstractSet: list,
        Counter: dict,
        **kwargs.get("unstruct_collection_overrides", {}),
    }
    res = JsonConverter(*args, **kwargs)
    configure_converter(res)

    return res