Source code for core.orm.types.json_type

# We use our own custom json implementation. In the libres library we made this
# configurable. Since onegov.core is a framework we don't do that though, we
# want all onegov.core applications with the same framework version to be able
# to read each others json.
#
# Therefore we use a common denominator kind of json encoder/decoder.
from sqlalchemy.ext.mutable import MutableDict
from sqlalchemy.types import TypeDecorator
from sqlalchemy.dialects.postgresql import JSONB


from typing import Any, TYPE_CHECKING
if TYPE_CHECKING:
    from sqlalchemy.engine.interfaces import Dialect
    # TODO: using an actual recursive JSON serializable dict type
    #       would be more type safe, but it might be very annoying
    #       to use, so for now we're completely unsafe. If mypy
    #       ever implements AnyOf, we could be slightly more safe
    #       without making it annoying to use.


    _Base = TypeDecorator[dict[str, Any]]

else:
    _Base = TypeDecorator




class JSON(_Base):
    """ A JSONB based type that coerces None's to empty dictionaries.

    That is, this JSONB column does not have NULL values, it only has
    falsy values (an empty dict).

    """



    impl = JSONB




    def process_bind_param(  # type:ignore[override]
        self,
        value: dict[str, Any] | None,
        dialect: 'Dialect'
    ) -> dict[str, Any]:

        return {} if value is None else value




    def process_result_value(
        self,
        value: dict[str, Any] | None,
        dialect: 'Dialect'
    ) -> dict[str, Any]:

        return {} if value is None else value




MutableDict.associate_with(JSON)