Custom serializer with Optional (aka | None)

[davetapley]

I think I can workaround with e.g.:

def field_timedelta():
    return field(
        serializer=lambda s: None if s is None else parse_duration(s))

@dataclass
class ReportConfig:
    schedule: timedelta | None = field_timedelta()

But I wonder if there's a better way? 🤔

[davetapley]

One problem with that workaround is that I can't make None the default value, so I need to explicitly ReportConfig(..., schedule=None else I get missing ... required positional arguments.

[yukinarit]

How about using *args and **kwargs?

def field_timedelta(*args, **kwrags):
    serde.field(*args, **kwargs, serializer=lambda s: None if s is None else parse_duration(s))


@dataclass
class ReportConfig:
    schedule: timedelta | None = field_timedelta(default=None)