Cannot handle message data with timedelta type

[gab23r]

Example with Reactable:

from datetime import timedelta
from reactable import Reactable
import polars as pl

Reactable(pl.DataFrame({"duration": timedelta(10)}))
# ValueError: Can't clean for JSON: datetime.timedelta(days=10)

[minrk]

I don't think this is a JupyterClient bug, it's a bug in whatever code is constructing a message that is valid JSON input with non-JSONable types. Looks like this is in Reactable.to_props and/or Reactable.to_widget, which must handle serialization to JSONable types.

If anything, we are moving in the opposite direction, towards deprecating automatic handling of non-JSON datetime objects as JSON-safe, since that's not actually the case: #1015

[gab23r]

Ah ok, i didn't know that you are moving in the opposite direction. This PR #1060 got merged recently, so i thought it would be nice to add support for timedelta as well.

[minrk]

I did do that, though it was fixing a regression in something that had worked previously and got lost in a refactor, not strictly adding new support. If it weren't unbreaking something that had worked before, I don't think I would have.

Whatever's building the JSONable dict here is what's responsible for handling the serialization. I think that should be ipyreact and/or reactable.