feat(rust): Support duration + date

[billylanchantin]

Description

Closes: #11034

This PR adds support for duration + date. Supporting that operation will bring the Rust API more in line with the Python API, which already supports it.

Changes

• Support duration + date
• Tests

[ritchie46]

Python API, which already supports it.

I don't understand. How can the python API already support it in this case? Shouldn't we go to both code branches for both apis?

[billylanchantin]

@alexander-beedie posted an example in the issue:

#11034 (comment)

TBH I was surprised that the Python side already supported it. I think what's happening is that PySeries ends up calling try_add instead of just add. And try_add seems to coerce the arguments.

I think the relevant code is here (but I had a little trouble confirming it):

https://github.com/pola-rs/polars/blob/main/crates/polars-core/src/series/arithmetic/borrowed.rs#L340-L347

[alexander-beedie]

Yup; the underlying PySeries add is called from the Python side (via _arithmetic), and that then kicks out to try_add.

On the Rust side we have precedence from chrono not liking "duration + date", but on the Python side the standard library is completely fine with "timedelta + date", and we seem to have (possibly inadvertently) allowed it via the Python Series for some time so it might be a bit harsh to take it away!

I'm not going to declare which one is "best", but it would be good to align both sides of the API, and the weight of things appears to support allowing it, so... ;)

[billylanchantin]

Also, there was already support for duration + datetime on the Rust side despite chrono not being a fan.

[ritchie46]

Alright, thanks for the clarification. 👍