List(Categorical/Enum).contains(Categorical/Enum) is broken since 0.20.2 about polars HOT 1 OPEN

There are a few missing is_in implementations:

• String is in Categorical
• String is in Enum

also fails, but perhaps should fail:

• Categorical is in Enum
• Enum is Categorical

I don't know if those last two should be implemented. Both Categorical and Enums should coerce strings into their revmap representation, but if your data is already a Categorical and/or Enum, then it means that you have explicitly placed them into particular sets, and those sets are not always comparable.

I do think we could benefit from a slightly more informative error message than, for example:

polars.exceptions.InvalidOperationError: `is_in` cannot check for Enum(Some(local), Physical) values in String data

e.g. explain why it cannot check. Also the enum innards are probably not very useful in the error message.

from polars.