How to create a UDF for built-in functions that accept variable arguments?

[kyrre]

I want to use the format_string function for the Databricks backend.

However, when I "create" a UDF:

@ibis.udf.scalar.builtin
def format_string(format, *args) -> str:
    ...

and use it like so:

(
    device_process_events
        .rename("snake_case")
        .mutate(
            message=format_string(
                "The process %s %s",
                _.initiating_process_file_name,
                _.process_id
            )
    )
)

it fails with the message:

too many positional arguments Expected signature: format_string_9(format: Any, args: Any)

If I explicitly set the number of args that I use, e.g., 2 in the above example, it works.

[cpcloud]

I don't think we support this yet. I can take a look at implementing it.