Maintain input series names, in rust, when a plugin is called within .over() context about pyo3-polars HOT 4 CLOSED

Hi Karl,

Thank you! Sorry, I totally missed that parameter to register plugin function. It seems it defaults to False for performance reasons (I guess implicitly assuming that most won't use pl.struct in their rust implementations).

In any case, I set it to "True" and my issue seems to have been resolved.

    pass_name_to_apply
        If set to `True`, the `Series` passed to the function in a group-by operation
        will ensure the name is set. This is an extra heap allocation per group.

I will close this issue as setting to True works for my usecase

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Hello! would it be possible to ask for a rough ETA for something like this to be fixed? Unfortunately I'm not familiar enough with the codebase to know where to look - but happy to try a PR if someone can provide guidance

Unf this is causing inconsistent behaviour in my pl.Struct outputs in the meantime

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There was a recent issue where this was fixed in Polars for qcut: pola-rs/polars#15715 (input name "empty" in a groupby context)

It seems this is controlled via the FunctionOptions pass_name_to_apply

            if self.pass_name_to_apply {
                s.rename(&name);
            }

It seems that register_plugin_function also has this option which should fix this.

register_plugin_function(
    ...,
    pass_name_to_apply=True
)

(I'm not sure why it defaults to False - perhaps someone with more knowledge can answer that.)

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for performance reasons

Ah! I didn't realize the function had its own docs page.

It seems like something that could be added to the User Guide or to @MarcoGorelli's Plugin Tutorial - as it could be considered a bit of a "gotcha".

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