Legend toggles visibility of all groupby groups

[rreusser]

Observed: clicking group toggles visibility of all groups.

Expected: clicking group in legend toggles only that group.

[rreusser]

A simple reproducible example:

https://codepen.io/rsreusser/pen/PJZWQq

What is the desired behavior here? @cldougl says there have been some complaints about this, so seems worth addressing. Should groupby simply not set the legendgroup? Or should there be an option not to set the legendgroup? Does the legendgroup do anything apart from linking visibility? Final question: is there any existing way around this?

[alexcjohnson]

@etpinard may have more to say about this, but I don't think we have a way around this right now, and I suspect we only set legendgroup originally because we didn't have a way to address the groups independently. But with the generic styles attribute it should be doable with explicit groupby handling, similar to #1919.

[etpinard]

Should groupby simply not set the legendgroup?

Hmm. Where is this set?

I'm only seeing this block as potentially being wrong.

[rreusser]

My mistake regarding legendgroup. Upon thinking about it, that's a bit of an oversimplification. I set it aside for a moment when I got hung up on testing, but almost have a PR ready that applies same the keyedContainer trick to set this in group-specific styles. The only downside then is that actually using legendgroup is somewhat trickier. For a first cut, I think I'll skip that part.

[rreusser]

Fixed in #2022. /cc @cldougl