same-position/within-trace bar placement when barmode=group

[nicolaskruchten]

Consider the following pen: https://codepen.io/nicolaskruchten/pen/RdYWdz?editors=0010

The red and cyan bars aren't being shown because within each trace at the same position, the bars are behaving as if the barmode was "overlay". I believe that the default behaviour should be "relative" instead because it's the only one that always shows all the data!).

If we can't agree that the current behaviour is a bug, then we should create a new attr that defaults to "overlay" but allows us to set it to "relative" or "stack" as required.

[etpinard]

Interestingly under barmode: 'relative', we appear to do the right thing already: https://codepen.io/etpinard/pen/GeeXmQ?editors=0010

This might just be an issue with barmode: 'group'.

[nicolaskruchten]

Yes, this is exclusively a problem with barmode=group.

[etpinard]

@nicolaskruchten I'm starting to think we could merge a "fix" for this bug w/o adding a new attribute.

Here's my first attempt: https://github.com/plotly/plotly.js/compare/unhide-grouped-bars-within-trace - which doesn't break any existing test.

Your codepen now looks like: https://codepen.io/etpinard/pen/YggmQx?editors=0010

and note that the new logic only has an effect when barmode: 'group', so under barmode: 'overlay' we (still) get:

[nicolaskruchten]

This is pretty much my ideal fix I think, without looking at the implementation