Draw() & update() fails to draw traces when first trace y property consists of nulls

[GlennMatthys]

Reproduction link (newPlot): https://jsfiddle.net/n1teax2o/2/
Reproduction link (update): https://jsfiddle.net/703a5bnf/1/

Observed behavior: When drawing two or more traces, and the first trace's y property is all nulls, no traces are drawn even if subsequent traces do not have nulls in their y property.

Expected behavior: Traces that don't have nulls in their y property are drawn correctly.

As a side note, the intention of this graph in particular is to only draw markers where (x, y) !== null and not draw markers where (x, y) === null. End result like this:

[alexcjohnson]

Thanks for the clear reproductions @GlennMatthys! The issue here is that we only look at the first trace to automatically determine the axis type - if you add yaxis: {type: 'category'} to your layout it works as you expect (unless you were hoping for trace 0 to still contribute a category - if you want that you'll need a different solution like yaxis.categoryarray, or use numbers for the y data along with ticktext/tickvals).

I suppose we could look at subsequent traces for the axis autotype if the first trace is empty like this... sure, I'll slap a bug label on this and at some point we'll try that.

[GlennMatthys]

Perhaps just documenting this is enough. I solved it in my code by detecting whether the array consists of all nulls (I was already looping through all the source values anyway) and then replacing the y property with an empty array (saves some memory too). That seems to make Plotly skip over to the next non-empty array to automatically determine axis type, is that the intended behavior?

[etpinard]

That seems to make Plotly skip over to the next non-empty array to automatically determine axis type, is that the intended behavior?

That's correct, traces with empty coordinate arrays are considered visible: false by plotly which are then skipped during the axis type defaults.

[gvwilson]

Hi - this issue has been sitting for a while, so as part of our effort to tidy up our public repositories I'm going to close it. If it's still a concern, we'd be grateful if you could open a new issue (with a short reproducible example if appropriate) so that we can add it to our stack. Cheers - @gvwilson