Missing support

[cstjean]

using PlotlyJS
using PlotlyJS: SyncPlot

SyncPlot(Plot(scattergl(x=[1,2,3], y=[1,missing, 3], mode=:markers)))

yields Cannot serialize type Missing. I think it would be OK to convert them to NaN? That's what Plots.jl does IIRC.

[sglyon]

Yeah I think that makes sense to me.

What do you think the right approach to that would be? Right now we lean on how JSON.jl wants to serialize things and define a few methods for JSON.lower here.

I don't think we should be type pirates and define JSON.lower(::Missing) = NaN, but as of right now we don't have a layer in PlotlyJS.jl to intercept something like that

[cstjean]

@TotalVerb We'd like to serialize (write) missing as null, with JSON.jl. I saw your big PR, but it doesn't seem to be documented anywhere. What would be the solution for us? I'm a bit confused whether we should implement a Writer, a Context, or a Serialization.

[TotalVerb]

JSON.jl already serializes Missing as null: https://github.com/JuliaIO/JSON.jl/blob/master/src/Writer.jl#L266

It's possible this has not been tagged. I'll check this. Edit: No, it should be in 0.20.0.

[TotalVerb]

I believe the issue is that one of the JSON.lower overrides is calling JSON.lower before returning the result, which is not the intended usage. Please see #266 for a solution.

[sglyon]

Thanks @TotalVerb!

@cstjean I just tried your example with the latest master of PlotlyJS.jl (doesn't include #266) and the code snippet you posted above and it works for me without any modification needed...

What version of JSON.jl and julia do you have? What about your OS (though I can't imagine why that would matter for this issue)?

[TotalVerb]

Right, #266 will have no effect if (::SyncPlot).plot is never Missing and is always a type that this package is aware has already defined lower. Nevertheless, the recursive lower call is not needed; I am aware the documentation for JSON recommends it and thus is actively misleading here (I regret that it was written when we had a different design philosophy in mind when the feature was first implemented.)

[cstjean]

I can't check right now, but I assume that I just had a lower JSON version installed because of some upper-bound somewhere. Thank you for your help both!

[sglyon]

ok sounds good, if you check and it it still an issue please reopen.

Thanks