adapt name search from JSONTables.jl

[rafaqz]

Use the JSONTables.jl methods of getting a list of column names and types. Unfortunately we cant just use their methods as we need to dig into the properties field of each object, rather than using the top level fields.

@visr this isn't quite finished, just pushing so you know I'm working on it and we don't duplicate efforts

So it turned out to be quite tricky getting this to work for both Object and NameTuple features.

There are likely still some issues with vectors of mixed field NamedTuple in broadcast or other places, but mostly things seem to be working.

See #48
Fixes #45

[visr]

Looks good overall, added some comments. Great to have this.

[rafaqz]

The current problem is I'm not sure if null geometries are meant to be represented by nothing or missing.

There is currently a mix ob both in different contexts.

In getproperty there is this line:

 return ifelse(x === nothing, missing, x)

And tests reflect this with checks for missing. But geometry(feature) returns nothing without swapping to missing.

The main issue with this is round-tripping Feature construction doesn't always work. If you build a feature with a missing geometry show will error in the REPL because the check is for nothing.

I think we need to decide either way, and if its missing move where the swap from nothing to missing happens so its more consistent.

@visr any ideas here?

The GeoInterface.jl tests want nothing as the empty value of geometry. I guess thats why there is a split in the behaviour? Is this so the table column will be a Union{Missing,GeomType} rather than Union{Nothing,Geomtype} ?

I guess we can also swap missing to nothing in geometry and keep both behaviours. (I've implemented this now)

[rafaqz]

@visr do you want to have a look at this?

[visr]

Is this so the table column will be a Union{Missing,GeomType} rather than Union{Nothing,Geomtype} ?

Yes this behavior was intended to copy JSONTables. JSON3 by default parses JSON null to nothing, and serialize both nothing and missing to null. And in Julia null elements in data/tables are usually set to missing. That is why JSONTables put some ifelse(x === nothing, missing, x) code over it, to present nothing as missing in the tables interface.

I'm not sure what the best approach is here.

[rafaqz]

I think how it is now is fine if you take a look at the changes

[visr]

Thanks, this looks good, sorry for the wait.