Add an interface for reverse lookups of package geometry types

[rafaqz]

I'm running some code over a feature collection where I'm converting GeoJSON objects to GeometryBasics objects.

It's annoying because the collection has a mix of geometry types, so I have to check for each type and find the correct GeometryBasics.jl object to convert to.

If we had a method like GeometryBasics.geomtrait_type(PolygonTrait()) I could use that like

convert(GeometryBasics.geomtrait_type(geomtrait_type(mygeom)), mygeom)

And the code would be generic for all objects GeometryBasics.jl actually implements.

This wouldn't be an interface method, but a package method with a consistent name across all packages so users can find it. A way to make it an actual interface method could be to dispatch on the Symbol name of the package like :

# In GeoInterface.jl
geomtrait_type(mod::Module, trait) = geomtrait_type(Val{nameof(mod)}(), trait)
# In the package
GeoInterface.geomtrait_type(::Val{:GeoJSON}, trait::GeoInterface.PolygonTrait) = Polygon 

but it's a bit of a hack and ignores that package UUIDs allow multiple identical named packages.

It would also be amazing to do:

convert(GeometryBasics, mygeom)
convert(ArchGDAL, mygeom)

And it just works without knowing the package geometry type. This method would be a step in that direction.

[evetion]

Fully agree, I think I described it somewhere as convert(::Module, geom), although that might not be the best API.

[rafaqz]

Do you think that in practice we can ignore that multiple packages can have the same name and dispatch on ::Val{:ModuleName}? It's pretty unlikely there will be two of any package name, but still not strictly correct.

[evetion]

I'd say yeah, let's ignore it, although it would be good to check what kind of error you would get if it happens (creating a clone package locally or similar). Probably just overwrites the method definition?

[rafaqz]

I think whatever package is loaded last will override the method.

[rafaqz]

implemented