Merge pull request #8 from JuliaGeo/feat/metadata

Add metadata passthrough

Author: evetion

src/io.jl

@@ -14,17 +14,32 @@ function write(path, t; geocolumns=GeoInterface.geometrycolumns(t), crs=GeoInter
         dcrs = Dict("crs" => GeoFormatTypes.val(jcrs))
     end
     ct = Tables.columntable(t)
-    colmetadata = Dict{Symbol,Vector{Pair{String,String}}}()
+    metadata = DataAPI.metadata(t)
+    if !isnothing(metadata)
+        metadata = (k=>string(v) for (k,v) in pairs(metadata))
+    end
+    colmetadata = Dict{Symbol,Dict{String,String}}()
+    tcolmetadata = DataAPI.colmetadata(t)
+    if !isnothing(tcolmetadata)
+        for (k, v) in pairs(tcolmetadata)
+            colmetadata[k] = Dict(k=>string(v) for (k, v) in pairs(v))
+        end
+    end
     for column in geocolumns
         column in Tables.columnnames(t) || error("Geometry column $column not found in table")
         data = Tables.getcolumn(t, column)
         T = nonmissingtype(Tables.columntype(t, column))
         GeoInterface.isgeometry(T) || error("Geometry in $column must support the GeoInterface")
         ct = merge(ct, NamedTuple{(column,)}((Wrapper.(Ref(encoding), data),)))
 
-        colmetadata[column] = ["ARROW:extension:metadata" => JSON3.write(dcrs)]
+        geometa = Dict("ARROW:extension:metadata" => JSON3.write(dcrs))
+        if haskey(colmetadata, column)
+            merge!(colmetadata[column], geometa)
+        else
+            colmetadata[column] = geometa
+        end
     end
-    Arrow.write(path, ct; colmetadata, kwargs...)
+    Arrow.write(path, ct; metadata, colmetadata, kwargs...)
 end
 
 """

src/type.jl

@@ -16,6 +16,10 @@ GeoInterface.isgeometry(::Type{<:Geometry}) = true
 GeoInterface.ncoord(_, ::Geometry{X,D}) where {X,D} = D
 GeoInterface.getcoord(::PointTrait, g::Geometry, i) = Base.getindex(g.geom, i)
 GeoInterface.getcoord(::PointTrait, g::Geometry{X,D,T,<:GeoFormatTypes.MixedFormat}, i) where {X,D,T} = getcoord(PointTrait(), g.geom, i)
+GeoInterface.x(t::PointTrait, g::Geometry) = getcoord(t, g, 1)
+GeoInterface.y(t::PointTrait, g::Geometry) = getcoord(t, g, 2)
+# GeoInterface.z(t::PointTrait, g::Geometry) = getcoord(t, g, 3)  # TODO Fix!
+GeoInterface.m(t::PointTrait, g::Geometry) = getcoord(t, g, 4)
 GeoInterface.geomtrait(::Geometry{X}) where {X} = X()
 GeoInterface.ngeom(_, g::Geometry) = length(g.geom)
 GeoInterface.ngeom(t, g::Geometry{X,D,T,<:GeoFormatTypes.MixedFormat}) where {X,D,T} = ngeom(t, g.geom)

test/runtests.jl

@@ -6,6 +6,7 @@ using Test
 using GeoFormatTypes
 using DataFrames
 using Extents
+using DataAPI
 
 mkpath(joinpath(@__DIR__, "data/write"))
 
@@ -111,4 +112,15 @@ mkpath(joinpath(@__DIR__, "data/write"))
         dfn = GeoArrow.read("simple.arrow")
         @test GeoInterface.isgeometry(dfn.geometry[1])
     end
+    @testset "Metadata" begin
+        df = DataFrame(a=1, geometry=[(1.,2.)])        
+        DataAPI.metadata!(df, "author", "test")
+        DataAPI.colmetadata!(df, :a, "description", "A normal column")
+        DataAPI.colmetadata!(df, :geometry, "description", "A point geometry")
+        GeoArrow.write("metadata.arrow", df)
+        dfn = GeoArrow.read("metadata.arrow")
+        @test DataAPI.metadata(dfn)["author"] == "test"
+        @test DataAPI.colmetadata(dfn)[:a]["description"] == "A normal column"
+        @test DataAPI.colmetadata(dfn)[:geometry]["description"] == "A point geometry"
+    end
 end