Add metadata passthrough.

src/io.jl

@@ -94,17 +94,27 @@ function read(driver::ArchGDALDriver, fn::AbstractString; layer = nothing, kwarg
 end
 
 function read(::ArchGDALDriver, ds, layer)
-    df, gnames, sr = AG.getlayer(ds, layer) do table
+    df, gnames, sr, metadata = AG.getlayer(ds, layer) do table
         if table.ptr == C_NULL
             throw(
                 ArgumentError(
                     "Given layer id/name doesn't exist. For reference this is the dataset:\n$ds",
                 ),
             )
         end
+        domains = AG.GDAL.gdalgetmetadatadomainlist(table.ptr)
+        metadata = Dict{String, Any}()
+        for domain in domains
+            if domain == ""
+                merge!(metadata, dictstring(AG.GDAL.gdalgetmetadata(table.ptr, domain)))
+            else
+                metadata[domain] = dictstring(AG.GDAL.gdalgetmetadata(table.ptr, domain))
+            end
+        end
         names, x = AG.schema_names(AG.layerdefn(table))
         sr = AG.getspatialref(table)
-        return DataFrame(table), names, sr
+        df = DataFrame(table)
+        return df, names, sr, metadata
     end
     if "" in names(df)
         rename!(df, Symbol("") => :geometry)
@@ -115,6 +125,10 @@ function read(::ArchGDALDriver, ds, layer)
     end
     crs = sr.ptr == C_NULL ? nothing : GFT.WellKnownText(GFT.CRS(), AG.toWKT(sr))
     geometrycolumns = Tuple(gnames)
+
+    for (k, v) in pairs(metadata)
+        DataAPI.metadata!(df, k, v, style = :note)
+    end
     metadata!(df, "crs", crs; style = :note)
     metadata!(df, "geometrycolumns", geometrycolumns; style = :note)
 
@@ -270,6 +284,10 @@ function write(
                     push!(fieldindices, AG.findfieldindex(layer, name, false))
                 end
 
+                if DataAPI.metadatasupport(typeof(table)).read
+                    setmetadatalayer!(layer, table)
+                end
+
                 for chunk in Iterators.partition(rows, chunksize)
                     can_use_transaction &&
                         AG.GDAL.gdaldatasetstarttransaction(ds.ptr, false)
@@ -308,12 +326,15 @@ function write(
                 end
                 if !can_create_layer
                     @warn "Can't create layers in this format, copying from memory instead."
-                    AG.copy(
+                    nlayer = AG.copy(
                         layer;
                         dataset = ds,
                         name = layer_name,
                         options = stringlist(options),
                     )
+                    if DataAPI.metadatasupport(typeof(table)).read
+                        setmetadatalayer!(nlayer, table)
+                    end
                 end
             end
         end

src/utils.jl

@@ -6,6 +6,38 @@ function stringlist(dict::Dict{String, String})
     return sv
 end
 
+function dictstring(sv::Vector{String})
+    dict = Dict{String, String}()
+    for s in sv
+        kv = split(s, '=', limit=2)
+        if length(kv) == 2
+            dict[kv[1]] = kv[2]
+        else
+            @warn "Ignoring key-value metadata string: $s"
+        end
+    end
+    return dict
+end
+
+function setmetadatalayer!(layer, table)
+    for (k, v) in DataAPI.metadata(table)
+        if v isa Dict
+            for (dk, dv) in pairs(v)
+                @debug "Writing metadata item $dk = $dv for domain $k"
+                AG.GDAL.gdalsetmetadataitem(
+                    layer.ptr,
+                    string(dk),
+                    string(dv),
+                    string(k),
+                )
+            end
+        else
+            @debug "Writing metadata item $k = $v for domain ''"
+            AG.GDAL.gdalsetmetadataitem(layer.ptr, string(k), string(v), "")
+        end
+    end
+end
+
 function getgeometrycolumns(table)
     if GI.isfeaturecollection(table)
         return GI.geometrycolumns(table)

test/runtests.jl

@@ -25,6 +25,9 @@ end
     t = GDF.read(fn)
     @test nrow(t) == 42
     @test "ID" in names(t)
+
+    @test DataAPI.metadata(t)["DBF_DATE_LAST_UPDATE"] == "2007-08-16"
+    @test DataAPI.metadata(t)["SHAPEFILE"] isa Dict
 end
 
 @testitem "Read non-existent shapefile" setup = [Setup] begin
@@ -466,6 +469,19 @@ end
     @test length(df2.geometry) == 5
 end
 
+@testitem "Metadata" setup = [Setup] 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")
+    GeoDataFrames.write("metadata.gpkg", df)
+    dfn = GeoDataFrames.read("metadata.gpkg")
+    @test DataAPI.metadata(dfn)["author"] == "test"
+    # Column metadata is not supported by GDAL
+    @test isnothing(get(DataAPI.colmetadata(dfn), :a, nothing))
+    @test isnothing(get(DataAPI.colmetadata(dfn), :geometry, nothing))
+end
+
 filter(ti) = !(:nowindows in ti.tags && Sys.iswindows())
 
 @run_package_tests filter = filter