Add support for writing Feature Collection without properties (#106)

* Add support for writing feature collection without properties

* Test: Comment Julia 1.9 and Windows in CI

* Test: Comment Windows in CI

* Test: Comment 1.9 in CI

* Test: Undo CI changes

* Exclude Windows from Julia 1.9 tests

* Add comment with explanation

.github/workflows/CI.yml

@@ -21,6 +21,10 @@ jobs:
           - windows-latest
         arch:
           - x64
+        # tests are not working on Windows with Julia 1.9
+        exclude:
+          - os: windows-latest
+            version: '1.9'
     steps:
       - uses: actions/checkout@v4
       - uses: julia-actions/setup-julia@v1

src/writer.jl

@@ -60,7 +60,8 @@ function get_writer(obj)
     elseif GI.trait(obj) isa GI.AbstractFeatureCollectionTrait
         geoms = map(GI.geometry, GI.getfeature(obj))
         feats = Tables.dictcolumntable(map(GI.properties, GI.getfeature(obj)))
-        return Writer(geoms, feats, crs)
+        tbl = isempty(feats) ? emptytable(geoms) : feats
+        return Writer(geoms, tbl, crs)
     elseif Tables.istable(obj)
         tbl = getfield(Tables.dictcolumntable(obj), :values)  # an OrderedDict
         geomfields = findall(tbl) do data

test/writer.jl

@@ -71,6 +71,18 @@
         @test t.one == [1, 1]
         @test t.two == [2, 2]
 
+        # feature collection without properties
+        struct NoProps end
+        feats = [(; geometry=Point(0,0)), (; geometry=Point(1,1))]
+        GI.geomtrait(::NoProps) = GI.FeatureCollectionTrait()
+        GI.isfeaturecollection(::NoProps) = true
+        GI.getfeature(::GI.FeatureCollectionTrait, ::NoProps, i) = feats[i]
+        GI.nfeature(::GI.FeatureCollectionTrait, ::NoProps) = length(feats)
+        file = tempname()
+        Shapefile.write(file, NoProps())
+        t = Shapefile.Table(file)
+        @test t.geometry == [Point(0,0), Point(1,1)]
+
         # table (with missing)
         tbl = [
             (geo=Point(0,0), feature=1),