geo: SpatialObjectToWKT() omits empty shapes in collections

[erikgrinaker]

Describe the problem

While implementing ST_ForceCollection, I have a test case which generates a geometry collection with an empty point. However, calling geo.SpatialObjectToWKT omits the empty point from the output.

To Reproduce

func TestEmptyPointWKT(t *testing.T) {
	gc := geom.NewGeometryCollection().SetSRID(int(geopb.DefaultGeographySRID))
	gc.MustPush(geom.NewPointEmpty(geom.XY))
	g, err := geo.MakeGeographyFromGeomT(gc)
	require.NoError(t, err)
	wkt, err := geo.SpatialObjectToWKT(g.SpatialObject(), 0)
	require.NoError(t, err)
	require.EqualValues(t, "GEOMETRYCOLLECTION (POINT EMPTY)", wkt)
}

This yields a test failure:

Not equal: 
expected: string("GEOMETRYCOLLECTION (POINT EMPTY)")
actual  : geopb.WKT("GEOMETRYCOLLECTION EMPTY")

PostGIS can represent this just fine:

postgis=# select st_astext(st_forcecollection('POINT EMPTY'));
            st_astext            
---------------------------------
 GEOMETRYCOLLECTION(POINT EMPTY)
(1 row)

Environment:

• CockroachDB version: master at 8b91062f93
• Server OS: macOS
• Client app: cockroach demo

CC @otan

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[otan]

It's this if condition in go-geom -- https://github.com/twpayne/go-geom/blob/master/encoding/wkt/encode.go#L96 -- it should be changed to NumGeoms() == 0.

Feel free to change it, if not I'll get to it on Monday.

[erikgrinaker]

Opened a go-geom PR here: twpayne/go-geom#184