Add cmprefimpl (PostGIS) tests for Dump

internal/cmprefimpl/cmppg/checks.go

@@ -453,6 +453,39 @@ func CheckForceOrientation(t *testing.T, want UnaryResult, g geom.Geometry) {
 	})
 }
 
+func CheckDump(t *testing.T, want UnaryResult, g geom.Geometry) {
+	if g.IsEmpty() {
+		// For empty geometries, PostGIS just returns no dumped geometries.
+		// Simplefeatures chooses not to do this behaviour to provide better
+		// consistency when it comes to Multi or GeometryCollections that
+		// contain only empty elements. If we were to follow the PostGIS
+		// behaviour, then 'MULTIPOLYGON(EMPTY)' would return 0 dumped
+		// geometries, whereas 'MULTIPOLYGON(((0 0,0 1,1 0,0 0)),EMPTY)' would
+		// return 2 dumped geometries (triangle, and empty polygon).
+		return
+	}
+	t.Run("CheckDump", func(t *testing.T) {
+		got := g.Dump()
+		if len(got) != len(want.Dump) {
+			for i, g := range got {
+				t.Logf("got %d: %s", i, g.AsText())
+			}
+			for i, g := range want.Dump {
+				t.Logf("want %d: %s", i, g.AsText())
+			}
+			t.Errorf("length mismatch, got=%d want=%d", len(got), len(want.Dump))
+		} else {
+			for i, g := range got {
+				if !geom.ExactEquals(g, want.Dump[i], geom.ToleranceXY(0.00001)) {
+					t.Logf("got:  %s", g.AsText())
+					t.Logf("want: %s", want.Dump[i].AsText())
+					t.Errorf("mismatch at position %d", i)
+				}
+			}
+		}
+	})
+}
+
 func containsOnlyPolygonsOrMultiPolygons(g geom.Geometry) bool {
 	switch g.Type() {
 	case geom.TypePolygon, geom.TypeMultiPolygon:

internal/cmprefimpl/cmppg/fuzz_test.go

@@ -57,6 +57,7 @@ func TestFuzz(t *testing.T) {
 			CheckReverse(t, want, g)
 			CheckType(t, want, g)
 			CheckForceOrientation(t, want, g)
+			CheckDump(t, want, g)
 		})
 	}
 }

internal/cmprefimpl/cmppg/pg.go

@@ -4,6 +4,7 @@ import (
 	"database/sql"
 	"strings"
 
+	"github.com/lib/pq"
 	"github.com/peterstace/simplefeatures/geom"
 )
 
@@ -33,6 +34,7 @@ type UnaryResult struct {
 	Force4D    geom.Geometry
 	ForceCW    geom.Geometry
 	ForceCCW   geom.Geometry
+	Dump       []geom.Geometry
 }
 
 const (
@@ -47,6 +49,7 @@ func (p BatchPostGIS) Unary(g geom.Geometry) (UnaryResult, error) {
 	var boundaryWKT sql.NullString
 	var convexHullWKT string
 	var reverseWKT string
+	var dumpWKTs []string
 
 	var result UnaryResult
 	err := p.db.QueryRow(`
@@ -110,7 +113,9 @@ func (p BatchPostGIS) Unary(g geom.Geometry) (UnaryResult, error) {
 		ST_AsBinary(ST_Force4D(ST_GeomFromWKB($1))),
 
 		ST_AsBinary(ST_ForcePolygonCW(ST_GeomFromWKB($1))),
-		ST_AsBinary(ST_ForcePolygonCCW(ST_GeomFromWKB($1)))
+		ST_AsBinary(ST_ForcePolygonCCW(ST_GeomFromWKB($1))),
+
+		array_agg(ST_AsText(geom)) FROM ST_Dump(ST_GeomFromWKB($1))
 
 		`, g, isNestedGeometryCollection(g), g.AsText(),
 	).Scan(
@@ -135,6 +140,7 @@ func (p BatchPostGIS) Unary(g geom.Geometry) (UnaryResult, error) {
 		&result.Force4D,
 		&result.ForceCW,
 		&result.ForceCCW,
+		pq.Array(&dumpWKTs),
 	)
 	if err != nil {
 		return result, err
@@ -160,6 +166,14 @@ func (p BatchPostGIS) Unary(g geom.Geometry) (UnaryResult, error) {
 
 	// remove ST_ prefix that ST_GeometryType returned, since we don't want ST_ prefix in our type
 	result.Type = strings.TrimPrefix(result.Type, postgisTypePrefix)
+
+	for _, wkt := range dumpWKTs {
+		dumpGeom, err := geom.UnmarshalWKT(wkt)
+		if err != nil {
+			return result, err
+		}
+		result.Dump = append(result.Dump, dumpGeom)
+	}
 	return result, nil
 }