Merge branch 'master' into multiple_geos_versions_in_ci

geos/entrypoints.go

@@ -15,6 +15,16 @@ package geos
 GEOSGeometry *GEOSMakeValid_r(GEOSContextHandle_t handle, const GEOSGeometry* g) { return NULL; }
 #endif
 
+#define COVERAGE_UNION_MIN_VERSION "3.8.0"
+#define COVERAGE_UNION_MISSING ( \
+	GEOS_VERSION_MAJOR < 3 || \
+	(GEOS_VERSION_MAJOR == 3 && GEOS_VERSION_MINOR < 8) \
+)
+#if COVERAGE_UNION_MISSING
+// This stub implementation always fails:
+GEOSGeometry *GEOSCoverageUnion_r(GEOSContextHandle_t handle, const GEOSGeometry* g) { return NULL; }
+#endif
+
 */
 import "C"
 
@@ -337,3 +347,29 @@ func MakeValid(g geom.Geometry, opts ...geom.ConstructorOption) (geom.Geometry,
 	})
 	return result, wrap(err, "executing GEOSMakeValid_r")
 }
+
+// The CoverageUnion function is used to union polygonal inputs that form a
+// coverage, which are typically provided as a GeometryCollection. This method
+// is much faster than other unioning methods, but there are some constraints
+// that must be met by the inputs to form a valid polygonal coverage. These
+// constraints are:
+//
+//  1. all input geometries must be polygonal,
+//  2. the interiors of the inputs must not intersect, and
+//  3. the common boundaries of adjacent polygons have the same set of vertices in both polygons.
+//
+// It should be noted that while CoverageUnion may detect constraint violations
+// and return an error, but this is not guaranteed, and an invalid result may
+// be returned without an error. It is the responsibility of the caller to
+// ensure that the constraints are met before using this function.
+func CoverageUnion(g geom.Geometry, opts ...geom.ConstructorOption) (geom.Geometry, error) {
+	if C.COVERAGE_UNION_MISSING != 0 {
+		return geom.Geometry{}, unsupportedGEOSVersionError{
+			C.COVERAGE_UNION_MIN_VERSION, "CoverageUnion",
+		}
+	}
+	result, err := unaryOpG(g, opts, func(ctx C.GEOSContextHandle_t, g *C.GEOSGeometry) *C.GEOSGeometry {
+		return C.GEOSCoverageUnion_r(ctx, g)
+	})
+	return result, wrap(err, "executing GEOSCoverageUnion_r")
+}

geos/entrypoints_test.go

@@ -829,3 +829,80 @@ func TestMakeValid(t *testing.T) {
 		})
 	}
 }
+
+func TestCoverageUnion(t *testing.T) {
+	for i, tc := range []struct {
+		input   string
+		output  string
+		wantErr bool
+	}{
+		{
+			// Noded correctly (shared edge).
+			input: `GEOMETRYCOLLECTION(
+				POLYGON((0 0,0 1,1 0,0 0)),
+				POLYGON((1 1,0 1,1 0,1 1))
+			)`,
+			output: `POLYGON((0 0,0 1,1 1,1 0,0 0))`,
+		},
+		{
+			// Noded correctly (shared vertex but no shared edge).
+			input: `GEOMETRYCOLLECTION(
+				POLYGON((0 0,0 1,1 1,1 0,0 0)),
+				POLYGON((1 1,1 2,2 2,2 1,1 1))
+			)`,
+			output: `MULTIPOLYGON(((0 0,0 1,1 1,1 0,0 0)),((1 1,1 2,2 2,2 1,1 1)))`,
+		},
+		{
+			// Noded correctly (completely disjoint).
+			input: `GEOMETRYCOLLECTION(
+				POLYGON((0 0,0 1,1 1,1 0,0 0)),
+				POLYGON((2 2,2 3,3 3,3 2,2 2))
+			)`,
+			output: `MULTIPOLYGON(((0 0,0 1,1 1,1 0,0 0)),((2 2,2 3,3 3,3 2,2 2)))`,
+		},
+		{
+			// Input constraint violated: inputs overlap.
+			input: `GEOMETRYCOLLECTION(
+				POLYGON((0 0,0 1,1 0,0 0)),
+				POLYGON((0 0,0 1,1 1,1 0,0 0))
+			)`,
+			wantErr: true,
+		},
+		{
+			// Input constraint violated: inputs overlap and not noded correctly.
+			input: `GEOMETRYCOLLECTION(
+				POLYGON((0 0,0 1,1 0,0 0)),
+				POLYGON((0 0,0 1,1 1,0 0))
+			)`,
+			wantErr: true,
+		},
+		{
+			// Input constraint violated: not noded correctly.
+			input: `GEOMETRYCOLLECTION(
+				POLYGON((0 0,0 1,1 1,1 0,0 0)),
+				POLYGON((0 1,2 1,2 2,0 2,0 1))
+			)`,
+			wantErr: true,
+		},
+		{
+			// Input constraint violation: not everything is a polygon.
+			input:   `GEOMETRYCOLLECTION(POINT(1 2),POLYGON((0 0,0 1,1 0,0 0)))`,
+			wantErr: true,
+		},
+	} {
+		t.Run(strconv.Itoa(i), func(t *testing.T) {
+			in := geomFromWKT(t, tc.input)
+			gotGeom, err := CoverageUnion(in)
+			if _, ok := err.(unsupportedGEOSVersionError); ok {
+				t.Skip(err)
+			}
+			if tc.wantErr {
+				expectErr(t, err)
+			} else {
+				expectNoErr(t, err)
+				wantGeom := geomFromWKT(t, tc.output)
+				expectGeomEq(t, gotGeom, wantGeom, geom.IgnoreOrder)
+			}
+		})
+	}
+}