Handle multipolygons with empty polygons

src/ol/geom/flat/deflate.js

@@ -94,6 +94,9 @@ export function deflateMultiCoordinatesArray(
       stride,
       endss[i]
     );
+    if (ends.length === 0) {
+      ends[0] = offset;
+    }
     endss[i++] = ends;
     offset = ends[ends.length - 1];
   }

src/ol/geom/flat/inflate.js

@@ -79,7 +79,10 @@ export function inflateMultiCoordinatesArray(
   let i = 0;
   for (let j = 0, jj = endss.length; j < jj; ++j) {
     const ends = endss[j];
-    coordinatesss[i++] = inflateCoordinatesArray(
+    coordinatesss[i++] =
+      ends.length === 1 && ends[0] === offset
+        ? []
+        : inflateCoordinatesArray(
             flatCoordinates,
             offset,
             ends,

test/node/ol/format/GeoJSON.test.js

@@ -516,6 +516,26 @@ describe('ol/format/GeoJSON.js', function () {
       expect(array[1]).to.be.a(LineString);
       expect(array[1].getLayout()).to.eql('XY');
     });
+
+    it('works with empty coordinate arrays', function () {
+      const coordinates = [
+        [
+          [
+            [1, 2],
+            [3, 4],
+            [5, 6],
+            [1, 2],
+          ],
+        ],
+        [],
+      ];
+      const geojson = {
+        type: 'MultiPolygon',
+        coordinates: coordinates,
+      };
+      const geometry = format.readGeometry(geojson);
+      expect(geometry.getCoordinates()).to.eql(coordinates);
+    });
   });
 
   describe('#readProjection', function () {
@@ -1025,5 +1045,28 @@ describe('ol/format/GeoJSON.js', function () {
         [43, 39],
       ]);
     });
+
+    it('works with empty coordinate arrays', function () {
+      const coordinates = [
+        [
+          [
+            [1, 2],
+            [3, 4],
+            [5, 6],
+            [1, 2],
+          ],
+        ],
+        [],
+      ];
+      const geometry = new MultiPolygon([
+        new Polygon(coordinates[0]),
+        new Polygon(coordinates[1]),
+      ]);
+      const geojson = format.writeGeometryObject(geometry);
+      expect(geojson).to.eql({
+        type: 'MultiPolygon',
+        coordinates: coordinates,
+      });
+    });
   });
 });

test/node/ol/geom/MultiPolygon.test.js

@@ -322,6 +322,7 @@ describe('ol/geom/MultiPolygon.js', function () {
         [cw, ccw],
         [cw2, ccw2],
       ]);
+      const withEmptyPolygon = new MultiPolygon([[ccw], []]);
 
       it('returns coordinates as they were constructed', function () {
         expect(right.getCoordinates()).to.eql([
@@ -332,6 +333,7 @@ describe('ol/geom/MultiPolygon.js', function () {
           [cw, ccw],
           [cw2, ccw2],
         ]);
+        expect(withEmptyPolygon.getCoordinates()).to.eql([[ccw], []]);
       });
 
       it('can return coordinates with right-hand orientation', function () {