Support reading polygons with curve rings

src/ol/format/GML3.js

@@ -134,6 +134,27 @@ class GML3 extends GMLBase {
     }
   }
 
+  /**
+   * @param {Element} node Node.
+   * @param {Array<*>} objectStack Object stack.
+   * @return {Array<number>|undefined} Polygon.
+   */
+  readFlatCurveRing(node, objectStack) {
+    /** @type {Array<LineString>} */
+    const lineStrings = pushParseAndPop(
+      [],
+      this.MULTICURVE_PARSERS,
+      node,
+      objectStack,
+      this
+    );
+    const flatCoordinates = [];
+    for (let i = 0, ii = lineStrings.length; i < ii; ++i) {
+      extend(flatCoordinates, lineStrings[i].getFlatCoordinates());
+    }
+    return flatCoordinates;
+  }
+
   /**
    * @param {Element} node Node.
    * @param {Array<*>} objectStack Object stack.
@@ -1162,6 +1183,17 @@ GML3.prototype.SEGMENTS_PARSERS = {
   },
 };
 
+/**
+ * @const
+ * @type {Object<string, Object<string, import("../xml.js").Parser>>}
+ */
+GMLBase.prototype.RING_PARSERS = {
+  'http://www.opengis.net/gml': {
+    'LinearRing': makeReplacer(GMLBase.prototype.readFlatLinearRing),
+    'Ring': makeReplacer(GML3.prototype.readFlatCurveRing),
+  },
+};
+
 /**
  * Encode an array of features in GML 3.1.1 Simple Features.
  *

src/ol/format/GML32.js

@@ -4,7 +4,12 @@
 import GML2 from './GML2.js';
 import GML3 from './GML3.js';
 import GMLBase from './GMLBase.js';
-import {makeArrayPusher, makeChildAppender, makeReplacer} from '../xml.js';
+import {
+  makeArrayExtender,
+  makeArrayPusher,
+  makeChildAppender,
+  makeReplacer,
+} from '../xml.js';
 import {writeStringTextNode} from '../format/xsd.js';
 
 /**
@@ -249,6 +254,7 @@ GML32.prototype.POLYGONMEMBER_PARSERS = {
 GML32.prototype.RING_PARSERS = {
   'http://www.opengis.net/gml/3.2': {
     'LinearRing': makeReplacer(GMLBase.prototype.readFlatLinearRing),
+    'Ring': makeReplacer(GML32.prototype.readFlatCurveRing),
   },
 };