fix(polar): forgot to commit a new file

src/chart/helper/sectorHelper.ts

@@ -0,0 +1,41 @@
+/*
+* Licensed to the Apache Software Foundation (ASF) under one
+* or more contributor license agreements.  See the NOTICE file
+* distributed with this work for additional information
+* regarding copyright ownership.  The ASF licenses this file
+* to you under the Apache License, Version 2.0 (the
+* "License"); you may not use this file except in compliance
+* with the License.  You may obtain a copy of the License at
+*
+*   http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing,
+* software distributed under the License is distributed on an
+* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+* KIND, either express or implied.  See the License for the
+* specific language governing permissions and limitations
+* under the License.
+*/
+
+import type Model from '../../model/Model';
+import type Sector from 'zrender/src/graphic/shape/Sector';
+import { isArray, map } from 'zrender/src/core/util';
+import { parsePercent } from 'zrender/src/contain/text';
+
+export function getSectorCornerRadius(
+    model: Model<{ borderRadius?: string | number | (string | number)[] }>,
+    shape: Pick<Sector['shape'], 'r0' | 'r'>,
+    zeroIfNull?: boolean
+) {
+    let cornerRadius = model.get('borderRadius');
+    if (cornerRadius == null) {
+        return zeroIfNull ? { cornerRadius: 0 } : null;
+    }
+    if (!isArray(cornerRadius)) {
+        cornerRadius = [cornerRadius, cornerRadius, cornerRadius, cornerRadius];
+    }
+    const dr = Math.abs(shape.r || 0 - shape.r0 || 0);
+    return {
+        cornerRadius: map(cornerRadius, cr => parsePercent(cr, dr))
+    };
+}