fix: allow `HierarchicalLayout` to manage circular dependencies (#233)

Uncomment the isAncestor method GraphHierachyNode, which is used by
HiearchlLayout. The uncommented implementation makes sure, that a
circular dependency is detected and resolved. Using the default
isAncestor does not work at this point, because the parent nodes of the
child nodes in the graph are not set.

The problem was unintentionally introduced during the initial refactoring of
the mxGraph code in 413796a.
The idea of the author was to remove an useless comment but they left an
extra /** behind which commented the isAncestor method.

packages/core/__tests__/view/layout/HierarchicalLayout.test.ts

@@ -0,0 +1,95 @@
+/*
+Copyright 2023-present The maxGraph project Contributors
+
+Licensed 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 { describe, test } from '@jest/globals';
+import { Graph, HierarchicalLayout } from '../../../src';
+
+function createGraph(): Graph {
+  // @ts-ignore - no need for a container, we don't check the view here
+  return new Graph(null);
+}
+
+describe('layout execute', () => {
+  test('Circular layout graph is created successfully', () => {
+    // prepare test
+    const graph: Graph = createGraph();
+    const parent = graph.getDefaultParent();
+    const layout = new HierarchicalLayout(graph);
+
+    // execute test
+    graph.batchUpdate(() => {
+      const v1 = graph.insertVertex(parent, null, '1', 0, 0, 80, 30);
+      const v2 = graph.insertVertex(parent, null, '2', 0, 0, 80, 30);
+      const v3 = graph.insertVertex(parent, null, '3', 0, 0, 80, 30);
+      const v4 = graph.insertVertex(parent, null, '4', 0, 0, 80, 30);
+      const v5 = graph.insertVertex(parent, null, '5', 0, 0, 80, 30);
+      const v6 = graph.insertVertex(parent, null, '6', 0, 0, 80, 30);
+      const v7 = graph.insertVertex(parent, null, '7', 0, 0, 80, 30);
+      const v8 = graph.insertVertex(parent, null, '8', 0, 0, 80, 30);
+      const v9 = graph.insertVertex(parent, null, '9', 0, 0, 80, 30);
+
+      const e1 = graph.insertEdge(parent, null, '', v1, v2);
+      const e2 = graph.insertEdge(parent, null, '', v2, v3);
+      const e3 = graph.insertEdge(parent, null, '', v3, v4);
+      const e4 = graph.insertEdge(parent, null, '', v4, v5);
+      const e5 = graph.insertEdge(parent, null, '', v5, v3);
+      const e6 = graph.insertEdge(parent, null, '', v5, v6);
+      const e7 = graph.insertEdge(parent, null, '', v6, v7);
+      const e8 = graph.insertEdge(parent, null, '', v7, v8);
+      const e9 = graph.insertEdge(parent, null, '', v8, v9);
+
+      // Execute the layout
+      layout.execute(parent);
+    });
+  });
+
+  test('Non-circular layout graph is created successfully', () => {
+    // prepare test
+    const graph: Graph = createGraph();
+    const parent = graph.getDefaultParent();
+    const layout = new HierarchicalLayout(graph);
+
+    // execute test - graph is based on HierarchicalLayout.stories.js
+    graph.batchUpdate(() => {
+      const v1 = graph.insertVertex(parent, null, '1', 0, 0, 80, 30);
+      const v2 = graph.insertVertex(parent, null, '2', 0, 0, 80, 30);
+      const v3 = graph.insertVertex(parent, null, '3', 0, 0, 80, 30);
+      const v4 = graph.insertVertex(parent, null, '4', 0, 0, 80, 30);
+      const v5 = graph.insertVertex(parent, null, '5', 0, 0, 80, 30);
+      const v6 = graph.insertVertex(parent, null, '6', 0, 0, 80, 30);
+      const v7 = graph.insertVertex(parent, null, '7', 0, 0, 80, 30);
+      const v8 = graph.insertVertex(parent, null, '8', 0, 0, 80, 30);
+      const v9 = graph.insertVertex(parent, null, '9', 0, 0, 80, 30);
+
+      const e1 = graph.insertEdge(parent, null, '', v1, v2);
+      const e2 = graph.insertEdge(parent, null, '', v1, v3);
+      const e3 = graph.insertEdge(parent, null, '', v3, v4);
+      const e4 = graph.insertEdge(parent, null, '', v2, v5);
+      const e5 = graph.insertEdge(parent, null, '', v1, v6);
+      const e6 = graph.insertEdge(parent, null, '', v2, v3);
+      const e7 = graph.insertEdge(parent, null, '', v6, v4);
+      const e8 = graph.insertEdge(parent, null, '', v6, v1);
+      const e9 = graph.insertEdge(parent, null, '', v6, v7);
+      const e10 = graph.insertEdge(parent, null, '', v7, v8);
+      const e11 = graph.insertEdge(parent, null, '', v7, v9);
+      const e12 = graph.insertEdge(parent, null, '', v7, v6);
+      const e13 = graph.insertEdge(parent, null, '', v7, v5);
+
+      // Execute the layout
+      layout.execute(parent);
+    });
+  });
+});

packages/core/src/view/layout/datatypes/GraphHierarchyNode.ts

@@ -149,7 +149,6 @@ class GraphHierarchyNode extends GraphAbstractHierarchyCell {
     this.temp[0] = value;
   }
 
-  /**
   isAncestor(otherNode: GraphHierarchyNode): boolean {
     // Firstly, the hash code of this node needs to be shorter than the
     // other node