Iterate over all inclusive ancestors using an ES6 iterator

Author: Joris-van-der-Wel

lib/SymbolTree.js

@@ -379,6 +379,46 @@ class SymbolTree {
                 return iterator;
         }
 
+        /**
+         * Iterate over all inclusive ancestors of the given object
+         *
+         * `O(1)` for a single iteration
+         *
+         * @method ancestorsIterator
+         * @memberOf module:symbol-tree#
+         * @param {Object} object
+         * @return {Object} An iterable iterator (ES6)
+         */
+        ancestorsIterator(object) {
+                const _node = this._node.bind(this);
+
+                let nextObject = object;
+                const iterator = {};
+
+                iterator.next = function() {
+                        if (!nextObject) {
+                                return {
+                                        done  : true,
+                                        value : object
+                                };
+                        }
+
+                        const value = nextObject;
+                        nextObject = _node(nextObject).parent;
+
+                        return {
+                                done  : false,
+                                value : value
+                        };
+                };
+
+                iterator[Symbol.iterator] = function() {
+                        return iterator;
+                };
+
+                return iterator;
+        }
+
         /**
          * Iterate over all descendants of the given object (in tree order).
          *

test/SymbolTree.js

@@ -777,6 +777,34 @@ test('ancestorsToArray with filter', function(t) {
         t.end();
 });
 
+test('ancestors iterator', function(t) {
+        const tree = new SymbolTree();
+        const a = {};
+        const aa = {};
+        const ab = {};
+        const aba = {};
+        const abaa = {};
+        const b = {};
+
+        tree.insertLast(aa, a);
+        tree.insertLast(ab, a);
+        tree.insertLast(aba, ab);
+        tree.insertLast(abaa, aba);
+        tree.insertAfter(b, a);
+
+        const results = [];
+        const iterator = tree.ancestorsIterator(abaa);
+
+        for (const object of iterator) {
+                results.push(object);
+        }
+        t.deepEqual([abaa, aba, ab, a], results);
+        t.deepEqual({done: true, value: abaa}, iterator.next());
+        t.deepEqual({done: true, value: abaa}, iterator.next()); // should keep returning done: true
+
+        t.end();
+});
+
 test('treeToArray', function(t) {
         const tree = new SymbolTree();
         const a = {};