fix isShared bug, making regression test pass

Author: Craig Macomber

b+tree.js

@@ -3,10 +3,12 @@ var __extends = (this && this.__extends) || (function () {
     var extendStatics = function (d, b) {
         extendStatics = Object.setPrototypeOf ||
             ({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
-            function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
+            function (d, b) { for (var p in b) if (Object.prototype.hasOwnProperty.call(b, p)) d[p] = b[p]; };
         return extendStatics(d, b);
     };
     return function (d, b) {
+        if (typeof b !== "function" && b !== null)
+            throw new TypeError("Class extends value " + String(b) + " is not a constructor or null");
         extendStatics(d, b);
         function __() { this.constructor = d; }
         d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
@@ -979,9 +981,16 @@ var BTree = /** @class */ (function () {
             return typeof r === "number" ? r : r.break;
         }
         finally {
-            while (root.keys.length <= 1 && !root.isLeaf)
+            var isShared = undefined;
+            while (root.keys.length <= 1 && !root.isLeaf) {
+                isShared || (isShared = root.isShared);
                 this._root = root = root.keys.length === 0 ? EmptyLeaf :
                     root.children[0];
+            }
+            // If any ancestor of the new root was shared, the new root must also be shared
+            if (isShared) {
+                root.isShared = true;
+            }
         }
     };
     /** Same as `editRange` except that the callback is called for all pairs. */

b+tree.ts

@@ -1094,9 +1094,16 @@ export default class BTree<K=any, V=any> implements ISortedMapF<K,V>, ISortedMap
       var r = root.forRange(low, high, includeHigh, true, this, initialCounter || 0, onFound);
       return typeof r === "number" ? r : r.break!;
     } finally {
-      while (root.keys.length <= 1 && !root.isLeaf)
+      let isShared: undefined | true = undefined;
+      while (root.keys.length <= 1 && !root.isLeaf) {
+        isShared ||= root.isShared;
         this._root = root = root.keys.length === 0 ? EmptyLeaf :
                     (root as any as BNodeInternal<K,V>).children[0];
+      }
+      // If any ancestor of the new root was shared, the new root must also be shared
+      if (isShared) {
+        root.isShared = true;
+      }
     }
   }
 

package-lock.json

@@ -58,7 +58,7 @@
     "testpack-cli": "^1.1.4",
     "ts-jest": "^26.4.3",
     "ts-node": "^7.0.1",
-    "typescript": "^3.8.3",
+    "typescript": "^4.0.8",
     "uglify-js": "^3.11.4"
   },
   "dependencies": {},