Add LegacyAdapters.sortStable()

octogonz · octogonz · commit e5eaedaf17ba · 2019-11-02T13:08:59.000-07:00
diff --git a/libraries/node-core-library/src/LegacyAdapters.ts b/libraries/node-core-library/src/LegacyAdapters.ts
@@ -1,6 +1,9 @@
 // Copyright (c) Microsoft Corporation. All rights reserved. Licensed under the MIT license.
 // See LICENSE in the project root for license information.
 
+import { sort as timsort } from 'timsort';
+import * as semver from 'semver';
+
 /**
  * Callback used by {@link LegacyAdapters}.
  * @public
@@ -12,6 +15,8 @@ export type LegacyCallback<TResult, TError> = (error: TError, result: TResult) =
  * @public
  */
 export class LegacyAdapters {
+  private static _useTimsort: boolean | undefined = undefined;
+
   /**
    * This function wraps a function with a callback in a promise.
    */
@@ -94,4 +99,23 @@ export class LegacyAdapters {
       return errorObject;
     }
   }
+
+  /**
+   * Prior to Node 11.x, the `Array.sort()` algorithm is not guaranteed to be stable.
+   * If you need a stable sort, you can use the `sortStable()` as a workaround.
+   *
+   * @remarks
+   * On NodeJS 11.x and later, this method simply calls the native `Array.sort()`.
+   * For earlier versions, it uses an implementation of Timsort, which is the same algorithm used by modern NodeJS.
+   */
+  public static sortStable<T>(array: T[], compare?: (a: T, b: T) => number): void {
+    if (LegacyAdapters._useTimsort === undefined) {
+      LegacyAdapters._useTimsort = semver.major(process.versions.node) < 11;
+    }
+    if (LegacyAdapters._useTimsort) {
+      timsort(array, compare);
+    } else {
+      Array.prototype.sort.call(array, compare);
+    }
+  }
 }
