Tests for delete operator

Author: ShortDevelopment

test/es12/optional-delete.js

@@ -0,0 +1,51 @@
+//-------------------------------------------------------------------------------------------------------
+// Copyright (C) Microsoft. All rights reserved.
+// Copyright (c) ChakraCore Project Contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE.txt file in the project root for full license information.
+//-------------------------------------------------------------------------------------------------------
+
+// @ts-check
+/// <reference path="../UnitTestFramework/UnitTestFramework.js" />
+
+WScript.LoadScriptFile("..\\UnitTestFramework\\UnitTestFramework.js");
+
+const createObj = () => ({ "null": null, "undefined": undefined, something: 42 });
+
+const tests = [
+    {
+        name: "`delete` should successfully delete from opt-chain",
+        body() {
+            const obj = createObj();
+
+            assert.strictEqual(null, obj?.null);
+            assert.isTrue(delete obj?.null);
+            assert.strictEqual(undefined, obj?.null);
+
+            assert.strictEqual(undefined, obj?.undefined);
+            assert.isTrue(delete obj?.undefined);
+            assert.strictEqual(undefined, obj?.undefined);
+
+            assert.strictEqual(42, obj?.something);
+            assert.isTrue(delete obj?.something);
+            assert.strictEqual(undefined, obj?.something);
+        }
+    },
+    {
+        name: "`delete` should return `true` if opt-chain short-circuits",
+        body() {
+            const obj = createObj();
+
+            assert.strictEqual(undefined, obj.doesNotExist);
+            assert.strictEqual(undefined, obj.doesNotExist?.something);
+            assert.isTrue(delete obj.doesNotExist?.something);
+            assert.strictEqual(undefined, obj.doesNotExist?.something);
+
+            assert.strictEqual(undefined, obj?.doesNotExist);
+            assert.strictEqual(undefined, obj?.doesNotExist?.something);
+            assert.isTrue(delete obj?.doesNotExist?.something);
+            assert.strictEqual(undefined, obj?.doesNotExist?.something);
+        }
+    }
+];
+
+testRunner.runTests(tests, { verbose: WScript.Arguments[0] != "summary" });

test/es12/rlexe.xml

@@ -17,5 +17,9 @@
       <files>optional-async.js</files>
       <compile-flags>-args summary -endargs</compile-flags>
     </default>
+    <default>
+      <files>optional-delete.js</files>
+      <compile-flags>-args summary -endargs</compile-flags>
+    </default>
   </test>
 </regress-exe>