make '__parent__' property no longer available in ES6

'__parent__' was already removed in 2010 from the browsers (https://whereswalden.com/2010/05/07/spidermonkey-change-du-jour-the-special-__parent__-property-has-been-removed/)

Author: rbri

rhino-tools/src/main/java/org/mozilla/javascript/tools/debugger/Dim.java

@@ -545,7 +545,7 @@ private Object getObjectPropertyImpl(Context cx, Object object, Object id) {
                 result = scriptable;
             } else if (name.equals(NativeObject.PROTO_PROPERTY)) {
                 result = scriptable.getPrototype();
-            } else if (name.equals("__parent__")) {
+            } else if (name.equals(NativeObject.PARENT_PROPERTY)) {
                 result = scriptable.getParentScope();
             } else {
                 result = ScriptableObject.getProperty(scriptable, name);
@@ -595,7 +595,7 @@ private Object[] getObjectIdsImpl(Context cx, Object object) {
                 ids[extra++] = NativeObject.PROTO_PROPERTY;
             }
             if (parent != null) {
-                ids[extra++] = "__parent__";
+                ids[extra++] = NativeObject.PARENT_PROPERTY;
             }
         }
 

rhino/src/main/java/org/mozilla/javascript/IRFactory.java

@@ -2025,8 +2025,8 @@ private Node createPropertyGet(
             }
             parser.checkActivationName(name, Token.GETPROP);
 
-            if (target.getType() == Token.SUPER && ScriptRuntime.isSpecialSuperProperty(name)) {
-                // We have access to super.__proto__ or super.__parent__.
+            if (target.getType() == Token.SUPER && NativeObject.PROTO_PROPERTY.equals(name)) {
+                // We have access to super.__proto__.
                 // This needs to behave in the same way as this.__proto__ - it really is not
                 // obvious why, but you can test it in v8 or any other engine. So, we just
                 // replace SUPER with THIS in the AST. It's a bit hacky, but it works - see the
@@ -2048,8 +2048,10 @@ private Node createPropertyGet(
                     getRef.putIntProp(Node.OPTIONAL_CHAINING, 1);
                 }
                 return getRef;
-            } else if (ScriptRuntime.isSpecialProperty(
-                    name, parser.compilerEnv.getLanguageVersion())) {
+            }
+
+            if (parser.compilerEnv.getLanguageVersion() < Context.VERSION_ES6
+                    && ScriptRuntime.isSpecialProperty(name)) {
                 Node ref = new Node(Token.REF_SPECIAL, target);
                 ref.putProp(Node.NAME_PROP, name);
                 Node getRef = new Node(Token.GET_REF, ref);

rhino/src/main/java/org/mozilla/javascript/NativeObject.java

@@ -31,6 +31,7 @@ public class NativeObject extends ScriptableObject implements Map {
     private static final String CLASS_NAME = "Object";
 
     public static final String PROTO_PROPERTY = "__proto__";
+    public static final String PARENT_PROPERTY = "__parent__";
 
     static LambdaConstructor init(Context cx, Scriptable s, boolean sealed) {
         LambdaConstructor ctor =

rhino/src/main/java/org/mozilla/javascript/ScriptRuntime.java

@@ -2143,19 +2143,8 @@ public static Object refDel(Ref ref, Context cx) {
         return wrapBoolean(ref.delete(cx));
     }
 
-    static boolean isSpecialProperty(String s, int languageVersion) {
-        if (languageVersion >= Context.VERSION_ES6) {
-            return s.equals("__parent__");
-        }
-
-        return s.equals(NativeObject.PROTO_PROPERTY) || s.equals("__parent__");
-    }
-
-    // for the super handling, we still not language dependent
-    // have a look at the comment in for more details
-    // org.mozilla.javascript.IRFactory.createPropertyGet()
-    static boolean isSpecialSuperProperty(String s) {
-        return s.equals(NativeObject.PROTO_PROPERTY) || s.equals("__parent__");
+    static boolean isSpecialProperty(String s) {
+        return s.equals(NativeObject.PROTO_PROPERTY) || s.equals(NativeObject.PARENT_PROPERTY);
     }
 
     /**
@@ -5429,7 +5418,8 @@ public static void fillObjectLiteral(
                         object.put(s.index, object, value);
                     } else {
                         String stringId = s.stringId;
-                        if (isSpecialProperty(stringId, cx.getLanguageVersion())) {
+                        if (cx.getLanguageVersion() < Context.VERSION_ES6
+                                && isSpecialProperty(stringId)) {
                             Ref ref = specialRef(object, stringId, cx, scope);
                             ref.set(cx, scope, value);
                         } else if (cx.getLanguageVersion() >= Context.VERSION_ES6

rhino/src/main/java/org/mozilla/javascript/SpecialRef.java

@@ -32,7 +32,7 @@ static Ref createSpecial(Context cx, Scriptable scope, Object object, String nam
         int type;
         if (name.equals(NativeObject.PROTO_PROPERTY)) {
             type = SPECIAL_PROTO;
-        } else if (name.equals("__parent__")) {
+        } else if (name.equals(NativeObject.PARENT_PROPERTY)) {
             type = SPECIAL_PARENT;
         } else {
             throw new IllegalArgumentException(name);

tests/src/test/java/org/mozilla/javascript/tests/es6/ParentPropertyTest.java

@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * Tests for the __parent__ property.
+ */
+package org.mozilla.javascript.tests.es6;
+
+import org.junit.Test;
+import org.mozilla.javascript.testutils.Utils;
+
+public class ParentPropertyTest {
+
+    @Test
+    public void parentGet() {
+        // __parent__ was removed in 2010 from the browsers
+        // https://whereswalden.com/2010/05/07/spidermonkey-change-du-jour-the-special-__parent__-property-has-been-removed/
+        String script = "var a = {};" + "'' + a.__parent__;";
+
+        Utils.assertWithAllModes_1_8("[object Object]", script);
+        Utils.assertWithAllModes_ES6("undefined", script);
+    }
+}

tests/src/test/java/org/mozilla/javascript/tests/es6/ProtoProperty2Test.java

@@ -13,7 +13,7 @@
  * https://exploringjs.com/es6/ch_oop-besides-classes.html#sec_proto
  *
  * <p>Test are written with asserts for older language versions, because the old code has some
- * switches for the used versions. This shold help to maintain backward compatibility.
+ * switches for the used versions. This should help to maintain backward compatibility.
  */
 public class ProtoProperty2Test {