arguments accessed from the function itself are readonly

Author: rbri

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

@@ -14,7 +14,7 @@
  * @see org.mozilla.javascript.NativeCall
  * @author Norris Boyd
  */
-final class Arguments extends ScriptableObject {
+class Arguments extends ScriptableObject {
     private static final long serialVersionUID = 4275508002492040609L;
 
     private static final String CLASS_NAME = "Arguments";
@@ -311,4 +311,61 @@ protected boolean defineOwnProperty(
         }
         return true;
     }
+
+    static final class ReadonlyArguments extends Arguments {
+        private boolean initialized;
+
+        public ReadonlyArguments(Arguments arguments, Context cx) {
+            super(arguments.activation, cx);
+            initialized = true;
+        }
+
+        @Override
+        public void put(int index, Scriptable start, Object value) {
+            if (initialized) {
+                return;
+            }
+            super.put(index, start, value);
+        }
+
+        @Override
+        public void put(String name, Scriptable start, Object value) {
+            if (initialized) {
+                return;
+            }
+            super.put(name, start, value);
+        }
+
+        @Override
+        public void put(Symbol key, Scriptable start, Object value) {
+            if (initialized) {
+                return;
+            }
+            super.put(key, start, value);
+        }
+
+        @Override
+        public void delete(int index) {
+            if (initialized) {
+                return;
+            }
+            super.delete(index);
+        }
+
+        @Override
+        public void delete(String name) {
+            if (initialized) {
+                return;
+            }
+            super.delete(name);
+        }
+
+        @Override
+        public void delete(Symbol key) {
+            if (initialized) {
+                return;
+            }
+            super.delete(key);
+        }
+    }
 }

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

@@ -713,7 +713,15 @@ private Object getArguments() {
         }
         Context cx = Context.getContext();
         NativeCall activation = ScriptRuntime.findFunctionActivation(cx, this);
-        return (activation == null) ? null : activation.get("arguments", activation);
+        // return (activation == null) ? null : activation.get("arguments", activation);
+        if (activation == null) {
+            return null;
+        }
+        Object arguments = activation.get("arguments", activation);
+        if (arguments instanceof Arguments && cx.getLanguageVersion() >= Context.VERSION_ES6) {
+            return new Arguments.ReadonlyArguments((Arguments) arguments, cx);
+        }
+        return arguments;
     }
 
     private static Scriptable jsConstructor(

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

@@ -361,8 +361,7 @@ public void readOnlyWhenAccessedThroughFunction() {
                         + "test('hello', 'world');\n"
                         + "res";
 
-        // Utils.assertWithAllModes_ES6("2 hello world undefined undefined", code);
-        Utils.assertWithAllModes_ES6("2 hello hi undefined you", code);
+        Utils.assertWithAllModes_ES6("2 hello world undefined undefined", code);
         Utils.assertWithAllModes_1_8("2 hello hi undefined you", code);
     }
 
@@ -605,8 +604,7 @@ public void argumentsEqualsFnArguments() {
                         + "test('hello', 'world');\n"
                         + "res";
 
-        // Utils.assertWithAllModes_ES6("null false false", code);
-        Utils.assertWithAllModes_ES6("null true true", code);
+        Utils.assertWithAllModes_ES6("null false false", code);
         Utils.assertWithAllModes_1_8("null true true", code);
     }