Allow updating of name of a function, as required by the standard

See mozilla#1297

Author: andreabergia

src/org/mozilla/javascript/BaseFunction.java

@@ -6,6 +6,8 @@
 
 package org.mozilla.javascript;
 
+import sun.font.ScriptRun;
+
 /**
  * The base class for Function objects. That is one of two purposes. It is also the prototype for
  * every "function" defined except those that are used as GeneratorFunctions via the ES6 "function
@@ -169,7 +171,7 @@ protected Object getInstanceIdValue(int id) {
             case Id_arity:
                 return arityPropertyAttributes >= 0 ? getArity() : NOT_FOUND;
             case Id_name:
-                return namePropertyAttributes >= 0 ? getFunctionName() : NOT_FOUND;
+                return namePropertyAttributes >= 0 ? (nameValue != null ? nameValue : getFunctionName()) : NOT_FOUND;
             case Id_prototype:
                 return getPrototypeProperty();
             case Id_arguments:
@@ -200,6 +202,9 @@ protected void setInstanceIdValue(int id, Object value) {
             case Id_name:
                 if (value == NOT_FOUND) {
                     namePropertyAttributes = -1;
+                    nameValue = null;
+                } else {
+                    nameValue = ScriptRuntime.toString(value);
                 }
                 return;
             case Id_arity:
@@ -650,6 +655,7 @@ protected int findPrototypeId(String s) {
 
     private Object prototypeProperty;
     private Object argumentsObj = NOT_FOUND;
+    private String nameValue = null;
     private boolean isGeneratorFunction = false;
 
     // For function object instances, attributes are
@@ -658,6 +664,6 @@ protected int findPrototypeId(String s) {
     private int prototypePropertyAttributes = PERMANENT | DONTENUM;
     private int argumentsAttributes = PERMANENT | DONTENUM;
     private int arityPropertyAttributes = PERMANENT | READONLY | DONTENUM;
-    private int namePropertyAttributes = PERMANENT | READONLY | DONTENUM;
+    private int namePropertyAttributes = READONLY | DONTENUM;
     private int lengthPropertyAttributes = PERMANENT | READONLY | DONTENUM;
 }

src/org/mozilla/javascript/IdScriptableObject.java

@@ -867,13 +867,14 @@ protected void defineOwnProperty(
                     checkPropertyChange(name, current, desc);
                     int attr = (info >>> 16);
                     Object value = getProperty(desc, "value");
+                    attr = applyDescriptorToAttributeBitset(attr, desc);
+                    setAttributes(name, attr);
                     if (value != NOT_FOUND && (attr & READONLY) == 0) {
                         Object currentValue = getInstanceIdValue(id);
                         if (!sameValue(value, currentValue)) {
                             setInstanceIdValue(id, value);
                         }
                     }
-                    setAttributes(name, applyDescriptorToAttributeBitset(attr, desc));
                     return;
                 }
             }

testsrc/org/mozilla/javascript/tests/Issue1297FunctionNameTest.java

@@ -0,0 +1,44 @@
+/* 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/. */
+
+package org.mozilla.javascript.tests;
+
+import static org.junit.Assert.assertEquals;
+
+import org.junit.Test;
+import org.mozilla.javascript.Context;
+import org.mozilla.javascript.Scriptable;
+
+/**
+ * Test that we can redefine a function's name.
+ */
+public class Issue1297FunctionNameTest {
+	private static final String source = "'use strict';" +
+			"function X() {};\n" +
+			"Object.defineProperty(X, 'name', {value: 'y', configurable: true, writable: true});" +
+			"X.name";
+
+	@Test
+	public void canSetFunctionNameInCompiledClasses() {
+		try (Context cx = Context.enter()) {
+			Scriptable scope = cx.initStandardObjects(null);
+			Object result = cx.evaluateString(scope,
+					source,
+					"test", 1, null);
+			assertEquals("y", result);
+		}
+	}
+
+	@Test
+	public void canSetFunctionNameInInterpreter() {
+		try (Context cx = Context.enter()) {
+			cx.setOptimizationLevel(-1);
+			Scriptable scope = cx.initStandardObjects(null);
+			Object result = cx.evaluateString(scope,
+					source,
+					"test", 1, null);
+			assertEquals("y", result);
+		}
+	}
+}