Bug 978235 - ES6 Proxies: Implement [[IsExtensible]] trap. (r=jorendorff)

js/src/js.msg

@@ -437,3 +437,4 @@ MSG_DEF(JSMSG_SETPROTOTYPEOF_FAIL,      382, 1, JSEXN_TYPEERR, "[[SetPrototypeOf
 MSG_DEF(JSMSG_INVALID_ARG_TYPE,         383, 3, JSEXN_TYPEERR, "Invalid type: {0} can't be a{1} {2}")
 MSG_DEF(JSMSG_TERMINATED,               384, 1, JSEXN_ERR, "Script terminated by timeout at:\n{0}")
 MSG_DEF(JSMSG_NO_SUCH_SELF_HOSTED_PROP, 385, 1, JSEXN_ERR, "No such property on self-hosted object: {0}")
+MSG_DEF(JSMSG_PROXY_EXTENSIBILITY,      386, 0, JSEXN_TYPEERR, "proxy must report same extensiblitity as target")

js/src/jsproxy.cpp

@@ -1077,12 +1077,6 @@ ScriptedIndirectProxyHandler::fun_toString(JSContext *cx, HandleObject proxy, un
 
 ScriptedIndirectProxyHandler ScriptedIndirectProxyHandler::singleton;
 
-static JSObject *
-GetDirectProxyHandlerObject(JSObject *proxy)
-{
-    return proxy->as<ProxyObject>().extra(0).toObjectOrNull();
-}
-
 /* Derived class for all scripted direct proxy handlers. */
 class ScriptedDirectProxyHandler : public DirectProxyHandler {
   public:
@@ -1114,6 +1108,9 @@ class ScriptedDirectProxyHandler : public DirectProxyHandler {
     virtual bool iterate(JSContext *cx, HandleObject proxy, unsigned flags,
                          MutableHandleValue vp) MOZ_OVERRIDE;
 
+    /* ES6 Harmony traps */
+    virtual bool isExtensible(JSContext *cx, HandleObject proxy, bool *extensible) MOZ_OVERRIDE;
+
     /* Spidermonkey extensions. */
     virtual bool call(JSContext *cx, HandleObject proxy, const CallArgs &args) MOZ_OVERRIDE;
     virtual bool construct(JSContext *cx, HandleObject proxy, const CallArgs &args) MOZ_OVERRIDE;
@@ -1365,6 +1362,16 @@ IdToValue(JSContext *cx, HandleId id, MutableHandleValue value)
     return true;
 }
 
+// Get the [[ProxyHandler]] of a scripted direct proxy.
+//
+// NB: This *must* stay synched with proxy().
+static JSObject *
+GetDirectProxyHandlerObject(JSObject *proxy)
+{
+    JS_ASSERT(proxy->as<ProxyObject>().handler() == &ScriptedDirectProxyHandler::singleton);
+    return proxy->as<ProxyObject>().extra(0).toObjectOrNull();
+}
+
 // TrapGetOwnProperty(O, P)
 static bool
 TrapGetOwnProperty(JSContext *cx, HandleObject proxy, HandleId id, MutableHandleValue rval)
@@ -2225,6 +2232,42 @@ ScriptedDirectProxyHandler::keys(JSContext *cx, HandleObject proxy, AutoIdVector
     return ArrayToIdVector(cx, proxy, target, trapResult, props, JSITER_OWNONLY, cx->names().keys);
 }
 
+// ES6 (5 April, 2014) 9.5.3 Proxy.[[IsExtensible]](P)
+bool
+ScriptedDirectProxyHandler::isExtensible(JSContext *cx, HandleObject proxy, bool *extensible)
+{
+    RootedObject handler(cx, GetDirectProxyHandlerObject(proxy));
+
+    RootedObject target(cx, proxy->as<ProxyObject>().target());
+
+    RootedValue trap(cx);
+    if (!JSObject::getProperty(cx, handler, handler, cx->names().isExtensible, &trap))
+        return false;
+
+    if (trap.isUndefined())
+        return DirectProxyHandler::isExtensible(cx, proxy, extensible);
+
+    Value argv[] = {
+        ObjectValue(*target)
+    };
+    RootedValue trapResult(cx);
+    if (!Invoke(cx, ObjectValue(*handler), trap, ArrayLength(argv), argv, &trapResult))
+        return false;
+
+    bool booleanTrapResult = ToBoolean(trapResult);
+    bool targetResult;
+    if (!JSObject::isExtensible(cx, target, &targetResult))
+        return false;
+
+    if (targetResult != booleanTrapResult) {
+       JS_ReportErrorNumber(cx, js_GetErrorMessage, nullptr, JSMSG_PROXY_EXTENSIBILITY);
+       return false;
+    }
+
+    *extensible = booleanTrapResult;
+    return true;
+}
+
 bool
 ScriptedDirectProxyHandler::iterate(JSContext *cx, HandleObject proxy, unsigned flags,
                                     MutableHandleValue vp)

js/src/vm/CommonPropertyNames.h

@@ -103,6 +103,7 @@
     macro(int8, int8, "int8") \
     macro(int16, int16, "int16") \
     macro(int32, int32, "int32") \
+    macro(isExtensible, isExtensible, "isExtensible") \
     macro(iterator, iterator, "iterator") \
     macro(iteratorIntrinsic, iteratorIntrinsic, "__iterator__") \
     macro(join, join, "join") \