C++ PropertyDescriptor::attributes方法代码示例

// https://tc39.github.io/ecma262/#sec-reflect.defineproperty
EncodedJSValue JSC_HOST_CALL reflectObjectDefineProperty(ExecState* exec)
{
    VM& vm = exec->vm();
    auto scope = DECLARE_THROW_SCOPE(vm);

    JSValue target = exec->argument(0);
    if (!target.isObject())
        return JSValue::encode(throwTypeError(exec, scope, ASCIILiteral("Reflect.defineProperty requires the first argument be an object")));
    auto propertyName = exec->argument(1).toPropertyKey(exec);
    RETURN_IF_EXCEPTION(scope, encodedJSValue());

    PropertyDescriptor descriptor;
    bool success = toPropertyDescriptor(exec, exec->argument(2), descriptor);
    ASSERT(!scope.exception() == success);
    if (UNLIKELY(!success))
        return encodedJSValue();
    ASSERT((descriptor.attributes() & Accessor) || (!descriptor.isAccessorDescriptor()));
    ASSERT(!scope.exception());

    // Reflect.defineProperty should not throw an error when the defineOwnProperty operation fails.
    bool shouldThrow = false;
    JSObject* targetObject = asObject(target);
    scope.release();
    return JSValue::encode(jsBoolean(targetObject->methodTable(vm)->defineOwnProperty(targetObject, exec, propertyName, descriptor, shouldThrow)));
}

EncodedJSValue JSC_HOST_CALL objectConstructorDefineProperty(ExecState* exec)
{
    if (!exec->argument(0).isObject())
        return throwVMError(exec, createTypeError(exec, ASCIILiteral("Properties can only be defined on Objects.")));
    JSObject* O = asObject(exec->argument(0));
    String propertyName = exec->argument(1).toString(exec)->value(exec);
    if (exec->hadException())
        return JSValue::encode(jsNull());
    PropertyDescriptor descriptor;
    if (!toPropertyDescriptor(exec, exec->argument(2), descriptor))
        return JSValue::encode(jsNull());
    ASSERT((descriptor.attributes() & Accessor) || (!descriptor.isAccessorDescriptor()));
    ASSERT(!exec->hadException());
    O->methodTable()->defineOwnProperty(O, exec, Identifier(exec, propertyName), descriptor, true);
    return JSValue::encode(O);
}

JSValue JSC_HOST_CALL objectConstructorDefineProperty(ExecState* exec, JSObject*, JSValue, const ArgList& args)
{
    if (!args.at(0).isObject())
        return throwError(exec, TypeError, "Properties can only be defined on Objects.");
    JSObject* O = asObject(args.at(0));
    UString propertyName = args.at(1).toString(exec);
    if (exec->hadException())
        return jsNull();
    PropertyDescriptor descriptor;
    if (!toPropertyDescriptor(exec, args.at(2), descriptor))
        return jsNull();
    ASSERT((descriptor.attributes() & (Getter | Setter)) || (!descriptor.isAccessorDescriptor()));
    ASSERT(!exec->hadException());
    O->defineOwnProperty(exec, Identifier(exec, propertyName), descriptor, true);
    return O;
}

// http://www.ecma-international.org/ecma-262/6.0/#sec-reflect.defineproperty
EncodedJSValue JSC_HOST_CALL reflectObjectDefineProperty(ExecState* exec)
{
    JSValue target = exec->argument(0);
    if (!target.isObject())
        return JSValue::encode(throwTypeError(exec, ASCIILiteral("Reflect.defineProperty requires the first argument be an object")));
    auto propertyName = exec->argument(1).toPropertyKey(exec);
    if (exec->hadException())
        return JSValue::encode(jsUndefined());

    PropertyDescriptor descriptor;
    if (!toPropertyDescriptor(exec, exec->argument(2), descriptor))
        return JSValue::encode(jsUndefined());
    ASSERT((descriptor.attributes() & Accessor) || (!descriptor.isAccessorDescriptor()));
    ASSERT(!exec->hadException());

    // Reflect.defineProperty should not throw an error when the defineOwnProperty operation fails.
    bool shouldThrow = false;
    JSObject* targetObject = asObject(target);
    return JSValue::encode(jsBoolean(targetObject->methodTable(exec->vm())->defineOwnProperty(targetObject, exec, propertyName, descriptor, shouldThrow)));
}

bool JSObject::defineOwnProperty(ExecState* exec, const Identifier& propertyName, PropertyDescriptor& descriptor, bool throwException)
{
    // If we have a new property we can just put it on normally
    PropertyDescriptor current;
    if (!getOwnPropertyDescriptor(exec, propertyName, current))
        return putDescriptor(exec, this, propertyName, descriptor, descriptor.attributes(), jsUndefined());

    if (descriptor.isEmpty())
        return true;

    if (current.equalTo(descriptor))
        return true;

    // Filter out invalid changes
    if (!current.configurable()) {
        if (descriptor.configurable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to configurable attribute of unconfigurable property.");
            return false;
        }
        if (descriptor.enumerablePresent() && descriptor.enumerable() != current.enumerable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change enumerable attribute of unconfigurable property.");
            return false;
        }
    }

    // A generic descriptor is simply changing the attributes of an existing property
    if (descriptor.isGenericDescriptor()) {
        if (!current.attributesEqual(descriptor)) {
            deleteProperty(exec, propertyName);
            putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value());
        }
        return true;
    }

    // Changing between a normal property or an accessor property
    if (descriptor.isDataDescriptor() != current.isDataDescriptor()) {
        if (!current.configurable()) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change access mechanism for an unconfigurable property.");
            return false;
        }
        deleteProperty(exec, propertyName);
        return putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value() ? current.value() : jsUndefined());
    }

    // Changing the value and attributes of an existing property
    if (descriptor.isDataDescriptor()) {
        if (!current.configurable()) {
            if (!current.writable() && descriptor.writable()) {
                if (throwException)
                    throwError(exec, TypeError, "Attempting to change writable attribute of unconfigurable property.");
                return false;
            }
            if (!current.writable()) {
                if (descriptor.value() || !JSValue::strictEqual(current.value(), descriptor.value())) {
                    if (throwException)
                        throwError(exec, TypeError, "Attempting to change value of a readonly property.");
                    return false;
                }
            }
        } else if (current.attributesEqual(descriptor)) {
            if (!descriptor.value())
                return true;
            PutPropertySlot slot;
            put(exec, propertyName, descriptor.value(), slot);
            if (exec->hadException())
                return false;
            return true;
        }
        deleteProperty(exec, propertyName);
        return putDescriptor(exec, this, propertyName, descriptor, current.attributesWithOverride(descriptor), current.value());
    }

    // Changing the accessor functions of an existing accessor property
    ASSERT(descriptor.isAccessorDescriptor());
    if (!current.configurable()) {
        if (descriptor.setterPresent() && !(current.setter() && JSValue::strictEqual(current.setter(), descriptor.setter()))) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change the setter of an unconfigurable property.");
            return false;
        }
        if (descriptor.getterPresent() && !(current.getter() && JSValue::strictEqual(current.getter(), descriptor.getter()))) {
            if (throwException)
                throwError(exec, TypeError, "Attempting to change the getter of an unconfigurable property.");
            return false;
        }
    }
    JSValue accessor = getDirect(propertyName);
    if (!accessor)
        return false;
    GetterSetter* getterSetter = asGetterSetter(accessor);
    if (current.attributesEqual(descriptor)) {
        if (descriptor.setter())
            getterSetter->setSetter(asObject(descriptor.setter()));
        if (descriptor.getter())
            getterSetter->setGetter(asObject(descriptor.getter()));
        return true;
    }
//.........这里部分代码省略.........