A question about Object.defineProperty

[YiWen-y]

Version

rhino-1.7.13

Test case

var a = 6; 
Object.defineProperty(this,"a",{
    writable: false
});

Execution steps

java -jar rhino-1.7.13.jar -debug -version 200 testcase.js

Output

TypeError: Cannot change the enumerable attribute of "a" because configurable is false.

Expected behavior

Description

When executing this test case, other engines passed normally without throwing any exceptions, such as v8, spiderMonkey, JavaScriptCore, etc. But rhino throws a TypeError exception. I would like to ask how this is achieved?

[tonygermano]

This appears to be an issue with the implementation of abstract operation ValidateAndApplyPropertyDescriptor, specifically part 4.b. https://tc39.es/ecma262/#sec-validateandapplypropertydescriptor

4. If current.[[Configurable]] is false, then
  a. If Desc.[[Configurable]] is present and its value is true, return false.
  b. If Desc.[[Enumerable]] is present and ! SameValue(Desc.[[Enumerable]], current.[[Enumerable]]) is false, return false.

Desc.[[Enumerable]] is not present, but it appears to be using a default value of false, which is not the same value as current.[[Enumerable]]