Symbol not getting removed when item is removed from tree

[jsdom]

Symbol not getting removed when item is removed from tree

[Joris-van-der-Wel]

This was indeed by design because it was the fastest solution for jsdom's use case. In jsdom objects are often removed from the SymbolTree and then added back a little while later. (Also note that jsdom uses a finite amount of SymbolTree instances). Deleting and then adding back the property would be slower, and also delete may cause deopts in v8.

Would it help if I added an option to the constructor?

const tree = new SymbolTree({cleanup: true});
tree.remove(someObj); // which would then trigger `delete someObj[this.symbol]`

And then jsdom could continue to use the {cleanup: false} behaviour.

[Ineluki]

That would be a good solution, yes. If delete is bad in these cases, I'd just recommend setting it to null if that makes a difference.
But if it's by design, don't feel pressured on my part. Turns out I can't use this awesome lib anyway, unfortunately, since it can't allow the same object multiple times. Just thought I'd mention the problem since I already wrote the test and thought somebody might one day run into the problem ;)