vanish player switch world cause vanish bug

[cyilin]

thanks @phoenixlzx to test this bug
if admin in vanish status and teleport to other worlds, Essentials will duplicate add player name to ess.vanishedPlayers
when a player join to the server, will can't see this admin even if this admin is unvanish status

EssentialsPlayerListener.java#L237
EssentialsPlayerListener.java#L578
User.java#L718

[mdcfe]

That's a great observation - I've been wondering what caused unpredictable issues with the vanish functionality, but never found the cause.

@khobbits Just out of interest, what was the reasoning behind having the vanishedPlayers list?

[khobbits]

@md678685 Two reasons I think:

It's part of the public API, so other plugins can see who's vanished.

It's used to handle the vanish.see permissions when logging in. Ie when a new player joins the server, he shouldnt see people who are 'vanished', unless he has 'ess.vanish.see'.

[phoenixlzx]

Thanks @cyilin for reporting this to EssentialsX. I believe this issue exists in origin Essentials as well.

Some details to reproduce:

1. Create a server, install EssentialsX and multi world management plugin (multiworld/multiverse... etc)
2. Create another world.
3. Issue server command /vanish
4. Teleport to another world.

Result:

You are not vanishing in Essentials, but when you move (anyway to move/teleport) to other players, they can't see you unless you toggle /v twice in front of them - However even toggled vanish status and let others see you, you are still in the list of 'ess.vanishedPlayers', confirmed by our plugin invoking this.

[caojohnny]

I must ask, why exactly was the vanished players collection not a Set in the first place? Isn't it common sense for it to not contain duplicates, or simply oversight?

[mdcfe]

I've worked on a very simple solution which simply avoids adding existing usernames to the list. However, I'm considering that we could replace the list with a Set and deprecate the existing getVanishedPlayers, especially considering since there's no reason for plugins to directly mutate the ess.vanishedPlayers list instead of using the appropriate User method.

[mdcfe]

This should be fixed by #1796.