EXP not correctly updated when using an anvil

[EBro912]

Expected behavior

On my server, we use a plugin that allows players to store experience in ender chests. Data for players is retrieved via getTotalExperience(), and given/taken via giveExp() (negative values for take). A player can deposit their experience and withdraw their experience, and the exp is stored as whole numbers between transactions, just like in Vanilla Minecraft. So if a player were to use an anvil, lose a few levels, and then go deposit their experience, the amount given to the plugin should be equal to their current total experience amount.

Observed/Actual behavior

When a player uses an anvil, their level is updated accordingly. However, on the server side, this data is not updated when removing levels from the player. This can be observed by a player using an anvil, and then depositing their exp, which will deposit the amount of experience before the anvil instead of the actual current amount.

Steps/models to reproduce

1. Player has 8 levels, XP bar progress doesn't matter
2. Player uses an anvil and loses X levels.
3. Player deposits all experience into an Ender Chest. Note that the plugin responds that Player has 8 levels worth of experience points.
4. Player withdraws all experience from the Ender Chest.
5. Player will be back at 8 levels, instead of X.

Plugin list

ExpStorage (custom)

Paper version

[22:40:23 INFO]: Checking version, please wait... [22:40:24 INFO]: This server is running Paper version git-Paper-124 (MC: 1.17.1) (Implementing API version 1.17.1-R0.1-SNAPSHOT) (Git: 170382f) You are running the latest version Previous version: git-Paper-119 (MC: 1.17.1)

Agreements

• [X] I am running the latest version of Paper available from https://papermc.io/downloads.
• [X] I have searched for and ensured there isn't already an open issue regarding this.
• [X] My version of Minecraft is supported by Paper.

Other

I have already confirmed the plugin is not the culprit, because the plugin actually suffered the same bug when trying to give and take whole levels to/from players. Also, the plugin has no interaction with anvils whatsoever. The reason there is only one plugin listed is because I tested it on a test server with no other plugins and the bug persisted.

[UnknownSilicon]

I looked at the Paper server code a bit and the bug appears to be in Player#giveExperienceLevels. Things like anvils use this (see AnvilMenu#onTake. I believe this method is just changing the player's level but NOT the total experience. Player#giveTotalExperience works as expected because it first updates the total experience then the level, but using giveExperienceLevels directly does not work, breaking minecraft functions and the API.

[Machine-Maker]

Does this happen in vanilla then too?

(I mean the underlying issue, I understand you cant replicate plugin behavior in vanilla)

I just don't see where cb, spigot, or paper modifies what giveExperienceLevels does.

[UnknownSilicon]

I just tested it. It's kind of hard to test the same way since the plugin we used made it easier to test the getTotalExperience method. I think it's related to/is this bug https://bugs.mojang.com/browse/MC-118008

[UnknownSilicon]

Ok turns out this seems to be more of a problem of misleading documentation. From what I understand, getTotalExperience is the total experience a player has collected since they last died (the score when a player dies). Setting the level isn't suppose to update total experience. All interaction with exp should probably be done with get/giveLevels and get/giveExp. I'm going to go add an API patch that has a more useful method for this.