Cancelling the EntityDamageEvent and using setHealth(0) will call PlayerDeathEvent twice

[Mykindos]

Expected behavior

PlayerDeathEvent should only be called once

Observed/Actual behavior

PlayerDeathEvent is called twice

Steps/models to reproduce

Listen to an EntityDamageEvent and PlayerDeathEvent.

if the entity in the damage event is a player, cancel the event and call entity.setHealth(0);

Take fall damage or something so that you die, and the player death event will be called twice

Plugin and Datapack List

Irrelevant, confirmed by @lynxplay

Paper version

This server is running Paper version 1.21.4-164-main@8eb8e44 (2025-02-16T22:13:26Z) (Implementing API version 1.21.4-R0.1-SNAPSHOT)
You are 8 version(s) behind
Download the new version at: https://papermc.io/downloads/paper
Previous version: 1.21.1-119-7cd4f2c (MC: 1.21.1)

Other

Did not used to happen on 1.21.1 or earlier

[lynxplay]

TL;DR, setHealth(0) will call die which will setClientLoaded(false)
The original damage of the process will call actuallyHurt with the cancelled event but, a non client loaded player is completely invuln, leading to that method returning true. That last bit of behaviour is new since the addition of the client loaded world packet and is the root cause of this issue.

Solutions are a bit out there. One attempt would be revisiting simply moving the event cancellation check outside of the invuln check. Seems incorrect to return true from that method if the event was cancelled but the player is invuln. That might however also lead to other issues not currently on my radar so, testing be advised.

[electronicboy]

Yea, was having a ponder too, the player is considered invulnerable and so skips that entire logic and jumps to the hard return true; I'd probably defer this to Machine as he's familiar with this logic

[lynxplay]

Well we have been very active on that method returning false for the cancelled event, but yea. MM's opinion on this is gonna be valuable.

[funnykeyboardsymbols]

Adding my own additional user report in case it helps.

This same thing occurs in EntityDamageByEntityEvent when calling Event#setCancelled(true) and then LivingEntity#damage() on the target with the DirectEntity and CausingEntity set on a DamageSource builder. If the target dies from the LivingEntity#damage(), both events will trigger a DeathEvent and send their death messages, unless you wrap your LivingEntity#damage() in a BukkitRunnable with a 1 tick delay.