Paper/patches/server/1019-Check-dead-flag-in-isAlive.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Newwind <support@newwindserver.com>
Date: Mon, 26 Aug 2024 14:01:37 +0200
Subject: [PATCH] Check dead flag in isAlive()

If a plugin sets the health of a living entity above 0 after it has already died, the entity will be "revived".
It will behave the exact same as before, except with the internal "dead" flag set, resulting in 2 behavior changes,
A: it's completely invulnerable to all damage
B: it's unable to pickup items

isValid() for these bugged entities will return true, isDead() will return false, despite the dead flag.
This patch checks that the mob isn't dead before saying its alive.

Also, even if the plugin is responsibly checking !isDead() before modifying health, on very rare circumstances
I am currently unable to replicate, these "revived" entities can still appear

diff --git a/src/main/java/net/minecraft/world/entity/LivingEntity.java b/src/main/java/net/minecraft/world/entity/LivingEntity.java
index ab9eec00c8c7d4b9501c6c860065909263da0b10..6db0613904c172fb6ae7e868f542f56aeaa63a5e 100644
--- a/src/main/java/net/minecraft/world/entity/LivingEntity.java
+++ b/src/main/java/net/minecraft/world/entity/LivingEntity.java
@@ -2147,7 +2147,7 @@ public abstract class LivingEntity extends Entity implements Attackable {
 
     @Override
     public boolean isAlive() {
-        return !this.isRemoved() && this.getHealth() > 0.0F;
+        return !this.isRemoved() && this.getHealth() > 0.0F && !this.dead; // Paper - Check this.dead
     }
 
     public boolean isLookingAtMe(LivingEntity entity, double d0, boolean flag, boolean visualShape, Predicate<LivingEntity> predicate, DoubleSupplier... entityYChecks) {