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Type:
Bug
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Resolution: Fixed
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Priority:
Major
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None
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Affects Version/s: None
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Environment:
Windows 10 x86_x64
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This server is running CraftBukkit version 4430-Spigot-d421948-d20d4c1 (MC: 1.21.4) (Implementing API version 1.21.4-R0.1-SNAPSHOT)
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Yes
A ConcurrentModificationException is thrown when modifying the potion effects of a LivingEntity on CreatureSpawnEvent when mobs are spawned due to a mob effect.
This is due to this code in in EntityLiving#hurtServer:
Iterator iterator = this.getActiveEffects().iterator(); while (iterator.hasNext()) { MobEffect mobeffect = (MobEffect) iterator.next(); mobeffect.onMobHurt(worldserver, this, damagesource, f); }
As MobEffect#onMobHurt spawns the mob (such as a sliverfish for the infested effect), it then calls CreatureSpawnEvent and (and our event handler) while iterating. When our plugin removes an effect, the next iteration throws the error.
The plugin code:
@EventHandler
public void onCreatureSpawn(CreatureSpawnEvent e) {
if (e.getEntityType() == EntityType.SILVERFISH) {
e.getLocation().getWorld().getNearbyEntities(e.getLocation(), 1, 1, 1).stream()
.filter(ent -> ent instanceof Player)
.map(ent -> (Player) ent)
.filter(ent -> ent.hasPotionEffect(PotionEffectType.INFESTED))
.findAny()
.ifPresent(ent -> ent.removePotionEffect(PotionEffectType.INFESTED));
}
}