Leaf/leaf-server/minecraft-patches/features/0304-Rewrite-entity-despawn-time.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: HaHaWTH <102713261+HaHaWTH@users.noreply.github.com>
Date: Tue, 9 Nov 2077 00:00:00 +0800
Subject: [PATCH] Rewrite entity despawn time

HOW IT WORKS:
In the default implementation, totalEntityAge only increments when an entity is actively ticked.
Consequently, if an entity resides in a weak-loaded chunk, its aging process effectively pauses, allowing it to exist far beyond the configured despawn time.

This patch addresses this discrepancy by synchronizing entity age with absolute server time:
Introduces lastTickTime to record the MinecraftServer.currentTick when an entity was last ticked.
Once the entity is ticked again or unloaded, the system calculates the elapsed time (currentTick - lastTickTime), and adds it to the totalEntityAge.
Also, it moves the despawn logic of projectiles to their own tick method (see ThrowableProjectile#tick), making it faster to despawn massive stuck projectiles.

Benchmarks (60,000 snowballs):
Before: Around 120 seconds, server thread is struggling to process projectile physics.
After: 1.5 seconds

Brings the ability to despawn weak-loaded entities once they are ticked,
a solution for https://github.com/PaperMC/Paper/issues/12986

diff --git a/net/minecraft/server/level/ServerLevel.java b/net/minecraft/server/level/ServerLevel.java
index cb1be4947ea2d85c6dcdc7424a4b712dcce0a40e..01f7390f3fb2a423cec373a2bb5ccbee57278783 100644
--- a/net/minecraft/server/level/ServerLevel.java
+++ b/net/minecraft/server/level/ServerLevel.java
@@ -1509,6 +1509,7 @@ public class ServerLevel extends Level implements ServerEntityGetter, WorldGenLe
         entity.tick();
         entity.postTick(); // CraftBukkit
         } else {entity.inactiveTick();} // Paper - EAR 2
+        entity.updateLastTick(); // Leaf - Rewrite entity despawn time
 
         for (Entity entity1 : entity.getPassengers()) {
             this.tickPassenger(entity, entity1, isActive); // Paper - EAR 2
@@ -1533,6 +1534,7 @@ public class ServerLevel extends Level implements ServerEntityGetter, WorldGenLe
                 ridingEntity.positionRider(passengerEntity);
             }
             // Paper end - EAR 2
+            passengerEntity.updateLastTick(); // Leaf - Rewrite entity despawn time
 
             for (Entity entity : passengerEntity.getPassengers()) {
                 this.tickPassenger(passengerEntity, entity, isActive); // Paper - EAR 2
diff --git a/net/minecraft/world/entity/Entity.java b/net/minecraft/world/entity/Entity.java
index fef583625899091b13439e0d459b7538c866d712..e84ff9d5a1b495170b503dece72f7766b347c2d0 100644
--- a/net/minecraft/world/entity/Entity.java
+++ b/net/minecraft/world/entity/Entity.java
@@ -373,6 +373,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
     public boolean fixedPose = false; // Paper - Expand Pose API
     private final int despawnTime; // Paper - entity despawn time limit
     public int totalEntityAge; // Paper - age-like counter for all entities
+    private int lastTickTime; // Leaf - Rewrite entity despawn time
     public boolean activatedPriorityReset = false; // Pufferfish - DAB
     public int activatedPriority = org.dreeam.leaf.config.modules.opt.DynamicActivationofBrain.maximumActivationPrio; // Pufferfish - DAB (golf score)
     public final io.papermc.paper.entity.activation.ActivationType activationType = io.papermc.paper.entity.activation.ActivationType.activationTypeFor(this); // Paper - EAR 2/tracking ranges
@@ -402,6 +403,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
     private int sectionZ = Integer.MIN_VALUE;
     private boolean updatingSectionStatus;
     private static final boolean enableFMA = Boolean.getBoolean("Leaf.enableFMA"); // Leaf - Optimize Entity distanceTo
+    private final boolean shouldSkipBaseDespawnCheck = this instanceof net.minecraft.world.entity.projectile.ThrowableProjectile; // Leaf - Rewrite entity despawn time
 
     @Override
     public final boolean moonrise$isHardColliding() {
@@ -626,6 +628,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
         this.setPos(0.0, 0.0, 0.0);
         this.eyeHeight = this.dimensions.eyeHeight();
         this.despawnTime = level == null || type == EntityType.PLAYER ? -1 : level.paperConfig().entities.spawning.despawnTime.getOrDefault(type, io.papermc.paper.configuration.type.number.IntOr.Disabled.DISABLED).or(-1); // Paper - entity despawn time limit
+        this.updateLastTick(); // Leaf - Rewrite entity despawn time
     }
 
     public boolean isColliding(BlockPos pos, BlockState state) {
@@ -887,15 +890,50 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
     }
 
     public void tick() {
+        // Leaf start - Rewrite entity despawn time
+        if (!this.shouldSkipBaseDespawnCheck && this.detectDespawnTime()) {
+            return;
+        }
+        /*
         // Paper start - entity despawn time limit
         if (this.despawnTime >= 0 && this.totalEntityAge >= this.despawnTime) {
             this.discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.DESPAWN);
             return;
         }
         // Paper end - entity despawn time limit
+         */
+        // Leaf end - Rewrite entity despawn time
         this.baseTick();
     }
 
+    // Leaf start - Rewrite entity despawn time
+    protected final boolean detectDespawnTime() {
+        this.syncEntityAge();
+        if (this.despawnTime >= 0) {
+            if (this.totalEntityAge >= this.despawnTime) {
+                this.discard(org.bukkit.event.entity.EntityRemoveEvent.Cause.DESPAWN);
+                return true;
+            }
+        }
+        return false;
+    }
+
+    private int calculateMissedTicks() {
+        return net.minecraft.server.MinecraftServer.currentTick - this.lastTickTime;
+    }
+
+    private void syncEntityAge() {
+        int missedTicks = this.calculateMissedTicks();
+        if (missedTicks > 1) {
+            this.totalEntityAge += missedTicks;
+        }
+    }
+
+    public void updateLastTick() {
+        this.lastTickTime = net.minecraft.server.MinecraftServer.currentTick;
+    }
+    // Leaf end - Rewrite entity despawn time
+
     // CraftBukkit start
     public void postTick() {
         // No clean way to break out of ticking once the entity has been copied to a new world, so instead we move the portalling later in the tick cycle
@@ -2564,6 +2602,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
             if (this.maxAirTicks != this.getDefaultMaxAirSupply()) {
                 output.putInt("Bukkit.MaxAirSupply", this.getMaxAirSupply());
             }
+            this.syncEntityAge(); // Leaf - Rewrite entity despawn time
             output.putInt("Spigot.ticksLived", this.totalEntityAge); // Paper
             // CraftBukkit end
             output.storeNullable("CustomName", ComponentSerialization.CODEC, this.getCustomName());
@@ -2721,7 +2760,7 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
 
             // CraftBukkit start
             // Spigot start
-            if (this instanceof net.minecraft.world.entity.LivingEntity) {
+            if (true || this instanceof net.minecraft.world.entity.LivingEntity) { // Leaf - Rewrite entity despawn time
                 this.totalEntityAge = input.getIntOr("Spigot.ticksLived", 0); // Paper
             }
             // Spigot end
@@ -5320,9 +5359,10 @@ public abstract class Entity implements SyncedDataHolder, Nameable, EntityAccess
 
     @Override
     public boolean shouldBeSaved() {
+        this.syncEntityAge(); // Leaf - Rewrite entity despawn time
         return (this.removalReason == null || this.removalReason.shouldSave())
             && !this.isPassenger()
-            && (!this.isVehicle() || !((ca.spottedleaf.moonrise.patches.chunk_system.entity.ChunkSystemEntity)this).moonrise$hasAnyPlayerPassengers()); // Paper - rewrite chunk system
+            && (!this.isVehicle() || !((ca.spottedleaf.moonrise.patches.chunk_system.entity.ChunkSystemEntity)this).moonrise$hasAnyPlayerPassengers()) && (this.despawnTime < 0 || this.totalEntityAge < this.despawnTime); // Paper - rewrite chunk system // Leaf - Rewrite entity despawn time
     }
 
     @Override
diff --git a/net/minecraft/world/entity/projectile/ThrowableProjectile.java b/net/minecraft/world/entity/projectile/ThrowableProjectile.java
index 4c61f4552dc64b1347c7b8dfe9502aac11c75888..be0ebc017bfe92fb2916a9e40971ad19614a33b4 100644
--- a/net/minecraft/world/entity/projectile/ThrowableProjectile.java
+++ b/net/minecraft/world/entity/projectile/ThrowableProjectile.java
@@ -44,6 +44,11 @@ public abstract class ThrowableProjectile extends Projectile {
 
     @Override
     public void tick() {
+        // Leaf start - Rewrite entity despawn time - Check earlier for projectiles
+        if (this.detectDespawnTime()) {
+            return;
+        }
+        // Leaf end - Rewrite entity despawn time - Check earlier for projectiles
         this.handleFirstTickBubbleColumn();
         this.applyGravity();
         this.applyInertia();