PaperMC/patches/server/0166-PreCreatureSpawnEvent.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Aikar <aikar@aikar.co>
Date: Sun, 14 Jan 2018 17:01:31 -0500
Subject: [PATCH] PreCreatureSpawnEvent

Adds an event to fire before an Entity is created, so that plugins that need to cancel
CreatureSpawnEvent can do so from this event instead.

Cancelling CreatureSpawnEvent rapidly causes a lot of garbage collection and CPU waste
as it's done after the Entity object has been fully created.

Mob Limiting plugins and blanket "ban this type of monster" plugins should use this event
instead and save a lot of server resources.

See: https://github.com/PaperMC/Paper/issues/917

diff --git a/src/main/java/net/minecraft/util/SpawnUtil.java b/src/main/java/net/minecraft/util/SpawnUtil.java
index e139ed6bc6f2dd07fe546588b31309ba30ed9755..34c3bf85473b3ad89355ebc21b68c59b3c683b84 100644
--- a/src/main/java/net/minecraft/util/SpawnUtil.java
+++ b/src/main/java/net/minecraft/util/SpawnUtil.java
@@ -22,10 +22,10 @@ public class SpawnUtil {
 
     public static <T extends Mob> Optional<T> trySpawnMob(EntityType<T> entityType, EntitySpawnReason reason, ServerLevel world, BlockPos pos, int tries, int horizontalRange, int verticalRange, SpawnUtil.Strategy requirements) {
         // CraftBukkit start
-        return SpawnUtil.trySpawnMob(entityType, reason, world, pos, tries, horizontalRange, verticalRange, requirements, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT);
+        return SpawnUtil.trySpawnMob(entityType, reason, world, pos, tries, horizontalRange, verticalRange, requirements, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT, null); // Paper
     }
 
-    public static <T extends Mob> Optional<T> trySpawnMob(EntityType<T> entitytypes, EntitySpawnReason entityspawnreason, ServerLevel worldserver, BlockPos blockposition, int i, int j, int k, SpawnUtil.Strategy spawnutil_a, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
+    public static <T extends Mob> Optional<T> trySpawnMob(EntityType<T> entitytypes, EntitySpawnReason entityspawnreason, ServerLevel worldserver, BlockPos blockposition, int i, int j, int k, SpawnUtil.Strategy spawnutil_a, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason, @javax.annotation.Nullable Runnable onAbort) {  // Paper - pre creature spawn event
         // CraftBukkit end
         BlockPos.MutableBlockPos blockposition_mutableblockposition = blockposition.mutable();
 
@@ -35,6 +35,22 @@ public class SpawnUtil {
 
             blockposition_mutableblockposition.setWithOffset(blockposition, i1, k, j1);
             if (worldserver.getWorldBorder().isWithinBounds((BlockPos) blockposition_mutableblockposition) && SpawnUtil.moveToPossibleSpawnPosition(worldserver, k, blockposition_mutableblockposition, spawnutil_a)) {
+                // Paper start - PreCreatureSpawnEvent
+                com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                    io.papermc.paper.util.MCUtil.toLocation(worldserver, blockposition),
+                    org.bukkit.craftbukkit.entity.CraftEntityType.minecraftToBukkit(entitytypes),
+                    reason
+                );
+                if (!event.callEvent()) {
+                    if (event.shouldAbortSpawn()) {
+                        if (onAbort != null) {
+                            onAbort.run();
+                        }
+                        return Optional.empty();
+                    }
+                    break;
+                }
+                // Paper end - PreCreatureSpawnEvent
                 T t0 = entitytypes.create(worldserver, (Consumer<T>) null, blockposition_mutableblockposition, entityspawnreason, false, false); // CraftBukkit - decompile error
 
                 if (t0 != null) {
diff --git a/src/main/java/net/minecraft/world/entity/EntityType.java b/src/main/java/net/minecraft/world/entity/EntityType.java
index 0782b2b58ed30d4ef2598e4b89f338a94a62bbe5..7fb2155b8d320f8871556083aef9ed8e1e91e6e7 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -507,6 +507,16 @@ public class EntityType<T extends Entity> implements FeatureElement, EntityTypeT
     @Nullable
     public T spawn(ServerLevel worldserver, @Nullable Consumer<T> consumer, BlockPos blockposition, EntitySpawnReason entityspawnreason, boolean flag, boolean flag1, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason spawnReason) {
         // CraftBukkit end
+        // Paper start - PreCreatureSpawnEvent
+        com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+            io.papermc.paper.util.MCUtil.toLocation(worldserver, blockposition),
+            org.bukkit.craftbukkit.entity.CraftEntityType.minecraftToBukkit(this),
+            spawnReason
+        );
+        if (!event.callEvent()) {
+            return null;
+        }
+        // Paper end - PreCreatureSpawnEvent
         T t0 = this.create(worldserver, consumer, blockposition, entityspawnreason, flag, flag1);
 
         if (t0 != null) {
diff --git a/src/main/java/net/minecraft/world/entity/npc/Villager.java b/src/main/java/net/minecraft/world/entity/npc/Villager.java
index 83bb48891d03534468d61cf7683438b3efb131cf..82ed0ce824e84ea09ea963caa61fbb75f6ce6fe7 100644
--- a/src/main/java/net/minecraft/world/entity/npc/Villager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/Villager.java
@@ -944,7 +944,7 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
             }).limit(5L).toList();
 
             if (list1.size() >= requiredCount) {
-                if (!SpawnUtil.trySpawnMob(EntityType.IRON_GOLEM, EntitySpawnReason.MOB_SUMMONED, world, this.blockPosition(), 10, 8, 6, SpawnUtil.Strategy.LEGACY_IRON_GOLEM, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.VILLAGE_DEFENSE).isEmpty()) { // CraftBukkit
+                if (SpawnUtil.trySpawnMob(EntityType.IRON_GOLEM, EntitySpawnReason.MOB_SUMMONED, world, this.blockPosition(), 10, 8, 6, SpawnUtil.Strategy.LEGACY_IRON_GOLEM, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.VILLAGE_DEFENSE, () -> {GolemSensor.golemDetected(this);}).isPresent()) { // CraftBukkit // Paper - Set Golem Last Seen to stop it from spawning another one
                     list.forEach(GolemSensor::golemDetected);
                 }
             }
diff --git a/src/main/java/net/minecraft/world/level/BaseSpawner.java b/src/main/java/net/minecraft/world/level/BaseSpawner.java
index 6c29e55239fdcf8df3b9dc012aa80cebcd3a837a..bb3f3bec350dda43dbf5eda0a8c8057a413694b2 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -132,6 +132,20 @@ public abstract class BaseSpawner {
                         } else if (!SpawnPlacements.checkSpawnRules((EntityType) optional.get(), world, EntitySpawnReason.SPAWNER, blockposition1, world.getRandom())) {
                             continue;
                         }
+                        // Paper start - PreCreatureSpawnEvent
+                        com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                            io.papermc.paper.util.MCUtil.toLocation(world, d0, d1, d2),
+                            org.bukkit.craftbukkit.entity.CraftEntityType.minecraftToBukkit(optional.get()),
+                            org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER
+                        );
+                        if (!event.callEvent()) {
+                            flag = true;
+                            if (event.shouldAbortSpawn()) {
+                                break;
+                            }
+                            continue;
+                        }
+                        // Paper end - PreCreatureSpawnEvent
 
                         Entity entity = EntityType.loadEntityRecursive(nbttagcompound, world, EntitySpawnReason.SPAWNER, (entity1) -> {
                             entity1.moveTo(d0, d1, d2, entity1.getYRot(), entity1.getXRot());
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 400166ad0199dd4b96684904ef4748cdb72381bb..0b41149ae134084cef4016241ce923dac0349846 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -230,7 +230,13 @@ public final class NaturalSpawner {
                                         j1 = biomesettingsmobs_c.minCount + world.random.nextInt(1 + biomesettingsmobs_c.maxCount - biomesettingsmobs_c.minCount);
                                     }
 
-                                    if (NaturalSpawner.isValidSpawnPostitionForType(world, group, structuremanager, chunkgenerator, biomesettingsmobs_c, blockposition_mutableblockposition, d2) && checker.test(biomesettingsmobs_c.type, blockposition_mutableblockposition, chunk)) {
+                                    // Paper start - PreCreatureSpawnEvent
+                                    PreSpawnStatus doSpawning = isValidSpawnPostitionForType(world, group, structuremanager, chunkgenerator, biomesettingsmobs_c, blockposition_mutableblockposition, d2);
+                                    if (doSpawning == PreSpawnStatus.ABORT) {
+                                        return;
+                                    }
+                                    if (doSpawning == PreSpawnStatus.SUCCESS && checker.test(biomesettingsmobs_c.type, blockposition_mutableblockposition, chunk)) {
+                                        // Paper end - PreCreatureSpawnEvent
                                         Mob entityinsentient = NaturalSpawner.getMobForSpawn(world, biomesettingsmobs_c.type);
 
                                         if (entityinsentient == null) {
@@ -278,10 +284,31 @@ public final class NaturalSpawner {
         return squaredDistance <= 576.0D ? false : (world.getSharedSpawnPos().closerToCenterThan(new Vec3((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D), 24.0D) ? false : Objects.equals(new ChunkPos(pos), chunk.getPos()) || world.isNaturalSpawningAllowed((BlockPos) pos));
     }
 
-    private static boolean isValidSpawnPostitionForType(ServerLevel world, MobCategory group, StructureManager structureAccessor, ChunkGenerator chunkGenerator, MobSpawnSettings.SpawnerData spawnEntry, BlockPos.MutableBlockPos pos, double squaredDistance) {
+    // Paper start - PreCreatureSpawnEvent
+    private enum PreSpawnStatus {
+        FAIL,
+        SUCCESS,
+        CANCELLED,
+        ABORT
+    }
+    private static PreSpawnStatus isValidSpawnPostitionForType(ServerLevel world, MobCategory group, StructureManager structureAccessor, ChunkGenerator chunkGenerator, MobSpawnSettings.SpawnerData spawnEntry, BlockPos.MutableBlockPos pos, double squaredDistance) {
+        // Paper end - PreCreatureSpawnEvent
         EntityType<?> entitytypes = spawnEntry.type;
 
-        return entitytypes.getCategory() == MobCategory.MISC ? false : (!entitytypes.canSpawnFarFromPlayer() && squaredDistance > (double) (entitytypes.getCategory().getDespawnDistance() * entitytypes.getCategory().getDespawnDistance()) ? false : (entitytypes.canSummon() && NaturalSpawner.canSpawnMobAt(world, structureAccessor, chunkGenerator, group, spawnEntry, pos) ? (!SpawnPlacements.isSpawnPositionOk(entitytypes, world, pos) ? false : (!SpawnPlacements.checkSpawnRules(entitytypes, world, EntitySpawnReason.NATURAL, pos, world.random) ? false : world.noCollision(entitytypes.getSpawnAABB((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D)))) : false));
+        // Paper start - PreCreatureSpawnEvent
+        com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+            io.papermc.paper.util.MCUtil.toLocation(world, pos),
+            org.bukkit.craftbukkit.entity.CraftEntityType.minecraftToBukkit(entitytypes), SpawnReason.NATURAL
+        );
+        if (!event.callEvent()) {
+            if (event.shouldAbortSpawn()) {
+                return PreSpawnStatus.ABORT;
+            }
+            return PreSpawnStatus.CANCELLED;
+        }
+        // Paper end - PreCreatureSpawnEvent
+
+        return entitytypes.getCategory() == MobCategory.MISC ? PreSpawnStatus.FAIL : (!entitytypes.canSpawnFarFromPlayer() && squaredDistance > (double) (entitytypes.getCategory().getDespawnDistance() * entitytypes.getCategory().getDespawnDistance()) ? PreSpawnStatus.FAIL : (entitytypes.canSummon() && NaturalSpawner.canSpawnMobAt(world, structureAccessor, chunkGenerator, group, spawnEntry, pos) ? (!SpawnPlacements.isSpawnPositionOk(entitytypes, world, pos) ? PreSpawnStatus.FAIL : (!SpawnPlacements.checkSpawnRules(entitytypes, world, EntitySpawnReason.NATURAL, pos, world.random) ? PreSpawnStatus.FAIL : world.noCollision(entitytypes.getSpawnAABB((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D)) ? PreSpawnStatus.SUCCESS : PreSpawnStatus.FAIL)) : PreSpawnStatus.FAIL)); // Paper - PreCreatureSpawnEvent
     }
 
     @Nullable