Paper/patches/server/0174-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/world/entity/EntityType.java b/src/main/java/net/minecraft/world/entity/EntityType.java
index 8d5c61a77bea2f2f5dbff26cb479f855945f9541..f38ccdecbade43983358dfbeadca86be7d15a68c 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -332,6 +332,20 @@ public class EntityType<T extends Entity> implements EntityTypeTest<Entity, T> {
 
     @Nullable
     public T spawnCreature(ServerLevel worldserver, @Nullable CompoundTag nbttagcompound, @Nullable Component ichatbasecomponent, @Nullable Player entityhuman, BlockPos blockposition, MobSpawnType enummobspawn, boolean flag, boolean flag1, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason spawnReason) {
+        // Paper start - Call PreCreatureSpawnEvent
+        org.bukkit.entity.EntityType type = org.bukkit.entity.EntityType.fromName(EntityType.getKey(this).getPath());
+        if (type != null) {
+            com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
+            event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                net.minecraft.server.MCUtil.toLocation(worldserver, blockposition),
+                type,
+                spawnReason
+            );
+            if (!event.callEvent()) {
+                return null;
+            }
+        }
+        // Paper end
         T t0 = this.create(worldserver, nbttagcompound, ichatbasecomponent, entityhuman, blockposition, enummobspawn, 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 b4a3469d85a388100092cc2a1305cdcae37df9fc..0ba4e6111726a1ca3cc5b6ce21e0500cc57a4aa3 100644
--- a/src/main/java/net/minecraft/world/entity/npc/Villager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/Villager.java
@@ -987,6 +987,21 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
             BlockPos blockposition1 = this.findSpawnPositionForGolemInColumn(blockposition, d0, d1);
 
             if (blockposition1 != null) {
+                // Paper start - Call PreCreatureSpawnEvent
+                com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
+                event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                    net.minecraft.server.MCUtil.toLocation(level, blockposition1),
+                    org.bukkit.entity.EntityType.IRON_GOLEM,
+                    org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.VILLAGE_DEFENSE
+                );
+                if (!event.callEvent()) {
+                    if (event.shouldAbortSpawn()) {
+                        GolemSensor.golemDetected(this); // Set Golem Last Seen to stop it from spawning another one
+                        return null;
+                    }
+                    break;
+                }
+                // Paper end
                 IronGolem entityirongolem = (IronGolem) EntityType.IRON_GOLEM.create(world, (CompoundTag) null, (Component) null, (Player) null, blockposition1, MobSpawnType.MOB_SUMMONED, false, false);
 
                 if (entityirongolem != null) {
diff --git a/src/main/java/net/minecraft/world/level/BaseSpawner.java b/src/main/java/net/minecraft/world/level/BaseSpawner.java
index 12a78685848b7fd945a472902d8200ea1d50b9ec..900cba8c2b04fc1b82a13af76d7079b6a6a2994d 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -132,6 +132,27 @@ public abstract class BaseSpawner {
                     double d2 = j >= 3 ? nbttaglist.getDouble(2) : (double) pos.getZ() + (world.random.nextDouble() - world.random.nextDouble()) * (double) this.spawnRange + 0.5D;
 
                     if (world.noCollision(((EntityType) optional.get()).getAABB(d0, d1, d2)) && SpawnPlacements.checkSpawnRules((EntityType) optional.get(), world, MobSpawnType.SPAWNER, new BlockPos(d0, d1, d2), world.getRandom())) {
+                        // Paper start
+                        EntityType<?> entityType = optional.get();
+                        String key = EntityType.getKey(entityType).getPath();
+
+                        org.bukkit.entity.EntityType type = org.bukkit.entity.EntityType.fromName(key);
+                        if (type != null) {
+                            com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
+                            event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                                net.minecraft.server.MCUtil.toLocation(world, d0, d1, d2),
+                                type,
+                                org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.SPAWNER
+                            );
+                            if (!event.callEvent()) {
+                                flag = true;
+                                if (event.shouldAbortSpawn()) {
+                                    break;
+                                }
+                                continue;
+                            }
+                        }
+                        // Paper end
                         Entity entity = EntityType.loadEntityRecursive(nbttagcompound, world, (entity1) -> {
                             entity1.moveTo(d0, d1, d2, entity1.getYRot(), entity1.getXRot());
                             return entity1;
diff --git a/src/main/java/net/minecraft/world/level/NaturalSpawner.java b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
index 4ea02bfe348cec26bbb2c15ddacbbc110033b2d3..f208239b69dbd8788b799d8b28e457017edef9d5 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -231,7 +231,13 @@ 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
+                                    Boolean doSpawning = isValidSpawnPostitionForType(world, group, structuremanager, chunkgenerator, biomesettingsmobs_c, blockposition_mutableblockposition, d2);
+                                    if (doSpawning == null) {
+                                        return;
+                                    }
+                                    if (doSpawning && checker.test(biomesettingsmobs_c.type, blockposition_mutableblockposition, chunk)) {
+                                        // Paper end
                                         Mob entityinsentient = NaturalSpawner.getMobForSpawn(world, biomesettingsmobs_c.type);
 
                                         if (entityinsentient == null) {
@@ -278,9 +284,25 @@ public final class NaturalSpawner {
         return squaredDistance <= 576.0D ? false : (world.getSharedSpawnPos().closerThan((Position) (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.isPositionEntityTicking((BlockPos) pos));
     }
 
-    private static boolean isValidSpawnPostitionForType(ServerLevel world, MobCategory group, StructureFeatureManager structureAccessor, ChunkGenerator chunkGenerator, MobSpawnSettings.SpawnerData spawnEntry, BlockPos.MutableBlockPos pos, double squaredDistance) {
+    private static Boolean isValidSpawnPostitionForType(ServerLevel world, MobCategory group, StructureFeatureManager structureAccessor, ChunkGenerator chunkGenerator, MobSpawnSettings.SpawnerData spawnEntry, BlockPos.MutableBlockPos pos, double squaredDistance) { // Paper
         EntityType<?> entitytypes = spawnEntry.type;
 
+        // Paper start
+        com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent event;
+        org.bukkit.entity.EntityType type = org.bukkit.entity.EntityType.fromName(EntityType.getKey(entitytypes).getPath());
+        if (type != null) {
+            event = new com.destroystokyo.paper.event.entity.PreCreatureSpawnEvent(
+                net.minecraft.server.MCUtil.toLocation(world, pos),
+                type, SpawnReason.NATURAL
+            );
+            if (!event.callEvent()) {
+                if (event.shouldAbortSpawn()) {
+                    return null;
+                }
+                return false;
+            }
+        }
+        // Paper end
         if (entitytypes.getCategory() == MobCategory.MISC) {
             return false;
         } else if (!entitytypes.canSpawnFarFromPlayer() && squaredDistance > (double) (entitytypes.getCategory().getDespawnDistance() * entitytypes.getCategory().getDespawnDistance())) {