PaperMC/patches/server/0165-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 116c0fe87776ebea88f47d1c98fd31d6046f3b86..a8903f087c75c851e8111b96e5aa9f271d618392 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, boolean requireEmptySpace) {
         // CraftBukkit start
-        return SpawnUtil.trySpawnMob(entityType, reason, world, pos, tries, horizontalRange, verticalRange, requirements, requireEmptySpace, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT);
+        return SpawnUtil.trySpawnMob(entityType, reason, world, pos, tries, horizontalRange, verticalRange, requirements, requireEmptySpace, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT, null); // Paper - pre creature spawn event
     }
 
-    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, boolean flag, 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, boolean flag, 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) && (!flag || worldserver.noCollision(entitytypes.getSpawnAABB((double) blockposition_mutableblockposition.getX() + 0.5D, (double) blockposition_mutableblockposition.getY(), (double) blockposition_mutableblockposition.getZ() + 0.5D)))) {
+                // Paper start - PreCreatureSpawnEvent
+                final 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 bb68fcef4b0cd89605f57f42ee5529d9c8e7e73e..768edafa018961ce38306f87e5cfe6aa99537305 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -497,6 +497,16 @@ 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 6681c8d9e76a7a1e470378479d2c55e62d05a0fe..77c8c09b3d74b0dd88321bdfdf19d0f089d4e432 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, false, 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, false, 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 da0ddb8285e157be0cc7b940a9590be5e3061e3d..5a0ea71dc39c582ef6c843dc0532adb04ba120ce 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -228,7 +228,13 @@ 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) {
@@ -276,10 +282,31 @@ 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