Paper/patches/server/0167-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 b77ebe04f1018962b85110258c8a0a2db8612485..1954fdc7b72700d5948e93ebcb0e6a26fe244a1b 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, MobSpawnType 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, MobSpawnType enummobspawn, 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, MobSpawnType enummobspawn, 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
         // 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, (CompoundTag) null, null, blockposition_mutableblockposition, enummobspawn, 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 382b55167dede435b034866bd394455f0f6f2a00..035af9ccf679a562203a4a2c4f2b38098c57b492 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -418,6 +418,16 @@ public class EntityType<T extends Entity> implements FeatureElement, EntityTypeT
     @Nullable
     public T spawn(ServerLevel worldserver, @Nullable CompoundTag nbttagcompound, @Nullable Consumer<T> consumer, BlockPos blockposition, MobSpawnType enummobspawn, 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, nbttagcompound, consumer, 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 f0d5e45d0d6ac51106379d20690d34a032a24c39..bfd156acbae31619234fffb1804726090802fbae 100644
--- a/src/main/java/net/minecraft/world/entity/npc/Villager.java
+++ b/src/main/java/net/minecraft/world/entity/npc/Villager.java
@@ -975,7 +975,7 @@ public class Villager extends AbstractVillager implements ReputationEventHandler
             }).limit(5L).collect(Collectors.toList());
 
             if (list1.size() >= requiredCount) {
-                if (!SpawnUtil.trySpawnMob(EntityType.IRON_GOLEM, MobSpawnType.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, MobSpawnType.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 fdd1fd084c46b0220c9e7e0389e9b52e782d2878..0166c5ff685490cbf67a9d26f48cb1a0be754488 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -130,6 +130,20 @@ public abstract class BaseSpawner {
                         } else if (!SpawnPlacements.checkSpawnRules((EntityType) optional.get(), world, MobSpawnType.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, (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 604766a286d00bb4b40c20482376fe80651beabe..352d230b365c512a4b9831265d3a57825f80fbfd 100644
--- a/src/main/java/net/minecraft/world/level/NaturalSpawner.java
+++ b/src/main/java/net/minecraft/world/level/NaturalSpawner.java
@@ -213,7 +213,13 @@ 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) {
@@ -261,19 +267,40 @@ 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;
 
+        // 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
         if (entitytypes.getCategory() == MobCategory.MISC) {
-            return false;
+            return PreSpawnStatus.FAIL; // Paper - PreCreatureSpawnEvent
         } else if (!entitytypes.canSpawnFarFromPlayer() && squaredDistance > (double) (entitytypes.getCategory().getDespawnDistance() * entitytypes.getCategory().getDespawnDistance())) {
-            return false;
+            return PreSpawnStatus.FAIL; // Paper - PreCreatureSpawnEvent
         } else if (entitytypes.canSummon() && NaturalSpawner.canSpawnMobAt(world, structureAccessor, chunkGenerator, group, spawnEntry, pos)) {
             SpawnPlacements.Type entitypositiontypes_surface = SpawnPlacements.getPlacementType(entitytypes);
 
-            return !NaturalSpawner.isSpawnPositionOk(entitypositiontypes_surface, world, pos, entitytypes) ? false : (!SpawnPlacements.checkSpawnRules(entitytypes, world, MobSpawnType.NATURAL, pos, world.random) ? false : world.noCollision(entitytypes.getAABB((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D)));
+            boolean isValid = !NaturalSpawner.isSpawnPositionOk(entitypositiontypes_surface, world, pos, entitytypes) ? false : (!SpawnPlacements.checkSpawnRules(entitytypes, world, MobSpawnType.NATURAL, pos, world.random) ? false : world.noCollision(entitytypes.getAABB((double) pos.getX() + 0.5D, (double) pos.getY(), (double) pos.getZ() + 0.5D))); // Paper - PreCreatureSpawnEvent
+            return isValid ? PreSpawnStatus.SUCCESS : PreSpawnStatus.FAIL; // Paper - PreCreatureSpawnEvent
         } else {
-            return false;
+            return PreSpawnStatus.FAIL; // Paper - PreCreatureSpawnEvent
         }
     }