Scissors/patches/server/0023-Prevent-abusable-entities-from-being-spawned-by-spaw.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Business Goose <arclicious@vivaldi.net>
Date: Mon, 4 Apr 2022 00:16:54 +0100
Subject: [PATCH] Prevent abusable entities from being spawned by spawners


diff --git a/src/main/java/net/minecraft/world/level/BaseSpawner.java b/src/main/java/net/minecraft/world/level/BaseSpawner.java
index 569cef8fcb1e3e1e8b66dad4fa9b956b44542bf1..f844e0b1e44f0b45b1febadf02d7b37d3099fbdb 100644
--- a/src/main/java/net/minecraft/world/level/BaseSpawner.java
+++ b/src/main/java/net/minecraft/world/level/BaseSpawner.java
@@ -19,7 +19,9 @@ import net.minecraft.util.StringUtil;
 import net.minecraft.util.random.WeightedRandomList;
 import net.minecraft.world.entity.Entity;
 import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.LivingEntity;
 import net.minecraft.world.entity.Mob;
+import net.minecraft.world.entity.MobCategory;
 import net.minecraft.world.entity.MobSpawnType;
 import net.minecraft.world.entity.SpawnGroupData;
 import net.minecraft.world.entity.SpawnPlacements;
@@ -31,6 +33,7 @@ public abstract class BaseSpawner {
 
     private static final Logger LOGGER = LogManager.getLogger();
     private static final int EVENT_SPAWN = 1;
+    public static List<MobCategory> whitelistedCategories = List.of(MobCategory.CREATURE, MobCategory.MONSTER, MobCategory.WATER_CREATURE, MobCategory.UNDERGROUND_WATER_CREATURE, MobCategory.AMBIENT); // Scissors
     public static WeightedRandomList<SpawnData> EMPTY_POTENTIALS = WeightedRandomList.create(); // Paper - private->public
     public int spawnDelay = 20;
     public WeightedRandomList<SpawnData> spawnPotentials;
@@ -64,6 +67,13 @@ public abstract class BaseSpawner {
     public ResourceLocation getEntityId(@Nullable Level world, BlockPos pos) {
         String s = this.nextSpawnData.getTag().getString("id");
 
+        // Scissors start
+        Optional<EntityType<?>> entityType = EntityType.byString(s);
+        if (entityType.isPresent() && !whitelistedCategories.contains(entityType.get().getCategory())) {
+            return null;
+        }
+        // Scissors end
+
         try {
             return StringUtil.isNullOrEmpty(s) ? null : new ResourceLocation(s);
         } catch (ResourceLocationException resourcekeyinvalidexception) {
@@ -73,6 +83,12 @@ public abstract class BaseSpawner {
     }
 
     public void setEntityId(EntityType<?> type) {
+        // Scissors start - Don't allow unnatural entities to be added to spawners
+        if (!whitelistedCategories.contains(type.getCategory())) {
+            return;
+        }
+        // Scissors end
+
         this.nextSpawnData.getTag().putString("id", Registry.ENTITY_TYPE.getKey(type).toString());
         this.spawnPotentials = BaseSpawner.EMPTY_POTENTIALS; // CraftBukkit - SPIGOT-3496, MC-92282
     }
@@ -121,7 +137,7 @@ public abstract class BaseSpawner {
                     CompoundTag nbttagcompound = this.nextSpawnData.getTag();
                     Optional<EntityType<?>> optional = EntityType.by(nbttagcompound);
 
-                    if (!optional.isPresent()) {
+                    if (!(optional.isPresent() && whitelistedCategories.contains(optional.get().getCategory()))) { // Scissors - Don't try spawning in entites that aren't whitelisted
                         this.delay(world, pos);
                         return;
                     }
@@ -254,12 +270,16 @@ public abstract class BaseSpawner {
             ListTag nbttaglist = nbt.getList("SpawnPotentials", 10);
 
             for (int i = 0; i < nbttaglist.size(); ++i) {
-                list.add(new SpawnData(nbttaglist.getCompound(i)));
+                // Scissors start - Filter unnatural entity types from being added
+                if (isValid(nbttaglist.getCompound(i))) {
+                    list.add(new SpawnData(nbttaglist.getCompound(i)));
+                }
+                // Scissors end
             }
         }
 
         this.spawnPotentials = WeightedRandomList.create((List) list);
-        if (nbt.contains("SpawnData", 10)) {
+        if (nbt.contains("SpawnData", 10) && isValid(nbt.getCompound("SpawnData"))) { // Scissors - Filter unnatural entity types from being added
             this.setNextSpawnData(world, pos, new SpawnData(1, nbt.getCompound("SpawnData")));
         } else if (!list.isEmpty()) {
             this.spawnPotentials.getRandom(this.random).ifPresent((mobspawnerdata) -> {
@@ -371,4 +391,11 @@ public abstract class BaseSpawner {
     public double getoSpin() {
         return this.oSpin;
     }
+
+    // Scissors start
+    public boolean isValid(CompoundTag tag) {
+        Optional<EntityType<?>> type = EntityType.by(tag);
+        return type.isPresent() && whitelistedCategories.contains(type.get().getCategory());
+    }
+    // Scissors end
 }