PaperMC/paper-server/patches/sources/net/minecraft/world/level/NaturalSpawner.java.patch

--- a/net/minecraft/world/level/NaturalSpawner.java
+++ b/net/minecraft/world/level/NaturalSpawner.java
@@ -47,8 +47,13 @@
 import net.minecraft.world.level.levelgen.structure.Structure;
 import net.minecraft.world.level.levelgen.structure.structures.NetherFortressStructure;
 import net.minecraft.world.level.material.FluidState;
+import net.minecraft.world.level.storage.LevelData;
 import net.minecraft.world.phys.Vec3;
 import org.slf4j.Logger;
+import org.bukkit.craftbukkit.util.CraftSpawnCategory;
+import org.bukkit.entity.SpawnCategory;
+import org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason;
+// CraftBukkit end
 
 public final class NaturalSpawner {
 
@@ -82,6 +87,13 @@
             MobCategory enumcreaturetype = entity.getType().getCategory();
 
             if (enumcreaturetype != MobCategory.MISC) {
+                // Paper start - Only count natural spawns
+                if (!entity.level().paperConfig().entities.spawning.countAllMobsForSpawning &&
+                    !(entity.spawnReason == org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.NATURAL ||
+                        entity.spawnReason == org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.CHUNK_GEN)) {
+                    continue;
+                }
+                // Paper end - Only count natural spawns
                 BlockPos blockposition = entity.blockPosition();
 
                 chunkSource.query(ChunkPos.asLong(blockposition), (chunk) -> {
@@ -107,15 +119,31 @@
         return (Biome) chunk.getNoiseBiome(QuartPos.fromBlock(pos.getX()), QuartPos.fromBlock(pos.getY()), QuartPos.fromBlock(pos.getZ())).value();
     }
 
-    public static List<MobCategory> getFilteredSpawningCategories(NaturalSpawner.SpawnState info, boolean spawnAnimals, boolean spawnMonsters, boolean rare) {
+    // CraftBukkit start - add server
+    public static List<MobCategory> getFilteredSpawningCategories(NaturalSpawner.SpawnState spawnercreature_d, boolean flag, boolean flag1, boolean flag2, ServerLevel worldserver) {
+        LevelData worlddata = worldserver.getLevelData(); // CraftBukkit - Other mob type spawn tick rate
+        // CraftBukkit end
         List<MobCategory> list = new ArrayList(NaturalSpawner.SPAWNING_CATEGORIES.length);
         MobCategory[] aenumcreaturetype = NaturalSpawner.SPAWNING_CATEGORIES;
         int i = aenumcreaturetype.length;
 
         for (int j = 0; j < i; ++j) {
             MobCategory enumcreaturetype = aenumcreaturetype[j];
+            // CraftBukkit start - Use per-world spawn limits
+            boolean spawnThisTick = true;
+            int limit = enumcreaturetype.getMaxInstancesPerChunk();
+            SpawnCategory spawnCategory = CraftSpawnCategory.toBukkit(enumcreaturetype);
+            if (CraftSpawnCategory.isValidForLimits(spawnCategory)) {
+                spawnThisTick = worldserver.ticksPerSpawnCategory.getLong(spawnCategory) != 0 && worlddata.getGameTime() % worldserver.ticksPerSpawnCategory.getLong(spawnCategory) == 0;
+                limit = worldserver.getWorld().getSpawnLimit(spawnCategory);
+            }
 
-            if ((spawnAnimals || !enumcreaturetype.isFriendly()) && (spawnMonsters || enumcreaturetype.isFriendly()) && (rare || !enumcreaturetype.isPersistent()) && info.canSpawnForCategoryGlobal(enumcreaturetype)) {
+            if (!spawnThisTick || limit == 0) {
+                continue;
+            }
+
+            if ((flag || !enumcreaturetype.isFriendly()) && (flag1 || enumcreaturetype.isFriendly()) && (flag2 || !enumcreaturetype.isPersistent()) && spawnercreature_d.canSpawnForCategoryGlobal(enumcreaturetype, limit)) {
+                // CraftBukkit end
                 list.add(enumcreaturetype);
             }
         }
@@ -144,6 +172,16 @@
         gameprofilerfiller.pop();
     }
 
+    // Paper start - Add mobcaps commands
+    public static int globalLimitForCategory(final ServerLevel level, final MobCategory category, final int spawnableChunkCount) {
+        final int categoryLimit = level.getWorld().getSpawnLimitUnsafe(CraftSpawnCategory.toBukkit(category));
+        if (categoryLimit < 1) {
+            return categoryLimit;
+        }
+        return categoryLimit * spawnableChunkCount / NaturalSpawner.MAGIC_NUMBER;
+    }
+    // Paper end - Add mobcaps commands
+
     public static void spawnCategoryForChunk(MobCategory group, ServerLevel world, LevelChunk chunk, NaturalSpawner.SpawnPredicate checker, NaturalSpawner.AfterSpawnCallback runner) {
         BlockPos blockposition = NaturalSpawner.getRandomPosWithin(world, chunk);
 
@@ -164,9 +202,9 @@
         StructureManager structuremanager = world.structureManager();
         ChunkGenerator chunkgenerator = world.getChunkSource().getGenerator();
         int i = pos.getY();
-        BlockState iblockdata = chunk.getBlockState(pos);
+        BlockState iblockdata = world.getBlockStateIfLoadedAndInBounds(pos); // Paper - don't load chunks for mob spawn
 
-        if (!iblockdata.isRedstoneConductor(chunk, pos)) {
+        if (iblockdata != null && !iblockdata.isRedstoneConductor(chunk, pos)) { // Paper - don't load chunks for mob spawn
             BlockPos.MutableBlockPos blockposition_mutableblockposition = new BlockPos.MutableBlockPos();
             int j = 0;
             int k = 0;
@@ -195,7 +233,7 @@
                             if (entityhuman != null) {
                                 double d2 = entityhuman.distanceToSqr(d0, (double) i, d1);
 
-                                if (NaturalSpawner.isRightDistanceToPlayerAndSpawnPoint(world, chunk, blockposition_mutableblockposition, d2)) {
+                                if (world.isLoadedAndInBounds(blockposition_mutableblockposition) && NaturalSpawner.isRightDistanceToPlayerAndSpawnPoint(world, chunk, blockposition_mutableblockposition, d2)) { // Paper - don't load chunks for mob spawn
                                     if (biomesettingsmobs_c == null) {
                                         Optional<MobSpawnSettings.SpawnerData> optional = NaturalSpawner.getRandomSpawnMobAt(world, structuremanager, chunkgenerator, group, world.random, blockposition_mutableblockposition);
 
@@ -207,7 +245,13 @@
                                         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) {
@@ -217,10 +261,15 @@
                                         entityinsentient.moveTo(d0, (double) i, d1, world.random.nextFloat() * 360.0F, 0.0F);
                                         if (NaturalSpawner.isValidPositionForMob(world, entityinsentient, d2)) {
                                             groupdataentity = entityinsentient.finalizeSpawn(world, world.getCurrentDifficultyAt(entityinsentient.blockPosition()), EntitySpawnReason.NATURAL, groupdataentity);
-                                            ++j;
-                                            ++k1;
-                                            world.addFreshEntityWithPassengers(entityinsentient);
-                                            runner.run(entityinsentient, chunk);
+                                            // CraftBukkit start
+                                            // SPIGOT-7045: Give ocelot babies back their special spawn reason. Note: This is the only modification required as ocelots count as monsters which means they only spawn during normal chunk ticking and do not spawn during chunk generation as starter mobs.
+                                            world.addFreshEntityWithPassengers(entityinsentient, (entityinsentient instanceof net.minecraft.world.entity.animal.Ocelot && !((org.bukkit.entity.Ageable) entityinsentient.getBukkitEntity()).isAdult()) ? SpawnReason.OCELOT_BABY : SpawnReason.NATURAL);
+                                            if (!entityinsentient.isRemoved()) {
+                                                ++j;
+                                                ++k1;
+                                                runner.run(entityinsentient, chunk);
+                                            }
+                                            // CraftBukkit end
                                             if (j >= entityinsentient.getMaxSpawnClusterSize()) {
                                                 return;
                                             }
@@ -250,10 +299,31 @@
         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
@@ -268,6 +338,7 @@
             NaturalSpawner.LOGGER.warn("Can't spawn entity of type: {}", BuiltInRegistries.ENTITY_TYPE.getKey(type));
         } catch (Exception exception) {
             NaturalSpawner.LOGGER.warn("Failed to create mob", exception);
+            com.destroystokyo.paper.exception.ServerInternalException.reportInternalException(exception); // Paper - ServerExceptionEvent
         }
 
         return null;
@@ -356,6 +427,7 @@
                                     entity = biomesettingsmobs_c.type.create(world.getLevel(), EntitySpawnReason.NATURAL);
                                 } catch (Exception exception) {
                                     NaturalSpawner.LOGGER.warn("Failed to create mob", exception);
+                                    com.destroystokyo.paper.exception.ServerInternalException.reportInternalException(exception); // Paper - ServerExceptionEvent
                                     continue;
                                 }
 
@@ -369,7 +441,7 @@
 
                                     if (entityinsentient.checkSpawnRules(world, EntitySpawnReason.CHUNK_GENERATION) && entityinsentient.checkSpawnObstruction(world)) {
                                         groupdataentity = entityinsentient.finalizeSpawn(world, world.getCurrentDifficultyAt(entityinsentient.blockPosition()), EntitySpawnReason.CHUNK_GENERATION, groupdataentity);
-                                        world.addFreshEntityWithPassengers(entityinsentient);
+                                        world.addFreshEntityWithPassengers(entityinsentient, SpawnReason.CHUNK_GEN); // CraftBukkit
                                         flag = true;
                                     }
                                 }
@@ -482,10 +554,12 @@
             return this.unmodifiableMobCategoryCounts;
         }
 
-        boolean canSpawnForCategoryGlobal(MobCategory group) {
-            int i = group.getMaxInstancesPerChunk() * this.spawnableChunkCount / NaturalSpawner.MAGIC_NUMBER;
+        // CraftBukkit start
+        boolean canSpawnForCategoryGlobal(MobCategory enumcreaturetype, int limit) {
+            int i = limit * this.spawnableChunkCount / NaturalSpawner.MAGIC_NUMBER;
+            // CraftBukkit end
 
-            return this.mobCategoryCounts.getInt(group) < i;
+            return this.mobCategoryCounts.getInt(enumcreaturetype) < i;
         }
 
         boolean canSpawnForCategoryLocal(MobCategory group, ChunkPos chunkPos) {