fix mobs not spawning in structures

src/main/java/carpet/mixins/ChunkGenerator_customMobSpawnsMixin.java

@@ -1,13 +1,10 @@
 package carpet.mixins;
 
-import carpet.CarpetSettings;
+import carpet.utils.SpawnOverrides;
 import it.unimi.dsi.fastutil.longs.LongSet;
 import net.minecraft.core.Holder;
-import net.minecraft.data.worldgen.StructureFeatures;
-import net.minecraft.world.entity.EntityType;
 import net.minecraft.world.level.levelgen.feature.ConfiguredStructureFeature;
 import org.spongepowered.asm.mixin.Mixin;
-import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
 import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
@@ -27,47 +24,20 @@ import java.util.Map;
 @Mixin(ChunkGenerator.class)
 public abstract class ChunkGenerator_customMobSpawnsMixin
 {
-
-    @Shadow protected abstract void ensureGenerated();
-
-    private static final WeightedRandomList<MobSpawnSettings.SpawnerData> PYRAMID_SPAWNS = WeightedRandomList.create(new MobSpawnSettings.SpawnerData(EntityType.HUSK, 1, 1, 1));
-    private static final WeightedRandomList<MobSpawnSettings.SpawnerData> SHULKER_SPAWNS = WeightedRandomList.create(new MobSpawnSettings.SpawnerData(EntityType.SHULKER, 10, 4, 4));
-    private static final WeightedRandomList<MobSpawnSettings.SpawnerData> BASTION_SPAWNS = WeightedRandomList.create(
-            new MobSpawnSettings.SpawnerData(EntityType.PIGLIN_BRUTE, 5, 1, 2),
-            new MobSpawnSettings.SpawnerData(EntityType.PIGLIN, 10, 2, 4),
-            new MobSpawnSettings.SpawnerData(EntityType.HOGLIN, 2, 1, 2)
-    );
-
     @Inject(
             method = "getMobsAt", locals = LocalCapture.CAPTURE_FAILHARD,
             at = @At(
                     value = "INVOKE",
                    target = "Ljava/util/Map$Entry;getKey()Ljava/lang/Object;"
             ), cancellable = true)
-    private void isInsidePyramid(Holder<Biome> holder, StructureFeatureManager structureFeatureManager, MobCategory mobCategory, BlockPos blockPos,
+    private void checkCMSpawns(Holder<Biome> holder, StructureFeatureManager structureFeatureManager, MobCategory mobCategory, BlockPos blockPos,
                                  CallbackInfoReturnable<WeightedRandomList<MobSpawnSettings.SpawnerData>> cir,
                                  Map<ConfiguredStructureFeature<?, ?>, LongSet> map, Iterator<?> var6, Map.Entry<ConfiguredStructureFeature<?, ?>, LongSet> entry)
     {
-        if (mobCategory == MobCategory.MONSTER)
+        WeightedRandomList<MobSpawnSettings.SpawnerData> res = SpawnOverrides.test(structureFeatureManager, entry.getValue(), mobCategory, entry.getKey(), blockPos);
+        if (res != null)
         {
-            ConfiguredStructureFeature<?, ?> str = entry.getKey();
+            cir.setReturnValue(res);
-            if (CarpetSettings.huskSpawningInTemples
-                    && str.feature == StructureFeatures.DESERT_PYRAMID.value().feature
-                    && structureFeatureManager.getStructureAt(blockPos, StructureFeatures.DESERT_PYRAMID.value()).isValid()) {
-                cir.setReturnValue(PYRAMID_SPAWNS);
-                return;
-            }
-            if (CarpetSettings.shulkerSpawningInEndCities
-                    && str.feature == StructureFeatures.END_CITY.value().feature
-                    && structureFeatureManager.getStructureAt(blockPos, StructureFeatures.END_CITY.value()).isValid()) {
-                cir.setReturnValue(SHULKER_SPAWNS);
-                return;
-            }
-            if (CarpetSettings.piglinsSpawningInBastions
-                    && str.feature == StructureFeatures.BASTION_REMNANT.value().feature
-                    && structureFeatureManager.getStructureAt(blockPos, StructureFeatures.BASTION_REMNANT.value()).isValid()) {
-                cir.setReturnValue(BASTION_SPAWNS);
-            }
         }
     }
 }

src/main/java/carpet/utils/SpawnOverrides.java

@@ -0,0 +1,74 @@
+package carpet.utils;
+
+import carpet.CarpetSettings;
+import it.unimi.dsi.fastutil.longs.LongSet;
+import net.minecraft.core.BlockPos;
+import net.minecraft.core.Holder;
+import net.minecraft.data.worldgen.StructureFeatures;
+import net.minecraft.util.random.WeightedRandomList;
+import net.minecraft.world.entity.EntityType;
+import net.minecraft.world.entity.MobCategory;
+import net.minecraft.world.level.StructureFeatureManager;
+import net.minecraft.world.level.biome.MobSpawnSettings;
+import net.minecraft.world.level.levelgen.feature.ConfiguredStructureFeature;
+import net.minecraft.world.level.levelgen.feature.StructureFeature;
+import net.minecraft.world.level.levelgen.structure.StructureSpawnOverride;
+import net.minecraft.world.level.levelgen.structure.StructureStart;
+import org.apache.commons.lang3.tuple.Pair;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.function.BooleanSupplier;
+
+public class SpawnOverrides {
+    final private static Map<Pair<MobCategory, StructureFeature<?>>, Pair<BooleanSupplier, StructureSpawnOverride>> carpetOverrides = new HashMap<>();
+    static {
+        addOverride(() -> CarpetSettings.huskSpawningInTemples, MobCategory.MONSTER, StructureFeatures.DESERT_PYRAMID, StructureSpawnOverride.BoundingBoxType.STRUCTURE,
+                        WeightedRandomList.create(new MobSpawnSettings.SpawnerData(EntityType.HUSK, 1, 1, 1))
+        );
+        addOverride(() -> CarpetSettings.shulkerSpawningInEndCities, MobCategory.MONSTER, StructureFeatures.END_CITY, StructureSpawnOverride.BoundingBoxType.PIECE,
+                WeightedRandomList.create(new MobSpawnSettings.SpawnerData(EntityType.SHULKER, 10, 4, 4))
+        );
+        addOverride(() -> CarpetSettings.piglinsSpawningInBastions, MobCategory.MONSTER, StructureFeatures.BASTION_REMNANT, StructureSpawnOverride.BoundingBoxType.PIECE,
+                WeightedRandomList.create(
+                        new MobSpawnSettings.SpawnerData(EntityType.PIGLIN_BRUTE, 5, 1, 2),
+                        new MobSpawnSettings.SpawnerData(EntityType.PIGLIN, 10, 2, 4),
+                        new MobSpawnSettings.SpawnerData(EntityType.HOGLIN, 2, 1, 2)
+                )
+        );
+
+    }
+
+    public static void addOverride(BooleanSupplier when, MobCategory cat, Holder<ConfiguredStructureFeature<?,?>> poo,
+                                   StructureSpawnOverride.BoundingBoxType type, WeightedRandomList<MobSpawnSettings.SpawnerData> spawns)
+    {
+        carpetOverrides.put(Pair.of(cat, poo.value().feature), Pair.of(when, new StructureSpawnOverride(type, spawns)));
+    }
+
+    public static WeightedRandomList<MobSpawnSettings.SpawnerData> test(StructureFeatureManager structureFeatureManager, LongSet foo,
+            MobCategory cat, ConfiguredStructureFeature<?,?> confExisting, BlockPos where)
+    {
+        final Pair<BooleanSupplier, StructureSpawnOverride> spawnData = carpetOverrides.get(Pair.of(cat, confExisting.feature));
+        if (spawnData == null || !spawnData.getKey().getAsBoolean()) return null;
+        StructureSpawnOverride override = spawnData.getRight();
+        if (override.boundingBox() == StructureSpawnOverride.BoundingBoxType.STRUCTURE)
+        {
+            if (structureFeatureManager.getStructureAt(where, confExisting).isValid())
+                return override.spawns();
+        }
+        else
+        {
+            List<StructureStart> starts = new ArrayList<>(1);
+            structureFeatureManager.fillStartsForFeature(confExisting, foo, starts::add);
+            for (StructureStart start: starts)
+            {
+                if (start != null && start.isValid() && structureFeatureManager.structureHasPieceAt(where, start)) {
+                    return override.spawns();
+                }
+            }
+        }
+        return null;
+    }
+}