Entity spawn function tag

src/main/java/draaft/command/CommandFunctionManagerInterface.java

@@ -0,0 +1,7 @@
+package draaft.command;
+
+import net.minecraft.entity.Entity;
+
+public interface CommandFunctionManagerInterface {
+    void draaft$entitySpawn(Entity entity);
+}

src/main/java/draaft/mixin/server/function/CommandFunctionManagerMixin.java

@@ -0,0 +1,48 @@
+package draaft.mixin.server.function;
+
+import draaft.command.CommandFunctionManagerInterface;
+import net.minecraft.entity.Entity;
+import net.minecraft.server.MinecraftServer;
+import net.minecraft.server.command.ServerCommandSource;
+import net.minecraft.server.function.CommandFunction;
+import net.minecraft.server.function.CommandFunctionManager;
+import net.minecraft.server.function.FunctionLoader;
+import net.minecraft.util.Identifier;
+import org.spongepowered.asm.mixin.Final;
+import org.spongepowered.asm.mixin.Mixin;
+import org.spongepowered.asm.mixin.Shadow;
+import org.spongepowered.asm.mixin.Unique;
+import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+
+import java.util.List;
+
+@Mixin(CommandFunctionManager.class)
+public abstract class CommandFunctionManagerMixin implements CommandFunctionManagerInterface {
+    @Shadow @Final private MinecraftServer server;
+
+    @Shadow public abstract int execute(CommandFunction function, ServerCommandSource source);
+
+    @Unique
+    private static final Identifier ENTITY_SPAWN = new Identifier("draaft", "entity_spawn");
+
+    @Unique
+    private List<CommandFunction> entitySpawnFunctions = List.of();
+
+    @Inject(method = "method_29773", remap = false, at = @At("TAIL"))
+    private void afterLoad(FunctionLoader functionLoader, CallbackInfo ci) {
+        entitySpawnFunctions = functionLoader.getTags().getOrCreate(ENTITY_SPAWN).values();
+    }
+
+    @Override
+    public void draaft$entitySpawn(Entity entity) {
+        this.server.getProfiler().push(ENTITY_SPAWN::toString);
+
+        for (var cmd : entitySpawnFunctions) {
+            this.execute(cmd, entity.getCommandSource().withLevel(2).withSilent());
+        }
+
+        this.server.getProfiler().pop();
+    }
+}

src/main/java/draaft/mixin/server/world/ServerWorldMixin.java

@@ -1,7 +1,9 @@
 package draaft.mixin.server.world;
 
+import draaft.command.CommandFunctionManagerInterface;
 import draaft.persistent.WorldManifest;
 import draaft.world.ServerWorldInterface;
+import net.minecraft.entity.Entity;
 import net.minecraft.server.MinecraftServer;
 import net.minecraft.server.world.ServerWorld;
 import net.minecraft.util.profiler.Profiler;
@@ -17,7 +19,10 @@
 import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.Unique;
 import org.spongepowered.asm.mixin.injection.At;
+import org.spongepowered.asm.mixin.injection.Inject;
 import org.spongepowered.asm.mixin.injection.ModifyArg;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
+import org.spongepowered.asm.mixin.injection.callback.CallbackInfoReturnable;
 
 import java.util.Random;
 import java.util.function.Supplier;
@@ -142,6 +147,18 @@ private int injectedRain(int rainTime) {
         return rainTime;
     }
 
+    @Inject(method = "addEntity", at = @At("TAIL"))
+    void afterSpawnEntity(Entity entity, CallbackInfoReturnable<Boolean> cir) {
+        // note: this injection point can cause some spurious draaft:entity_spawn triggers, but that's fine (?)
+        if (cir.getReturnValue()) {
+            var server = entity.getServer();
+
+            assert server != null;
+
+            ((CommandFunctionManagerInterface) server.getCommandFunctionManager()).draaft$entitySpawn(entity);
+        }
+    }
+
     @Override
     public WorldManifest draaft$getWorldManifest() {
         return this.worldManifest;

src/main/resources/draaft.mixins.json

@@ -49,6 +49,7 @@
     "screen.slot.TradeOutputSlotMixin",
     "server.MinecraftServerAccessor",
     "server.PlayerManagerMixin",
+    "server.function.CommandFunctionManagerMixin",
     "server.world.ServerWorldMixin",
     "structure.IglooGeneratorMixin",
     "structure.StructurePieceMixin",