Fix crash making step sounds on servers.

src/main/java/com/simibubi/create/foundation/mixin/StepSoundMixin.java

@@ -16,6 +16,7 @@ import net.minecraft.util.math.Vec3d;
 import net.minecraft.world.World;
 import net.minecraft.world.gen.feature.template.Template;
 import org.apache.logging.log4j.util.TriConsumer;
+import org.spongepowered.asm.mixin.Final;
 import org.spongepowered.asm.mixin.Mixin;
 import org.spongepowered.asm.mixin.Shadow;
 import org.spongepowered.asm.mixin.injection.At;
@@ -30,6 +31,7 @@ import java.util.stream.Collectors;
 
 @Mixin(Entity.class)
 public abstract class StepSoundMixin {
+	private final Entity self = (Entity) (Object) this;
 
 	@Shadow
 	public boolean collided;
@@ -37,6 +39,7 @@ public abstract class StepSoundMixin {
 	@Shadow
 	public World world;
 
+	@Final
 	@Shadow
 	protected Random rand;
 
@@ -58,21 +61,20 @@ public abstract class StepSoundMixin {
 	@Shadow
 	protected abstract void playStepSound(BlockPos p_180429_1_, BlockState p_180429_2_);
 
-	private Set<AbstractContraptionEntity> getIntersectingContraptions(Entity entity) {
+	private Set<AbstractContraptionEntity> getIntersectingContraptions() {
-		Set<AbstractContraptionEntity> contraptions = ContraptionHandler.loadedContraptions.get(entity.world)
+		Set<AbstractContraptionEntity> contraptions = ContraptionHandler.loadedContraptions.get(this.world)
 			.values()
 			.stream()
 			.map(Reference::get)
-			.filter(cEntity -> cEntity != null && cEntity.collidingEntities.containsKey(entity))
+			.filter(cEntity -> cEntity != null && cEntity.collidingEntities.containsKey(self))
 			.collect(Collectors.toSet());
 
-		contraptions.addAll(entity.world.getEntitiesWithinAABB(AbstractContraptionEntity.class, getBoundingBox().grow(1f)));
+		contraptions.addAll(this.world.getEntitiesWithinAABB(AbstractContraptionEntity.class, getBoundingBox().grow(1f)));
 		return contraptions;
 	}
 
 	private void forCollision(Vec3d anchorPos, TriConsumer<Contraption, BlockState, BlockPos> action) {
-		Entity thi = (Entity) (Object) this;
+		getIntersectingContraptions().forEach(cEntity -> {
-		getIntersectingContraptions(thi).forEach(cEntity -> {
 			Vec3d localPos = ContraptionCollider.getWorldToLocalTranslation(anchorPos, cEntity);
 
 			localPos = anchorPos.add(localPos);
@@ -90,15 +92,14 @@ public abstract class StepSoundMixin {
 
 	@Inject(at = @At(
 		value = "JUMP",
-		opcode = 154, //IFNE
+		opcode = 154, // IFNE line 587 injecting before `!blockstate.isAir(this.world, blockpos)`
 		ordinal = 4
 	),
 		method = "move"
 	)
 	private void movementMixin(MoverType mover, Vec3d movement, CallbackInfo ci) {
-		Entity thi = (Entity) (Object) this;
 		World entityWorld = world;
-		Vec3d worldPos = thi.getPositionVector().add(0, -0.2, 0);
+		Vec3d worldPos = self.getPositionVector().add(0, -0.2, 0);
 		AtomicBoolean stepped = new AtomicBoolean(false);
 
 		forCollision(worldPos, (contraption, blockstate, blockPos) -> {
@@ -113,18 +114,17 @@ public abstract class StepSoundMixin {
 		world = entityWorld;
 	}
 
-	@Inject(method = {"Lnet/minecraft/entity/Entity;createRunningParticles()V"}, at = @At(value = "TAIL"))
+	@Inject(method = "createRunningParticles", at = @At("TAIL"))
 	private void createRunningParticlesMixin(CallbackInfo ci) {
-		Entity thi = (Entity) (Object) this;
+		Vec3d worldPos = self.getPositionVector().add(0, -0.2, 0);
-		Vec3d worldPos = thi.getPositionVector().add(0, -0.2, 0);
 		BlockPos pos = new BlockPos(worldPos); // pos where particles are spawned
 
 		forCollision(worldPos, (contraption, blockstate, blockpos) -> {
-			if (!blockstate.addRunningEffects(world, blockpos, thi) && blockstate.getRenderType() != BlockRenderType.INVISIBLE) {
+			if (!blockstate.addRunningEffects(world, blockpos, self) && blockstate.getRenderType() != BlockRenderType.INVISIBLE) {
-				Vec3d vec3d = thi.getMotion();
+				Vec3d vec3d = self.getMotion();
 				this.world.addParticle(new BlockParticleData(ParticleTypes.BLOCK, blockstate).setPos(pos),
-					thi.getX() + ((double) rand.nextFloat() - 0.5D) * (double) thi.getWidth(),
+					self.getX() + ((double) rand.nextFloat() - 0.5D) * (double) self.getWidth(),
-					thi.getY() + 0.1D, thi.getZ() + ((double) rand.nextFloat() - 0.5D) * (double) thi.getWidth(),
+					self.getY() + 0.1D, self.getZ() + ((double) rand.nextFloat() - 0.5D) * (double) self.getWidth(),
 					vec3d.x * -4.0D, 1.5D, vec3d.z * -4.0D);
 			}
 		});

src/main/resources/create.mixins.json

@@ -4,7 +4,6 @@
     "package": "com.simibubi.create.foundation.mixin",
     "compatibilityLevel": "JAVA_8",
     "refmap": "create.refmap.json",
-    "mixins": ["StepSoundMixin"],
     "client": [
         "TileWorldHookMixin",
         "CancelTileEntityRenderMixin",
@@ -13,7 +12,8 @@
         "NetworkLightUpdateMixin",
         "RenderHooksMixin",
         "ShaderCloseMixin",
-        "TileRemoveMixin"
+        "TileRemoveMixin",
+        "StepSoundMixin"
     ],
     "injectors": {
         "defaultRequire": 1