#1266: Add support for virtual entities

By: Jishuna <joshl5324@gmail.com>

paper-server/nms-patches/net/minecraft/server/level/WorldServer.patch

@@ -592,7 +592,18 @@
      }
  
      @Override
-@@ -1751,6 +1967,7 @@
+@@ -1703,7 +1919,9 @@
+ 
+         a() {}
+ 
+-        public void onCreated(Entity entity) {}
++        public void onCreated(Entity entity) {
++            entity.inWorld = true; // CraftBukkit - Mark entity as in world
++        }
+ 
+         public void onDestroyed(Entity entity) {
+             WorldServer.this.getScoreboard().entityRemoved(entity);
+@@ -1751,6 +1969,7 @@
              }
  
              entity.updateDynamicGameEventListener(DynamicGameEventListener::add);
@@ -600,7 +611,7 @@
          }
  
          public void onTrackingEnd(Entity entity) {
-@@ -1787,6 +2004,14 @@
+@@ -1787,6 +2006,14 @@
              }
  
              entity.updateDynamicGameEventListener(DynamicGameEventListener::remove);

paper-server/nms-patches/net/minecraft/world/entity/Entity.patch

@@ -75,7 +75,7 @@
      public int tickCount;
      private int remainingFireTicks;
      public boolean wasTouchingWater;
-@@ -241,6 +298,25 @@
+@@ -241,6 +298,26 @@
      public boolean hasVisualFire;
      @Nullable
      private IBlockData feetBlockState;
@@ -83,6 +83,7 @@
 +    public boolean persist = true;
 +    public boolean visibleByDefault = true;
 +    public boolean valid;
++    public boolean inWorld = false;
 +    public boolean generation;
 +    public int maxAirTicks = getDefaultMaxAirSupply(); // CraftBukkit - SPIGOT-6907: re-implement LivingEntity#setMaximumAir()
 +    public org.bukkit.projectiles.ProjectileSource projectileSource; // For projectiles only
@@ -101,7 +102,7 @@
  
      public Entity(EntityTypes<?> entitytypes, World world) {
          this.id = Entity.ENTITY_COUNTER.incrementAndGet();
-@@ -374,6 +450,12 @@
+@@ -374,6 +451,12 @@
      public void onClientRemoval() {}
  
      public void setPose(EntityPose entitypose) {
@@ -114,7 +115,7 @@
          this.entityData.set(Entity.DATA_POSE, entitypose);
      }
  
-@@ -398,6 +480,33 @@
+@@ -398,6 +481,33 @@
      }
  
      protected void setRot(float f, float f1) {
@@ -148,7 +149,7 @@
          this.setYRot(f % 360.0F);
          this.setXRot(f1 % 360.0F);
      }
-@@ -439,6 +548,15 @@
+@@ -439,6 +549,15 @@
          this.baseTick();
      }
  
@@ -164,7 +165,7 @@
      public void baseTick() {
          this.level().getProfiler().push("entityBaseTick");
          this.feetBlockState = null;
-@@ -453,7 +571,7 @@
+@@ -453,7 +572,7 @@
          this.walkDistO = this.walkDist;
          this.xRotO = this.getXRot();
          this.yRotO = this.getYRot();
@@ -173,7 +174,7 @@
          if (this.canSpawnSprintParticle()) {
              this.spawnSprintParticle();
          }
-@@ -488,6 +606,10 @@
+@@ -488,6 +607,10 @@
          if (this.isInLava()) {
              this.lavaHurt();
              this.fallDistance *= 0.5F;
@@ -184,7 +185,7 @@
          }
  
          this.checkBelowWorld();
-@@ -539,15 +661,48 @@
+@@ -539,15 +662,48 @@
  
      public void lavaHurt() {
          if (!this.fireImmune()) {
@@ -234,7 +235,7 @@
          int j = i * 20;
  
          if (this instanceof EntityLiving) {
-@@ -698,6 +853,28 @@
+@@ -698,6 +854,28 @@
                      block.updateEntityAfterFallOn(this.level(), this);
                  }
  
@@ -263,7 +264,7 @@
                  if (this.onGround()) {
                      block.stepOn(this.level(), blockposition, iblockdata, this);
                  }
-@@ -1025,6 +1202,20 @@
+@@ -1025,6 +1203,20 @@
          return SoundEffects.GENERIC_SPLASH;
      }
  
@@ -284,7 +285,7 @@
      protected void checkInsideBlocks() {
          AxisAlignedBB axisalignedbb = this.getBoundingBox();
          BlockPosition blockposition = BlockPosition.containing(axisalignedbb.minX + 1.0E-7D, axisalignedbb.minY + 1.0E-7D, axisalignedbb.minZ + 1.0E-7D);
-@@ -1439,6 +1630,7 @@
+@@ -1439,6 +1631,7 @@
          this.yo = d1;
          this.zo = d4;
          this.setPos(d3, d1, d4);
@@ -292,7 +293,7 @@
      }
  
      public void moveTo(Vec3D vec3d) {
-@@ -1633,6 +1825,12 @@
+@@ -1633,6 +1826,12 @@
          return false;
      }
  
@@ -305,7 +306,18 @@
      public void awardKillScore(Entity entity, int i, DamageSource damagesource) {
          if (entity instanceof EntityPlayer) {
              CriterionTriggers.ENTITY_KILLED_PLAYER.trigger((EntityPlayer) entity, this, damagesource);
-@@ -1666,7 +1864,7 @@
+@@ -1661,16 +1860,22 @@
+     }
+ 
+     public boolean saveAsPassenger(NBTTagCompound nbttagcompound) {
++        // CraftBukkit start - allow excluding certain data when saving
++        return saveAsPassenger(nbttagcompound, true);
++    }
++
++    public boolean saveAsPassenger(NBTTagCompound nbttagcompound, boolean includeAll) {
++        // CraftBukkit end
+         if (this.removalReason != null && !this.removalReason.shouldSave()) {
+             return false;
          } else {
              String s = this.getEncodeId();
  
@@ -314,7 +326,36 @@
                  return false;
              } else {
                  nbttagcompound.putString("id", s);
-@@ -1691,6 +1889,18 @@
+-                this.saveWithoutId(nbttagcompound);
++                this.saveWithoutId(nbttagcompound, includeAll); // CraftBukkit - pass on includeAll
+                 return true;
+             }
+         }
+@@ -1681,16 +1886,38 @@
+     }
+ 
+     public NBTTagCompound saveWithoutId(NBTTagCompound nbttagcompound) {
++        // CraftBukkit start - allow excluding certain data when saving
++        return saveWithoutId(nbttagcompound, true);
++    }
++
++    public NBTTagCompound saveWithoutId(NBTTagCompound nbttagcompound, boolean includeAll) {
++        // CraftBukkit end
+         try {
+-            if (this.vehicle != null) {
+-                nbttagcompound.put("Pos", this.newDoubleList(this.vehicle.getX(), this.getY(), this.vehicle.getZ()));
+-            } else {
+-                nbttagcompound.put("Pos", this.newDoubleList(this.getX(), this.getY(), this.getZ()));
++            // CraftBukkit start - selectively save position
++            if (includeAll) {
++                if (this.vehicle != null) {
++                    nbttagcompound.put("Pos", this.newDoubleList(this.vehicle.getX(), this.getY(), this.vehicle.getZ()));
++                } else {
++                    nbttagcompound.put("Pos", this.newDoubleList(this.getX(), this.getY(), this.getZ()));
++                }
+             }
++            // CraftBukkit end
+ 
              Vec3D vec3d = this.getDeltaMovement();
  
              nbttagcompound.put("Motion", this.newDoubleList(vec3d.x, vec3d.y, vec3d.z));
@@ -333,14 +374,18 @@
              nbttagcompound.put("Rotation", this.newFloatList(this.getYRot(), this.getXRot()));
              nbttagcompound.putFloat("FallDistance", this.fallDistance);
              nbttagcompound.putShort("Fire", (short) this.remainingFireTicks);
-@@ -1699,6 +1909,25 @@
+@@ -1698,7 +1925,28 @@
+             nbttagcompound.putBoolean("OnGround", this.onGround());
              nbttagcompound.putBoolean("Invulnerable", this.invulnerable);
              nbttagcompound.putInt("PortalCooldown", this.portalCooldown);
-             nbttagcompound.putUUID("UUID", this.getUUID());
-+            // CraftBukkit start
+-            nbttagcompound.putUUID("UUID", this.getUUID());
++            // CraftBukkit start - selectively save uuid and world
++            if (includeAll) {
++                nbttagcompound.putUUID("UUID", this.getUUID());
 +                // PAIL: Check above UUID reads 1.8 properly, ie: UUIDMost / UUIDLeast
 +                nbttagcompound.putLong("WorldUUIDLeast", ((WorldServer) this.level).getWorld().getUID().getLeastSignificantBits());
 +                nbttagcompound.putLong("WorldUUIDMost", ((WorldServer) this.level).getWorld().getUID().getMostSignificantBits());
++            }
 +            nbttagcompound.putInt("Bukkit.updateLevel", CURRENT_LEVEL);
 +            if (!this.persist) {
 +                nbttagcompound.putBoolean("Bukkit.persist", this.persist);
@@ -359,7 +404,25 @@
              IChatBaseComponent ichatbasecomponent = this.getCustomName();
  
              if (ichatbasecomponent != null) {
-@@ -1766,6 +1995,11 @@
+@@ -1747,7 +1995,7 @@
+                 nbttagcompound.put("Tags", nbttaglist);
+             }
+ 
+-            this.addAdditionalSaveData(nbttagcompound);
++            this.addAdditionalSaveData(nbttagcompound, includeAll); // CraftBukkit - pass on includeAll
+             if (this.isVehicle()) {
+                 nbttaglist = new NBTTagList();
+                 iterator = this.getPassengers().iterator();
+@@ -1756,7 +2004,7 @@
+                     Entity entity = (Entity) iterator.next();
+                     NBTTagCompound nbttagcompound1 = new NBTTagCompound();
+ 
+-                    if (entity.saveAsPassenger(nbttagcompound1)) {
++                    if (entity.saveAsPassenger(nbttagcompound1, includeAll)) { // CraftBukkit - pass on includeAll
+                         nbttaglist.add(nbttagcompound1);
+                     }
+                 }
+@@ -1766,6 +2014,11 @@
                  }
              }
  
@@ -371,7 +434,7 @@
              return nbttagcompound;
          } catch (Throwable throwable) {
              CrashReport crashreport = CrashReport.forThrowable(throwable, "Saving entity NBT");
-@@ -1849,6 +2083,45 @@
+@@ -1849,6 +2102,45 @@
              } else {
                  throw new IllegalStateException("Entity has invalid position");
              }
@@ -417,7 +480,20 @@
          } catch (Throwable throwable) {
              CrashReport crashreport = CrashReport.forThrowable(throwable, "Loading entity NBT");
              CrashReportSystemDetails crashreportsystemdetails = crashreport.addCategory("Entity being loaded");
-@@ -1924,9 +2197,22 @@
+@@ -1870,6 +2162,12 @@
+         return entitytypes.canSerialize() && minecraftkey != null ? minecraftkey.toString() : null;
+     }
+ 
++    // CraftBukkit start - allow excluding certain data when saving
++    protected void addAdditionalSaveData(NBTTagCompound nbttagcompound, boolean includeAll) {
++        addAdditionalSaveData(nbttagcompound);
++    }
++    // CraftBukkit end
++
+     protected abstract void readAdditionalSaveData(NBTTagCompound nbttagcompound);
+ 
+     protected abstract void addAdditionalSaveData(NBTTagCompound nbttagcompound);
+@@ -1924,9 +2222,22 @@
          } else if (this.level().isClientSide) {
              return null;
          } else {
@@ -440,7 +516,7 @@
              this.level().addFreshEntity(entityitem);
              return entityitem;
          }
-@@ -2024,6 +2310,18 @@
+@@ -2024,6 +2335,18 @@
              if (!flag && (!this.canRide(entity) || !entity.canAddPassenger(this))) {
                  return false;
              } else {
@@ -459,7 +535,7 @@
                  if (this.isPassenger()) {
                      this.stopRiding();
                  }
-@@ -2057,7 +2355,7 @@
+@@ -2057,7 +2380,7 @@
              Entity entity = this.vehicle;
  
              this.vehicle = null;
@@ -468,7 +544,7 @@
          }
  
      }
-@@ -2088,10 +2386,29 @@
+@@ -2088,10 +2411,29 @@
          }
      }
  
@@ -499,7 +575,7 @@
              if (this.passengers.size() == 1 && this.passengers.get(0) == entity) {
                  this.passengers = ImmutableList.of();
              } else {
-@@ -2103,6 +2420,7 @@
+@@ -2103,6 +2445,7 @@
              entity.boardingCooldown = 60;
              this.gameEvent(GameEvent.ENTITY_DISMOUNT, entity);
          }
@@ -507,7 +583,7 @@
      }
  
      protected boolean canAddPassenger(Entity entity) {
-@@ -2189,14 +2507,20 @@
+@@ -2189,14 +2532,20 @@
  
              if (this.isInsidePortal) {
                  MinecraftServer minecraftserver = worldserver.getServer();
@@ -531,7 +607,7 @@
                      this.level().getProfiler().pop();
                  }
  
-@@ -2320,6 +2644,13 @@
+@@ -2320,6 +2669,13 @@
      }
  
      public void setSwimming(boolean flag) {
@@ -545,7 +621,7 @@
          this.setSharedFlag(4, flag);
      }
  
-@@ -2369,8 +2700,12 @@
+@@ -2369,8 +2725,12 @@
          return this.getTeam() != null ? this.getTeam().isAlliedTo(scoreboardteambase) : false;
      }
  
@@ -559,7 +635,7 @@
      }
  
      public boolean getSharedFlag(int i) {
-@@ -2389,7 +2724,7 @@
+@@ -2389,7 +2749,7 @@
      }
  
      public int getMaxAirSupply() {
@@ -568,7 +644,7 @@
      }
  
      public int getAirSupply() {
-@@ -2397,7 +2732,18 @@
+@@ -2397,7 +2757,18 @@
      }
  
      public void setAirSupply(int i) {
@@ -588,7 +664,7 @@
      }
  
      public int getTicksFrozen() {
-@@ -2424,11 +2770,41 @@
+@@ -2424,11 +2795,41 @@
  
      public void thunderHit(WorldServer worldserver, EntityLightning entitylightning) {
          this.setRemainingFireTicks(this.remainingFireTicks + 1);
@@ -632,7 +708,7 @@
      }
  
      public void onAboveBubbleCol(boolean flag) {
-@@ -2593,15 +2969,38 @@
+@@ -2593,15 +2994,38 @@
  
      @Nullable
      public Entity changeDimension(WorldServer worldserver) {
@@ -673,27 +749,33 @@
                  this.level().getProfiler().popPush("reloading");
                  Entity entity = this.getType().create(worldserver);
  
-@@ -2610,9 +3009,17 @@
+@@ -2609,10 +3033,22 @@
+                     entity.restoreFrom(this);
                      entity.moveTo(shapedetectorshape.pos.x, shapedetectorshape.pos.y, shapedetectorshape.pos.z, shapedetectorshape.yRot, entity.getXRot());
                      entity.setDeltaMovement(shapedetectorshape.speed);
-                     worldserver.addDuringTeleport(entity);
+-                    worldserver.addDuringTeleport(entity);
 -                    if (worldserver.dimension() == World.END) {
 -                        WorldServer.makeObsidianPlatform(worldserver);
++                    // CraftBukkit start - Don't spawn the new entity if the current entity isn't spawned
++                    if (this.inWorld) {
++                        worldserver.addDuringTeleport(entity);
 +                        if (worldserver.getTypeKey() == WorldDimension.END) { // CraftBukkit
 +                            WorldServer.makeObsidianPlatform(worldserver, this); // CraftBukkit
-                     }
++                        }
++                    }
++                    // CraftBukkit end
 +                    // CraftBukkit start - Forward the CraftEntity to the new entity
 +                    this.getBukkitEntity().setHandle(entity);
 +                    entity.bukkitEntity = this.getBukkitEntity();
 +
 +                    if (this instanceof EntityInsentient) {
 +                        ((EntityInsentient) this).dropLeash(true, false); // Unleash to prevent duping of leads.
-+                    }
+                     }
 +                    // CraftBukkit end
                  }
  
                  this.removeAfterChangingDimensions();
-@@ -2633,20 +3040,34 @@
+@@ -2633,20 +3069,34 @@
  
      @Nullable
      protected ShapeDetectorShape findDimensionEntryPoint(WorldServer worldserver) {
@@ -733,7 +815,7 @@
                      IBlockData iblockdata = this.level().getBlockState(this.portalEntrancePos);
                      EnumDirection.EnumAxis enumdirection_enumaxis;
                      Vec3D vec3d;
-@@ -2663,8 +3084,8 @@
+@@ -2663,8 +3113,8 @@
                          vec3d = new Vec3D(0.5D, 0.0D, 0.0D);
                      }
  
@@ -744,7 +826,7 @@
              }
          } else {
              BlockPosition blockposition1;
-@@ -2674,8 +3095,14 @@
+@@ -2674,8 +3124,14 @@
              } else {
                  blockposition1 = worldserver.getHeightmapPos(HeightMap.Type.MOTION_BLOCKING_NO_LEAVES, worldserver.getSharedSpawnPos());
              }
@@ -760,7 +842,7 @@
          }
      }
  
-@@ -2683,8 +3110,23 @@
+@@ -2683,8 +3139,23 @@
          return BlockPortalShape.getRelativePosition(blockutil_rectangle, enumdirection_enumaxis, this.position(), this.getDimensions(this.getPose()));
      }
  
@@ -786,7 +868,7 @@
      }
  
      public boolean canChangeDimensions() {
-@@ -2804,6 +3246,12 @@
+@@ -2804,6 +3275,12 @@
          }
      }
  
@@ -799,7 +881,20 @@
      public boolean teleportTo(WorldServer worldserver, double d0, double d1, double d2, Set<RelativeMovement> set, float f, float f1) {
          float f2 = MathHelper.clamp(f1, -90.0F, 90.0F);
  
-@@ -2929,7 +3377,26 @@
+@@ -2823,7 +3300,11 @@
+             entity.moveTo(d0, d1, d2, f, f2);
+             entity.setYHeadRot(f);
+             this.setRemoved(Entity.RemovalReason.CHANGED_DIMENSION);
+-            worldserver.addDuringTeleport(entity);
++            // CraftBukkit start - Don't spawn the new entity if the current entity isn't spawned
++            if (inWorld) {
++                worldserver.addDuringTeleport(entity);
++            }
++            // CraftBukkit end
+         }
+ 
+         return true;
+@@ -2929,7 +3410,26 @@
      }
  
      public final void setBoundingBox(AxisAlignedBB axisalignedbb) {
@@ -827,7 +922,7 @@
      }
  
      protected float getEyeHeight(EntityPose entitypose, EntitySize entitysize) {
-@@ -3240,6 +3707,11 @@
+@@ -3240,6 +3740,11 @@
                                      vec3d = vec3d.add(vec3d1);
                                      ++k1;
                                  }

paper-server/nms-patches/net/minecraft/world/entity/animal/EntityBee.patch

@@ -13,7 +13,29 @@
  public class EntityBee extends EntityAnimal implements IEntityAngerable, EntityBird {
  
      public static final float FLAP_DEGREES_PER_TICK = 120.32113F;
-@@ -242,7 +248,7 @@
+@@ -187,12 +193,19 @@
+ 
+     @Override
+     public void addAdditionalSaveData(NBTTagCompound nbttagcompound) {
++        // CraftBukkit start - selectively save data
++        addAdditionalSaveData(nbttagcompound, true);
++    }
++
++    @Override
++    public void addAdditionalSaveData(NBTTagCompound nbttagcompound, boolean includeAll) {
++        // CraftBukkit end
+         super.addAdditionalSaveData(nbttagcompound);
+-        if (this.hasHive()) {
++        if (includeAll && this.hasHive()) { // CraftBukkit - selectively save hive
+             nbttagcompound.put("HivePos", GameProfileSerializer.writeBlockPos(this.getHivePos()));
+         }
+ 
+-        if (this.hasSavedFlowerPos()) {
++        if (includeAll && this.hasSavedFlowerPos()) { // CraftBukkit - selectively save flower
+             nbttagcompound.put("FlowerPos", GameProfileSerializer.writeBlockPos(this.getSavedFlowerPos()));
+         }
+ 
+@@ -242,7 +255,7 @@
                  }
  
                  if (b0 > 0) {
@@ -22,7 +44,7 @@
                  }
              }
  
-@@ -640,11 +646,14 @@
+@@ -640,11 +653,14 @@
          if (this.isInvulnerableTo(damagesource)) {
              return false;
          } else {
@@ -39,7 +61,7 @@
          }
      }
  
-@@ -999,7 +1008,7 @@
+@@ -999,7 +1015,7 @@
  
          e() {
              super();
@@ -48,7 +70,7 @@
              this.blacklistedTargets = Lists.newArrayList();
              this.setFlags(EnumSet.of(PathfinderGoal.Type.MOVE));
          }
-@@ -1116,7 +1125,7 @@
+@@ -1116,7 +1132,7 @@
  
          f() {
              super();
@@ -57,7 +79,7 @@
              this.setFlags(EnumSet.of(PathfinderGoal.Type.MOVE));
          }
  
-@@ -1216,7 +1225,7 @@
+@@ -1216,7 +1232,7 @@
                              }
                          }
  
@@ -66,7 +88,7 @@
                              EntityBee.this.level().levelEvent(2005, blockposition, 0);
                              EntityBee.this.level().setBlockAndUpdate(blockposition, iblockdata1);
                              EntityBee.this.incrementNumCropsGrownSincePollination();
-@@ -1289,7 +1298,7 @@
+@@ -1289,7 +1305,7 @@
          @Override
          protected void alertOther(EntityInsentient entityinsentient, EntityLiving entityliving) {
              if (entityinsentient instanceof EntityBee && this.mob.hasLineOfSight(entityliving)) {
@@ -75,7 +97,7 @@
              }
  
          }
-@@ -1298,7 +1307,7 @@
+@@ -1298,7 +1314,7 @@
      private static class c extends PathfinderGoalNearestAttackableTarget<EntityHuman> {
  
          c(EntityBee entitybee) {

paper-server/nms-patches/net/minecraft/world/entity/decoration/EntityHanging.patch

@@ -147,7 +147,7 @@
              this.kill();
              this.dropItem((Entity) null);
          }
-@@ -186,7 +251,7 @@
+@@ -186,13 +251,22 @@
  
      @Override
      public void push(double d0, double d1, double d2) {
@@ -156,3 +156,18 @@
              this.kill();
              this.dropItem((Entity) null);
          }
+ 
+     }
+ 
++    // CraftBukkit start - selectively save tile position
++    @Override
++    public void addAdditionalSaveData(NBTTagCompound nbttagcompound, boolean includeAll) {
++        if (includeAll) {
++            addAdditionalSaveData(nbttagcompound);
++        }
++    }
++    // CraftBukkit end
++
+     @Override
+     public void addAdditionalSaveData(NBTTagCompound nbttagcompound) {
+         BlockPosition blockposition = this.getPos();

paper-server/nms-patches/net/minecraft/world/entity/projectile/EntityEgg.patch

@@ -54,7 +54,7 @@
 +
                  for (int i = 0; i < b0; ++i) {
 -                    EntityChicken entitychicken = (EntityChicken) EntityTypes.CHICKEN.create(this.level());
-+                    Entity entitychicken = this.level().getWorld().createEntity(new org.bukkit.Location(this.level().getWorld(), this.getX(), this.getY(), this.getZ(), this.getYRot(), 0.0F), hatchingType.getEntityClass()); // CraftBukkit
++                    Entity entitychicken = this.level().getWorld().makeEntity(new org.bukkit.Location(this.level().getWorld(), this.getX(), this.getY(), this.getZ(), this.getYRot(), 0.0F), hatchingType.getEntityClass()); // CraftBukkit
  
                      if (entitychicken != null) {
 -                        entitychicken.setAge(-24000);

paper-server/src/main/java/org/bukkit/craftbukkit/CraftRegionAccessor.java

@@ -64,6 +64,7 @@ import org.bukkit.block.data.BlockData;
 import org.bukkit.craftbukkit.block.CraftBiome;
 import org.bukkit.craftbukkit.block.CraftBlock;
 import org.bukkit.craftbukkit.block.data.CraftBlockData;
+import org.bukkit.craftbukkit.entity.CraftEntity;
 import org.bukkit.craftbukkit.inventory.CraftItemStack;
 import org.bukkit.craftbukkit.potion.CraftPotionUtil;
 import org.bukkit.craftbukkit.util.BlockStateListPopulator;
@@ -528,6 +529,18 @@ public abstract class CraftRegionAccessor implements RegionAccessor {
 
     public abstract Iterable<net.minecraft.world.entity.Entity> getNMSEntities();
 
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T extends Entity> T createEntity(Location location, Class<T> clazz) throws IllegalArgumentException {
+        net.minecraft.world.entity.Entity entity = createEntity(location, clazz, true);
+
+        if (!isNormalWorld()) {
+            entity.generation = true;
+        }
+
+        return (T) entity.getBukkitEntity();
+    }
+
     @Override
     public <T extends Entity> T spawn(Location location, Class<T> clazz) throws IllegalArgumentException {
         return spawn(location, clazz, null, CreatureSpawnEvent.SpawnReason.CUSTOM);
@@ -553,6 +566,19 @@ public abstract class CraftRegionAccessor implements RegionAccessor {
         return addEntity(entity, reason, function, randomizeData);
     }
 
+    @Override
+    @SuppressWarnings("unchecked")
+    public <T extends Entity> T addEntity(T entity) {
+        Preconditions.checkArgument(!entity.isInWorld(), "Entity has already been added to a world");
+        net.minecraft.world.entity.Entity nmsEntity = ((CraftEntity) entity).getHandle();
+        if (nmsEntity.level() != getHandle().getLevel()) {
+            nmsEntity = nmsEntity.changeDimension(getHandle().getLevel());
+        }
+
+        addEntityWithPassengers(nmsEntity, CreatureSpawnEvent.SpawnReason.CUSTOM);
+        return (T) nmsEntity.getBukkitEntity();
+    }
+
     @SuppressWarnings("unchecked")
     public <T extends Entity> T addEntity(net.minecraft.world.entity.Entity entity, CreatureSpawnEvent.SpawnReason reason) throws IllegalArgumentException {
         return addEntity(entity, reason, null, true);
@@ -580,8 +606,10 @@ public abstract class CraftRegionAccessor implements RegionAccessor {
 
     public abstract void addEntityToWorld(net.minecraft.world.entity.Entity entity, CreatureSpawnEvent.SpawnReason reason);
 
+    public abstract void addEntityWithPassengers(net.minecraft.world.entity.Entity entity, CreatureSpawnEvent.SpawnReason reason);
+
     @SuppressWarnings("unchecked")
-    public net.minecraft.world.entity.Entity createEntity(Location location, Class<? extends Entity> clazz) throws IllegalArgumentException {
+    public net.minecraft.world.entity.Entity makeEntity(Location location, Class<? extends Entity> clazz) throws IllegalArgumentException {
         return createEntity(location, clazz, true);
     }
 

paper-server/src/main/java/org/bukkit/craftbukkit/CraftWorld.java

@@ -822,6 +822,11 @@ public class CraftWorld extends CraftRegionAccessor implements World {
         getHandle().addFreshEntity(entity, reason);
     }
 
+    @Override
+    public void addEntityWithPassengers(net.minecraft.world.entity.Entity entity, SpawnReason reason) {
+        getHandle().tryAddFreshEntityWithPassengers(entity, reason);
+    }
+
     @Override
     public Collection<Entity> getNearbyEntities(Location location, double x, double y, double z) {
         return this.getNearbyEntities(location, x, y, z, null);

paper-server/src/main/java/org/bukkit/craftbukkit/block/CraftCreatureSpawner.java

@@ -1,15 +1,25 @@
 package org.bukkit.craftbukkit.block;
 
 import com.google.common.base.Preconditions;
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
 import java.util.Optional;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.util.InclusiveRange;
 import net.minecraft.util.RandomSource;
 import net.minecraft.util.random.SimpleWeightedRandomList;
+import net.minecraft.util.random.WeightedEntry.b;
 import net.minecraft.world.entity.EntityTypes;
 import net.minecraft.world.level.MobSpawnerData;
 import net.minecraft.world.level.block.entity.TileEntityMobSpawner;
 import org.bukkit.World;
 import org.bukkit.block.CreatureSpawner;
+import org.bukkit.block.spawner.SpawnRule;
+import org.bukkit.block.spawner.SpawnerEntry;
+import org.bukkit.craftbukkit.entity.CraftEntitySnapshot;
 import org.bukkit.craftbukkit.entity.CraftEntityType;
+import org.bukkit.entity.EntitySnapshot;
 import org.bukkit.entity.EntityType;
 
 public class CraftCreatureSpawner extends CraftBlockEntityState<TileEntityMobSpawner> implements CreatureSpawner {
@@ -46,6 +56,78 @@ public class CraftCreatureSpawner extends CraftBlockEntityState<TileEntityMobSpa
         this.getSnapshot().setEntityId(CraftEntityType.bukkitToMinecraft(entityType), rand);
     }
 
+    @Override
+    public EntitySnapshot getSpawnedEntity() {
+        MobSpawnerData spawnData = this.getSnapshot().getSpawner().nextSpawnData;
+        if (spawnData == null) {
+            return null;
+        }
+
+        return CraftEntitySnapshot.create(spawnData.getEntityToSpawn());
+    }
+
+    @Override
+    public void setSpawnedEntity(EntitySnapshot snapshot) {
+        NBTTagCompound compoundTag = ((CraftEntitySnapshot) snapshot).getData();
+
+        this.getSnapshot().getSpawner().spawnPotentials = SimpleWeightedRandomList.empty();
+        this.getSnapshot().getSpawner().nextSpawnData = new MobSpawnerData(compoundTag, Optional.empty());
+    }
+
+    @Override
+    public void addPotentialSpawn(EntitySnapshot snapshot, int weight, SpawnRule spawnRule) {
+        NBTTagCompound compoundTag = ((CraftEntitySnapshot) snapshot).getData();
+
+        SimpleWeightedRandomList.a<MobSpawnerData> builder = SimpleWeightedRandomList.builder(); // PAIL rename Builder
+        this.getSnapshot().getSpawner().spawnPotentials.unwrap().forEach(entry -> builder.add(entry.getData(), entry.getWeight().asInt()));
+        builder.add(new MobSpawnerData(compoundTag, Optional.ofNullable(toMinecraftRule(spawnRule))), weight);
+        this.getSnapshot().getSpawner().spawnPotentials = builder.build();
+    }
+
+    @Override
+    public void addPotentialSpawn(SpawnerEntry spawnerEntry) {
+        addPotentialSpawn(spawnerEntry.getSnapshot(), spawnerEntry.getSpawnWeight(), spawnerEntry.getSpawnRule());
+    }
+
+    @Override
+    public void setPotentialSpawns(Collection<SpawnerEntry> entries) {
+        SimpleWeightedRandomList.a<MobSpawnerData> builder = SimpleWeightedRandomList.builder();
+        for (SpawnerEntry spawnerEntry : entries) {
+            NBTTagCompound compoundTag = ((CraftEntitySnapshot) spawnerEntry.getSnapshot()).getData();
+            builder.add(new MobSpawnerData(compoundTag, Optional.ofNullable(toMinecraftRule(spawnerEntry.getSpawnRule()))), spawnerEntry.getSpawnWeight());
+        }
+        this.getSnapshot().getSpawner().spawnPotentials = builder.build();
+    }
+
+    @Override
+    public List<SpawnerEntry> getPotentialSpawns() {
+        List<SpawnerEntry> entries = new ArrayList<>();
+
+        for (b<MobSpawnerData> entry : this.getSnapshot().getSpawner().spawnPotentials.unwrap()) { // PAIL rename Wrapper
+            CraftEntitySnapshot snapshot = CraftEntitySnapshot.create(entry.getData().getEntityToSpawn());
+
+            if (snapshot != null) {
+                SpawnRule rule = entry.getData().customSpawnRules().map(this::fromMinecraftRule).orElse(null);
+                entries.add(new SpawnerEntry(snapshot, entry.getWeight().asInt(), rule));
+            }
+        }
+        return entries;
+    }
+
+    private MobSpawnerData.a toMinecraftRule(SpawnRule rule) { // PAIL rename CustomSpawnRules
+        if (rule == null) {
+            return null;
+        }
+        return new MobSpawnerData.a(new InclusiveRange<>(rule.getMinBlockLight(), rule.getMaxBlockLight()), new InclusiveRange<>(rule.getMinSkyLight(), rule.getMaxSkyLight()));
+    }
+
+    private SpawnRule fromMinecraftRule(MobSpawnerData.a rule) {
+       InclusiveRange<Integer> blockLight = rule.blockLightLimit();
+       InclusiveRange<Integer> skyLight = rule.skyLightLimit();
+
+       return new SpawnRule(blockLight.maxInclusive(), blockLight.maxInclusive(), skyLight.minInclusive(), skyLight.maxInclusive());
+    }
+
     @Override
     public String getCreatureTypeName() {
         MobSpawnerData spawnData = this.getSnapshot().getSpawner().nextSpawnData;

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftEntity.java

@@ -24,6 +24,7 @@ import net.minecraft.world.entity.EntityFlying;
 import net.minecraft.world.entity.EntityLightning;
 import net.minecraft.world.entity.EntityLiving;
 import net.minecraft.world.entity.EntityTameableAnimal;
+import net.minecraft.world.entity.EntityTypes;
 import net.minecraft.world.entity.GlowSquid;
 import net.minecraft.world.entity.Interaction;
 import net.minecraft.world.entity.Marker;
@@ -164,6 +165,7 @@ import net.minecraft.world.entity.vehicle.EntityMinecartTNT;
 import net.minecraft.world.phys.AxisAlignedBB;
 import org.bukkit.EntityEffect;
 import org.bukkit.Location;
+import org.bukkit.Registry;
 import org.bukkit.Server;
 import org.bukkit.Sound;
 import org.bukkit.World;
@@ -177,8 +179,10 @@ import org.bukkit.craftbukkit.persistence.CraftPersistentDataContainer;
 import org.bukkit.craftbukkit.persistence.CraftPersistentDataTypeRegistry;
 import org.bukkit.craftbukkit.util.CraftChatMessage;
 import org.bukkit.craftbukkit.util.CraftLocation;
+import org.bukkit.craftbukkit.util.CraftNamespacedKey;
 import org.bukkit.craftbukkit.util.CraftSpawnCategory;
 import org.bukkit.craftbukkit.util.CraftVector;
+import org.bukkit.entity.EntitySnapshot;
 import org.bukkit.entity.EntityType;
 import org.bukkit.entity.Player;
 import org.bukkit.entity.Pose;
@@ -641,7 +645,7 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
 
     @Override
     public boolean isValid() {
-        return entity.isAlive() && entity.valid && entity.isChunkLoaded();
+        return entity.isAlive() && entity.valid && entity.isChunkLoaded() && isInWorld();
     }
 
     @Override
@@ -1114,6 +1118,42 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
         return CraftSpawnCategory.toBukkit(getHandle().getType().getCategory());
     }
 
+    @Override
+    public boolean isInWorld() {
+        return getHandle().inWorld;
+    }
+
+    @Override
+    public EntitySnapshot createSnapshot() {
+        return CraftEntitySnapshot.create(this);
+    }
+
+    @Override
+    public org.bukkit.entity.Entity copy() {
+        Entity copy = copy(getHandle().level());
+        Preconditions.checkArgument(copy != null, "Error creating new entity.");
+
+        return copy.getBukkitEntity();
+    }
+
+    @Override
+    public org.bukkit.entity.Entity copy(Location location) {
+        Preconditions.checkArgument(location.getWorld() != null, "Location has no world");
+
+        Entity copy = copy(((CraftWorld) location.getWorld()).getHandle());
+        Preconditions.checkArgument(copy != null, "Error creating new entity.");
+
+        copy.setPos(location.getX(), location.getY(), location.getZ());
+        return location.getWorld().addEntity(copy.getBukkitEntity());
+    }
+
+    private Entity copy(net.minecraft.world.level.World level) {
+        NBTTagCompound compoundTag = new NBTTagCompound();
+        getHandle().saveAsPassenger(compoundTag, false);
+
+        return EntityTypes.loadEntityRecursive(compoundTag, level, java.util.function.Function.identity());
+    }
+
     public void storeBukkitValues(NBTTagCompound c) {
         if (!this.persistentDataContainer.isEmpty()) {
             c.put("BukkitValues", this.persistentDataContainer.toTagCompound());

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftEntitySnapshot.java

@@ -0,0 +1,83 @@
+package org.bukkit.craftbukkit.entity;
+
+import com.google.common.base.Preconditions;
+import java.util.function.Function;
+import net.minecraft.nbt.NBTTagCompound;
+import net.minecraft.world.entity.EntityTypes;
+import org.bukkit.Location;
+import org.bukkit.World;
+import org.bukkit.craftbukkit.CraftWorld;
+import org.bukkit.entity.Entity;
+import org.bukkit.entity.EntitySnapshot;
+import org.bukkit.entity.EntityType;
+
+public class CraftEntitySnapshot implements EntitySnapshot {
+    private final NBTTagCompound data;
+    private final EntityType type;
+
+    private CraftEntitySnapshot(NBTTagCompound data, EntityType type) {
+        this.data = data;
+        this.type = type;
+    }
+
+    @Override
+    public EntityType getEntityType() {
+        return type;
+    }
+
+    @Override
+    public Entity createEntity(World world) {
+        net.minecraft.world.entity.Entity internal = createInternal(world);
+
+        return internal.getBukkitEntity();
+    }
+
+    @Override
+    public Entity createEntity(Location location) {
+        Preconditions.checkArgument(location.getWorld() != null, "Location has no world");
+
+        net.minecraft.world.entity.Entity internal = createInternal(location.getWorld());
+
+        internal.setPos(location.getX(), location.getY(), location.getZ());
+        return location.getWorld().addEntity(internal.getBukkitEntity());
+    }
+
+    private net.minecraft.world.entity.Entity createInternal(World world) {
+        net.minecraft.world.level.World nms = ((CraftWorld) world).getHandle();
+        net.minecraft.world.entity.Entity internal = EntityTypes.loadEntityRecursive(data, nms, Function.identity());
+        if (internal == null) { // Try creating by type
+            internal = CraftEntityType.bukkitToMinecraft(type).create(nms);
+        }
+
+        Preconditions.checkArgument(internal != null, "Error creating new entity."); // This should only fail if the stored NBTTagCompound is malformed.
+        internal.load(data);
+
+        return internal;
+    }
+
+    public NBTTagCompound getData() {
+        return data;
+    }
+
+    public static CraftEntitySnapshot create(CraftEntity entity) {
+        NBTTagCompound tag = new NBTTagCompound();
+        if (!entity.getHandle().saveAsPassenger(tag, false)) {
+            return null;
+        }
+
+        return new CraftEntitySnapshot(tag, entity.getType());
+    }
+
+    public static CraftEntitySnapshot create(NBTTagCompound tag, EntityType type) {
+        if (tag == null || tag.isEmpty() || type == null) {
+            return null;
+        }
+
+        return new CraftEntitySnapshot(tag, type);
+    }
+
+    public static CraftEntitySnapshot create(NBTTagCompound tag) {
+        EntityType type = EntityTypes.by(tag).map(CraftEntityType::minecraftToBukkit).orElse(null);
+        return create(tag, type);
+    }
+}

paper-server/src/main/java/org/bukkit/craftbukkit/entity/CraftHumanEntity.java

@@ -38,6 +38,7 @@ import org.bukkit.Material;
 import org.bukkit.NamespacedKey;
 import org.bukkit.block.Block;
 import org.bukkit.craftbukkit.CraftServer;
+import org.bukkit.craftbukkit.CraftWorld;
 import org.bukkit.craftbukkit.entity.memory.CraftMemoryMapper;
 import org.bukkit.craftbukkit.event.CraftEventFactory;
 import org.bukkit.craftbukkit.inventory.CraftContainer;
@@ -684,4 +685,14 @@ public class CraftHumanEntity extends CraftLivingEntity implements HumanEntity {
         boolean success = getHandle().level().addFreshEntity(fireworks, SpawnReason.CUSTOM);
         return success ? (Firework) fireworks.getBukkitEntity() : null;
     }
+
+    @Override
+    public org.bukkit.entity.Entity copy() {
+        throw new UnsupportedOperationException("Cannot copy human entities");
+    }
+
+    @Override
+    public org.bukkit.entity.Entity copy(Location location) {
+        throw new UnsupportedOperationException("Cannot copy human entities");
+    }
 }

paper-server/src/main/java/org/bukkit/craftbukkit/generator/CraftLimitedRegion.java

@@ -116,12 +116,12 @@ public class CraftLimitedRegion extends CraftRegionAccessor implements LimitedRe
             if (entity.isAlive()) {
                 // check if entity is still in region or if it got teleported outside it
                 Preconditions.checkState(region.contains(entity.getX(), entity.getY(), entity.getZ()), "Entity %s is not in the region", entity);
-                access.addFreshEntity(entity);
+                access.addFreshEntityWithPassengers(entity);
             }
         }
 
         for (net.minecraft.world.entity.Entity entity : outsideEntities) {
-            access.addFreshEntity(entity);
+            access.addFreshEntityWithPassengers(entity);
         }
     }
 
@@ -250,4 +250,9 @@ public class CraftLimitedRegion extends CraftRegionAccessor implements LimitedRe
     public void addEntityToWorld(net.minecraft.world.entity.Entity entity, CreatureSpawnEvent.SpawnReason reason) {
         entities.add(entity);
     }
+
+    @Override
+    public void addEntityWithPassengers(net.minecraft.world.entity.Entity entity, CreatureSpawnEvent.SpawnReason reason) {
+        entities.add(entity);
+    }
 }

paper-server/src/main/java/org/bukkit/craftbukkit/inventory/CraftMetaSpawnEgg.java

@@ -1,5 +1,6 @@
 package org.bukkit.craftbukkit.inventory;
 
+import com.google.common.base.Preconditions;
 import com.google.common.collect.ImmutableMap.Builder;
 import com.google.common.collect.Sets;
 import java.util.Map;
@@ -9,7 +10,9 @@ import net.minecraft.nbt.NBTTagCompound;
 import net.minecraft.resources.MinecraftKey;
 import org.bukkit.Material;
 import org.bukkit.configuration.serialization.DelegateDeserialization;
+import org.bukkit.craftbukkit.entity.CraftEntitySnapshot;
 import org.bukkit.craftbukkit.util.CraftLegacy;
+import org.bukkit.entity.EntitySnapshot;
 import org.bukkit.entity.EntityType;
 import org.bukkit.inventory.meta.SpawnEggMeta;
 import org.bukkit.material.MaterialData;
@@ -216,6 +219,17 @@ public class CraftMetaSpawnEgg extends CraftMetaItem implements SpawnEggMeta {
         throw new UnsupportedOperationException("Must change item type to set spawned type");
     }
 
+    @Override
+    public EntitySnapshot getSpawnedEntity() {
+        return CraftEntitySnapshot.create(this.entityTag);
+    }
+
+    @Override
+    public void setSpawnedEntity(EntitySnapshot snapshot) {
+        Preconditions.checkArgument(snapshot.getEntityType().isSpawnable(), "Entity is not spawnable");
+        this.entityTag = ((CraftEntitySnapshot) snapshot).getData();
+    }
+
     @Override
     boolean equalsCommon(CraftMetaItem meta) {
         if (!super.equalsCommon(meta)) {