Add Raw Byte Entity Serialization

== AT ==
public net.minecraft.world.entity.Entity setLevel(Lnet/minecraft/world/level/Level;)V

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

@@ -485,15 +485,15 @@
              }
  
          }
-@@ -587,9 +874,25 @@
+@@ -587,7 +874,23 @@
      }
  
      public final void igniteForSeconds(float seconds) {
 -        this.igniteForTicks(Mth.floor(seconds * 20.0F));
 +        // CraftBukkit start
 +        this.igniteForSeconds(seconds, true);
-     }
++    }
- 
++
 +    public final void igniteForSeconds(float f, boolean callEvent) {
 +        if (callEvent) {
 +            EntityCombustEvent event = new EntityCombustEvent(this.getBukkitEntity(), f);
@@ -507,11 +507,9 @@
 +        }
 +        // CraftBukkit end
 +        this.igniteForTicks(Mth.floor(f * 20.0F));
-+    }
+     }
-+
+ 
      public void igniteForTicks(int ticks) {
-         if (this.remainingFireTicks < ticks) {
-             this.setRemainingFireTicks(ticks);
 @@ -610,7 +913,7 @@
      }
  
@@ -550,15 +548,17 @@
                  if (!this.level().isClientSide() || this.isControlledByLocalInstance()) {
                      Entity.MovementEmission entity_movementemission = this.getMovementEmission();
  
-@@ -1133,6 +1458,20 @@
+@@ -1131,8 +1456,22 @@
-         return SoundEvents.GENERIC_SPLASH;
-     }
  
+     protected SoundEvent getSwimHighSpeedSplashSound() {
+         return SoundEvents.GENERIC_SPLASH;
++    }
++
 +    // CraftBukkit start - Add delegate methods
 +    public SoundEvent getSwimSound0() {
 +        return this.getSwimSound();
-+    }
+     }
-+
+ 
 +    public SoundEvent getSwimSplashSound0() {
 +        return this.getSwimSplashSound();
 +    }
@@ -646,7 +646,7 @@
      public void awardKillScore(Entity entityKilled, DamageSource damageSource) {
          if (entityKilled instanceof ServerPlayer) {
              CriteriaTriggers.ENTITY_KILLED_PLAYER.trigger((ServerPlayer) entityKilled, this, damageSource);
-@@ -1889,16 +2263,22 @@
+@@ -1889,74 +2263,133 @@
      }
  
      public boolean saveAsPassenger(CompoundTag nbt) {
@@ -672,7 +672,19 @@
                  return true;
              }
          }
-@@ -1909,54 +2289,98 @@
+     }
+ 
++    // Paper start - Entity serialization api
++    public boolean serializeEntity(CompoundTag compound) {
++        List<Entity> pass = new java.util.ArrayList<>(this.getPassengers());
++        this.passengers = ImmutableList.of();
++        boolean result = save(compound);
++        this.passengers = ImmutableList.copyOf(pass);
++        return result;
++    }
++    // Paper end - Entity serialization api
+     public boolean save(CompoundTag nbt) {
+         return this.isPassenger() ? false : this.saveAsPassenger(nbt);
      }
  
      public CompoundTag saveWithoutId(CompoundTag nbt) {
@@ -791,7 +803,7 @@
              }
  
              ListTag nbttaglist;
-@@ -1972,10 +2396,10 @@
+@@ -1972,10 +2405,10 @@
                      nbttaglist.add(StringTag.valueOf(s));
                  }
  
@@ -804,7 +816,7 @@
              if (this.isVehicle()) {
                  nbttaglist = new ListTag();
                  iterator = this.getPassengers().iterator();
-@@ -1984,17 +2408,41 @@
+@@ -1984,17 +2417,41 @@
                      Entity entity = (Entity) iterator.next();
                      CompoundTag nbttagcompound1 = new CompoundTag();
  
@@ -849,7 +861,7 @@
          } catch (Throwable throwable) {
              CrashReport crashreport = CrashReport.forThrowable(throwable, "Saving entity NBT");
              CrashReportCategory crashreportsystemdetails = crashreport.addCategory("Entity being saved");
-@@ -2079,7 +2527,69 @@
+@@ -2079,7 +2536,69 @@
                  }
              } else {
                  throw new IllegalStateException("Entity has invalid position");
@@ -919,7 +931,7 @@
          } catch (Throwable throwable) {
              CrashReport crashreport = CrashReport.forThrowable(throwable, "Loading entity NBT");
              CrashReportCategory crashreportsystemdetails = crashreport.addCategory("Entity being loaded");
-@@ -2101,6 +2611,12 @@
+@@ -2101,6 +2620,12 @@
          return entitytypes.canSerialize() && minecraftkey != null ? minecraftkey.toString() : null;
      }
  
@@ -932,7 +944,7 @@
      protected abstract void readAdditionalSaveData(CompoundTag nbt);
  
      protected abstract void addAdditionalSaveData(CompoundTag nbt);
-@@ -2153,9 +2669,23 @@
+@@ -2153,9 +2678,23 @@
          if (stack.isEmpty()) {
              return null;
          } else {
@@ -957,7 +969,7 @@
              world.addFreshEntity(entityitem);
              return entityitem;
          }
-@@ -2184,7 +2714,16 @@
+@@ -2184,7 +2723,16 @@
          if (this.isAlive() && this instanceof Leashable leashable) {
              if (leashable.getLeashHolder() == player) {
                  if (!this.level().isClientSide()) {
@@ -975,7 +987,7 @@
                          leashable.removeLeash();
                      } else {
                          leashable.dropLeash();
-@@ -2200,6 +2739,13 @@
+@@ -2200,6 +2748,13 @@
  
              if (itemstack.is(Items.LEAD) && leashable.canHaveALeashAttachedToIt()) {
                  if (!this.level().isClientSide()) {
@@ -989,7 +1001,7 @@
                      leashable.setLeashedTo(player, true);
                  }
  
-@@ -2265,7 +2811,7 @@
+@@ -2265,7 +2820,7 @@
      }
  
      public boolean showVehicleHealth() {
@@ -998,7 +1010,7 @@
      }
  
      public boolean startRiding(Entity entity, boolean force) {
-@@ -2273,7 +2819,7 @@
+@@ -2273,7 +2828,7 @@
              return false;
          } else if (!entity.couldAcceptPassenger()) {
              return false;
@@ -1007,7 +1019,7 @@
              return false;
          } else {
              for (Entity entity1 = entity; entity1.vehicle != null; entity1 = entity1.vehicle) {
-@@ -2285,11 +2831,32 @@
+@@ -2285,11 +2840,32 @@
              if (!force && (!this.canRide(entity) || !entity.canAddPassenger(this))) {
                  return false;
              } else {
@@ -1041,7 +1053,7 @@
                  this.vehicle = entity;
                  this.vehicle.addPassenger(this);
                  entity.getIndirectPassengersStream().filter((entity2) -> {
-@@ -2314,19 +2881,30 @@
+@@ -2314,19 +2890,30 @@
      }
  
      public void removeVehicle() {
@@ -1074,7 +1086,7 @@
      protected void addPassenger(Entity passenger) {
          if (passenger.getVehicle() != this) {
              throw new IllegalStateException("Use x.startRiding(y), not y.addPassenger(x)");
-@@ -2349,21 +2927,53 @@
+@@ -2349,21 +2936,53 @@
          }
      }
  
@@ -1134,7 +1146,7 @@
      }
  
      protected boolean canAddPassenger(Entity passenger) {
-@@ -2464,7 +3074,7 @@
+@@ -2464,7 +3083,7 @@
                      if (teleporttransition != null) {
                          ServerLevel worldserver1 = teleporttransition.newLevel();
  
@@ -1143,7 +1155,7 @@
                              this.teleport(teleporttransition);
                          }
                      }
-@@ -2547,7 +3157,7 @@
+@@ -2547,7 +3166,7 @@
      }
  
      public boolean isCrouching() {
@@ -1152,7 +1164,7 @@
      }
  
      public boolean isSprinting() {
-@@ -2563,7 +3173,7 @@
+@@ -2563,7 +3182,7 @@
      }
  
      public boolean isVisuallySwimming() {
@@ -1161,7 +1173,7 @@
      }
  
      public boolean isVisuallyCrawling() {
-@@ -2571,6 +3181,13 @@
+@@ -2571,6 +3190,13 @@
      }
  
      public void setSwimming(boolean swimming) {
@@ -1175,7 +1187,7 @@
          this.setSharedFlag(4, swimming);
      }
  
-@@ -2609,6 +3226,7 @@
+@@ -2609,6 +3235,7 @@
  
      @Nullable
      public PlayerTeam getTeam() {
@@ -1183,7 +1195,7 @@
          return this.level().getScoreboard().getPlayersTeam(this.getScoreboardName());
      }
  
-@@ -2624,8 +3242,12 @@
+@@ -2624,8 +3251,12 @@
          return this.getTeam() != null ? this.getTeam().isAlliedTo(team) : false;
      }
  
@@ -1197,7 +1209,7 @@
      }
  
      public boolean getSharedFlag(int index) {
-@@ -2644,7 +3266,7 @@
+@@ -2644,7 +3275,7 @@
      }
  
      public int getMaxAirSupply() {
@@ -1206,7 +1218,7 @@
      }
  
      public int getAirSupply() {
-@@ -2652,7 +3274,18 @@
+@@ -2652,7 +3283,18 @@
      }
  
      public void setAirSupply(int air) {
@@ -1226,7 +1238,7 @@
      }
  
      public int getTicksFrozen() {
-@@ -2679,11 +3312,40 @@
+@@ -2679,11 +3321,40 @@
  
      public void thunderHit(ServerLevel world, LightningBolt lightning) {
          this.setRemainingFireTicks(this.remainingFireTicks + 1);
@@ -1269,7 +1281,7 @@
      }
  
      public void onAboveBubbleCol(boolean drag) {
-@@ -2713,7 +3375,7 @@
+@@ -2713,7 +3384,7 @@
          this.resetFallDistance();
      }
  
@@ -1278,7 +1290,7 @@
          return true;
      }
  
-@@ -2818,7 +3480,7 @@
+@@ -2818,7 +3489,7 @@
      public String toString() {
          String s = this.level() == null ? "~NULL~" : this.level().toString();
  
@@ -1287,7 +1299,7 @@
      }
  
      public final boolean isInvulnerableToBase(DamageSource damageSource) {
-@@ -2850,8 +3512,57 @@
+@@ -2850,8 +3521,57 @@
      public Entity teleport(TeleportTransition teleportTarget) {
          Level world = this.level();
  
@@ -1345,7 +1357,7 @@
                  ServerLevel worldserver1 = teleportTarget.newLevel();
                  boolean flag = worldserver1.dimension() != worldserver.dimension();
  
-@@ -2918,10 +3629,19 @@
+@@ -2918,10 +3638,19 @@
              gameprofilerfiller.pop();
              return null;
          } else {
@@ -1366,7 +1378,7 @@
              Iterator iterator1 = list1.iterator();
  
              while (iterator1.hasNext()) {
-@@ -2947,7 +3667,7 @@
+@@ -2947,7 +3676,7 @@
      }
  
      private void sendTeleportTransitionToRidingPlayers(TeleportTransition teleportTarget) {
@@ -1375,7 +1387,7 @@
          Iterator iterator = this.getIndirectPassengers().iterator();
  
          while (iterator.hasNext()) {
-@@ -2995,9 +3715,17 @@
+@@ -2995,9 +3724,17 @@
      }
  
      protected void removeAfterChangingDimensions() {
@@ -1396,7 +1408,7 @@
          }
  
      }
-@@ -3006,11 +3734,26 @@
+@@ -3006,11 +3743,26 @@
          return PortalShape.getRelativePosition(portalRect, portalAxis, this.position(), this.getDimensions(this.getPose()));
      }
  
@@ -1423,7 +1435,7 @@
          if (from.dimension() == Level.END && to.dimension() == Level.OVERWORLD) {
              Iterator iterator = this.getPassengers().iterator();
  
-@@ -3134,10 +3877,16 @@
+@@ -3134,10 +3886,16 @@
          return (Boolean) this.entityData.get(Entity.DATA_CUSTOM_NAME_VISIBLE);
      }
  
@@ -1443,7 +1455,7 @@
          return entity != null;
      }
  
-@@ -3187,7 +3936,7 @@
+@@ -3187,7 +3945,7 @@
      /** @deprecated */
      @Deprecated
      protected void fixupDimensions() {
@@ -1452,7 +1464,7 @@
          EntityDimensions entitysize = this.getDimensions(entitypose);
  
          this.dimensions = entitysize;
-@@ -3196,7 +3945,7 @@
+@@ -3196,7 +3954,7 @@
  
      public void refreshDimensions() {
          EntityDimensions entitysize = this.dimensions;
@@ -1461,7 +1473,7 @@
          EntityDimensions entitysize1 = this.getDimensions(entitypose);
  
          this.dimensions = entitysize1;
-@@ -3258,10 +4007,29 @@
+@@ -3258,10 +4016,29 @@
      }
  
      public final void setBoundingBox(AABB boundingBox) {
@@ -1493,7 +1505,7 @@
          return this.getDimensions(pose).eyeHeight();
      }
  
-@@ -3335,7 +4103,7 @@
+@@ -3335,7 +4112,7 @@
      }
  
      @Nullable
@@ -1502,7 +1514,7 @@
          return null;
      }
  
-@@ -3373,20 +4141,34 @@
+@@ -3373,20 +4150,34 @@
      }
  
      private Stream<Entity> getIndirectPassengersStream() {
@@ -1537,7 +1549,7 @@
          return () -> {
              return this.getIndirectPassengersStream().iterator();
          };
-@@ -3399,6 +4181,7 @@
+@@ -3399,6 +4190,7 @@
      }
  
      public boolean hasExactlyOnePlayerPassenger() {
@@ -1545,7 +1557,7 @@
          return this.countPlayerPassengers() == 1;
      }
  
-@@ -3435,7 +4218,7 @@
+@@ -3435,7 +4227,7 @@
      }
  
      public boolean isControlledByLocalInstance() {
@@ -1554,7 +1566,7 @@
  
          if (entityliving instanceof Player entityhuman) {
              return entityhuman.isLocalPlayer();
-@@ -3445,7 +4228,7 @@
+@@ -3445,7 +4237,7 @@
      }
  
      public boolean isControlledByClient() {
@@ -1563,7 +1575,7 @@
  
          return entityliving != null && entityliving.isControlledByClient();
      }
-@@ -3463,7 +4246,7 @@
+@@ -3463,7 +4255,7 @@
          return new Vec3((double) f1 * d2 / (double) f3, 0.0D, (double) f2 * d2 / (double) f3);
      }
  
@@ -1572,17 +1584,18 @@
          return new Vec3(this.getX(), this.getBoundingBox().maxY, this.getZ());
      }
  
-@@ -3489,8 +4272,37 @@
+@@ -3488,9 +4280,38 @@
+     public int getFireImmuneTicks() {
          return 1;
      }
- 
++
 +    // CraftBukkit start
 +    private final CommandSource commandSource = new CommandSource() {
 +
 +        @Override
 +        public void sendSystemMessage(Component message) {
 +        }
-+
+ 
 +        @Override
 +        public CommandSender getBukkitSender(CommandSourceStack wrapper) {
 +            return Entity.this.getBukkitEntity();
@@ -1611,7 +1624,7 @@
      }
  
      public void lookAt(EntityAnchorArgument.Anchor anchorPoint, Vec3 target) {
-@@ -3551,6 +4363,11 @@
+@@ -3551,6 +4372,11 @@
                                      vec3d = vec3d.add(vec3d1);
                                      ++k1;
                                  }
@@ -1623,7 +1636,7 @@
                              }
                          }
                      }
-@@ -3613,7 +4430,7 @@
+@@ -3613,7 +4439,7 @@
          return new ClientboundAddEntityPacket(this, entityTrackerEntry);
      }
  
@@ -1632,7 +1645,7 @@
          return this.type.getDimensions();
      }
  
-@@ -3714,7 +4531,39 @@
+@@ -3714,7 +4540,39 @@
          return this.getZ((2.0D * this.random.nextDouble() - 1.0D) * widthScale);
      }
  
@@ -1672,7 +1685,7 @@
          if (this.position.x != x || this.position.y != y || this.position.z != z) {
              this.position = new Vec3(x, y, z);
              int i = Mth.floor(x);
-@@ -3732,6 +4581,12 @@
+@@ -3732,6 +4590,12 @@
              this.levelCallback.onMove();
          }
  
@@ -1685,7 +1698,7 @@
      }
  
      public void checkDespawn() {}
-@@ -3818,8 +4673,16 @@
+@@ -3818,8 +4682,16 @@
  
      @Override
      public final void setRemoved(Entity.RemovalReason reason) {
@@ -1703,7 +1716,7 @@
          }
  
          if (this.removalReason.shouldDestroy()) {
-@@ -3827,8 +4690,8 @@
+@@ -3827,8 +4699,8 @@
          }
  
          this.getPassengers().forEach(Entity::stopRiding);
@@ -1714,7 +1727,7 @@
      }
  
      public void unsetRemoved() {
-@@ -3887,7 +4750,7 @@
+@@ -3887,7 +4759,7 @@
      }
  
      public Vec3 getKnownMovement() {
@@ -1723,7 +1736,7 @@
  
          if (entityliving instanceof Player entityhuman) {
              if (this.isAlive()) {
-@@ -3962,4 +4825,14 @@
+@@ -3962,4 +4834,14 @@
  
          void accept(Entity entity, double x, double y, double z);
      }

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

@@ -1083,6 +1083,18 @@ public abstract class CraftEntity implements org.bukkit.entity.Entity {
     }
     // Paper end - tracked players API
 
+    // Paper start - raw entity serialization API
+    @Override
+    public boolean spawnAt(Location location, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
+        Preconditions.checkNotNull(location, "location cannot be null");
+        Preconditions.checkNotNull(reason, "reason cannot be null");
+        this.entity.setLevel(((CraftWorld) location.getWorld()).getHandle());
+        this.entity.setPos(location.getX(), location.getY(), location.getZ());
+        this.entity.setRot(location.getYaw(), location.getPitch());
+        return !this.entity.valid && this.entity.level().addFreshEntity(this.entity, reason);
+    }
+    // Paper end - raw entity serialization API
+
     // Paper start - missing entity api
     @Override
     public boolean isInvisible() {  // Paper - moved up from LivingEntity

paper-server/src/main/java/org/bukkit/craftbukkit/util/CraftMagicNumbers.java

@@ -510,7 +510,33 @@ public final class CraftMagicNumbers implements UnsafeValues {
         return CraftItemStack.asCraftMirror(net.minecraft.world.item.ItemStack.parse(MinecraftServer.getServer().registryAccess(), compound).orElseThrow());
     }
 
-    private byte[] serializeNbtToBytes(CompoundTag compound) {
+    @Override
+    public byte[] serializeEntity(org.bukkit.entity.Entity entity) {
+        Preconditions.checkNotNull(entity, "null cannot be serialized");
+        Preconditions.checkArgument(entity instanceof org.bukkit.craftbukkit.entity.CraftEntity, "only CraftEntities can be serialized");
+
+        net.minecraft.nbt.CompoundTag compound = new net.minecraft.nbt.CompoundTag();
+        ((org.bukkit.craftbukkit.entity.CraftEntity) entity).getHandle().serializeEntity(compound);
+        return serializeNbtToBytes(compound);
+    }
+
+    @Override
+    public org.bukkit.entity.Entity deserializeEntity(byte[] data, org.bukkit.World world, boolean preserveUUID) {
+        Preconditions.checkNotNull(data, "null cannot be deserialized");
+        Preconditions.checkArgument(data.length > 0, "cannot deserialize nothing");
+
+        net.minecraft.nbt.CompoundTag compound = deserializeNbtFromBytes(data);
+        int dataVersion = compound.getInt("DataVersion");
+        compound = (net.minecraft.nbt.CompoundTag) MinecraftServer.getServer().fixerUpper.update(References.ENTITY, new Dynamic<>(NbtOps.INSTANCE, compound), dataVersion, this.getDataVersion()).getValue();
+        if (!preserveUUID) {
+            // Generate a new UUID so we don't have to worry about deserializing the same entity twice
+            compound.remove("UUID");
+        }
+        return net.minecraft.world.entity.EntityType.create(compound, ((org.bukkit.craftbukkit.CraftWorld) world).getHandle(), net.minecraft.world.entity.EntitySpawnReason.LOAD)
+            .orElseThrow(() -> new IllegalArgumentException("An ID was not found for the data. Did you downgrade?")).getBukkitEntity();
+    }
+
+    private byte[] serializeNbtToBytes(net.minecraft.nbt.CompoundTag compound) {
         compound.putInt("DataVersion", getDataVersion());
         java.io.ByteArrayOutputStream outputStream = new java.io.ByteArrayOutputStream();
         try {