SPIGOT-6186: Canceling a CreatureSpawnEvent​ results in a "Unable to summon entity due to duplicate UUIDs" error

By: md_5 <git@md-5.net>

paper-server/nms-patches/EntityTypes.patch

@@ -18,7 +18,7 @@
          return (EntityTypes) IRegistry.a((IRegistry) IRegistry.ENTITY_TYPE, s, (Object) entitytypes_builder.a(s));
      }
  
-@@ -169,10 +169,17 @@
+@@ -169,10 +169,18 @@
  
      @Nullable
      public T spawnCreature(WorldServer worldserver, @Nullable NBTTagCompound nbttagcompound, @Nullable IChatBaseComponent ichatbasecomponent, @Nullable EntityHuman entityhuman, BlockPosition blockposition, EnumMobSpawn enummobspawn, boolean flag, boolean flag1) {
@@ -32,12 +32,13 @@
  
          if (t0 != null) {
 -            worldserver.addAllEntities(t0);
-+            return worldserver.addAllEntities(t0, spawnReason) ? t0 : null; // Don't return an entity when CreatureSpawnEvent is canceled
++            worldserver.addAllEntities(t0, spawnReason);
++            return !t0.dead ? t0 : null; // Don't return an entity when CreatureSpawnEvent is canceled
 +            // CraftBukkit end
          }
  
          return t0;
-@@ -208,7 +215,7 @@
+@@ -208,7 +216,7 @@
                  t0.setCustomName(ichatbasecomponent);
              }
  
@@ -46,7 +47,7 @@
              return t0;
          }
      }
-@@ -351,7 +358,7 @@
+@@ -351,7 +359,7 @@
              }
  
              return entity;
@@ -55,7 +56,7 @@
      }
  
      private static Optional<Entity> b(NBTTagCompound nbttagcompound, World world) {
-@@ -403,7 +410,7 @@
+@@ -403,7 +411,7 @@
              this.g = enumcreaturetype == EnumCreatureType.CREATURE || enumcreaturetype == EnumCreatureType.MISC;
          }
  

paper-server/nms-patches/SpawnerCreature.patch

@@ -72,7 +72,7 @@
                  a(enumcreaturetype, worldserver, chunk, (entitytypes, blockposition, ichunkaccess) -> {
                      return spawnercreature_d.a(entitytypes, blockposition, ichunkaccess);
                  }, (entityinsentient, ichunkaccess) -> {
-@@ -147,10 +191,13 @@
+@@ -147,10 +191,14 @@
                                          entityinsentient.setPositionRotation(d0, (double) i, d1, worldserver.random.nextFloat() * 360.0F, 0.0F);
                                          if (a(worldserver, entityinsentient, d2)) {
                                              groupdataentity = entityinsentient.prepare(worldserver, worldserver.getDamageScaler(entityinsentient.getChunkCoordinates()), EnumMobSpawn.NATURAL, groupdataentity, (NBTTagCompound) null);
@@ -81,7 +81,8 @@
 -                                            worldserver.addAllEntities(entityinsentient);
 -                                            spawnercreature_a.run(entityinsentient, ichunkaccess);
 +                                            // CraftBukkit start
-+                                            if (worldserver.addAllEntities(entityinsentient, SpawnReason.NATURAL)) {
++                                            worldserver.addAllEntities(entityinsentient, SpawnReason.NATURAL);
++                                            if (!entityinsentient.dead) {
 +                                                ++j;
 +                                                ++k1;
 +                                                spawnercreature_a.run(entityinsentient, ichunkaccess);
@@ -90,7 +91,7 @@
                                              if (j >= entityinsentient.getMaxSpawnGroup()) {
                                                  return;
                                              }
-@@ -333,7 +380,7 @@
+@@ -333,7 +381,7 @@
  
                                  if (entityinsentient.a((GeneratorAccess) worldaccess, EnumMobSpawn.CHUNK_GENERATION) && entityinsentient.a((IWorldReader) worldaccess)) {
                                      groupdataentity = entityinsentient.prepare(worldaccess, worldaccess.getDamageScaler(entityinsentient.getChunkCoordinates()), EnumMobSpawn.CHUNK_GENERATION, groupdataentity, (NBTTagCompound) null);
@@ -99,7 +100,7 @@
                                      flag = true;
                                  }
                              }
-@@ -456,8 +503,10 @@
+@@ -456,8 +504,10 @@
              return this.d;
          }
  

paper-server/nms-patches/WorldAccess.patch

@@ -1,6 +1,6 @@
 --- a/net/minecraft/server/WorldAccess.java
 +++ b/net/minecraft/server/WorldAccess.java
-@@ -5,6 +5,13 @@
+@@ -5,6 +5,12 @@
      WorldServer getMinecraftWorld();
  
      default void addAllEntities(Entity entity) {
@@ -9,9 +9,8 @@
 +        this.addAllEntities(entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason.DEFAULT);
      }
 +
-+    default boolean addAllEntities(Entity entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
++    default void addAllEntities(Entity entity, org.bukkit.event.entity.CreatureSpawnEvent.SpawnReason reason) {
 +        entity.cp().forEach((e) -> this.addEntity(e, reason));
-+        return !entity.dead;
 +    }
 +    // CraftBukkit end
  }

paper-server/nms-patches/WorldServer.patch

@@ -395,7 +395,7 @@
              return true;
          }
      }
-@@ -813,11 +954,16 @@
+@@ -813,10 +954,16 @@
      }
  
      public boolean addAllEntitiesSafely(Entity entity) {
@@ -409,12 +409,11 @@
              return false;
          } else {
 -            this.addAllEntities(entity);
--            return true;
++            this.addAllEntities(entity, reason); // CraftBukkit
-+            return this.addAllEntities(entity, reason); // CraftBukkit
+             return true;
          }
      }
- 
+@@ -867,10 +1014,17 @@
-@@ -867,10 +1013,17 @@
          }
  
          this.getScoreboard().a(entity);
@@ -432,7 +431,7 @@
      }
  
      private void registerEntity(Entity entity) {
-@@ -891,9 +1044,16 @@
+@@ -891,9 +1045,16 @@
  
              this.entitiesByUUID.put(entity.getUniqueID(), entity);
              this.getChunkProvider().addEntity(entity);
@@ -449,7 +448,7 @@
          }
  
      }
-@@ -923,10 +1083,33 @@
+@@ -923,10 +1084,33 @@
          this.everyoneSleeping();
      }
  
@@ -483,7 +482,7 @@
          while (iterator.hasNext()) {
              EntityPlayer entityplayer = (EntityPlayer) iterator.next();
  
-@@ -935,6 +1118,12 @@
+@@ -935,6 +1119,12 @@
                  double d1 = (double) blockposition.getY() - entityplayer.locY();
                  double d2 = (double) blockposition.getZ() - entityplayer.locZ();
  
@@ -496,7 +495,7 @@
                  if (d0 * d0 + d1 * d1 + d2 * d2 < 1024.0D) {
                      entityplayer.playerConnection.sendPacket(new PacketPlayOutBlockBreakAnimation(i, blockposition, j));
                  }
-@@ -995,10 +1184,20 @@
+@@ -995,10 +1185,20 @@
  
      @Override
      public Explosion createExplosion(@Nullable Entity entity, @Nullable DamageSource damagesource, @Nullable ExplosionDamageCalculator explosiondamagecalculator, double d0, double d1, double d2, float f, boolean flag, Explosion.Effect explosion_effect) {
@@ -517,7 +516,7 @@
          if (explosion_effect == Explosion.Effect.NONE) {
              explosion.clearBlocks();
          }
-@@ -1063,13 +1262,20 @@
+@@ -1063,13 +1263,20 @@
      }
  
      public <T extends ParticleParam> int a(T t0, double d0, double d1, double d2, int i, double d3, double d4, double d5, double d6) {
@@ -540,7 +539,7 @@
                  ++j;
              }
          }
-@@ -1111,7 +1317,7 @@
+@@ -1111,7 +1318,7 @@
  
      @Nullable
      public BlockPosition a(StructureGenerator<?> structuregenerator, BlockPosition blockposition, int i, boolean flag) {
@@ -549,7 +548,7 @@
      }
  
      @Nullable
-@@ -1149,7 +1355,13 @@
+@@ -1149,7 +1356,13 @@
      @Override
      public WorldMap a(String s) {
          return (WorldMap) this.getMinecraftServer().E().getWorldPersistentData().b(() -> {
@@ -564,7 +563,7 @@
          }, s);
      }
  
-@@ -1460,6 +1672,11 @@
+@@ -1460,6 +1673,11 @@
      @Override
      public void update(BlockPosition blockposition, Block block) {
          if (!this.isDebugWorld()) {
@@ -576,7 +575,7 @@
              this.applyPhysics(blockposition, block);
          }
  
-@@ -1474,12 +1691,12 @@
+@@ -1474,12 +1692,12 @@
      }
  
      public boolean isFlatWorld() {
@@ -591,7 +590,7 @@
      }
  
      @Nullable
-@@ -1499,9 +1716,9 @@
+@@ -1499,9 +1717,9 @@
  
      @VisibleForTesting
      public String F() {
@@ -603,7 +602,7 @@
              return IRegistry.BLOCK_ENTITY_TYPE.getKey(tileentity.getTileType());
          }), this.getBlockTickList().a(), this.getFluidTickList().a(), this.P());
      }
-@@ -1509,7 +1726,7 @@
+@@ -1509,7 +1727,7 @@
      private static <T> String a(Collection<T> collection, Function<T, MinecraftKey> function) {
          try {
              Object2IntOpenHashMap<MinecraftKey> object2intopenhashmap = new Object2IntOpenHashMap();
@@ -612,7 +611,7 @@
  
              while (iterator.hasNext()) {
                  T t0 = iterator.next();
-@@ -1518,7 +1735,8 @@
+@@ -1518,7 +1736,8 @@
                  object2intopenhashmap.addTo(minecraftkey, 1);
              }
  
@@ -622,7 +621,7 @@
                  return it_unimi_dsi_fastutil_objects_object2intmap_entry.getKey() + ":" + it_unimi_dsi_fastutil_objects_object2intmap_entry.getIntValue();
              }).collect(Collectors.joining(","));
          } catch (Exception exception) {
-@@ -1527,16 +1745,32 @@
+@@ -1527,16 +1746,32 @@
      }
  
      public static void a(WorldServer worldserver) {