Prevent Double PlayerChunkMap adds crashing server

Suspected case would be around the technique used in .stopRiding
Stack will identify any causer of this and warn instead of crashing.

paper-server/patches/sources/net/minecraft/server/level/ChunkMap.java.patch

@@ -320,11 +320,18 @@
          }
      }
  
-@@ -1215,9 +1291,11 @@
+@@ -1215,9 +1291,18 @@
      }
  
      public void addEntity(Entity entity) {
 +        org.spigotmc.AsyncCatcher.catchOp("entity track"); // Spigot
++        // Paper start - ignore and warn about illegal addEntity calls instead of crashing server
++        if (!entity.valid || entity.level() != this.level || this.entityMap.containsKey(entity.getId())) {
++            LOGGER.error("Illegal ChunkMap::addEntity for world " + this.level.getWorld().getName()
++                + ": " + entity  + (this.entityMap.containsKey(entity.getId()) ? " ALREADY CONTAINED (This would have crashed your server)" : ""), new Throwable());
++            return;
++        }
++        // Paper end - ignore and warn about illegal addEntity calls instead of crashing server
          if (!(entity instanceof EnderDragonPart)) {
              EntityType<?> entitytypes = entity.getType();
              int i = entitytypes.clientTrackingRange() * 16;
@@ -332,7 +339,7 @@
  
              if (i != 0) {
                  int j = entitytypes.updateInterval();
-@@ -1250,6 +1328,7 @@
+@@ -1250,6 +1335,7 @@
      }
  
      protected void removeEntity(Entity entity) {
@@ -340,7 +347,7 @@
          if (entity instanceof ServerPlayer entityplayer) {
              this.updatePlayerStatus(entityplayer, false);
              ObjectIterator objectiterator = this.entityMap.values().iterator();
-@@ -1391,7 +1470,7 @@
+@@ -1391,7 +1477,7 @@
          });
      }
  
@@ -349,7 +356,7 @@
  
          protected ChunkDistanceManager(final Executor workerExecutor, final Executor mainThreadExecutor) {
              super(workerExecutor, mainThreadExecutor);
-@@ -1424,7 +1503,7 @@
+@@ -1424,7 +1510,7 @@
          public final Set<ServerPlayerConnection> seenBy = Sets.newIdentityHashSet();
  
          public TrackedEntity(final Entity entity, final int i, final int j, final boolean flag) {
@@ -358,7 +365,7 @@
              this.entity = entity;
              this.range = i;
              this.lastSectionPos = SectionPos.of((EntityAccess) entity);
-@@ -1469,6 +1548,7 @@
+@@ -1469,6 +1555,7 @@
          }
  
          public void removePlayer(ServerPlayer player) {
@@ -366,7 +373,7 @@
              if (this.seenBy.remove(player.connection)) {
                  this.serverEntity.removePairing(player);
              }
-@@ -1476,6 +1556,7 @@
+@@ -1476,6 +1563,7 @@
          }
  
          public void updatePlayer(ServerPlayer player) {
@@ -374,7 +381,7 @@
              if (player != this.entity) {
                  Vec3 vec3d = player.position().subtract(this.entity.position());
                  int i = ChunkMap.this.getPlayerViewDistance(player);
-@@ -1484,6 +1565,11 @@
+@@ -1484,6 +1572,11 @@
                  double d2 = d0 * d0;
                  boolean flag = d1 <= d2 && this.entity.broadcastToPlayer(player) && ChunkMap.this.isChunkTracked(player, this.entity.chunkPosition().x, this.entity.chunkPosition().z);
  
@@ -386,7 +393,7 @@
                  if (flag) {
                      if (this.seenBy.add(player.connection)) {
                          this.serverEntity.addPairing(player);
-@@ -1506,6 +1592,7 @@
+@@ -1506,6 +1599,7 @@
              while (iterator.hasNext()) {
                  Entity entity = (Entity) iterator.next();
                  int j = entity.getType().clientTrackingRange() * 16;

paper-server/patches/sources/net/minecraft/server/level/ServerLevel.java.patch

@@ -79,7 +79,7 @@
 +    public final LevelStorageSource.LevelStorageAccess convertable;
 +    public final UUID uuid;
 +    public boolean hasPhysicsEvent = true; // Paper - BlockPhysicsEvent
-+
+ 
 +    public LevelChunk getChunkIfLoaded(int x, int z) {
 +        return this.chunkSource.getChunk(x, z, false);
 +    }
@@ -129,7 +129,7 @@
 +        }
 +        int minBlockX = Mth.floor(axisalignedbb.minX - 1.0E-7D) - 3;
 +        int minBlockZ = Mth.floor(axisalignedbb.minZ - 1.0E-7D) - 3;
- 
++
 +        int maxBlockX = Mth.floor(axisalignedbb.maxX + 1.0E-7D) + 3;
 +        int maxBlockZ = Mth.floor(axisalignedbb.maxZ + 1.0E-7D) + 3;
 +
@@ -947,20 +947,23 @@
      @Override
      public CrashReportCategory fillReportDetails(CrashReport report) {
          CrashReportCategory crashreportsystemdetails = super.fillReportDetails(report);
-@@ -1836,6 +2216,7 @@
+@@ -1836,7 +2216,8 @@
          }
  
          public void onTrackingStart(Entity entity) {
+-            ServerLevel.this.getChunkSource().addEntity(entity);
 +            org.spigotmc.AsyncCatcher.catchOp("entity register"); // Spigot
-             ServerLevel.this.getChunkSource().addEntity(entity);
++            // ServerLevel.this.getChunkSource().addEntity(entity); // Paper - ignore and warn about illegal addEntity calls instead of crashing server; moved down below valid=true
              if (entity instanceof ServerPlayer entityplayer) {
                  ServerLevel.this.players.add(entityplayer);
-@@ -1864,9 +2245,52 @@
+                 ServerLevel.this.updateSleepingPlayerList();
+@@ -1864,9 +2245,53 @@
              }
  
              entity.updateDynamicGameEventListener(DynamicGameEventListener::add);
 +            entity.inWorld = true; // CraftBukkit - Mark entity as in world
 +            entity.valid = true; // CraftBukkit
++            ServerLevel.this.getChunkSource().addEntity(entity); // Paper - ignore and warn about illegal addEntity calls instead of crashing server
 +            // Paper start - Entity origin API
 +            if (entity.getOriginVector() == null) {
 +                entity.setOrigin(entity.getBukkitEntity().getLocation());
@@ -1008,7 +1011,7 @@
              ServerLevel.this.getChunkSource().removeEntity(entity);
              if (entity instanceof ServerPlayer entityplayer) {
                  ServerLevel.this.players.remove(entityplayer);
-@@ -1895,6 +2319,15 @@
+@@ -1895,6 +2320,15 @@
              }
  
              entity.updateDynamicGameEventListener(DynamicGameEventListener::remove);