When a plugin listens to the EntityAddToWorld and EntityRemoveFromWorld events, I don't believe there is currently any method of directly obtaining which world the entity was actually added to/removed from. Using event.getEntity().getWorld() works in many cases, but not all. Specifically, when an entity is teleported from one world to another, the location of the entity is updated prior to the removal event being called. This means that when an entity goes through a nether/end portal or is teleported between worlds with a command, a plugin listening to the EntityRemoveFromWorldEvent has no way of determining which world the entity was actually removed from (without relying on other events).
To resolve this, I've added the world as a field in the events along with a getter to retrieve it. I also removed an unused import and made the documentation more clear on the event behaviour when chunks load/unload.
Upstream has released updates that appear to apply and compile correctly.
This update has not been tested by PaperMC and as with ANY update, please do your own testing
Bukkit Changes:
63c208dd Remove no longer used import
70be76c7 PR-958: Further clarify deprecation of TAG_CONTAINER_ARRAY
ae21f4ac PR-955: Add methods to place structures with block/entity transformers
e3d960f2 SPIGOT-7547: Remark that Damageable#setAbsorptionAmount() is capped to a specific value
b125516c Fix typo in RecipeChoice.ExactChoice docs
309497c1 Add EntityMountEvent and EntityDismount Event
2fd45ae3 Improve ItemFactory#enchantItem consistency
2b198268 PR-933: Define native persistent data types for lists
CraftBukkit Changes:
771182f70 PR-1327: Add methods to place structures with block/entity transformers
e41ad4c82 SPIGOT-7567: SpawnReason for SNOWMAN is reported as BUILD_IRONGOLEM
76931e8bd Add EntityMountEvent and EntityDismount Event
9b29b21c7 PR-1183: Better handle lambda expression and renaming of classes in Commodore
1462ebe85 Reformat Commodore.java
9fde4c037 PR-1324: Improve ItemFactory#enchantItem consistency
4e419c774 PR-1295: Define native persistent data types for lists
dd8cca388 SPIGOT-7562: Fix Score#getScore and Score#isScoreSet
690278200 Only fetch an online UUID in online mode
1da8d9a53 Fire PreLogin events even in offline mode
2e88514ad PR-1325: Use CraftBlockType and CraftItemType instead of CraftMagicNumbers to convert between minecraft and bukkit block / item representation
Spigot Changes:
864e4acc Restore accidentally removed package-info.java
f91a10d5 Remove obsolete EntityMountEvent and EntityDismountEvent
828f0593 SPIGOT-7558: Deprecate silenceable lightning API as sound is now client-side and cannot be removed
cdc4e035 Remove obsolete patch fetching correct mode UUIDs
49e36b8e Merge related BungeeCord patches
6e87b9ab Remove obsolete firing of PreLogin events in offline mode
5c76b183 Remove redundant patch dealing with exceptions in the crash reporter
3a2219d1 Remove redundant patch logging cause of unexpected exception
Nassim Jahnke