Upstream has released updates that appears to apply and compile correctly.
This update has been tested to ensure that World Conversion still occurs correctly.
Bukkit Changes:
0812ce2c SPIGOT-4397: isChunkGenerated API
CraftBukkit Changes:
4824655c SPIGOT-4398: Upgrade to ASM 6.2.1 for better Java 11 support
eea43870 MC-134115: Fix issues converting tile entities
1a7f2d10 SPIGOT-4397: isChunkGenerated API
40aed54d SPIGOT-4396: Improve vehicle movement
Spigot Changes:
f6a273b1 Rebuild patches
getDimensionId() returns the dimension id - 1. So without this patch
we would reuse an existing dimension id, if some other dimension was
unloaded before.
In Spigot this is nearly invisible because DimensionManager has no equals(),
so dimension id collisions just create 2 worlds with the same dimension.
The PaperWorldMap (Added in
https://github.com/PaperMC/Paper/blob/master/Spigot-Server-Patches/0376-Optimize-Server-World-Map.patch ) changes this - Now the dimension is overwritten if there is some collision,
what causes players to teleport to incorrect worlds, World checks will no longer work
and many more evil things.
Aikar
Brokkonaut