1.21 Tracking

To do list, roughly in order of importance

• verify all dispensers correctly shrink stack only 1 time
• disableTeleportationSuffocationCheck no longer needed, no collision check in PlayerList#respawn
• Revisit portal logic on end gateways (Cooldown on EndGateway no longer cancellable by PortalEvent) https://github.com/PaperMC/Paper/pull/10892
• Mace Knockback logic for respective events
• Test ShaplessRecipe ExactChoice
• https://github.com/PaperMC/Paper/pull/12835
• Expose world spawn angle patch
• Check on fix DamageSource API (specifically, BlockAttachedEntity hurt)
• unsafe end portal teleportation patch still needed? ~~ (owen) Don't think so, MC fixed underlying issue.
• Ensure book disconnect called on main is redundant?
• Any possibility of keeping EntityPortalReadyEvent#setTargetWorld? Yep, kept it working
• Discuss removal of PlayerItemMendEvent's IntUnary durability -> xp (potentially keep consumedXp)
• Check on upstreams AttributeModifier#getUUID logic (its terrible): https://github.com/PaperMC/Paper/issues/11015
• Forward https://github.com/PaperMC/Paper/pull/10880
• Check in on BlockData#getDestroySpeed
• Fix enchantWIthLevels treasureOnly boolean
• Forward https://github.com/PaperMC/Paper/pull/10886
• Test WitherBoss can portal API
• Test "Fix block place logic"'s Jukebox (This is now handled on JukeboxBlock, no server logic runs beyond interact event)
• Test leashes and respective events
• Done (Xs)! message shows wrong time
• Investigate if "Fix entity tracker desync when new players are added to the tracker" is still needed
• Recheck Experimental Annotations
• test mass craft perf improvement w/spark
• Revisit https://github.com/PaperMC/Paper/commit/7bbe6820c24cf3f8c7ec521a0712184c67816343 before stable
• Check in on alternate-current (https://github.com/SpaceWalkerRS/alternate-current/commit/eb405af873e75185f7fde581c2237d2b2b249f41#diff-087eb51f8c173a688076fe844b5cd6529953aea995e9ae6a7230fda2d3c44d60L1063-R1063)

Start with the remaining unchecked items: AttributeModifier#getUUID in issue #11015, WitherBoss portal API behavior, entity-tracker desync, and the referenced commit before stable. The payload names no files or test paths; done means each remaining checklist item is investigated and resolved or explicitly closed.