In general, the client now has an acknowledgment system that will cause block changes made by the client to be reverted correctly.
Essentially:
The client enters a "prediction" stage, where any block changes made will have its old blockstate captured (this is referred to as "server state").
If you update blocks during this stage, the client will update this captured server state as long as they're still currently predicting.
After prediction is done (via an ack packet) all captured blockstates are reverted to their captured server state.
This means that if the server actually updated a block and send a block update packet, it's correctly set, while if a block wasn't updated on the server but WAS updated on the client (server state wasn't updated), that change will be reverted.
It should be noted that this system does not yet support block entities, so those still need to be resynced when needed.
I discovered this when noticing that blocks broken outside of the player's valid interaction distance are still properly reverted, even though the server doesn't send any block updates, only an ack packet.
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:
82af5dc6 SPIGOT-7396: Add PlayerSignOpenEvent
3f0281ca SPIGOT-7063, PR-763: Add DragonBattle#initiateRespawn with custom EnderCrystals
f83c8df4 PR-873: Add PlayerRecipeBookClickEvent
14560d39 SPIGOT-7435: Add TeleportCause#EXIT_BED
2cc6db92 SPIGOT-7422, PR-887: Add API to set sherds on decorated pots
36022f02 PR-883: Add ItemFactory#getSpawnEgg
12eb5c46 PR-881: Update Scoreboard Javadocs, remove explicit exception throwing
f6d8d44a PR-882: Add modern time API methods to ban API
21a7b710 Upgrade some Maven plugins to reduce warnings
11fd1225 PR-886: Deprecate the SmithingRecipe constructor as it now does nothing
dbd1761d SPIGOT-7406: Improve documentation for getDragonBattle
CraftBukkit Changes:
d548daac2 SPIGOT-7446: BlockState#update not updating a spawner's type to null
70e0bc050 SPIGOT-7447: Fix --forceUpgrade
6752f1d63 SPIGOT-7396: Add PlayerSignOpenEvent
847b4cad5 SPIGOT-7063, PR-1071: Add DragonBattle#initiateRespawn with custom EnderCrystals
c335a555f PR-1212: Add PlayerRecipeBookClickEvent
4be756ecb SPIGOT-7445: Fix opening smithing inventory
db70bd6ed SPIGOT-7441: Fix issue placing certain items in creative/op
f7fa6d993 SPIGOT-7435: Add TeleportCause#EXIT_BED
b435e8e8d SPIGOT-7349: Player#setDisplayName not working when message/format unmodified
a2fafdd1d PR-1232: Re-add fix for player rotation
7cf863de1 PR-1233: Remove some old MC bug fixes now fixed in vanilla
08ec344ad Fix ChunkGenerator#generateCaves never being called
5daeb502a SPIGOT-7422, PR-1228: Add API to set sherds on decorated pots
52faa6b32 PR-1224: Add ItemFactory#getSpawnEgg
01cae71b7 SPIGOT-7429: Fix LEFT_CLICK_AIR not working for passable entities and spectators
a94277a18 PR-1223: Remove non-existent scoreboard display name/prefix/suffix limits
36b107660 PR-1225: Add modern time API methods to ban API
59ead25bc Upgrade some Maven plugins to reduce warnings
202fc5c4e Increase outdated build delay
ce545de57 SPIGOT-7398: TextDisplay#setInterpolationDuration incorrectly updates the line width
Spigot Changes:
b41c46db Rebuild patches
3374045a SPIGOT-7431: Fix EntityMountEvent returning opposite entities
0ca4eb66 Rebuild patches
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:
01aa02eb PR-858: Add LivingEntity#playHurtAnimation()
9421320f PR-884: Refinements to new ban API for improved compatibility and correctness
37a60b45 SPIGOT-6455, SPIGOT-7030, PR-750: Improve ban API
4eeb174b All smithing inventories are now the new smithing inventory
f2bb168e PR-880: Add methods to get/set FallingBlock CancelDrop
e7a807fa PR-879: Add Player#sendHealthUpdate()
692b8e96 SPIGOT-7370: Remove float value conversion in plugin.yml
2d033390 SPIGOT-7403: Add direct API for waxed signs
16a08373 PR-876: Add missing Raider API and 'no action ticks'
CraftBukkit Changes:
b60a95c8c PR-1189: Add LivingEntity#playHurtAnimation()
95c335c63 PR-1226: Fix VehicleEnterEvent not being called for certain entities
0a0fc3bee PR-1227: Refinements to new ban API for improved compatibility and correctness
0d0b1e5dc Revert bad change to PathfinderGoalSit causing all cats to sit
648196070 SPIGOT-6455, SPIGOT-7030, PR-1054: Improve ban API
31fe848d6 All smithing inventories are now the new smithing inventory
9a919a143 SPIGOT-7416: SmithItemEvent not firing in Smithing Table
9f64f0d22 PR-1221: Add methods to get/set FallingBlock CancelDrop
3be9ac171 PR-1220: Add Player#sendHealthUpdate()
c1279f775 PR-1209: Clean up various patches
c432e4397 Fix Raider#setCelebrating() implementation
504d96665 SPIGOT-7403: Add direct API for waxed signs
c68c1f1b3 PR-1216: Add missing Raider API and 'no action ticks'
85b89c3dd Increase outdated build delay
Spigot Changes:
9ebce8af Rebuild patches
64b565e6 Rebuild patches
