From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Trigary <trigary0@gmail.com>
Date: Sat, 27 Mar 2021 11:13:30 +0100
Subject: [PATCH] fix cancelling block falling causing client desync


diff --git a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
index 2ba81e7179c7f9e2e1add1ad6bd6b96ee12c5da1..718e20f83a9b510c095d7e12241616cdce33d2d6 100644
--- a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
@@ -13,6 +13,7 @@ import net.minecraft.network.protocol.game.ClientboundAddEntityPacket;
 import net.minecraft.network.syncher.EntityDataAccessor;
 import net.minecraft.network.syncher.EntityDataSerializers;
 import net.minecraft.network.syncher.SynchedEntityData;
+import net.minecraft.server.level.ServerLevel;
 import net.minecraft.tags.BlockTags;
 import net.minecraft.tags.FluidTags;
 import net.minecraft.tags.Tag;
@@ -41,6 +42,7 @@ import net.minecraft.world.level.material.Fluids;
 import net.minecraft.world.phys.BlockHitResult;
 import net.minecraft.world.phys.HitResult;
 import net.minecraft.world.phys.Vec3;
+import org.bukkit.craftbukkit.block.CraftBlock;
 import org.bukkit.craftbukkit.event.CraftEventFactory; // CraftBukkit
 
 public class FallingBlockEntity extends Entity {
@@ -114,8 +116,18 @@ public class FallingBlockEntity extends Entity {
 
             if (this.time++ == 0) {
                 blockposition = this.blockPosition();
-                if (this.level.getBlockState(blockposition).is(block) && !CraftEventFactory.callEntityChangeBlockEvent(this, blockposition, Blocks.AIR.defaultBlockState()).isCancelled()) {
-                    this.level.removeBlock(blockposition, false);
+                // Paper start - fix cancelling block falling causing client desync
+                if (this.level.getBlockState(blockposition).isSameInstance(block)) {
+                    if (CraftEventFactory.callEntityChangeBlockEvent(this, blockposition, Blocks.AIR.defaultBlockState()).isCancelled()) {
+                        if (this.level.getBlockState(blockposition).isSameInstance(block)) { //if listener didn't update the block
+                            ((ServerLevel) level).getChunkSource().blockChanged(blockposition);
+                        }
+                        this.remove();
+                        return;
+                    } else {
+                        this.level.setAir(blockposition, false);
+                    }
+                    // Paper end - fix cancelling block falling causing client desync
                 } else if (!this.level.isClientSide) {
                     this.remove();
                     return;
diff --git a/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java b/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
index 17baae6b11f191f4738a107c7e62ea5bdac17a3c..32cda8c2e14cf8b218cb006a9b25330f0dab849a 100644
--- a/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
+++ b/src/main/java/net/minecraft/world/level/block/state/BlockBehaviour.java
@@ -682,6 +682,7 @@ public abstract class BlockBehaviour {
             return this.getBlock().is(tag) && predicate.test(this);
         }
 
+        public final boolean isSameInstance(Block block) { return is(block); } // Paper - OBFHELPER
         public boolean is(Block block) {
             return this.getBlock().is(block);
         }