Paper/patches/server/0646-fix-cancelling-block-falling-causing-client-desync.patch

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 15ec064cb9336924e16a7c9b3f76a9b6ef18d947..8336ea928faa92c6f58f8cdfb9faf1d8e26c9ccf 100644
--- a/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
+++ b/src/main/java/net/minecraft/world/entity/item/FallingBlockEntity.java
@@ -119,8 +119,18 @@ 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).is(block)) {
+                    if (CraftEventFactory.callEntityChangeBlockEvent(this, blockposition, Blocks.AIR.defaultBlockState()).isCancelled()) {
+                        if (this.level.getBlockState(blockposition).is(block)) { //if listener didn't update the block
+                            ((ServerLevel) level).getChunkSource().blockChanged(blockposition);
+                        }
+                        this.discard();
+                        return;
+                    } else {
+                        this.level.removeBlock(blockposition, false);
+                    }
+                    // Paper end - fix cancelling block falling causing client desync
                 } else if (!this.level.isClientSide) {
                     this.discard();
                     return;