From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Nassim Jahnke <nassim@njahnke.dev>
Date: Fri, 7 Jan 2022 11:45:15 +0100
Subject: [PATCH] Reset placed block on exception


diff --git a/src/main/java/net/minecraft/world/item/BlockItem.java b/src/main/java/net/minecraft/world/item/BlockItem.java
index 78cac63e5bd7c84f59b8e00ee40899be78e8cdb1..00d31df5ba7e147b4b969a89cfc2b5088a988169 100644
--- a/src/main/java/net/minecraft/world/item/BlockItem.java
+++ b/src/main/java/net/minecraft/world/item/BlockItem.java
@@ -78,6 +78,7 @@ public class BlockItem extends Item {
                 if (this instanceof PlaceOnWaterBlockItem || this instanceof SolidBucketItem) {
                     blockstate = org.bukkit.craftbukkit.block.CraftBlockStates.getBlockState(blockactioncontext1.getLevel(), blockactioncontext1.getClickedPos());
                 }
+                final org.bukkit.block.BlockState oldBlockstate = blockstate != null ? blockstate : org.bukkit.craftbukkit.block.CraftBlockStates.getBlockState(blockactioncontext1.getLevel(), blockactioncontext1.getClickedPos()); // Paper
                 // CraftBukkit end
 
                 if (iblockdata == null) {
@@ -93,7 +94,19 @@ public class BlockItem extends Item {
 
                     if (iblockdata1.is(iblockdata.getBlock())) {
                         iblockdata1 = this.updateBlockStateFromTag(blockposition, world, itemstack, iblockdata1);
+                        // Paper start - reset block on exception
+                        try {
                         this.updateCustomBlockEntityTag(blockposition, world, entityhuman, itemstack, iblockdata1);
+                        } catch (Exception e) {
+                            oldBlockstate.update(true, false);
+                            if (entityhuman instanceof ServerPlayer player) {
+                                org.apache.logging.log4j.LogManager.getLogger().error("Player {} tried placing invalid block", player.getScoreboardName(), e);
+                                player.getBukkitEntity().kickPlayer("Packet processing error");
+                                return InteractionResult.FAIL;
+                            }
+                            throw e; // Rethrow exception if not placed by a player
+                        }
+                        // Paper end
                         iblockdata1.getBlock().setPlacedBy(world, blockposition, iblockdata1, entityhuman, itemstack);
                         // CraftBukkit start
                         if (blockstate != null) {