From d5c2e00a30aa96c665393676e4dc49aa0a2feed2 Mon Sep 17 00:00:00 2001
From: Shane Freeder <theboyetronic@gmail.com>
Date: Wed, 17 Apr 2019 00:48:59 +0100
Subject: [PATCH] Fix NPE from sign placement

This fixes issues with upstreams changes to solve a private issue on
their side, as signs are placed, they may replace existing blocks, e.g.
grass, which breaks upstreams assumption that the sign is always placed
adjacent to a surface

diff --git a/src/main/java/net/minecraft/server/EntityHuman.java b/src/main/java/net/minecraft/server/EntityHuman.java
index f5d9b4abc2..fdbe9a2adc 100644
--- a/src/main/java/net/minecraft/server/EntityHuman.java
+++ b/src/main/java/net/minecraft/server/EntityHuman.java
@@ -70,6 +70,7 @@ public abstract class EntityHuman extends EntityLiving {
     public EntityFishingHook hookedFish;
     // Paper start
     public boolean affectsSpawning = true;
+    public BlockPosition openingSign = null; // Paper - fix NPE when opening signs
     // Paper end
     // Paper start - Player view distance API
     private int viewDistance = -1;
diff --git a/src/main/java/net/minecraft/server/ItemSign.java b/src/main/java/net/minecraft/server/ItemSign.java
index 11045ee1e1..7808aed0c0 100644
--- a/src/main/java/net/minecraft/server/ItemSign.java
+++ b/src/main/java/net/minecraft/server/ItemSign.java
@@ -16,6 +16,7 @@ public class ItemSign extends ItemBlockWallable {
         if (!world.isClientSide && !flag && entityhuman != null) {
             // CraftBukkit start - SPIGOT-4678
             // entityhuman.openSign((TileEntitySign) world.getTileEntity(blockposition));
+            entityhuman.openingSign = blockposition; // Paper - fix NPE when opening signs
             ItemSign.openSign = true;
             // CraftBukkit end
         }
diff --git a/src/main/java/net/minecraft/server/ItemStack.java b/src/main/java/net/minecraft/server/ItemStack.java
index f8d82a0276..ccc0826bc6 100644
--- a/src/main/java/net/minecraft/server/ItemStack.java
+++ b/src/main/java/net/minecraft/server/ItemStack.java
@@ -305,7 +305,12 @@ public final class ItemStack {
                     // SPIGOT-4678
                     if (this.item instanceof ItemSign && ItemSign.openSign) {
                         ItemSign.openSign = false;
-                        entityhuman.openSign((TileEntitySign) world.getTileEntity(new BlockActionContext(itemactioncontext).getClickPosition()));
+                        // Paper start - fix NPE when opening signs
+                        if (entityhuman.openingSign != null) {
+                            entityhuman.openSign((TileEntitySign) world.getTileEntity(entityhuman.openingSign));
+                            entityhuman.openingSign = null;
+                        }
+                        // Paper end
                     }
 
                     // SPIGOT-1288 - play sound stripped from ItemBlock
-- 
2.21.0