fix tripwire hook BlockPlaceEvent (fixes #2969) (#2971)

Spigot-Server-Patches/0440-fix-blockstate-capture-undoing.patch

@@ -0,0 +1,32 @@
+From a9c21212ccc71c68ef17076e300d53a23a7ed836 Mon Sep 17 00:00:00 2001
+From: Trigary <trigary0@gmail.com>
+Date: Mon, 17 Feb 2020 22:53:33 +0100
+Subject: [PATCH] fix blockstate capture undoing
+
+
+diff --git a/src/main/java/net/minecraft/server/World.java b/src/main/java/net/minecraft/server/World.java
+index 3c966b4ab..baad98517 100644
+--- a/src/main/java/net/minecraft/server/World.java
++++ b/src/main/java/net/minecraft/server/World.java
+@@ -349,7 +349,9 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
+             Block block = iblockdata.getBlock();
+ 
+             // CraftBukkit start - capture blockstates
++            boolean capturedBlockState = false; //Paper - fix blockstate capture undoing
+             if (this.captureBlockStates && !this.capturedBlockStates.containsKey(blockposition)) {
++                capturedBlockState = true; //Paper - fix blockstate capture undoing
+                 CraftBlockState blockstate = (CraftBlockState) world.getBlockAt(blockposition.getX(), blockposition.getY(), blockposition.getZ()).getState(); // Paper - use CB getState to get a suitable snapshot
+                 this.capturedBlockStates.put(blockposition.immutableCopy(), blockstate);
+             }
+@@ -360,7 +362,7 @@ public abstract class World implements GeneratorAccess, AutoCloseable {
+ 
+             if (iblockdata1 == null) {
+                 // CraftBukkit start - remove blockstate if failed
+-                if (this.captureBlockStates) {
++                if (/*this.captureBlockStates*/ capturedBlockState) { //Paper - fix blockstate capture undoing
+                     this.capturedBlockStates.remove(blockposition);
+                 }
+                 // CraftBukkit end
+-- 
+2.16.1.windows.4
+