From 54ce8682aa683d537638b3a6226ff5a40002fb3f Mon Sep 17 00:00:00 2001
From: commandblockguy <commandblockguy1@gmail.com>
Date: Fri, 14 Aug 2020 14:44:14 -0500
Subject: [PATCH] Prevent headless pistons from being created

Prevent headless pistons from being created by explosions or tree/mushroom growth.
---
 .../world/level/ServerExplosion.java.patch    | 32 ++++++++++++++-----
 1 file changed, 24 insertions(+), 8 deletions(-)

diff --git a/paper-server/patches/sources/net/minecraft/world/level/ServerExplosion.java.patch b/paper-server/patches/sources/net/minecraft/world/level/ServerExplosion.java.patch
index cc2588d14c..36deb65d8a 100644
--- a/paper-server/patches/sources/net/minecraft/world/level/ServerExplosion.java.patch
+++ b/paper-server/patches/sources/net/minecraft/world/level/ServerExplosion.java.patch
@@ -62,7 +62,23 @@
  
                              if (!this.level.isInWorldBounds(blockposition)) {
                                  break;
-@@ -171,7 +186,7 @@
+@@ -149,6 +164,15 @@
+ 
+                             if (f > 0.0F && this.damageCalculator.shouldBlockExplode(this, this.level, blockposition, iblockdata, f)) {
+                                 set.add(blockposition);
++                                // Paper start - prevent headless pistons from forming
++                                if (!io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowHeadlessPistons && iblockdata.getBlock() == Blocks.MOVING_PISTON) {
++                                    net.minecraft.world.level.block.entity.BlockEntity extension = this.level.getBlockEntity(blockposition);
++                                    if (extension instanceof net.minecraft.world.level.block.piston.PistonMovingBlockEntity blockEntity && blockEntity.isSourcePiston()) {
++                                        net.minecraft.core.Direction direction = iblockdata.getValue(net.minecraft.world.level.block.piston.PistonHeadBlock.FACING);
++                                        set.add(blockposition.relative(direction.getOpposite()));
++                                    }
++                                }
++                                // Paper end - prevent headless pistons from forming
+                             }
+ 
+                             d4 += d0 * 0.30000001192092896D;
+@@ -171,7 +195,7 @@
          int l = Mth.floor(this.center.y + (double) f + 1.0D);
          int i1 = Mth.floor(this.center.z - (double) f - 1.0D);
          int j1 = Mth.floor(this.center.z + (double) f + 1.0D);
@@ -71,7 +87,7 @@
          Iterator iterator = list.iterator();
  
          while (iterator.hasNext()) {
-@@ -192,10 +207,38 @@
+@@ -192,10 +216,38 @@
                          d3 /= d4;
                          boolean flag = this.damageCalculator.shouldDamageEntity(this, entity);
                          float f1 = this.damageCalculator.getKnockbackMultiplier(entity);
@@ -112,7 +128,7 @@
                          }
  
                          double d5 = (1.0D - d0) * (double) f2 * (double) f1;
-@@ -204,7 +247,7 @@
+@@ -204,7 +256,7 @@
                          if (entity instanceof LivingEntity) {
                              LivingEntity entityliving = (LivingEntity) entity;
  
@@ -121,7 +137,7 @@
                          } else {
                              d6 = d5;
                          }
-@@ -214,11 +257,19 @@
+@@ -214,11 +266,19 @@
                          d3 *= d6;
                          Vec3 vec3d = new Vec3(d1, d2, d3);
  
@@ -142,7 +158,7 @@
                                  this.hitPlayers.put(entityhuman, vec3d);
                              }
                          }
-@@ -235,10 +286,62 @@
+@@ -235,10 +295,62 @@
          List<ServerExplosion.StackCollector> list1 = new ArrayList();
  
          Util.shuffle(positions, this.level.random);
@@ -205,7 +221,7 @@
  
              this.level.getBlockState(blockposition).onExplosionHit(this.level, blockposition, this, (itemstack, blockposition1) -> {
                  ServerExplosion.addOrAppendStack(list1, itemstack, blockposition1);
-@@ -262,13 +365,22 @@
+@@ -262,13 +374,22 @@
              BlockPos blockposition = (BlockPos) iterator.next();
  
              if (this.level.random.nextInt(3) == 0 && this.level.getBlockState(blockposition).isAir() && this.level.getBlockState(blockposition.below()).isSolidRender()) {
@@ -229,7 +245,7 @@
          this.level.gameEvent(this.source, (Holder) GameEvent.EXPLODE, this.center);
          List<BlockPos> list = this.calculateExplodedPositions();
  
-@@ -288,6 +400,7 @@
+@@ -288,6 +409,7 @@
      }
  
      private static void addOrAppendStack(List<ServerExplosion.StackCollector> droppedItemsOut, ItemStack item, BlockPos pos) {
@@ -237,7 +253,7 @@
          Iterator iterator = droppedItemsOut.iterator();
  
          do {
-@@ -372,4 +485,85 @@
+@@ -372,4 +494,85 @@
  
          }
      }