From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001 From: Spottedleaf Date: Thu, 11 Jun 2020 17:29:42 -0700 Subject: [PATCH] Fix piston physics inconsistency - MC-188840 Pistons invoke physics when they move blocks. The physics can cause tnt blocks to ignite. However, pistons (when storing the blocks they "moved") don't actually go back to the world state sometimes to check if something like that happened. As a result they end up moving the tnt like it was never ignited. This resulted in the ability to create machines that can duplicate tnt, called "world eaters". This patch makes the piston logic retrieve the block state from the world prevent this from occuring. This patch also sets the moved pos to air immediately after creating the moving piston TE. This prevents the block from being updated from other physics calls by the piston. Tested against the following tnt duper design: https://www.youtube.com/watch?v=mS7xxNGhjxs This patch also affects every type of machine that utilises this mechanic. For example, dead coral is removed by a physics update when being moved while it is attached to slimeblocks. Standard piston machines that don't destroy or modify the blocks they move by physics updates should be entirely unaffected. This patch fixes https://bugs.mojang.com/browse/MC-188840 This patch also fixes rail duping and carpet duping. diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java index 29755807fdb6c30e31c0ec2bbf33bed9afd5d478..8d73893100884c08aa552ff41c2a07a3e714df47 100644 --- a/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java +++ b/src/main/java/net/minecraft/world/level/block/piston/PistonBaseBlock.java @@ -411,14 +411,26 @@ public class PistonBaseBlock extends DirectionalBlock { } for (k = list.size() - 1; k >= 0; --k) { - blockposition3 = (BlockPos) list.get(k); - iblockdata1 = world.getBlockState(blockposition3); + // Paper start - fix a variety of piston desync dupes + boolean allowDesync = io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowPistonDuplication; + BlockPos oldPos = blockposition3 = (BlockPos) list.get(k); + iblockdata1 = allowDesync ? world.getBlockState(oldPos) : null; + // Paper end - fix a variety of piston desync dupes blockposition3 = blockposition3.relative(enumdirection1); map.remove(blockposition3); BlockState iblockdata2 = (BlockState) Blocks.MOVING_PISTON.defaultBlockState().setValue(PistonBaseBlock.FACING, dir); world.setBlock(blockposition3, iblockdata2, 68); - world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(blockposition3, iblockdata2, (BlockState) list1.get(k), dir, retract, false)); + // Paper start - fix a variety of piston desync dupes + if (!allowDesync) { + iblockdata1 = world.getBlockState(oldPos); + map.replace(oldPos, iblockdata1); + } + world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(blockposition3, iblockdata2, allowDesync ? list1.get(k) : iblockdata1, dir, retract, false)); + if (!allowDesync) { + world.setBlock(oldPos, Blocks.AIR.defaultBlockState(), 2 | 4 | 16 | 1024); // set air to prevent later physics updates from seeing this block + } + // Paper end - fix a variety of piston desync dupes aiblockdata[j++] = iblockdata1; } diff --git a/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java index 4f7b12d8f213d43f4ef5538b7e05809a1a106cbd..221c5d080d55326e458c1182823d6b49224ef498 100644 --- a/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java +++ b/src/main/java/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java @@ -288,7 +288,7 @@ public class PistonMovingBlockEntity extends BlockEntity { if (world.getBlockState(pos).is(Blocks.MOVING_PISTON)) { BlockState blockState = Block.updateFromNeighbourShapes(blockEntity.movedState, world, pos); if (blockState.isAir()) { - world.setBlock(pos, blockEntity.movedState, 84); + world.setBlock(pos, blockEntity.movedState, io.papermc.paper.configuration.GlobalConfiguration.get().unsupportedSettings.allowPistonDuplication ? 84 : (84 | 2)); // Paper - force notify (flag 2), it's possible the set type by the piston block (which doesn't notify) set this block to air Block.updateOrDestroy(blockEntity.movedState, blockState, world, pos, 3); } else { if (blockState.hasProperty(BlockStateProperties.WATERLOGGED) && blockState.getValue(BlockStateProperties.WATERLOGGED)) {