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Fix piston physics inconsistency - MC-188840

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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.
This commit is contained in:
Spottedleaf 2020-06-11 17:29:42 -07:00
parent 2e59889281
commit 47dd7e1c0a
2 changed files with 40 additions and 0 deletions
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29
paper-server/patches/sources/net/minecraft/world/level/block/piston/PistonBaseBlock.java.patch
View file

@ -83,3 +83,32 @@
BlockPos blockposition3;
int j;
BlockState iblockdata1;
@@ -358,13 +419,25 @@
BlockState iblockdata2;
for (j = list.size() - 1; j >= 0; --j) {
- blockposition3 = (BlockPos) list.get(j);
- 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(j);
+ iblockdata1 = allowDesync ? world.getBlockState(oldPos) : null;
+ // Paper end - fix a variety of piston desync dupes
blockposition3 = blockposition3.relative(enumdirection1);
map.remove(blockposition3);
iblockdata2 = (BlockState) Blocks.MOVING_PISTON.defaultBlockState().setValue(PistonBaseBlock.FACING, dir);
world.setBlock(blockposition3, iblockdata2, 68);
- world.setBlockEntity(MovingPistonBlock.newMovingBlockEntity(blockposition3, iblockdata2, (BlockState) list1.get(j), dir, extend, 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 ? (BlockState) list1.get(j) : iblockdata1, dir, extend, false));
+ if (!allowDesync) {
+ world.setBlock(oldPos, Blocks.AIR.defaultBlockState(), Block.UPDATE_CLIENTS | Block.UPDATE_KNOWN_SHAPE | Block.UPDATE_MOVE_BY_PISTON | 1024); // set air to prevent later physics updates from seeing this block
+ }
+ // Paper end - fix a variety of piston desync dupes
aiblockdata[i++] = iblockdata1;
}

11
paper-server/patches/sources/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java.patch Normal file
View file

@ -0,0 +1,11 @@
--- a/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
+++ b/net/minecraft/world/level/block/piston/PistonMovingBlockEntity.java
@@ -306,7 +306,7 @@
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 | Block.UPDATE_CLIENTS)); // Paper - fix a variety of piston desync dupes; 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)) {