fix piston retracting

bootstrap/mod/src/main/java/org/geysermc/geyser/platform/mod/mixin/server/PistonBaseBlockMixin.java

@@ -82,6 +82,7 @@ public class PistonBaseBlockMixin {
 
         for (Map.Entry<UUID, GeyserSession> entry : GeyserImpl.getInstance().getSessionManager().getSessions().entrySet()) {
             Player player = level.getPlayerByUUID(entry.getKey());
+            //noinspection resource
             if (player == null || !player.level().equals(level)) {
                 continue;
             }

core/src/main/java/org/geysermc/geyser/registry/populator/BlockRegistryPopulator.java

@@ -162,7 +162,6 @@ public final class BlockRegistryPopulator {
             // as we no longer send a block palette
             Object2ObjectMap<NbtMap, GeyserBedrockBlock> blockStateOrderedMap = new Object2ObjectOpenHashMap<>(blockStates.size());
             GeyserBedrockBlock[] bedrockRuntimeMap = new GeyserBedrockBlock[blockStates.size()];
-            GeyserImpl.getInstance().getLogger().info(blockStates.size() + " block states found");
             for (int i = 0; i < blockStates.size(); i++) {
                 NbtMap tag = blockStates.get(i);
                 if (blockStateOrderedMap.containsKey(tag)) {

core/src/main/java/org/geysermc/geyser/translator/level/block/entity/PistonBlockEntity.java

@@ -37,7 +37,6 @@ import org.cloudburstmc.math.vector.Vector3i;
 import org.cloudburstmc.nbt.NbtMap;
 import org.cloudburstmc.nbt.NbtMapBuilder;
 import org.cloudburstmc.protocol.bedrock.packet.UpdateBlockPacket;
-import org.geysermc.geyser.api.util.PlatformType;
 import org.geysermc.geyser.level.block.BlockStateValues;
 import org.geysermc.geyser.level.block.Blocks;
 import org.geysermc.geyser.level.block.property.Properties;
@@ -230,9 +229,8 @@ public class PistonBlockEntity {
         BlockState state = session.getGeyser().getWorldManager().blockAt(session, blockInFront);
         if (state.is(Blocks.PISTON_HEAD)) {
             ChunkUtils.updateBlock(session, Block.JAVA_AIR_ID, blockInFront);
-        } else if ((session.getGeyser().getPlatformType() == PlatformType.SPIGOT || session.getErosionHandler().isActive()) && state.is(Blocks.AIR)) {
+        } else if ((session.getGeyser().getWorldManager().hasOwnChunkCache() || session.getErosionHandler().isActive()) && state.is(Blocks.AIR)) {
-            // TODO pistons fabric????
+            // The platform removes the piston head from the cache, but we need to send the block update ourselves
-            // Spigot removes the piston head from the cache, but we need to send the block update ourselves
             ChunkUtils.updateBlock(session, Block.JAVA_AIR_ID, blockInFront);
         }
     }

core/src/main/java/org/geysermc/geyser/translator/protocol/java/level/JavaBlockEventTranslator.java

@@ -82,17 +82,22 @@ public class JavaBlockEventTranslator extends PacketTranslator<ClientboundBlockE
             Direction direction = Direction.fromPistonValue(pistonValue.getDirection());
             PistonCache pistonCache = session.getPistonCache();
 
-            // TODO pistons modded
+            if (session.getGeyser().getWorldManager().hasOwnChunkCache() || session.getErosionHandler().isActive()) {
-            if (session.getGeyser().getPlatformType() == PlatformType.SPIGOT || session.getErosionHandler().isActive()) {
+                // Mostly handled in the GeyserPistonEvents class (Spigot) / the PistonBlockBaseMixin (Mod platforms)
-                // Mostly handled in the GeyserPistonEvents class
+                // However, the retracting event is not fully covered. (Spigot)
-                // Retracting sticky pistons is an exception, since the event is not called on Spigot from 1.13.2 - 1.17.1
+                // Mod platforms only handle pistons moving blocks; not the retracting of pistons.
-                // See https://github.com/PaperMC/Paper/blob/6fa1983e9ce177a4a412d5b950fd978620174777/patches/server/0304-Fire-BlockPistonRetractEvent-for-all-empty-pistons.patch
                 if (action == PistonValueType.PULLING || action == PistonValueType.CANCELLED_MID_PUSH) {
                     BlockState pistonBlock = session.getGeyser().getWorldManager().blockAt(session, position);
-                    if (!isSticky(pistonBlock)) {
+
+                    // Retracting sticky pistons is an exception, since the event is not called on Spigot from 1.13.2 - 1.17.1
+                    // See https://github.com/PaperMC/Paper/blob/6fa1983e9ce177a4a412d5b950fd978620174777/patches/server/0304-Fire-BlockPistonRetractEvent-for-all-empty-pistons.patch
+                    boolean isSticky = isSticky(pistonBlock);
+                    if (session.getGeyser().getPlatformType() == PlatformType.SPIGOT && !isSticky) {
                         return;
                     }
-                    if (action != PistonValueType.CANCELLED_MID_PUSH) {
+
+                    // Only sticky pistons that don't pull any blocks are affected
+                    if (action != PistonValueType.CANCELLED_MID_PUSH && isSticky) {
                         Vector3i blockInFrontPos = position.add(direction.getUnitVector());
                         int blockInFront = session.getGeyser().getWorldManager().getBlockAt(session, blockInFrontPos);
                         if (blockInFront != Block.JAVA_AIR_ID) {
@@ -100,7 +105,7 @@ public class JavaBlockEventTranslator extends PacketTranslator<ClientboundBlockE
                             return;
                         }
                     }
-                    PistonBlockEntity blockEntity = pistonCache.getPistons().computeIfAbsent(position, pos -> new PistonBlockEntity(session, pos, direction, true, true));
+                    PistonBlockEntity blockEntity = pistonCache.getPistons().computeIfAbsent(position, pos -> new PistonBlockEntity(session, pos, direction, isSticky, true));
                     if (blockEntity.getAction() != action) {
                         blockEntity.setAction(action, Object2ObjectMaps.emptyMap());
                     }