Program: 27582
Project: 27582
Buggy source:
public static ChangeBlockEvent.Place callBlockPlaceEvent(Event event){
  if (!(event instanceof ChangeBlockEvent.Place)) {
    throw new IllegalArgumentException("String_Node_Str");
  }
  ChangeBlockEvent.Place spongeEvent=(ChangeBlockEvent.Place)event;
  if (spongeEvent.getCause().first(Player.class).isPresent()) {
    EntityPlayer player=(EntityPlayer)spongeEvent.getCause().first(Player.class).get();
    net.minecraft.world.World world=(net.minecraft.world.World)spongeEvent.getTargetWorld();
    if (spongeEvent.getTransactions().size() == 1) {
      BlockPos pos=VecHelper.toBlockPos(spongeEvent.getTransactions().get(0).getOriginal().getPosition());
      IBlockState state=(IBlockState)spongeEvent.getTransactions().get(0).getOriginal().getState();
      net.minecraftforge.common.util.BlockSnapshot blockSnapshot=new net.minecraftforge.common.util.BlockSnapshot(world,pos,state);
      IBlockState placedAgainst=Blocks.air.getDefaultState();
      if (StaticMixinHelper.packetPlayer != null && StaticMixinHelper.processingPacket instanceof C08PacketPlayerBlockPlacement) {
        C08PacketPlayerBlockPlacement packet=(C08PacketPlayerBlockPlacement)StaticMixinHelper.processingPacket;
        EnumFacing facing=EnumFacing.getFront(packet.getPlacedBlockDirection());
        placedAgainst=blockSnapshot.world.getBlockState(blockSnapshot.pos.offset(facing.getOpposite()));
      }
      BlockEvent.PlaceEvent forgeEvent=new BlockEvent.PlaceEvent(blockSnapshot,placedAgainst,player);
      ((IMixinEventBus)MinecraftForge.EVENT_BUS).post(forgeEvent,true);
      if (forgeEvent.isCanceled()) {
        spongeEvent.getTransactions().get(0).setValid(false);
      }
    }
 else {
      Iterator<Transaction<BlockSnapshot>> iterator=spongeEvent.getTransactions().iterator();
      List<net.minecraftforge.common.util.BlockSnapshot> blockSnapshots=new ArrayList<>();
      while (iterator.hasNext()) {
        Transaction<BlockSnapshot> transaction=iterator.next();
        Location<World> location=transaction.getOriginal().getLocation().get();
        IBlockState state=(IBlockState)transaction.getOriginal().getState();
        BlockPos pos=new BlockPos(location.getBlockX(),location.getBlockY(),location.getBlockZ());
        net.minecraftforge.common.util.BlockSnapshot blockSnapshot=new net.minecraftforge.common.util.BlockSnapshot(world,pos,state);
        blockSnapshots.add(blockSnapshot);
      }
      IBlockState placedAgainst=Blocks.air.getDefaultState();
      if (StaticMixinHelper.packetPlayer != null && StaticMixinHelper.processingPacket instanceof C08PacketPlayerBlockPlacement) {
        C08PacketPlayerBlockPlacement packet=(C08PacketPlayerBlockPlacement)StaticMixinHelper.processingPacket;
        EnumFacing facing=EnumFacing.getFront(packet.getPlacedBlockDirection());
        placedAgainst=blockSnapshots.get(0).world.getBlockState(blockSnapshots.get(0).pos.offset(facing.getOpposite()));
      }
      BlockEvent.MultiPlaceEvent forgeEvent=new BlockEvent.MultiPlaceEvent(blockSnapshots,placedAgainst,player);
      ((IMixinEventBus)MinecraftForge.EVENT_BUS).post(forgeEvent,true);
      if (forgeEvent.isCanceled()) {
        while (iterator.hasNext()) {
          iterator.next().setValid(false);
        }
      }
    }
  }
  return spongeEvent;
}

Fixed version (ground truth):
public static ChangeBlockEvent.Place callBlockPlaceEvent(Event event){
  if (!(event instanceof ChangeBlockEvent.Place)) {
    throw new IllegalArgumentException("String_Node_Str");
  }
  ChangeBlockEvent.Place spongeEvent=(ChangeBlockEvent.Place)event;
  if (spongeEvent.getCause().first(Player.class).isPresent()) {
    EntityPlayer player=(EntityPlayer)spongeEvent.getCause().first(Player.class).get();
    net.minecraft.world.World world=(net.minecraft.world.World)spongeEvent.getTargetWorld();
    final CauseTracker causeTracker=((IMixinWorld)world).getCauseTracker();
    if (spongeEvent.getTransactions().size() == 1) {
      BlockPos pos=VecHelper.toBlockPos(spongeEvent.getTransactions().get(0).getOriginal().getPosition());
      IBlockState state=(IBlockState)spongeEvent.getTransactions().get(0).getOriginal().getState();
      net.minecraftforge.common.util.BlockSnapshot blockSnapshot=new net.minecraftforge.common.util.BlockSnapshot(world,pos,state);
      IBlockState placedAgainst=Blocks.air.getDefaultState();
      if (causeTracker.getCurrentPlayerPacket() instanceof C08PacketPlayerBlockPlacement) {
        C08PacketPlayerBlockPlacement packet=(C08PacketPlayerBlockPlacement)causeTracker.getCurrentPlayerPacket();
        EnumFacing facing=EnumFacing.getFront(packet.getPlacedBlockDirection());
        placedAgainst=blockSnapshot.world.getBlockState(blockSnapshot.pos.offset(facing.getOpposite()));
      }
      BlockEvent.PlaceEvent forgeEvent=new BlockEvent.PlaceEvent(blockSnapshot,placedAgainst,player);
      ((IMixinEventBus)MinecraftForge.EVENT_BUS).post(forgeEvent,true);
      if (forgeEvent.isCanceled()) {
        spongeEvent.getTransactions().get(0).setValid(false);
      }
    }
 else {
      Iterator<Transaction<BlockSnapshot>> iterator=spongeEvent.getTransactions().iterator();
      List<net.minecraftforge.common.util.BlockSnapshot> blockSnapshots=new ArrayList<>();
      while (iterator.hasNext()) {
        Transaction<BlockSnapshot> transaction=iterator.next();
        Location<World> location=transaction.getOriginal().getLocation().get();
        IBlockState state=(IBlockState)transaction.getOriginal().getState();
        BlockPos pos=new BlockPos(location.getBlockX(),location.getBlockY(),location.getBlockZ());
        net.minecraftforge.common.util.BlockSnapshot blockSnapshot=new net.minecraftforge.common.util.BlockSnapshot(world,pos,state);
        blockSnapshots.add(blockSnapshot);
      }
      IBlockState placedAgainst=Blocks.air.getDefaultState();
      if (causeTracker.getCurrentPlayerPacket() instanceof C08PacketPlayerBlockPlacement) {
        C08PacketPlayerBlockPlacement packet=(C08PacketPlayerBlockPlacement)causeTracker.getCurrentPlayerPacket();
        EnumFacing facing=EnumFacing.getFront(packet.getPlacedBlockDirection());
        placedAgainst=blockSnapshots.get(0).world.getBlockState(blockSnapshots.get(0).pos.offset(facing.getOpposite()));
      }
      BlockEvent.MultiPlaceEvent forgeEvent=new BlockEvent.MultiPlaceEvent(blockSnapshots,placedAgainst,player);
      ((IMixinEventBus)MinecraftForge.EVENT_BUS).post(forgeEvent,true);
      if (forgeEvent.isCanceled()) {
        while (iterator.hasNext()) {
          iterator.next().setValid(false);
        }
      }
    }
  }
  return spongeEvent;
}