Tips and Tricks

Setting NBT, metadata and quantity

All LootTweaker methods that take an IItemStack will attempt to preserve the metadata, NBT tag, and stacksize of the passed IItemStack.
This is done by automatically generating set_damage, set_data and set_count functions.
A function will not be auto-generated for a loot entry if the entry already has a function of the same type.
This means that
pool.addItemEntry(<minecraft:apple> * 2, 1);
is equivalent to
pool.addItemEntryHelper(<minecraft:apple>, 1, 1, [Functions.setCount(2, 2)], []);