ServerGamePacketListenerImpl.addBlockDataToItem: with Ctrl held in creative,
Pick Block gives the block's item the block entity's data. What each type
turns into item components (removeComponentsFromTag and
collectImplicitComponents: container, custom_name, lock, container_loot,
sign text, waxed, bees, banner patterns, pot decorations, skull profile)
leaves its NBT; the rest becomes minecraft:block_entity_data, tagged with
the type's id. Placing the item does the reverse
(BlockItem.updateCustomBlockEntityTag, op-only types only for a game
master, then applyComponentsFromItemStack), for every block entity type,
which also fills placed chests, barrels, hoppers and the like from their
container component, as vanilla does, where only shulker boxes were.
The client sends includeData on Ctrl in multiplayer, a picked banner keeps
its patterns without Ctrl (AbstractBannerBlock.getCloneItemStack), a picked
beehive carries its honey level, a placed command block with data keeps its
own auto and output tracking, and a placed waxed sign opens no editor.
tools/test_pick_block_data_parity.py compares both directions with vanilla's
own block entities: 148/148 cases.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Ludovic Marie