Spawners were never ticked: Horizon kept their block entity as loaded NBT,
and a freshly generated dungeon or mineshaft spawner lost even that, so no
mob ever came out, nothing turned inside and a spawn egg used on one spawned
a mob next to it instead of setting the spawner's.
The spawner is now a modelled block entity (mobs::spawner): BaseSpawner's
load and save with SpawnData's codec (normalised ids, custom spawn rules,
weighted potentials, the next data shared with the one potential when the
potentials are missing), serverTick (the player range, spawner_blocks_work,
the delay, getOrCreateNextSpawnData, Pos, the spawn box against blocks and
solid shulkers, custom light rules and peaceful, SpawnPlacements, the nearby
cap, the yaw, checkSpawnRules and checkSpawnObstruction, finalizeSpawn for
an id alone, the 2004 burst, entity_place and the spawn poof) and delay with
its block event, in the level random's order. The client copy keeps its own
delay for the spin and puffs smoke and flames; SpawnerRenderer draws the
next mob small and turning. SpawnEggItem.useOn on a spawner sets its mob
(setEntityId), tells the player when spawner_blocks_work is off and fails in
peaceful for monsters. Breaking one pops 15 + nextInt(15) + nextInt(15)
experience whatever the tool. LAN guests get the update tag, the block event
and the entity event.
tools/test_spawner_parity.py ticks vanilla's SpawnerBlockEntity on the
natural spawn oracle's level against mobs::spawner on the same worlds (6,000
cases); tools/test_use_item_on_parity.py now covers spawn eggs on spawners.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Ludovic Marie