Minecraft wiki entry for Development_versions, associated text: Added player check to every trigger (except impossible).
Due to addition of player, existing contents of location, slept_in_bed, hero_of_the_village, voluntary_exile can now be placed in location field instead of top-level object.
Old syntax is still supported, but deprecated.
Entity checks in triggers can now use loot table condition syntax.
All conditions in top level array must be met for whole condition to trigger.
To access new functionality, top level element must be JSON array.
JSON objects are interpreted as old notation.
Full list of extended triggers:
New field player in every trigger.
bred_animals: parent, partner, child
channeled_lightning: victims
cured_zombie_villager: zombie, villager
fishing_rod_hooked: entity
killed_by_crossbow: victims
player_killed_entity: entity
entity_killed_player: entity
player_hurt_entity: entity
summoned_entity: entity
tame_animal: entity
target_hit: projectile
villager_trade: villager