The bug
Mobs summoned with no health (Health:0f) will not drop any loot.
I expected that mobs summoned this way drop loot.
Steps to reproduce
Summon a mob with Health:0f in their NBT tag
/summon zombie ~ ~ ~ {Health:0f}/summon zombie ~ ~ ~ {Health:0f}For comparison summoning a mob with health then killing it will drop loot
/summon zombie ~ ~ ~ {Health:1f}/summon zombie ~ ~ ~ {Health:1f}Comments 2
You can't kill what is already dead 😉
It's too much hassle to "fix" this problem, so I suggest you summon your mobs with the Wither effect if you want it to die properly.
/summon minecraft:zombie ~ ~ ~ {ActiveEffects:[{Id:20b,Amplifier:3b,Duration:999}],Health:0.1f}/summon minecraft:zombie ~ ~ ~ {ActiveEffects:[{Id:20b,Amplifier:3b,Duration:999}],Health:0.1f}
Also occurs if you change their health to 0f using entitydata (using a command similar to the one below):