[MC-180001] Reducing max health using /attribute does not reduce current health

Summary:

Using /attribute to change minecraft:generic.max_health base value to a value lower than the Health value does not reduce the Health value as would be expected.

Repo Steps:

Create a new world and run:

/attribute @s minecraft:generic.max_health base set 1

Expected Result:

Only 1, half-filled heart container visible.

Actual Result:

Only 1, fully filled heart container visible.

Verifying:

Running the following will show a value of 20.0f:

/data get entity @s Health

Linked issues

duplicates 1

MC-16345 Reducing the player's base max health using /attribute does not always reduce their current health Resolved

Attachments

MC-180001.mp4

Comments 14

migrated 2020-04-22T22:16:21Z

Not only does it give you full heart instead of a half, but if you take half a heart of damage you can't regenerate to a full heart. Weird bug.

lapppy 2020-04-23T07:03:45Z

Taking damage will set the players current health to whatever is set by generic.max_health if it is lower than 20.

Respawning will cause the attribute to reset to 20, but the amount of health that is visible is whatever it was set to before the player had died. See MC-179940.

lapppy 2020-04-29T22:06:10Z

Affects version 20w18a.

migrated 2020-05-10T21:18:12Z

Affects version 20w19a

migrated 2020-06-27T13:05:41Z

Affects 1.16.1

4 more comments

MMK21 2021-12-12T13:16:47Z

Affects 1.18.1. The full 10 hearts are now shown in the HUD after setting the base to 1.

clamlol 2021-12-21T04:14:37Z

Could someone explain the difference between this issue and MC-16345? It seems to me that the core issue is the same (so this ticket should be closed as a duplicate) but this ticket specifically mentions /attribute as a means of reproducing it.

migrated 2022-08-04T14:43:08Z

I don't know if it has already been mentioned but this also affects 1.19.1

I also don't know if this has been mentioned but I think it is also important to note that after taking any form of damage, it will display the correct amount, but the damage you take can be up to the original amount of health you had (eg. if you set the attribute for health to 1, you could still take 19 points of damage and still be alive because it displayed 20 hearts. Then it would display the half heart. Even if you only took 1 or 2 damage, it would revert to the half heart)

migrated 2022-08-05T18:34:13Z

Can confirm in 1.19.2

migrated 2023-04-21T22:18:47Z

Can confirm for 1.19.4.

This affects attribute modifiers, too. I distinctly remember it used to work as expected back in 1.8. At the time, I made some mob heads that reduced max health modifiers, and the health bar was updated instantly when the head was equipped. Now, the player has to be healed or hurt on the next tick in order for the health bar to update.