Arrows fired into the side of bamboo or pointed dripstone never despawn

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I see. Wasn't thinking about the fabric mod. You may have a point! Thanks for the catch.

As they say in the movies.... "not so fast!"

Booted a single player world, no mods. Set up a test environ in creative, switched to survival and let it run. Arrows are persisting still after several day/night cycles and after logout/login.

To reproduce: spawned pillagers, and put them into boats. Grew a field of bamboo in between us. Turned on survival and let them fire at me.  Waited a little bit to build up some arrows, then killed the pillagers and waited for the arrows to naturally despawn. Gave it a few full day/night cycles to confirm.

Might test some other mobs/obstacles to help narrow it down as time permits.

OK, I've done some testing, including a large timeframe where I couldn't reproduce the error and tried to figure out why.

I tried: pillagers, skeletons, and myself (with Infinity), and I tried firing at bamboo, fences, iron bars, chains, and glass panes (all 1w x 2h).  I was not able to reproduce arrow persisting in any other material than bamboo. Both skeletons and pillagers reproduce the problem.

Noticed that the arrows persisting in the bamboo were not actually "in" the bamboo, but near it, inside their hitbox but not "stuck into the bamboo" itself.

Bamboo has a hitbox that is 2 times as wide as the stalk itself (maybe due to the head of the bamboo being wider?). The other items hitboxes are the size of the item, except chains which are 50% larger.

During the period of time I couldn't reproduce, I was only allowing a few arrows to fire, and those were stuck firmly into the bamboo. They would despawn as normal. It's only these arrows sticking into this "in between" space that remain.

I was able to duplicate this firing an arrow myself using an Infinity bow. I fired many arrows into the hitbox of the bamboo, but not directly at the bamboo. In Creative, you are able to pick up your own arrows, even if fired by the Infnity bow. I am able to pick up all arrows but one that now persists, and it is next to the bamboo:

Manually shot some arrows: this one is not despawning

Steps to reproduce:

use a mostly empty world

/tp @s 72 10 -93

/setblock 72 0 -93 grass_block

/fill 72 1 -93 72 10 -93 bamboo

/summon minecraft:arrow 72.2 12.00 -92.8

Then the arrow will be stuck mid air like this and not despawn, it can also not be picked up. This also confirms the theory that this is about the invalid data in the shape cache.

/summon minecraft:arrow 72.2 12.00 -92.8

Confirmed in 20w48a. Also affects the new pointed dripstone blocks.

Is anyone able to reproduce this in the latest snapshot?

Looks like the problem is that the arrows have

{inGround:0b}

instead of

{inGround:1b}

, which prevents you from picking them up and preventing them from despawning. I can only reproduce this when shooting them from the north of the bamboo.

How to reproduce:

1. Build a pillar of bamboo

2. Shoot multiple arrows at the north side of the bamboo (the direction you are facing should be south)

3. /execute as @e[type=minecraft:arrow] run data merge entity @s {life:1200}

   ❌ Some of them don’t despawn.