ConcurrentModificationException caused by async command sending patch

[test12345710]

Expected behavior

No errors and a clean reload.

Observed/Actual behavior

A ConcurrentModificationException.

Steps/models to reproduce

Start server
Reload until you see the error. ( it's at the bottom kinda )

Plugin and Datapack List

Plugins (all Bukkit) : FacilisCommon, MultiWorld and SkinsRestorer
Datapacks: vanilla (built-in), file/bukkit (world), bundle (feature), paper (built-in)

Paper version

[19:56:32 INFO]: Checking version, please wait...
[19:56:32 INFO]: This server is running Paper version 1.21-83-master@967f98a (2024-07-17T14:55:35Z) (Implementing API version 1.21-R0.1-SNAPSHOT)
You are running the latest version
Previous version: 1.21-81-ceeb8c1 (MC: 1.21)

Other

I noticed that every time I start my server, reload it a couple of times ( because I am developing my own plugin ) and look at the console ( to check for bugs ), I see a ConcurrentModificationException with a number that increments every time I see the error ( not every time I reload ).

So, I remove my plugin from the list and I see that it's still happening every couple of reloads. So I test it a bit more and then it starts happening every 2 reloads.

[test12345710]

I noticed that it also says something about commands? Maybe Paper just doesn't support Bukkit commands that well?

EDIT: When I removed all plugins, it started happening every reload.
EDIT 2: When I restart the server, the number that increments goes back to 0.
EDIT 3: I am using the Bukkit reload also ( yes I know I am not supposed to but I can't restart my server for every minor change in my plugin.)

[electronicboy]

There is a long known issue in the logic for sending commands to clients async, this is generally harmless and afaik, there is already issues open for this (or, at least, it's known about)

[test12345710]

There is a long known issue in the logic for sending commands to clients async, this is generally harmless and afaik, there is already issues open for this (or, at least, it's known about)

So, it's known about. But can it be resolved or at least suppressed? I like a clean console.
Also there aren't any issues about this specific method of getting it. ( but there are about it existing )

[electronicboy]

it's on my eternal todo list, however, I'm currently out of action as I just recently had eye surgery; I generally suggested that we just suppress and reshoot

[codebycam]

Can you please provide your entire latest.log?

[test12345710]

So, upon further testing, I found out that this bug is really sketchy.

After I made the original post, I closed the server, along with my Minecraft client. ( I was on the server while this error was occurring)

So, after your reply, I fired up the server again ( because all the logs contained my custom plugin so I wanted to eliminate the possibility) and began testing and I realized that it doesn't happen when I'm not on the server ( or at least I didn't get it ). Then I restarted it (for a clean log) and logged on and after a couple reloads, it started happening again. Here's the log:

latest.log

[electronicboy]

if there is no player online then there is nobody to send a commands packet to, and thus, the bug is not exposed. This is only an issue when something mutates the command system late when people are being sent info about commands

[test12345710]

if there is no player online then there is nobody to send a commands packet to, and thus, the bug is not exposed. This is only an issue when something mutates the command system late when people are being sent info about commands

Can I do anything about it?

[test12345710]

revive comment

[electronicboy]

you will need to wait until we patch it, or, don't register commands outside of the expected lifecycle if you're a dev

[Warriorrrr]

Resolved by 736c78c