Points and guidelines occasionally stop appearing for all players when doing //bcpos clearall

[Frumple]

Description

We've noticed after using the plugin for a bit that the //bcpos clearall occasionally causes a NullPointerException in console, and then all points and guidelines stop appearing in game for all players. We've seen two different NullPointerExceptions so far:

[20:21:09 INFO]: FredTheTimeLord issued server command: //bcpos clearall
[20:21:09 WARN]: Exception in thread "Timer-1" java.lang.NullPointerException: Cannot invoke "java.util.Map$Entry.getKey()" because the return value of "java.util.NavigableMap.lastEntry()" is null
[20:21:09 WARN]:        at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.sendParticlePlayer(SendParticles.java:75)
[20:21:09 WARN]:        at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.send(SendParticles.java:62)
[20:21:09 WARN]:        at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.run(SendParticles.java:54)
[20:21:09 WARN]:        at java.base/java.util.TimerThread.mainLoop(Timer.java:566)
[20:21:09 WARN]:        at java.base/java.util.TimerThread.run(Timer.java:516)

[20:33:42] [Server thread/INFO]: FredTheTimeLord issued server command: //bcpos clearall
[20:33:42] [Timer-1/WARN]: Exception in thread "Timer-1" java.lang.NullPointerException
[20:33:42] [Timer-1/WARN]:     at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:904)
[20:33:42] [Timer-1/WARN]:     at worldedit-bukkit-7.3.10.jar//com.sk89q.worldedit.bukkit.BukkitAdapter.adapt(BukkitAdapter.java:203)
[20:33:42] [Timer-1/WARN]:     at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.getLocation(SendParticles.java:250)
[20:33:42] [Timer-1/WARN]:     at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.sendLine(SendParticles.java:195)
[20:33:42] [Timer-1/WARN]:     at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.sendParticlePlayer(SendParticles.java:92)
[20:33:42] [Timer-1/WARN]:     at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.send(SendParticles.java:62)
[20:33:42] [Timer-1/WARN]:     at curvebuilding-bukkit-0.6.3.jar//me.kous500.curvebuilding.bukkit.SendParticles.run(SendParticles.java:54)
[20:33:42] [Timer-1/WARN]:     at java.base/java.util.TimerThread.mainLoop(Timer.java:566)
[20:33:42] [Timer-1/WARN]:     at java.base/java.util.TimerThread.run(Timer.java:516)

Players can still set points using //bcpos afterwards, but the visualization of these points no longer works.

When we do /curvebuilding reload or restart the server afterwards, the visualization comes back, at least until the next time this bug occurs.

Software Used

• Paper 1.21.4 build 147
• WorldEdit 7.3.10
• CurveBuilding 0.6.3

Steps to Reproduce

We're not sure if there are any conditions to make this bug happen, or if it just happens randomly.

1. Set some points with //bcpos.
2. Clear the points with //bcpos clearall.

Expected Behaviour

All points selected by the player should be cleared.

Actual Behaviour

Occasionally, all points and guidelines stop appearing for all players. A NullPointerException appears in console. Players can still select points using //bcpos but the visualization of them no longer works.

[kous500]

Thank you very much for the detailed bug report!

This strongly suggests a potential timing issue (a race condition) between the //bcpos clearall command clearing data (likely lists or maps of players/points) and the SendParticles task trying to read or use that data concurrently.

This issue seems related to thread safety in the background processing. I will investigate the SendParticles logic and its interaction with the clearall command, focusing on ensuring safe concurrent data access.

I will work on a fix and will notify you once an updated version is ready. In the meantime, I appreciate your patience and suggest using the workaround (/curvebuilding reload or server restart) when the issue occurs.

Thank you again for providing such valuable and detailed information!