Fix rare exception due to no function definition with multiple script loading threads

[Efnilite]

Problem

In rare cases, reloading a script which used a function definition in a different script with multiple script loading threads would cause the function implementation to be undefined, which would cause an exception.

Solution

Instead of setting the function implementation to null, now marks the function implementation to be unloaded. The function reference will continue to use the old implementation until a new one can be found.

Testing Completed

Spam sk reload x with 1 worker thread in config.

Supporting Information

---

Completes: #8468
Related: none
AI assistance: none

[TheLimeGlass]

Caused by: java.lang.NullPointerException: Cannot invoke "org.skriptlang.skript.common.function.Function.execute(ch.njol.skript.lang.function.FunctionEvent, org.skriptlang.skript.common.function.FunctionArguments)" because "function" is null
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//org.skriptlang.skript.common.function.FunctionReference.execute(FunctionReference.java:185)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.function.ExprFunctionCall.get(ExprFunctionCall.java:54)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.util.SimpleExpression.getArray(SimpleExpression.java:86)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.effects.EffChange.execute(EffChange.java:306)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.Effect.run(Effect.java:42)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:40)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:67)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.Trigger.execute(Trigger.java:33)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.events.EvtPeriodical.execute(EvtPeriodical.java:103)
[19:41:56 ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.events.EvtPeriodical.lambda$postLoad$0(EvtPeriodical.java:62)
[19:41:56 ERROR]: #!#!     at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:78)
[19:41:56 ERROR]: #!#!     at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:474)
[19:41:56 ERROR]: #!#!     at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1657)
[19:41:56 ERROR]: #!#!     at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1527)
[19:41:56 ERROR]: #!#!     at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1249)
[19:41:56 ERROR]: #!#!     at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:308)
[19:41:56 ERROR]: #!#!     at java.base/java.lang.Thread.run(Thread.java:1583)

I still get errors with this

[TheLimeGlass]

[19:59:36] [Server thread/ERROR]: #!#! Caused by: java.lang.NullPointerException: Cannot read the array length because "<local1>" is null
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.events.EvtPeriodical.unload(EvtPeriodical.java:80)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.structures.StructEvent.unload(StructEvent.java:116)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.ScriptLoader.unloadScripts(ScriptLoader.java:895)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.ScriptLoader.unloadScript(ScriptLoader.java:934)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.SkriptCommand.onCommand(SkriptCommand.java:188)
[19:59:36] [Server thread/ERROR]: #!#!     at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45)
[19:59:36] [Server thread/ERROR]: #!#!     at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:158)
[19:59:36] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:1004)
[19:59:36] [Server thread/ERROR]: #!#!     at org.bukkit.Bukkit.dispatchCommand(Bukkit.java:1116)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.Skript.dispatchCommand(Skript.java:1828)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.effects.EffCommand.execute(EffCommand.java:82)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.Effect.run(Effect.java:42)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:40)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:67)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.Trigger.execute(Trigger.java:33)
[19:59:36] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.events.EvtScript.lambda$runTrigger$0(EvtScript.java:73)
[19:59:36] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:78)
[19:59:36] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:474)
[19:59:36] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1657)
[19:59:36] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1527)
[19:59:36] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1249)
[19:59:36] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:308)
[19:59:36] [Server thread/ERROR]: #!#!     at java.base/java.lang.Thread.run(Thread.java:1583)

This causes serious issues making it worse than the original bug

[TheLimeGlass]

[20:03:44] [Server thread/ERROR]: #!#! Caused by: java.lang.NullPointerException: signature cannot be null
[20:03:44] [Server thread/ERROR]: #!#!     at com.google.common.base.Preconditions.checkNotNull(Preconditions.java:922)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.function.FunctionRegistry.remove(FunctionRegistry.java:584)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.function.Functions.unregisterFunction(Functions.java:373)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.structures.StructFunction.unload(StructFunction.java:159)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.ScriptLoader.unloadScripts(ScriptLoader.java:895)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.ScriptLoader.unloadScript(ScriptLoader.java:934)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.SkriptCommand.onCommand(SkriptCommand.java:188)
[20:03:44] [Server thread/ERROR]: #!#!     at org.bukkit.command.PluginCommand.execute(PluginCommand.java:45)
[20:03:44] [Server thread/ERROR]: #!#!     at org.bukkit.command.SimpleCommandMap.dispatch(SimpleCommandMap.java:158)
[20:03:44] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.CraftServer.dispatchCommand(CraftServer.java:1004)
[20:03:44] [Server thread/ERROR]: #!#!     at org.bukkit.Bukkit.dispatchCommand(Bukkit.java:1116)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.Skript.dispatchCommand(Skript.java:1828)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.effects.EffCommand.execute(EffCommand.java:82)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.Effect.run(Effect.java:42)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:40)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.lang.TriggerItem.walk(TriggerItem.java:67)
[20:03:44] [Server thread/ERROR]: #!#!     at Skript-2.15.0.jar//ch.njol.skript.effects.Delay.lambda$walk$0(Delay.java:92)
[20:03:44] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.scheduler.CraftTask.run(CraftTask.java:78)
[20:03:44] [Server thread/ERROR]: #!#!     at org.bukkit.craftbukkit.scheduler.CraftScheduler.mainThreadHeartbeat(CraftScheduler.java:474)
[20:03:44] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.tickChildren(MinecraftServer.java:1657)
[20:03:44] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.tickServer(MinecraftServer.java:1527)
[20:03:44] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.runServer(MinecraftServer.java:1249)
[20:03:44] [Server thread/ERROR]: #!#!     at net.minecraft.server.MinecraftServer.lambda$spin$2(MinecraftServer.java:308)
[20:03:44] [Server thread/ERROR]: #!#!     at java.base/java.lang.Thread.run(Thread.java:1583)

Crashes the server

[TheLimeGlass]

Original issues needs a priority bump

[sovdeeth]

Can you post the log as a whole rather than just the stacktraces? it'll be helpful to see context around the errors.

[Efnilite]

can you post the code you used to achieve this? im not seeing these errors

[TheLimeGlass]

@sovdeeth @UnderscoreTud not fixed, it's even worse now. See original issue.