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Bug
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Resolution: Fixed
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Minor
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None
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None
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None
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This server is running CraftBukkit version 3540-Spigot-56be6a8-0231a37 (MC: 1.19) (Implementing API version 1.19-R0.1-SNAPSHOT)
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Yes
This report is based on Paper#6072.
The attached plugin adds the command /testloadworld, which runs the following code:
@Override
public boolean onCommand(@NotNull CommandSender sender, @NotNull Command command, @NotNull String label, @NotNull String[] args) {
World world = WorldCreator.name("testworld")
.environment(World.Environment.NORMAL)
.type(WorldType.NORMAL)
.createWorld();
getLogger().info(String.valueOf(world));
return true;
}
When a player or the console runs this command, a new world is created without issue. However, when a command block runs the command, the server promptly crashes after the world is created with the following error:
[11:05:37] [Server thread/ERROR]: Encountered an unexpected exception java.util.ConcurrentModificationException: null at java.util.LinkedHashMap$LinkedHashIterator.nextNode(LinkedHashMap.java:756) ~[?:?] at java.util.LinkedHashMap$LinkedValueIterator.next(LinkedHashMap.java:783) ~[?:?] at net.minecraft.server.MinecraftServer.b(MinecraftServer.java:1273) ~[spigot-1.19-R0.1-SNAPSHOT.jar:3540-Spigot-56be6a8-0231a37] at net.minecraft.server.dedicated.DedicatedServer.b(DedicatedServer.java:394) ~[spigot-1.19-R0.1-SNAPSHOT.jar:3540-Spigot-56be6a8-0231a37] at net.minecraft.server.MinecraftServer.a(MinecraftServer.java:1197) ~[spigot-1.19-R0.1-SNAPSHOT.jar:3540-Spigot-56be6a8-0231a37] at net.minecraft.server.MinecraftServer.v(MinecraftServer.java:1010) ~[spigot-1.19-R0.1-SNAPSHOT.jar:3540-Spigot-56be6a8-0231a37] at net.minecraft.server.MinecraftServer.lambda$0(MinecraftServer.java:291) ~[spigot-1.19-R0.1-SNAPSHOT.jar:3540-Spigot-56be6a8-0231a37] at java.lang.Thread.run(Thread.java:833) [?:?]
The paper issue mentioned above was resolved by this pull request, which adds a check to make sure a world is not created while the worlds are being ticked. This explains the issue to developers more clearly with the following exception:
java.lang.IllegalStateException: Cannot create a world while worlds are being ticked
Even though this issue was resolved by Paper, a similar fix should probably exist for Spigot. Throwing an error that explains why the crash happens would be helpful. I don't know if this already exsists, but it would also be helpful if there was a method plugin developers could use to tell if the worlds are being ticked so they can avoid triggering this crash in the first place