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  1. Minecraft: Java Edition
  2. MC-184653

[Crash] "java.lang.IllegalArgumentException: value already present:" - Game crashes when worldgen dimension type presets are not unique


    • Icon: Bug Bug
    • Resolution: Fixed
    • 1.16 Pre-release 3
    • 20w21a, 20w22a, 1.16 Pre-release 2
    • None
    • Confirmed
    • Crash
    • Very Important

      The bug

      When there are multiple dimensions with the same dimension type, the game crashes. When type is a string, it is supposedly a preset for dimension options like ultrawarm, shrunk, etc. However only one dimension can use the default values overworld, the_nether and the_end.

      How to reproduce

      1. Download the worldgen settings duplicate.json
      2. Create a new world and select the downloaded file when importing world settings
        The game crashes because the custom:overworld also used the overworld dimension type preset.


      Instead of using one of the presets, specify all the default properties like this:

      "type": {
        "ultrawarm": false,
        "natural": true,
        "shrunk": false,
        "ambient_light": 0,
        "has_skylight": true,
        "has_ceiling": false

      Stack trace

      Description: Exception in server tick loop
      java.lang.IllegalArgumentException: value already present: chf@6204b89e
          at com.google.common.collect.HashBiMap.put(HashBiMap.java:287)
          at com.google.common.collect.HashBiMap.put(HashBiMap.java:262)
          at gg.a(SourceFile:51)
          at gg.a(SourceFile:62)
          at gl$a.a(SourceFile:28)
          at net.minecraft.server.MinecraftServer.a(SourceFile:407)
          at net.minecraft.server.MinecraftServer.i_(SourceFile:334)
          at enr.d(SourceFile:65)
          at net.minecraft.server.MinecraftServer.run(SourceFile:666)
          at java.lang.Thread.run(Thread.java:745)

            fry [Mojang] Georgii Gavrichev
            MicherBugs Zeta
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