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Bug
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Resolution: Fixed
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20w21a, 1.17.1, 21w39a, 1.18.1, 1.18.2, 1.19.1 Release Candidate 2, 1.20.2, 24w12a
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Confirmed
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Datafixer
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Important
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Platform
May relate to MC-134115 due to 1.13 changes being the current suspect.
The bug
In 13w02a, changes were made to the minecart entity ID. World saves from this version onwards can be safely upgraded to the current version (1.18.2). However, worlds from 13w01b or earlier (back to 12w07a) will cause any chunk that contains a minecart to be completely reset.
How to reproduce
This is as simple as creating a world in 13w01b or earlier, placing a minecart, and then loading that world in the latest version.
Example case
The following is a link to a world save last played in Java Edition 1.4.7 (the file size is rather large so it may be worth making a dedicated world yourself):
http://www.mediafire.com/file/pp1h388kzu2n7p7/Dataless822s_Survival_World_v1.0.zip/file
When loaded up and played in version 1.4.7, it plays completely fine. However, when loaded in the latest supported version, several chunks in the world fail to load, and are replaced with newly generated chunks. In pre-13w02a, the game log also produces errors indicating this:
Example output
Couldn't load chunk [-19, 14] java.lang.ClassCastException: class com.mojang.serialization.DataResult cannot be cast to class com.mojang.datafixers.util.Pair (com.mojang.serialization.DataResult and com.mojang.datafixers.util.Pair are in unnamed module of loader 'app') at com.mojang.datafixers.optics.Proj2.view(Proj2.java:7) at com.mojang.datafixers.optics.Lens.lambda$null$0(Lens.java:48) at com.mojang.datafixers.optics.Affine$Instance.lambda$null$0(Affine.java:45) at com.mojang.datafixers.optics.Optics$5.preview(Optics.java:117) at com.mojang.datafixers.types.templates.TaggedChoice$TaggedChoiceType$2.capPreview(TaggedChoice.java:283) at com.mojang.datafixers.types.templates.TaggedChoice$TaggedChoiceType$2.preview(TaggedChoice.java:278) at com.mojang.datafixers.types.templates.TaggedChoice$TaggedChoiceType$2.preview(TaggedChoice.java:271) at com.mojang.datafixers.optics.Affine.lambda$null$2(Affine.java:34) at com.mojang.datafixers.optics.Traversal$Instance$1.lambda$wander$0(Traversal.java:34) at com.mojang.datafixers.util.Pair$Instance.traverse(Pair.java:90) at com.mojang.datafixers.optics.profunctors.TraversalP$1.lambda$wander$0(TraversalP.java:50) at com.mojang.datafixers.optics.Traversal$Instance$1.lambda$wander$0(Traversal.java:34) at com.mojang.datafixers.optics.Traversal$Instance$1.lambda$wander$0(Traversal.java:34) at com.mojang.datafixers.Typed.updateCap(Typed.java:164) at com.mojang.datafixers.Typed.update(Typed.java:138) at com.mojang.datafixers.Typed.update(Typed.java:133) at akb.a(SourceFile:18) at com.mojang.datafixers.DataFix.lambda$null$3(DataFix.java:86) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Fold.lambda$null$2(Fold.java:48) at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Fold.lambda$null$2(Fold.java:48) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.FunctionType$Instance.lambda$null$3(FunctionType.java:93) at com.mojang.datafixers.optics.ListTraversal.lambda$wander$0(ListTraversal.java:19) at com.mojang.datafixers.FunctionType$Instance.lambda$wander$4(FunctionType.java:94) at com.mojang.datafixers.util.Either.lambda$mapRight$1(Either.java:166) at com.mojang.datafixers.util.Either$Right.map(Either.java:99) at com.mojang.datafixers.util.Either.mapRight(Either.java:166) at com.mojang.datafixers.FunctionType$Instance.lambda$right$6(FunctionType.java:104) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.FunctionType$Instance.lambda$first$1(FunctionType.java:81) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at java.base/java.util.function.Function.lambda$compose$0(Function.java:68) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.functions.Comp.lambda$null$5(Comp.java:69) at com.mojang.datafixers.types.Type.capWrite(Type.java:167) at com.mojang.datafixers.types.Type.lambda$readAndWrite$9(Type.java:159) at com.mojang.serialization.DataResult.lambda$flatMap$10(DataResult.java:138) at com.mojang.datafixers.util.Either$Left.map(Either.java:38) at com.mojang.serialization.DataResult.flatMap(DataResult.java:136) at com.mojang.datafixers.types.Type.readAndWrite(Type.java:158) at com.mojang.datafixers.DataFixerUpper.update(DataFixerUpper.java:84) at nm.a(SourceFile:488) at cnk.a(SourceFile:37) at abe.i(SourceFile:831) at abe.l(SourceFile:508) at java.base/java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1764) at aqv.c(SourceFile:151) at abp$a.c(SourceFile:528) at aqv.z(SourceFile:125) at abp$a.z(SourceFile:537) at abp.d(SourceFile:280) at net.minecraft.server.MinecraftServer.bf(SourceFile:776) at net.minecraft.server.MinecraftServer.z(SourceFile:764) at aqv.c(SourceFile:134) at net.minecraft.server.MinecraftServer.y(SourceFile:749) at net.minecraft.server.MinecraftServer.b(SourceFile:521) at net.minecraft.server.MinecraftServer.e_(SourceFile:353) at faq.e(SourceFile:71) at net.minecraft.server.MinecraftServer.x(SourceFile:670) at net.minecraft.server.MinecraftServer.a(SourceFile:270) at java.base/java.lang.Thread.run(Thread.java:831)
Indeed, chunk [-19, 14] is in fact corrupted:
Expected results
Upgrading world would work regardless of whether a given chunk contains a minecart or not. Upgrading worlds (especially pure vanilla Survival worlds) should be as safe of a process as possible and cause no unexpected damage unrelated to intended game mechanic changes.
Actual results
The chunks containing a minecart are just completely reset. No attempt is made to even keep the terrain and delete the entity, the whole chunk is just gone.
Workarounds
This can be avoided by loading the world in a slightly later version (probably 13w02a to 17w46a but I can't be sure of it; 1.6.4 definitely works though) before the latest version, as this should convert the minecarts over to the new format which the current version can understand.
