The bug
Cartographer villager crashes the game when unlocking explorer maps.
How to reproduce
Generate a new world
Spawn a cartographer villager with spawn egg / interact with naturally spawned villager
Unlock its trades
When the cartographer unlocks the explorer maps, click on it
→ The villager GUI doesn't show, instead the game crashes
Crash report
18w21b\: [^crash-2018-05-28_18.00.28-server.txt]
Description: Exception in server tick loop
java.lang.RuntimeException: java.util.concurrent.ExecutionException: java.lang.UnsupportedOperationException
at net.minecraft.server.MinecraftServer.g_(SourceFile:392)
at dii.a(SourceFile:116)
at dii.d(SourceFile:132)
at net.minecraft.server.MinecraftServer.run(SourceFile:501)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.util.concurrent.ExecutionException: java.lang.UnsupportedOperationException
at java.util.concurrent.CompletableFuture.get(CompletableFuture.java:2272)
at net.minecraft.server.MinecraftServer.g_(SourceFile:390)
... 4 more
Caused by: java.lang.UnsupportedOperationException
at bpw.e(SourceFile:100)
at sq.i(SourceFile:245)
at sq.a(SourceFile:238)
at bsi.a(SourceFile:29)
at bsi.a(SourceFile:13)
at bxf.a(SourceFile:26)
at bxf.a(SourceFile:13)
at bsl.a(SourceFile:27)
at bby.a(SourceFile:515)
at bpy.a(SourceFile:109)
at sz.a(SourceFile:12)
at sy.a(SourceFile:34)
at bqc.a(SourceFile:87)
at te.a(SourceFile:59)
at te.a(SourceFile:23)
at agg$a.a(SourceFile:131)
at agg$a$$Lambda$1255/104214654.apply(Unknown Source)
at java.util.concurrent.CompletableFuture$AsyncApply.exec(CompletableFuture.java:501)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:902)
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1689)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1644)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Linked issues
is duplicated by 24
relates to 6
Attachments
Comments 48
Thank you for your report!
However, this issue has been temporarily closed as Awaiting Response.
We do not have enough information to find the cause of this issue.
Please attach the crash report (.minecraft/crash-reports/crash-<DATE>-client.txt) here.
If no crash report was created, please attach the launcher log (.minecraft/launcher_log.txt) here.
Once attached, the report will be reopened automatically.
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The launcher log was from a launcher start and stop, but there was no Minecraft start and thus no crash.
Please re-run the crash and attach the crash report then.
This is still a problem in pre release 2. Confirmed.

Is this related to MC-126244 ?

@unknown, @unknown, and @unknown, if any of you are using OptiFine, see MC-228721.
This issue has not resurfaced in vanilla 1.17 and 1.17.1 at all.
I can confirm that this is happening on 1.17.1. Minecraft Java just hang in the UI (unable to open chest, etc.) but can still walk around. Trying to save and quit the game will just get the game stuck in the Saving screen. Had to terminate the Java process to get out. Happened every single time I unlock the next level for the cartographer (using the glass pane trade to level up the villager). Was in skyblock
@unknown, this issue was actually fixed in 20w45a. What you're experiencing here is a case of MC-228721. This is caused by the use of optifine, so simply disable this modification in order to resolve the problem.
Ah... you are right... It was Optifine. Using vanilla 1.17.1 I was able to level up the cartographer just fine... weird 🙂 Thanks.
spent about an hour trying to figure out the problem, thanks for the help
This is pretty similar to me, but instead it doesn't crash me, it doesn't show the explorer maps.