Solved: [1.13.2] Duplicate key error

[Floydman]

I am using Forge 25.0.44. I only have one @Mod annotation, but whenever I run or debug from within Eclipse, I get this error:

 

[19:18:35.605] [pool-2-thread-1/DEBUG] [ne.mi.fm.lo.mo.Scanner/SCAN]: Scanning C:\Users\danie\Documents\GitHub\modid\bin\main with language loader javafml
[19:18:35.605] [pool-2-thread-1/DEBUG] [ne.mi.fm.ja.FMLJavaModLanguageProvider/SCAN]: Found @Mod class thefloydman.modid.ModId with id modid
[19:18:35.605] [pool-2-thread-1/DEBUG] [ne.mi.fm.ja.FMLJavaModLanguageProvider/SCAN]: Found @Mod class thefloydman.modid.ModId with id modid
[19:18:35.606] [pool-2-thread-1/ERROR] [ne.mi.fm.lo.mo.BackgroundScanHandler/SCAN]: An error occurred scanning file Mod File: C:\Users\danie\Documents\GitHub\modid\bin\main
java.util.concurrent.CompletionException: java.lang.IllegalStateException: Duplicate key net.minecraftforge.fml.javafmlmod.FMLJavaModLanguageProvider$FMLModTarget@5c11fbc6

 

This causes Minecraft to crash the moment it loads. A few other folks on Discord have said they have the same issue. One said it just stopped happening. The other said they switched to IntelliJ. The error does not occur when using runClient from the command prompt. I have tried a clean install (and copying over the source files).

Edited February 23, 2019 by Floydman

[Floydman]

I just found the fix: For whatever reason, in runClient.launch and runServer.launch the mapEntry MOD_CLASSES includes the main class multiple times. Removing all but the first two resolves the issue.

Edited February 23, 2019 by Floydman