• Minecraft, 1.21.10
• Fusion, 1.2.11b
• NeoForge, 21.10.38
• No OptiFine

Description of the Bug
Game fails to initialize when fusion and lootr mod are installed. However Lootr works without fusion and fusion works without lootr.

Steps to Reproduce
Install lootr and Fusion on Neoforge 1.21.10

net.neoforged.fml.ModLoadingException: Loading errors encountered:

• Lootr (lootr) encountered an error while dispatching the net.neoforged.neoforge.event.AddPackFindersEvent event
  org.spongepowered.asm.mixin.transformer.throwables.MixinTransformerError: An unexpected critical error was encountered

I do not know if this is because of fusion or lootr so i have reported the issue to both mods

The lootr dev says "this appears to be an issue with Fusion's JarContentsPackResources mixin. "

latest(5).log

From the file provided by the submitter on the Lootr issue tracker, it appears to be an issue with the @Final @Shadow private JarContents contents in https://github.com/SuperMartijn642/Fusion/blob/neoforge-1.21.9/src/main/java/com/supermartijn642/fusion/mixin/JarContentsPackResourcesMixin.java.

I'm not sure if this is simply due to the differences in NeoForge between 1.21.10 and 1.21.9, or if it's because Lootr's event handler class-loads JarContentsPackResources and triggers the mixin -- potentially at the wrong time? I'm unsure.

I believe this is indeed due to a NeoForge update which changed the implementation of JarContentsPackResources.
Either way though it is an issue on Fusion's end and not Lootr.