I raised this on the mods GitHub but they are unsure so hoping someone can assist them
Dariensg/Hellions-Sniffer-Plus#5

I'm trying to create compatibility for Sniffer+ in a number of my 'Variant' style mods,

I've added Sniffer+ to build.gradle
modImplementation("curse.maven:hellionssiffer-871962:4591532")

Error log states :

Caused by: java.lang.IllegalStateException: Errors during registry creation
Suppressed: java.lang.IllegalStateException: Unreferenced key: ResourceKey[minecraft:worldgen/biome / snifferplus:timeless_grotto]
at net.minecraft.registry.RegistryBuilder$Registries.validateReferences(RegistryBuilder.java:128) ~[minecraft-merged-project-root-1.20.1-net.fabricmc.yarn.1_20_1.1.20.1+build.9-v2.jar:?]
at net.minecraft.registry.RegistryBuilder.createWrapperLookup(RegistryBuilder.java:268) ~[minecraft-merged-project-root-1.20.1-net.fabricmc.yarn.1_20_1.1.20.1+build.9-v2.jar:?]
at net.fabricmc.fabric.impl.datagen.FabricDataGenHelper.createRegistryWrapper(FabricDataGenHelper.java:194) ~[fabric-data-generation-api-v1-12.1.12+b3afc78b77.jar:?]
at net.fabricmc.fabric.impl.datagen.FabricDataGenHelper.lambda$runInternal$0(FabricDataGenHelper.java:108) ~[fabric-data-generation-api-v1-12.1.12+b3afc78b77.jar:?]
at java.util.concurrent.CompletableFuture$AsyncSupply.run(CompletableFuture.java:1768) ~[?:?]
at java.util.concurrent.CompletableFuture$AsyncSupply.exec(CompletableFuture.java:1760) ~[?:?]
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:373) ~[?:?]
at java.util.concurrent.ForkJoinPool$WorkQueue.topLevelExec(ForkJoinPool.java:1182) ~[?:?]
at java.util.concurrent.ForkJoinPool.scan(ForkJoinPool.java:1655) ~[?:?]
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1622) ~[?:?]
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:165) ~[?:?]

If i remove the Sniffer+ implementation from Gradle my datagen runs perfectly fine.
Link to 1 of my mods with gradle setup
https://github.com/xanthian/variantcraftingtables/tree/1.20

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