Caused by: java.lang.IllegalStateException: Missing loottable 'minecraft:entities/allay' for 'minecraft:allay'
	at TRANSFORMER/[email protected]/net.minecraft.data.loot.EntityLootSubProvider.lambda$generate$1(EntityLootSubProvider.java:62)
	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
	at java.base/java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:197)
	at java.base/java.util.Iterator.forEachRemaining(Iterator.java:133)
	at java.base/java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1845)
	at java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:509)
	at java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:499)
	at java.base/java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
	at java.base/java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
	at java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.base/java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:596)
	at TRANSFORMER/[email protected]/net.minecraft.data.loot.EntityLootSubProvider.generate(EntityLootSubProvider.java:55)
	at TRANSFORMER/[email protected]/net.minecraft.data.loot.LootTableProvider.lambda$run$1(LootTableProvider.java:39)
	at MC-BOOTSTRAP/[email protected]/com.google.common.collect.ImmutableList.forEach(ImmutableList.java:422)
	at TRANSFORMER/[email protected]/net.minecraft.data.loot.LootTableProvider.run(LootTableProvider.java:38)
	at TRANSFORMER/[email protected]/net.minecraft.data.HashCache.generateUpdate(HashCache.java:92)
	at TRANSFORMER/[email protected]/net.minecraft.data.DataGenerator.lambda$run$0(DataGenerator.java:47)
	at java.base/java.util.LinkedHashMap.forEach(LinkedHashMap.java:721)
	at TRANSFORMER/[email protected]/net.minecraft.data.DataGenerator.run(DataGenerator.java:40)
	at TRANSFORMER/[email protected]/net.minecraftforge.data.event.GatherDataEvent$DataGeneratorConfig.lambda$runAll$2(GatherDataEvent.java:110)
	at MC-BOOTSTRAP/[email protected]/cpw.mods.modlauncher.api.LamdbaExceptionUtils.lambda$rethrowConsumer$0(LamdbaExceptionUtils.java:34)
	at java.base/java.util.LinkedHashMap$LinkedValues.forEach(LinkedHashMap.java:647)
	at TRANSFORMER/[email protected]/net.minecraftforge.data.event.GatherDataEvent$DataGeneratorConfig.runAll(GatherDataEvent.java:106)
	at TRANSFORMER/[email protected]/net.minecraftforge.data.loading.DatagenModLoader.begin(DatagenModLoader.java:54)
	at TRANSFORMER/[email protected]/net.minecraft.data.Main.main(Main.java:93)
	... 13 more

I get this error when i try to generate my loot tables. Here is my code

public class ModBlockLootTables extends BlockLootSubProvider {
    protected ModBlockLootTables() {
        super(Set.of(), FeatureFlags.REGISTRY.allFlags());
    }

    @Override
    protected void generate() {
        // ores
        add(BlockInit.BLACK_DIAMOND_ORE.get(), createOreDrop(BlockInit.BLACK_DIAMOND_ORE.get(),
                ItemInit.BLACK_DIAMOND_SCRAP.get()));

        add(BlockInit.DEEPSLATE_BLACK_DIAMOND_ORE.get(), createOreDrop(
                BlockInit.BLACK_DIAMOND_ORE.get(), ItemInit.BLACK_DIAMOND_SCRAP.get()));

        add(BlockInit.INFINITUM_ORE.get(),
                createOreDrop(BlockInit.INFINITUM_ORE.get(), ItemInit.INFINITUM_SCRAP.get()));

        add(BlockInit.SPEED_ORE.get(),
                createOreDrop(BlockInit.SPEED_ORE.get(), ItemInit.SPEED.get()));

        add(BlockInit.DEEPSLATE_SPEED_ORE.get(),
                createOreDrop(BlockInit.DEEPSLATE_SPEED_ORE.get(), ItemInit.SPEED.get()));

        add(BlockInit.OMNITRIX_ORE.get(),
                createOreDrop(BlockInit.OMNITRIX_ORE.get(), ItemInit.RAW_OMNITRIX.get()));

        add(BlockInit.DEEPSLATE_OMNITRIX_ORE.get(),
                createOreDrop(BlockInit.DEEPSLATE_OMNITRIX_ORE.get(), ItemInit.RAW_OMNITRIX.get()));

        add(BlockInit.IMPERIUM_ORE.get(),
                createOreDrop(BlockInit.IMPERIUM_ORE.get(), ItemInit.RAW_IMPERIUM.get()));

        add(BlockInit.DEEPSLATE_IMPERIUM_ORE.get(),
                createOreDrop(BlockInit.DEEPSLATE_IMPERIUM_ORE.get(), ItemInit.RAW_IMPERIUM.get()));

        add(BlockInit.LEGENDARY_ORE.get(),
                createOreDrop(BlockInit.LEGENDARY_ORE.get(), ItemInit.RAW_LEGENDARY.get()));

        add(BlockInit.DEEPSLATE_LEGENDARY_ORE.get(), createOreDrop(
                BlockInit.DEEPSLATE_LEGENDARY_ORE.get(), ItemInit.RAW_LEGENDARY.get()));

        add(BlockInit.RUBY_ORE.get(), createOreDrop(BlockInit.RUBY_ORE.get(), ItemInit.RUBY.get()));

        add(BlockInit.DEEPSLATE_RUBY_ORE.get(),
                createOreDrop(BlockInit.DEEPSLATE_LEGENDARY_ORE.get(), ItemInit.RUBY.get()));

        // blocks
        dropSelf(BlockInit.OMNITRIX_BLOCK.get());
        dropSelf(BlockInit.FIRE_BLOCK.get());
        dropSelf(BlockInit.RUBY_BLOCK.get());
        dropSelf(BlockInit.SPEED_BLOCK.get());
        dropSelf(BlockInit.INFINITUM_BLOCK.get());
        dropSelf(BlockInit.BLACK_DIAMOND_BLOCK.get());
        dropSelf(BlockInit.LEGENDARY_BLOCK.get());
        dropSelf(BlockInit.IMPERIUM_BLOCK.get());
        dropSelf(BlockInit.FIRE_ORE.get());
        dropSelf(BlockInit.OmnitrixCrafter.get());
    }

    @Override
    protected Iterable<Block> getKnownBlocks() {
        return ForgeRegistries.BLOCKS.getValues()
            .stream()
            .filter(block -> BenTenMod.MOD_ID
                .equals(ForgeRegistries.BLOCKS.getKey(block).getNamespace()))
            .collect(Collectors.toSet());
    }
}

public class ModLootTables extends LootTableProvider {
    public ModLootTables(DataGenerator dataGeneratorIn) {
        super(dataGeneratorIn.getPackOutput(), Set.of(), ImmutableList.of(
                new SubProviderEntry(ModBlockLootTables::new, LootContextParamSets.BLOCK),
                new SubProviderEntry(ModEntityLootTables::new, LootContextParamSets.ENTITY)));
    }

    @Override
    public List<SubProviderEntry> getTables() {
        return ImmutableList.of(
                new SubProviderEntry(ModBlockLootTables::new, LootContextParamSets.BLOCK),
                new SubProviderEntry(ModEntityLootTables::new, LootContextParamSets.ENTITY));
    }

    @Override
    protected void validate(Map<ResourceLocation, LootTable> map,
            ValidationContext validationtracker) {
        map.forEach((id, table) -> LootTables.validate(validationtracker, id, table));
    }
}

 

Fixed this issue it was caused by my ModEntityLootTables and i was missing the getKnownEntityTypes function