The problem is, i got block with custom inventory and json recipes, it also has it's own item inside renderer.

But when i'm triyng to get item in slot for Client side (For Server side it's fine) i also need to check if recipe.isPresent().

But it doesn't return anything for client side, without this method the game will crash.

 

Here's some code for crafting ->

public static void tick(Level level, BlockPos pos, BlockState state, SpecialCauldronBlockEntity entity) {
        if (level.isClientSide) {
            if (!entity.itemStackHandler.getStackInSlot(0).is(ItemStack.EMPTY.getItem())) {
                entity.progress++;
                if (entity.progress >= entity.maxProgress) {
                    //entity.itemStackHandler.setStackInSlot(0, Items.DIAMOND.getDefaultInstance());
                    craftItem(entity, level);
                    level.playLocalSound(pos.getX(), pos.getY(), pos.getZ(), SoundEvents.END_PORTAL_SPAWN, SoundSource.BLOCKS, 1.0f, 1.0f, true);
                    entity.resetProgress();
                }
            } else {
                entity.resetProgress();
            }
        }

        if (!level.isClientSide) {
            if (!entity.itemStackHandler.getStackInSlot(0).is(ItemStack.EMPTY.getItem())) {
                entity.progress++;
                if (entity.progress >= entity.maxProgress) {
                    //entity.itemStackHandler.setStackInSlot(0, Items.DIAMOND.getDefaultInstance());
                    craftItem(entity, level);
                    entity.resetProgress();
                }
            } else {
                entity.resetProgress();
            }
        }
    }

     // Craft
     private static void craftItem(SpecialCauldronBlockEntity pEntity, Level level) {
         SimpleContainer inventory = new SimpleContainer(pEntity.itemStackHandler.getStackInSlot(0));

        if (level.isClientSide) {
            Optional<SpecialCauldronRecipe> recipe = level.getRecipeManager()
                    .getRecipeFor(SpecialCauldronRecipe.Type.INSTANCE, inventory, level);
            System.out.println(level.isClientSide);
            if (recipe.isPresent()) {
                pEntity.itemStackHandler.setStackInSlot(0, new ItemStack(recipe.get().getResultItem().getItem()));
            }
        }

        if (!level.isClientSide) {
            Optional<SpecialCauldronRecipe> recipe = level.getRecipeManager()
                    .getRecipeFor(SpecialCauldronRecipe.Type.INSTANCE, inventory, level);
            if (recipe.isPresent()) {
                pEntity.itemStackHandler.setStackInSlot(0, new ItemStack(recipe.get().getResultItem().getItem()));
            }
         }
     }

 

FIXED