Looking at the code it seems like the issue is that Item class has a method called getItemEnchantability which returns 0, except for classes that override it like bow, tools, armor... but not ItemShield.

 

So my question is, how can I modify the ItemShield class to make shields enchantable? I already have the enchantments added and working with /enchant command. I just need them to be available at enchanting table, which should hopefully be fixed by overriding getItemEnchantability for ItemShield to return 1.

I found out that I need to use GameRegistry.addSubstitutionAlias, but Eclipse doesn't seem to recognize that method, is it outdated??? Is there a new way to do this? Please help  All this just to change a 0 by a 1. And no, I don't want to make a new shield item, I want this to work for the vanilla one, so people can get the mod in started worlds and get their enchantments in their already crafted shields.

You can’t. You want registry overrides. What you could do is run your registration after all others and wrap all the instances in the registry with your own class that only changes that specific function and redirects all other calls to a delegate.

Thank you, it worked!