I'm wondering if it is possible (or is planned for 1.20) for a mod to create their own custom feature flags. I know that config files are a thing and should probably be used, but it would also be cool if you can have some features of your mod under a feature flag, allowing the player to choose which ones to have inside a world (just like vanilla feature flags).

I've tried using the vanilla implementation
 

public static final FeatureFlag MY_FEATURE_FLAG = new FeatureFlagRegistry.Builder("main").create(new ResourceLocation("modid", "my_feature_flag"));

and providing the feature flag to the block properties inside the requiredFeatures method, but unfortunately the game crashes as soon as it loads up with the following error

Exception caught during firing event: Mismatched feature universe, expected 'main', but got 'main'

Full crash report here: https://pastebin.com/1NtaAeeM

And you can see where I create a Feature Flag here: https://github.com/JimiIT92/MineWorld/blob/master/src/main/java/org/mineworld/core/MWFeatureFlags.java

So I don't know if I'm actually doing something wrong or is just something that is currently impossible to do

It's intended purpose is only for vanilla, so you can treat it as impossible for mods. It wouldn't matter anyways since if three additional feature flags was registered, the game would crash.

Really? I was reading about a limit of 64... I think is a really missed opportunity, but can't complain too much. I guess the closest I can get is to have a config setting and then disable the crafting recipes or the use of blocks/items based on that config

From the code, the limit is 64 (it is stored in game as a bitmask in a long).

 

It looks like you can create your own FeatureFlagRegistry with its own "universe".

But then you would have to implement your own way of configuring, referencing and saving it.

So probably more effort than a server config file.

13 hours ago, warjort said:

From the code, the limit is 64 (it is stored in game as a bitmask in a long).

My bad, I might have been misremembering the implementation.

Still, it would require rewriting a huge portion of the feature flag logic to make it possible with a massive bump in computation time since any dynamic solution would take longer than the nanoseconds needed to check a bitmask. 

On 4/18/2023 at 1:43 AM, warjort said:

It looks like you can create your own FeatureFlagRegistry with its own "universe".

That was exactly what I was looking into, but can't seem to make it work properly at all. Even trying to register a Feature Flag using a different "universe" than main completely brokes the game. So yeah, I guess config file is the way to go