[1.20.1 Forge] java.lang.NullPointerException: Registry entry not present

[LocalRaccoon]

Context

Server refuses to start. Same error with and without the addon installed.

Crash Report

https://mclo.gs/ezCFAEM

[TaraDaReal]

Reference from another repo:

Alright, I've got an update for y'all.

There was a very useful log in #629, which has revealed the problem.

In 6.0.?, Create made its Create.REGISTRATE field private, and provided an alternate API for mods to create registration callbacks. Unfortunately, this API is completely non-functional, for the reasons mentioned below.

The API in question is CreateRegistrateRegistrationCallback.register

1. if you call the API after Create loads, it will not register the callback (doesn't show up in logs that I can tell, but still bad)
2. if you call the API while Create is loading, it will throw a ConcurrentModificationException (see https://mclo.gs/hAk2CsU)
3. even if you manage to register the callback, it will explode when called, since the callback handler tries to get the registered object immediately when a RegistryEntry is added, even though the object won't be registered (into Minecraft registries) for a long time yet (this is the culprit responsible for the most common crash, Registry entry not present: create:copycat)

The code responsible for (3) is at

Create/src/main/java/com/simibubi/create/foundation/data/CreateRegistrate.java

Line 130 in e0c859a

((Consumer<T>) callback.callback()).accept(entry.get());

Ultimately, I think the solution here is to create an inner class in CreateRegistrate that exposes the various methods that are safe for other mods to call (notably, addRegisterCallback)

cc: @IThundxr I'll open a proper issue on the Create repo tomorrow, just wanted to write this all down here before I forgot.

[VoidLeech]

Remove the Steam n Rails alpha for now.