[BUG] Infinite hang: ETF scans every single texture when ResourceLocation is "minecraft:<empty string>"

[ByThePowerOfScience]

Modmaker here: I tracked down the cause in a debugger. Skip to the end for the problematic area.

Describe the issue

• What happened? [e.g. crashed, texture is broken]
  • Turning a villager from "Minecraft Comes Alive Reborn" into a Zombie Villager causes an infinite hang.
• What were you doing when it happened? [e.g. loading the game, playing multiplayer, single-player]
  • Playing multiplayer in a modpack containing about 300 mods. However, the debugger shows that the problem is in an interaction with MCA giving a dummy ResourceLocation and ETF not knowing what to do with that.

Screenshots

Your setup: (please complete the following information):

• Minecraft version: 1.20.2
• ModLoader: Forge
• ETF Version: 5.2.3
• Does the issue persist with only ETF installed?
  • Due to the interactions at play here, it is not easy to reproduce with only ETF installed. [x] Have you checked the FAQ in the Readme, or Discord, to see if it is a known issue?

The Problem Area:

https://github.com/Traben-0/Entity_Texture_Features/blob/2441486fc1ae8bc71038707f16239fd9b3fc50d7/common/src/main/java/traben/entity_texture_features/features/property_reading/TrueRandomProvider.java#L43-L44

From what I can tell, MCA Reborn gives a dummy resource location ("minecraft" : "") to Minecraft because it wants to use its own dynamic texture based on the villager's pre-existing custom skin.

The problem arises because ETFDirectory.getDirectoryVersionOf returns non-null forever when given a resource location like this, even with the suffix added. When I got to it in IDEA's JVM-attach debugger, totalTextureCount was 563133802.

The Fix:

https://github.com/Traben-0/Entity_Texture_Features/blob/2441486fc1ae8bc71038707f16239fd9b3fc50d7/common/src/main/java/traben/entity_texture_features/ETFApi.java#L438-L473

It's pretty easy: at the top of ETFApi.ETFVariantSuffixProvider#getVariantProviderOrNull, check if vanillaIdentifier is a valid identifier to begin with before matching textures for it. That or just check if it's empty. Should fix the issue right up.

Stacktrace from IDEA Debugger

lambda$negate$3:5613, Pattern$CharPredicate (java.util.regex)
is:-1, Pattern$CharPredicate$$Lambda$30+0x0000000800081a80 (java.util.regex)
match:4281, Pattern$CharPropertyGreedy (java.util.regex)
match:1755, Matcher (java.util.regex)
matches:712, Matcher (java.util.regex)
matches:1176, Pattern (java.util.regex)
matches:2844, String (java.lang)
addVariantNumberSuffix:112, ETFUtils2 (traben.entity_texture_features.utils)
addVariantNumberSuffix:98, ETFUtils2 (traben.entity_texture_features.utils)
of:41, TrueRandomProvider (traben.entity_texture_features.features.property_reading)
getVariantProviderOrNull:446, ETFApi$ETFVariantSuffixProvider (traben.entity_texture_features)
of:24, ETFTextureVariator (traben.entity_texture_features.features.texture_handlers)
getETFTextureVariant:263, ETFManager (traben.entity_texture_features.features)
getETFVariantNotNullForInjector:45, ETFUtils2 (traben.entity_texture_features.utils)
localvar$gaf000$entity_texture_features$etf$mixinAllEntityLayers:3270, RenderType (net.minecraft.client.renderer)
m_110443_:201, RenderType (net.minecraft.client.renderer)
m_110458_:205, RenderType (net.minecraft.client.renderer)
renderModel:109, VillagerLayer (forge.net.mca.client.render.layer)
renderFinal:99, VillagerLayer (forge.net.mca.client.render.layer)
render:90, VillagerLayer (forge.net.mca.client.render.layer)
m_6494_:29, VillagerLayer (forge.net.mca.client.render.layer)
m_7392_:131, LivingEntityRenderer (net.minecraft.client.renderer.entity)
m_7392_:45, MobRenderer (net.minecraft.client.renderer.entity)
m_7392_:18, MobRenderer (net.minecraft.client.renderer.entity)
m_114384_:140, EntityRenderDispatcher (net.minecraft.client.renderer.entity)
m_109517_:1440, LevelRenderer (net.minecraft.client.renderer)
m_109599_:1223, LevelRenderer (net.minecraft.client.renderer)
m_109089_:1126, GameRenderer (net.minecraft.client.renderer)
m_109093_:909, GameRenderer (net.minecraft.client.renderer)
m_91383_:1146, Minecraft (net.minecraft.client)
m_91374_:718, Minecraft (net.minecraft.client)
handleClientCrash:37, InGameCatcher (fudge.notenoughcrashes.mixinhandlers)
modify$ejd000$notenoughcrashes$atTheEndOfFirstCatchBeforePrintingCrashReport:12990, Minecraft (net.minecraft.client)
m_91374_:738, Minecraft (net.minecraft.client)
main:218, Main (net.minecraft.client.main)
invoke0:-1, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:77, NativeMethodAccessorImpl (jdk.internal.reflect)
invoke:43, DelegatingMethodAccessorImpl (jdk.internal.reflect)
invoke:568, Method (java.lang.reflect)
runTarget:111, CommonLaunchHandler (net.minecraftforge.fml.loading.targets)
clientService:99, CommonLaunchHandler (net.minecraftforge.fml.loading.targets)
lambda$makeService$0:25, CommonClientLaunchHandler (net.minecraftforge.fml.loading.targets)
run:-1, CommonClientLaunchHandler$$Lambda$1315+0x000000080076a6c8 (net.minecraftforge.fml.loading.targets)
launch:30, LaunchServiceHandlerDecorator (cpw.mods.modlauncher)
launch:53, LaunchServiceHandler (cpw.mods.modlauncher)
launch:71, LaunchServiceHandler (cpw.mods.modlauncher)
run:108, Launcher (cpw.mods.modlauncher)
main:78, Launcher (cpw.mods.modlauncher)
accept:26, BootstrapLaunchConsumer (cpw.mods.modlauncher)
accept:23, BootstrapLaunchConsumer (cpw.mods.modlauncher)
main:141, BootstrapLauncher (cpw.mods.bootstraplauncher)