Add STARTUP configs for early config loading/usage

loader/src/main/java/net/neoforged/fml/ModContainer.java

@@ -16,10 +16,12 @@
 import net.neoforged.bus.api.Event;
 import net.neoforged.bus.api.EventPriority;
 import net.neoforged.bus.api.IEventBus;
+import net.neoforged.fml.config.ConfigTracker;
 import net.neoforged.fml.config.IConfigSpec;
 import net.neoforged.fml.config.ModConfig;
 import net.neoforged.fml.event.IModBusEvent;
 import net.neoforged.fml.event.lifecycle.FMLConstructModEvent;
+import net.neoforged.fml.loading.FMLPaths;
 import net.neoforged.neoforgespi.language.IModInfo;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
@@ -96,6 +98,10 @@ public <T extends IExtensionPoint> void registerExtensionPoint(Class<T> point, S
 
     public void addConfig(final ModConfig modConfig) {
         configs.put(modConfig.getType(), modConfig);
+
+        if (modConfig.getType() == ModConfig.Type.STARTUP) {
+            ConfigTracker.INSTANCE.openConfig(modConfig, FMLPaths.CONFIGDIR.get(), null);
+        }
     }
 
     /**

loader/src/main/java/net/neoforged/fml/config/ConfigTracker.java

@@ -17,11 +17,13 @@
 import java.util.Optional;
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
+import org.jetbrains.annotations.ApiStatus;
 import org.jetbrains.annotations.Nullable;
 import org.slf4j.Logger;
 import org.slf4j.Marker;
 import org.slf4j.MarkerFactory;
 
+@ApiStatus.Internal
 public class ConfigTracker {
     private static final Logger LOGGER = LogUtils.getLogger();
     static final Marker CONFIG = MarkerFactory.getMarker("CONFIG");
@@ -36,8 +38,8 @@ private ConfigTracker() {
         this.configsByMod = new ConcurrentHashMap<>();
         this.configSets.put(ModConfig.Type.CLIENT, Collections.synchronizedSet(new LinkedHashSet<>()));
         this.configSets.put(ModConfig.Type.COMMON, Collections.synchronizedSet(new LinkedHashSet<>()));
-//        this.configSets.put(ModConfig.Type.PLAYER, new ConcurrentSkipListSet<>());
         this.configSets.put(ModConfig.Type.SERVER, Collections.synchronizedSet(new LinkedHashSet<>()));
+        this.configSets.put(ModConfig.Type.STARTUP, Collections.synchronizedSet(new LinkedHashSet<>()));
     }
 
     void trackConfig(final ModConfig config) {
@@ -76,7 +78,7 @@ private Path resolveBasePath(ModConfig config, Path configBasePath, @Nullable Pa
         return configBasePath;
     }
 
-    private void openConfig(final ModConfig config, final Path configBasePath, @Nullable Path configOverrideBasePath) {
+    public void openConfig(final ModConfig config, final Path configBasePath, @Nullable Path configOverrideBasePath) {
         LOGGER.trace(CONFIG, "Loading config file type {} at {} for {}", config.getType(), config.getFileName(), config.getModId());
         final Path basePath = resolveBasePath(config, configBasePath, configOverrideBasePath);
         final CommentedFileConfig configData = ConfigFileTypeHandler.TOML.reader(basePath).apply(config);

loader/src/main/java/net/neoforged/fml/config/ModConfig.java

@@ -94,19 +94,24 @@ public enum Type {
          * Suffix is "-client" by default.
          */
         CLIENT,
-//        /**
-//         * Player type config is configuration that is associated with a player.
-//         * Preferences around machine states, for example.
-//         */
-//        PLAYER,
         /**
          * Server type config is configuration that is associated with a server instance.
          * Only loaded during server startup.
          * Stored in a server/save specific "serverconfig" directory.
          * Synced to clients during connection.
          * Suffix is "-server" by default.
          */
-        SERVER;
+        SERVER,
+        /**
+         * Startup configs are for configurations that need to run as early as possible.
+         * Loaded as soon as the config is registered to FML.
+         * Please be aware when using them, as using these configs to enable/disable registration and anything that must be present on both sides
+         * can cause clients to have issues connecting to servers with different config values.
+         * Stored in the global config directory.
+         * Not synced.
+         * Suffix is "-startup" by default.
+         */
+        STARTUP;
 
         public String extension() {
             return StringUtils.toLowerCase(name());