Undo unnecessary changes

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

@@ -111,7 +111,7 @@ private void addConfig(final ModConfig modConfig) {
      * @param configSpec A config spec
      */
     public void registerConfig(ModConfig.Type type, IConfigSpec configSpec) {
-        if (configSpec.getDefaultConfig().isEmpty()) {
+        if (configSpec.isEmpty()) {
             // This handles the case where a mod tries to register a config, without any options configured inside it.
             LOGGER.debug("Attempted to register an empty config for type {} on mod {}", type, modId);
             return;
@@ -128,7 +128,7 @@ public void registerConfig(ModConfig.Type type, IConfigSpec configSpec) {
      * @param configSpec A config spec
      */
     public void registerConfig(ModConfig.Type type, IConfigSpec configSpec, String fileName) {
-        if (configSpec.getDefaultConfig().isEmpty()) {
+        if (configSpec.isEmpty()) {
             // This handles the case where a mod tries to register a config, without any options configured inside it.
             LOGGER.debug("Attempted to register an empty config for type {} on mod {} using file name {}", type, modId, fileName);
             return;

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

@@ -159,7 +159,7 @@ static void loadConfig(ModConfig modConfig, CommentedFileConfig config) {
                 throw new RuntimeException("Failed to recreate config file " + modConfig.getFileName() + " of type " + modConfig.getType() + " for modid " + modConfig.getModId(), ex);
             }
         }
-        modConfig.getSpec().load(config);
+        modConfig.getSpec().acceptConfig(config);
     }
 
     public void acceptSyncedConfig(ModConfig modConfig, byte[] bytes) {
@@ -168,7 +168,7 @@ public void acceptSyncedConfig(ModConfig modConfig, byte[] bytes) {
         }
         modConfig.config = TomlFormat.instance().createParser().parse(new ByteArrayInputStream(bytes));
         // TODO: do we want to do any validation? (what do we do if it fails?)
-        modConfig.getSpec().load(modConfig.config);
+        modConfig.getSpec().acceptConfig(modConfig.config);
         modConfig.postConfigEvent(ModConfigEvent.Reloading::new); // TODO: should maybe be Loading on the first load?
     }
 
@@ -177,12 +177,18 @@ public void loadDefaultServerConfigs() {
             if (modConfig.config != null) {
                 LOGGER.warn("Overwriting non-null config {} at path {} with default server config", modConfig.config, modConfig.getFileName());
             }
-            modConfig.config = CommentedConfig.copy(modConfig.getSpec().getDefaultConfig());
-            modConfig.getSpec().load(modConfig.config);
+            modConfig.config = createDefaultConfig(modConfig.getSpec());
+            modConfig.getSpec().acceptConfig(modConfig.config);
             modConfig.postConfigEvent(ModConfigEvent.Loading::new);
         });
     }
 
+    private static CommentedConfig createDefaultConfig(IConfigSpec spec) {
+        var commentedConfig = CommentedConfig.inMemory();
+        spec.correct(commentedConfig);
+        return commentedConfig;
+    }
+
     private void closeConfig(final ModConfig config) {
         if (config.config != null) {
             if (config.config instanceof CommentedFileConfig) {
@@ -214,7 +220,7 @@ private static boolean setupConfigFile(final ModConfig modConfig, final Path fil
             LOGGER.info(CONFIG, "Loading default config file from path {}", p);
             Files.copy(p, file);
         } else {
-            conf.createWriter().write(modConfig.getSpec().getDefaultConfig(), file, WritingMode.REPLACE_ATOMIC);
+            conf.createWriter().write(createDefaultConfig(modConfig.getSpec()), file, WritingMode.REPLACE_ATOMIC);
         }
         return true;
     }

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

@@ -6,18 +6,25 @@
 package net.neoforged.fml.config;
 
 import com.electronwill.nightconfig.core.CommentedConfig;
+import com.electronwill.nightconfig.core.Config;
 import com.electronwill.nightconfig.core.UnmodifiableCommentedConfig;
 
 /**
  * A config spec is responsible for interpreting (loading, correcting) raw {@link CommentedConfig}s from NightConfig.
  *
  * <p>NeoForge provides {@code ModConfigSpec} for the most common cases.
+ *
+ * <h3>Thread-safety</h3>
+ * <p>The {@link Config} objects themselves are thread-safe, but mod config code should not be assumed to be thread-safe in general.
+ * FML will guard event dispatches behind a lock when necessary.
+ * A spec can safely mutate {@code Config} objects, but should let FML fire events,
+ * for example using {@link ModConfig#onConfigChanged()}.
  */
 public interface IConfigSpec {
     /**
-     * Returns the default content of the config.
+     * Returns {@code true} if this spec is empty.
      */
-    UnmodifiableCommentedConfig getDefaultConfig();
+    boolean isEmpty();
 
     /**
      * Checks that a config is correct.
@@ -32,7 +39,9 @@ public interface IConfigSpec {
      * <p>This can be used to fix broken entries, add back missing entries or comments, etc...
      * The returned config will be saved to disk.
      *
-     * <p>The config should not be loaded into the spec yet. A call to {@link #load} will be made for that.
+     * <p>This function is also used to construct the default instance of a config, by passing in an empty config.
+     *
+     * <p>The config should not be loaded into the spec yet. A call to {@link #acceptConfig} will be made for that.
      *
      * <p>The config should not be saved yet. FML will take care of that after this method.
      */
@@ -43,5 +52,5 @@ public interface IConfigSpec {
      * This is called on loading and on reloading.
      * The config is guaranteed to be valid according to {@link #isCorrect}.
      */
-    void load(CommentedConfig config);
+    void acceptConfig(CommentedConfig config);
 }

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

@@ -69,7 +69,7 @@ public Path getFullPath() {
 
     /**
      * To be called when the config changed in code, for example via {@code ModConfigSpec.ConfigValue#set}.
-     * This function will update the config on disk, and fire the reloading event.
+     * This function will update the config on disk, and fire the reloading event, taking the appropriate lock first.
      */
     public void onConfigChanged() {
         if (!(this.config instanceof FileConfig fileConfig)) {

loader/src/test/java/net/neoforged/fml/config/ConfigTrackerTest.java

@@ -185,19 +185,11 @@ private void waitUntil(Runnable assertion) throws InterruptedException {
     }
 
     private static class SimpleConfigSpec implements IConfigSpec {
-        private final UnmodifiableCommentedConfig defaultConfig;
         private int loadedValue = 4;
 
-        public SimpleConfigSpec() {
-            var defaultConfig = CommentedConfig.inMemory();
-            defaultConfig.set("configEntry", 4);
-            defaultConfig.setComment("configEntry", "Test comment:");
-            this.defaultConfig = defaultConfig.unmodifiable();
-        }
-
         @Override
-        public UnmodifiableCommentedConfig getDefaultConfig() {
-            return defaultConfig;
+        public boolean isEmpty() {
+            return false;
         }
 
         @Override
@@ -227,7 +219,7 @@ private boolean correct(UnmodifiableCommentedConfig config, boolean dryRun) {
         }
 
         @Override
-        public void load(CommentedConfig config) {
+        public void acceptConfig(CommentedConfig config) {
             loadedValue = config.getInt("configEntry");
         }
     }