Load default configs from the defaultconfig directory by default. (Can

be overridden in the fml.toml config file if desired).

Will load any type of config tracked file from there - client, common, server
or custom tracked file. This means you can ship defaults for your pack
in a defaultconfig directory. I am thinking about ways to force a specific
config override for an existing config.

Signed-off-by: cpw <cpw+github@weeksfamily.ca>

src/main/java/net/minecraftforge/fml/config/ConfigFileTypeHandler.java

@@ -19,13 +19,18 @@
 
 package net.minecraftforge.fml.config;
 
+import com.electronwill.nightconfig.core.ConfigFormat;
 import com.electronwill.nightconfig.core.file.CommentedFileConfig;
+import com.electronwill.nightconfig.core.file.FileNotFoundAction;
 import com.electronwill.nightconfig.core.file.FileWatcher;
 import com.electronwill.nightconfig.core.io.WritingMode;
+import net.minecraftforge.fml.loading.FMLConfig;
+import net.minecraftforge.fml.loading.FMLPaths;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 
 import java.io.IOException;
+import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.function.Function;
 
@@ -34,6 +39,7 @@ import static net.minecraftforge.fml.config.ConfigTracker.CONFIG;
 public class ConfigFileTypeHandler {
     private static final Logger LOGGER = LogManager.getLogger();
     static ConfigFileTypeHandler TOML = new ConfigFileTypeHandler();
+    private static final Path defaultConfigPath = FMLPaths.GAMEDIR.get().resolve(FMLConfig.defaultConfigPath());
 
     public Function<ModConfig, CommentedFileConfig> reader(Path configBasePath) {
         return (c) -> {
@@ -41,6 +47,7 @@ public class ConfigFileTypeHandler {
             final CommentedFileConfig configData = CommentedFileConfig.builder(configPath).sync().
                     preserveInsertionOrder().
                     autosave().
+                    onFileNotFound((newfile, configFormat)-> setupConfigFile(c, newfile, configFormat)).
                     writingMode(WritingMode.REPLACE).
                     build();
             LOGGER.debug(CONFIG, "Built TOML config for {}", configPath.toString());
@@ -56,6 +63,18 @@ public class ConfigFileTypeHandler {
         };
     }
 
+    private boolean setupConfigFile(final ModConfig modConfig, final Path file, final ConfigFormat<?> conf) throws IOException {
+        Path p = defaultConfigPath.resolve(modConfig.getFileName());
+        if (Files.exists(p)) {
+            LOGGER.info(CONFIG, "Loading default config file from path {}", p);
+            Files.copy(p, file);
+        } else {
+            Files.createFile(file);
+            conf.initEmptyFile(file);
+        }
+        return true;
+    }
+
     private static class ConfigWatcher implements Runnable {
         private final ModConfig modConfig;
         private final CommentedFileConfig commentedFileConfig;