From 03878808c70fbf2151b0735478b9febdae644ed5 Mon Sep 17 00:00:00 2001
From: Jonas Herzig <jonas@spark-squared.com>
Date: Thu, 10 Jul 2025 12:57:23 +0200
Subject: [PATCH] stage2/ml9: Support NeoForge merging ModLauncher into
 FancyModLoader

---
 .../stage2/EssentialTransformationService.java    | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/stage2/modlauncher9/src/main/java/gg/essential/loader/stage2/EssentialTransformationService.java b/stage2/modlauncher9/src/main/java/gg/essential/loader/stage2/EssentialTransformationService.java
index 15cce21..fa71e71 100644
--- a/stage2/modlauncher9/src/main/java/gg/essential/loader/stage2/EssentialTransformationService.java
+++ b/stage2/modlauncher9/src/main/java/gg/essential/loader/stage2/EssentialTransformationService.java
@@ -24,11 +24,16 @@
 
 public class EssentialTransformationService implements ITransformationService {
     private static final Logger LOGGER = LogManager.getLogger(EssentialTransformationService.class);
-    private static final Map<String, String> COMPATIBILITY_IMPLEMENTATIONS = Map.of(
+    private static final Map<String, String> ML_COMPATIBILITY_IMPLEMENTATIONS = Map.of(
         "11.", "ML11CompatibilityLayer",
         "10.", "ML10CompatibilityLayer",
         "9.", "ML9CompatibilityLayer"
     );
+    // NeoForge as of 1.21.7 has merged ModLauncher into FancyModLoader and reports the version of that instead of
+    // ModLauncher.
+    private static final Map<String, String> FMLML_COMPATIBILITY_IMPLEMENTATIONS = Map.of(
+        "9.", "ML11CompatibilityLayer"
+    );
     private static CompatibilityLayer compatibilityLayer;
 
     private final Path gameDir;
@@ -82,7 +87,13 @@ public void initialize(IEnvironment environment) {
     @SuppressWarnings("unchecked")
     private CompatibilityLayer findCompatibilityLayerImpl(String mlVersion) {
         String implementation = null;
-        for (Map.Entry<String, String> entry : COMPATIBILITY_IMPLEMENTATIONS.entrySet()) {
+        Map<String, String> impls;
+        if ("fml_loader".equals(ITransformationService.class.getModule().getName())) {
+            impls = FMLML_COMPATIBILITY_IMPLEMENTATIONS;
+        } else {
+            impls = ML_COMPATIBILITY_IMPLEMENTATIONS;
+        }
+        for (Map.Entry<String, String> entry : impls.entrySet()) {
             if (mlVersion.startsWith(entry.getKey())) {
                 implementation = entry.getValue();
                 break;