From 3adccc1a2bbdcaa67a0b7adf0992a5a828de3009 Mon Sep 17 00:00:00 2001
From: embeddedt <42941056+embeddedt@users.noreply.github.com>
Date: Sun, 4 Feb 2024 15:50:47 -0500
Subject: [PATCH] [1.20.1] Prevent mixins from crashing the game when there are
 missing mods (#85)

---
 .../loading/moddiscovery/ModValidator.java    | 25 ++++++++++++++-----
 1 file changed, 19 insertions(+), 6 deletions(-)

diff --git a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModValidator.java b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModValidator.java
index 08e3275b5..6300b5061 100644
--- a/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModValidator.java
+++ b/loader/src/main/java/net/minecraftforge/fml/loading/moddiscovery/ModValidator.java
@@ -15,11 +15,9 @@
 import org.jetbrains.annotations.NotNull;
 import org.slf4j.Logger;
 
-import java.util.ArrayList;
-import java.util.Iterator;
-import java.util.List;
-import java.util.Map;
+import java.util.*;
 import java.util.stream.Collectors;
+import java.util.stream.Stream;
 
 public class ModValidator {
     private static final Logger LOGGER = LogUtils.getLogger();
@@ -29,11 +27,13 @@ public class ModValidator {
     private LoadingModList loadingModList;
     private List<IModFile> brokenFiles;
     private final List<EarlyLoadingException.ExceptionData> discoveryErrorData;
+    private final List<ModFile> gameLibraries;
 
     public ModValidator(final Map<IModFile.Type, List<ModFile>> modFiles, final List<IModFileInfo> brokenFiles, final List<EarlyLoadingException.ExceptionData> discoveryErrorData) {
         this.modFiles = modFiles;
         this.candidateMods = lst(modFiles.get(IModFile.Type.MOD));
-        this.candidateMods.addAll(lst(modFiles.get(IModFile.Type.GAMELIBRARY)));
+        this.gameLibraries = lst(modFiles.get(IModFile.Type.GAMELIBRARY));
+        this.candidateMods.addAll(this.gameLibraries);
         this.candidatePlugins = lst(modFiles.get(IModFile.Type.LANGPROVIDER));
         this.candidatePlugins.addAll(lst(modFiles.get(IModFile.Type.LIBRARY)));
         this.discoveryErrorData = discoveryErrorData;
@@ -72,7 +72,20 @@ public ITransformationService.Resource getPluginResources() {
     }
 
     public ITransformationService.Resource getModResources() {
-        return new ITransformationService.Resource(IModuleLayerManager.Layer.GAME, this.candidateMods.stream().map(IModFile::getSecureJar).toList());
+        Stream<ModFile> modFileStream;
+        if (FMLEnvironment.production) {
+            // In production, only allow game libraries and/or mods in the loading mod list
+            // This prevents custom mixins from loading if there is a dependency error
+            // Usually, these mixins will break due to a missing class or AT, and that
+            // will prevent our error screen from ever becoming visible.
+            Set<ModFile> validMods = new HashSet<>();
+            validMods.addAll(this.loadingModList.getModFiles().stream().map(ModFileInfo::getFile).toList());
+            validMods.addAll(this.gameLibraries);
+            modFileStream = validMods.stream();
+        } else {
+            modFileStream = this.candidateMods.stream();
+        }
+        return new ITransformationService.Resource(IModuleLayerManager.Layer.GAME, modFileStream.map(IModFile::getSecureJar).toList());
     }
 
     private List<EarlyLoadingException.ExceptionData> validateLanguages() {