From 74232d86b42086bb544ebd6f160ac26b9ba4e906 Mon Sep 17 00:00:00 2001
From: Juuz <6596629+Juuxel@users.noreply.github.com>
Date: Wed, 3 Jul 2024 16:30:34 +0300
Subject: [PATCH] Patch ModDirTransformerDiscoverer to not crash with UnionFS
 paths

---
 .../ModDirTransformerDiscovererPatch.java     | 43 +++++++++++++++++++
 .../loom/util/ClassVisitorUtil.java           |  2 +-
 .../forge/ForgeLibrariesProvider.java         |  6 +++
 3 files changed, 50 insertions(+), 1 deletion(-)
 create mode 100644 src/main/java/dev/architectury/loom/forge/ModDirTransformerDiscovererPatch.java

diff --git a/src/main/java/dev/architectury/loom/forge/ModDirTransformerDiscovererPatch.java b/src/main/java/dev/architectury/loom/forge/ModDirTransformerDiscovererPatch.java
new file mode 100644
index 00000000..0bd59456
--- /dev/null
+++ b/src/main/java/dev/architectury/loom/forge/ModDirTransformerDiscovererPatch.java
@@ -0,0 +1,43 @@
+package dev.architectury.loom.forge;
+
+import org.objectweb.asm.ClassVisitor;
+import org.objectweb.asm.Label;
+import org.objectweb.asm.MethodVisitor;
+import org.objectweb.asm.Opcodes;
+
+/**
+ * Patches {@code ModDirTransformerDiscovererPatch} in Forge 49.0.50+ so that it doesn't try to create modules
+ * directly out of UnionFS root paths created by Union Relauncher. SecureModules can't infer the module names
+ * from those paths, so the game crashes without this patch.
+ */
+public final class ModDirTransformerDiscovererPatch extends ClassVisitor {
+	public ModDirTransformerDiscovererPatch(ClassVisitor classVisitor) {
+		super(Opcodes.ASM9, classVisitor);
+	}
+
+	@Override
+	public MethodVisitor visitMethod(int access, String name, String descriptor, String signature, String[] exceptions) {
+		MethodVisitor next = super.visitMethod(access, name, descriptor, signature, exceptions);
+
+		if (name.equals("isServiceProvider") && descriptor.equals("(Ljava/nio/file/Path;)Z")) {
+			return new MethodVisitor(Opcodes.ASM9, next) {
+				@Override
+				public void visitCode() {
+					super.visitCode();
+
+					// Don't even try to examine the path if it's not a default fs path, just return false.
+					var after = new Label();
+					visitVarInsn(Opcodes.ALOAD, 0);
+					visitMethodInsn(Opcodes.INVOKEINTERFACE, "java/nio/file/Path", "getFileSystem", "()Ljava/nio/file/FileSystem;", true);
+					visitMethodInsn(Opcodes.INVOKESTATIC, "java/nio/file/FileSystems", "getDefault", "()Ljava/nio/file/FileSystem;", false);
+					visitJumpInsn(Opcodes.IF_ACMPEQ, after);
+					visitInsn(Opcodes.ICONST_0);
+					visitInsn(Opcodes.IRETURN);
+					visitLabel(after);
+				}
+			};
+		}
+
+		return next;
+	}
+}
diff --git a/src/main/java/dev/architectury/loom/util/ClassVisitorUtil.java b/src/main/java/dev/architectury/loom/util/ClassVisitorUtil.java
index f0e0003a..a6bec6c0 100644
--- a/src/main/java/dev/architectury/loom/util/ClassVisitorUtil.java
+++ b/src/main/java/dev/architectury/loom/util/ClassVisitorUtil.java
@@ -17,7 +17,7 @@ public final class ClassVisitorUtil {
 		try {
 			final byte[] inputBytes = Files.readAllBytes(path);
 			final var reader = new ClassReader(inputBytes);
-			final var writer = new ClassWriter(0);
+			final var writer = new ClassWriter(ClassWriter.COMPUTE_FRAMES);
 			reader.accept(visitorFactory.apply(writer), 0);
 			final byte[] outputBytes = writer.toByteArray();
 
diff --git a/src/main/java/net/fabricmc/loom/configuration/providers/forge/ForgeLibrariesProvider.java b/src/main/java/net/fabricmc/loom/configuration/providers/forge/ForgeLibrariesProvider.java
index 31be3cfa..7243f27d 100644
--- a/src/main/java/net/fabricmc/loom/configuration/providers/forge/ForgeLibrariesProvider.java
+++ b/src/main/java/net/fabricmc/loom/configuration/providers/forge/ForgeLibrariesProvider.java
@@ -32,6 +32,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 import com.google.common.hash.Hashing;
+import dev.architectury.loom.forge.ModDirTransformerDiscovererPatch;
 import dev.architectury.loom.neoforge.LaunchHandlerPatcher;
 import dev.architectury.loom.util.ClassVisitorUtil;
 import org.gradle.api.Project;
@@ -63,6 +64,7 @@ public class ForgeLibrariesProvider {
 	private static final String FANCYML_LOADER_NAME = "loader";
 
 	private static final String FORGE_OBJECT_HOLDER_FILE = "net/minecraftforge/fml/common/asm/ObjectHolderDefinalize.class";
+	private static final String FORGE_MOD_DIR_TRANSFORMER_DISCOVERER_FILE = "net/minecraftforge/fml/loading/ModDirTransformerDiscoverer.class";
 	private static final String NEOFORGE_OBJECT_HOLDER_FILE = "net/neoforged/fml/common/asm/ObjectHolderDefinalize.class";
 	private static final String NEOFORGE_LAUNCH_HANDLER_FILE = "net/neoforged/fml/loading/targets/CommonUserdevLaunchHandler.class";
 
@@ -176,6 +178,10 @@ public class ForgeLibrariesProvider {
 					remapObjectHolder(project, outputJar, mappingConfiguration);
 				}
 
+				if (Files.exists(fs.getPath(FORGE_MOD_DIR_TRANSFORMER_DISCOVERER_FILE))) {
+					ClassVisitorUtil.rewriteClassFile(fs.getPath(FORGE_MOD_DIR_TRANSFORMER_DISCOVERER_FILE), ModDirTransformerDiscovererPatch::new);
+				}
+
 				if (Files.exists(fs.getPath(NEOFORGE_OBJECT_HOLDER_FILE))) {
 					remapNeoForgeObjectHolder(project, outputJar, mappingConfiguration);
 				}