Deal with old malformed UUID's being invalid after Java 8

src/main/java/com/cleanroommc/loader/javafix/UUIDFix.java

@@ -0,0 +1,52 @@
+package com.cleanroommc.loader.javafix;
+
+import net.minecraftforge.fml.common.FMLLog;
+
+import java.util.UUID;
+
+public class UUIDFix {
+
+    public static UUID fromString(String uuid)
+    {
+        try
+        {
+            return UUID.fromString(uuid);
+        }
+        catch (IllegalArgumentException e)
+        {
+            if ("UUID string too large".equals(e.getMessage()))
+            {
+                return oldFromString(uuid);
+            }
+            throw e;
+        }
+    }
+
+    private static UUID oldFromString(String uuid)
+    {
+        String[] components = uuid.split("-");
+        if (components.length != 5)
+        {
+            throw new IllegalArgumentException("Invalid UUID string: " + uuid);
+        }
+        FMLLog.log.error("UUID [{}] is being processed with the approach from Java 8 for compatibility's sake. This UUID is malformed!", uuid);
+        for (int i = 0; i < 5; i++)
+        {
+            components[i] = "0x" + components[i];
+        }
+        long mostSigBits = Long.decode(components[0]);
+        mostSigBits <<= 16;
+        mostSigBits |= Long.decode(components[1]);
+        mostSigBits <<= 16;
+        mostSigBits |= Long.decode(components[2]);
+
+        long leastSigBits = Long.decode(components[3]);
+        leastSigBits <<= 48;
+        leastSigBits |= Long.decode(components[4]);
+
+        return new UUID(mostSigBits, leastSigBits);
+    }
+
+    private UUIDFix() { }
+
+}

src/main/java/net/minecraftforge/fml/common/asm/transformers/MalformedUUIDTransformer.java

@@ -0,0 +1,54 @@
+package net.minecraftforge.fml.common.asm.transformers;
+
+import net.minecraft.launchwrapper.IClassTransformer;
+import org.objectweb.asm.ClassReader;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
+import org.objectweb.asm.tree.*;
+
+public class MalformedUUIDTransformer implements IClassTransformer
+{
+
+    @Override
+    public byte[] transform(String s, String s1, byte[] bytes)
+    {
+        if (bytes == null)
+        {
+            return null;
+        }
+        ClassNode classNode = new ClassNode();
+        ClassReader classReader = new ClassReader(bytes);
+        classReader.accept(classNode, 0);
+        boolean modified = false;
+        if (classNode.methods != null)
+        {
+            for (MethodNode methodNode : classNode.methods)
+            {
+                InsnList instructions = methodNode.instructions;
+                if (instructions != null)
+                {
+                    for (AbstractInsnNode insnNode : instructions)
+                    {
+                        if (insnNode.getOpcode() == Opcodes.INVOKESTATIC && insnNode instanceof MethodInsnNode methodInsnNode)
+                        {
+                            if ("java/util/UUID".equals(methodInsnNode.owner) && "fromString".equalsIgnoreCase(methodInsnNode.name))
+                            {
+                                methodInsnNode.owner = "com/cleanroommc/loader/javafix/UUIDFix";
+                                modified = true;
+                            }
+                        }
+                    }
+                }
+            }
+        }
+        if (modified)
+        {
+            ClassWriter classWriter = new ClassWriter(0);
+
+            classNode.accept(classWriter);
+            return classWriter.toByteArray();
+        }
+        return bytes;
+    }
+
+}

src/main/java/net/minecraftforge/fml/relauncher/FMLCorePlugin.java

@@ -32,6 +32,7 @@ public String[] getASMTransformerClass()
                              "net.minecraftforge.fml.common.asm.transformers.EventSubscriberTransformer",
                              "net.minecraftforge.fml.common.asm.transformers.SoundEngineFixTransformer",
                              "net.minecraftforge.fml.common.asm.transformers.JavaxTransformer",
+                             "net.minecraftforge.fml.common.asm.transformers.MalformedUUIDTransformer",
                              "net.minecraftforge.fml.common.asm.transformers.ReflectionFieldTransformer",
                              "net.minecraftforge.fml.common.asm.transformers.ScriptEngineTransformer"
                             };