Implemented Melon Preprocessor to prevent Loading Duplicates

MelonLoader/Melons/MelonFolderHandler.cs

@@ -90,41 +90,6 @@ internal static void ScanMelons<T>(string path) where T : MelonTypeBase<T>
             firstSpacer = true;
         }
 
-        private static void LoadFolder(string path,
-            bool addToList,
-            ref bool hasWroteLine,
-            ref List<MelonAssembly> melonAssemblies)
-        {
-            // Validate Path
-            if (!Directory.Exists(path))
-                return;
-
-            // Get DLLs in Directory
-            var files = Directory.GetFiles(path, "*.dll", SearchOption.TopDirectoryOnly);
-            foreach (var f in files)
-            {
-                // Ignore Native DLLs
-                if (!MelonUtils.IsManagedDLL(f)) 
-                    continue;
-
-                // Log
-                if (!hasWroteLine)
-                {
-                    hasWroteLine = true;
-                    MelonLogger.WriteLine(Color.Magenta);
-                }
-
-                // Load Assembly
-                var asm = MelonAssembly.LoadMelonAssembly(f, false);
-                if (asm == null)
-                    continue;
-
-                // Queue Assembly for Melon Parsing
-                if (addToList)
-                    melonAssemblies.Add(asm);
-            }
-        }
-
         private static void ProcessFolder(eScanType scanType,
             string path,
             ref bool hasWroteLine,
@@ -156,13 +121,11 @@ private static void ProcessFolder(eScanType scanType,
                     Resolver.MelonAssemblyResolver.AddSearchDirectory(directory);
 
             // Load UserLibs
-            foreach (var dir in userLibDirectories)
-                LoadFolder(dir, false, ref hasWroteLine, ref melonAssemblies);
+            MelonPreprocessor.LoadFolders(userLibDirectories, false, ref hasWroteLine, ref melonAssemblies);
 
             // Load Melons from Folders
             if (scanType != eScanType.UserLibs)
-                foreach (var dir in melonDirectories)
-                    LoadFolder(dir, true, ref hasWroteLine, ref melonAssemblies);
+                MelonPreprocessor.LoadFolders(melonDirectories, true, ref hasWroteLine, ref melonAssemblies);
         }
 
         private static void ScanFolder(eScanType scanType,

MelonLoader/Melons/MelonPreprocessor.cs

@@ -0,0 +1,95 @@
+using System;
+using System.Collections.Generic;
+using System.Drawing;
+using System.IO;
+using Mono.Cecil;
+
+namespace MelonLoader.Melons
+{
+    internal static class MelonPreprocessor
+    {
+        internal static void LoadFolders(List<string> directoryPaths,
+            bool isMelon,
+            ref bool hasWroteLine,
+            ref List<MelonAssembly> melonAssemblies)
+        {
+            // Find All Assemblies
+            Dictionary<string, (Version, string)> foundAssemblies = new();
+            foreach (string path in directoryPaths)
+                PreprocessFolder(path, isMelon, ref foundAssemblies);
+
+            // Load from File Paths
+            foreach (var foundFile in foundAssemblies)
+            {
+                // Log
+                if (!hasWroteLine)
+                {
+                    hasWroteLine = true;
+                    MelonLogger.WriteLine(Color.Magenta);
+                }
+
+                // Load Assembly
+                var asm = MelonAssembly.LoadMelonAssembly(foundFile.Value.Item2, false);
+                if (asm == null)
+                    continue;
+
+                // Queue Assembly for Melon Parsing
+                if (isMelon)
+                    melonAssemblies.Add(asm);
+            }
+        }
+
+        private static void PreprocessFolder(string path,
+            bool isMelon,
+            ref Dictionary<string, (Version, string)> foundAssemblies)
+        {
+            // Validate Path
+            if (!Directory.Exists(path))
+                return;
+
+            // Get DLLs in Directory
+            var files = Directory.GetFiles(path, "*.dll", SearchOption.TopDirectoryOnly);
+            foreach (var f in files)
+            {
+                // Ignore Native DLLs
+                if (!MelonUtils.IsManagedDLL(f))
+                    continue;
+
+                // Load Definition using Cecil
+                AssemblyDefinition asmDef = LoadDefinition(f);
+                if (asmDef == null)
+                    continue;
+
+                // Pull Name and Version from AssemblyDefinitionName
+                string name = $"{asmDef.Name.Name}";
+                Version version = new(asmDef.Name.Version.ToString());
+
+                // Dispose of Definition
+                asmDef.Dispose();
+
+                // Check for Existing Version
+                if (foundAssemblies.TryGetValue(name, out (Version, string) existingVersion)
+                    && (existingVersion.Item1 >= version))
+                    continue;
+
+                // Add File to List
+                foundAssemblies[name] = (version, f);
+            }
+        }
+
+        private static AssemblyDefinition LoadDefinition(string path)
+        {
+            path = Path.GetFullPath(path);
+
+            try
+            {
+                return AssemblyDefinition.ReadAssembly(path);
+            }
+            catch (Exception ex)
+            {
+                MelonLogger.Error($"Failed to load AssemblyDefinition from '{path}':\n{ex}");
+                return null;
+            }
+        }
+    }
+}