add unloading for mod assemblies

CringeLauncher/Patches/ModScriptCompilerPatch.cs

@@ -0,0 +1,67 @@
+using System.Reflection;
+using System.Reflection.Emit;
+using System.Runtime.Loader;
+using CringeLauncher.Utils;
+using HarmonyLib;
+using NLog;
+using Sandbox.Game.World;
+using VRage.Scripting;
+
+namespace CringeLauncher.Patches;
+
+[HarmonyPatch]
+public static class ModScriptCompilerPatch
+{
+     private static ILogger Log = LogManager.GetCurrentClassLogger();
+     
+     private static AssemblyLoadContext _context = new(null, true);
+
+     static ModScriptCompilerPatch()
+     {
+          MySession.OnUnloaded += OnUnloaded;
+     }
+
+     private static void OnUnloaded()
+     {
+          if (!_context.Assemblies.Any())
+               return;
+          
+          Log.Info("Unloading mod scripts context");
+          _context.Unload();
+          
+          _context = new(null, true);
+     }
+
+     private static MethodInfo TargetMethod()
+     {
+          return MethodTools.AsyncMethodBody(
+               AccessTools.Method(typeof(MyScriptCompiler), nameof(MyScriptCompiler.Compile)));
+     }
+
+     private static IEnumerable<CodeInstruction> Transpiler(IEnumerable<CodeInstruction> instructions)
+     {
+          var ins = instructions.ToList();
+          
+          for (var i = 0; i < ins.Count; i++)
+          {
+               var instruction = ins[i];
+               
+               if (instruction.Calls(AccessTools.Method(typeof(Assembly), nameof(Assembly.Load),
+                                                        new[] { typeof(byte[]) })))
+               {
+                    ins[i - 1] = new(OpCodes.Nop); // memStream toArray call
+                    ins[i] = CodeInstruction.CallClosure((Stream assembly) => _context.LoadFromStream(assembly));
+               }
+               else if (instruction.Calls(AccessTools.Method(typeof(Assembly), nameof(Assembly.Load),
+                                                             new[] { typeof(byte[]), typeof(byte[]) })))
+               {
+                    ins[i - 4] = new(OpCodes.Nop); // memStream toArray calls
+                    ins[i - 1] = new(OpCodes.Nop);
+                    ins[i] = CodeInstruction.CallClosure((Stream assembly, Stream assemblySymbols) =>
+                                                              _context.LoadFromStream(assembly, assemblySymbols));
+               }
+          }
+
+          return ins;
+     }
+}

CringeLauncher/Utils/MethodTools.cs

@@ -0,0 +1,20 @@
+using System.Reflection;
+using HarmonyLib;
+using MonoMod.Utils;
+
+namespace CringeLauncher.Utils;
+
+public static class MethodTools
+{
+    public static MethodInfo AsyncMethodBody(MethodInfo method)
+    {
+        var (_, operand) = PatchProcessor.ReadMethodBody(method).First();
+        
+        if (operand is not LocalVariableInfo localVar)
+            throw new InvalidOperationException($"Method {method.GetID()} does not contain a valid async state machine");
+
+        return AccessTools.Method(localVar.LocalType, "MoveNext") ??
+               throw new InvalidOperationException(
+                   $"Async State machine of method {method.GetID()} does not contain a valid MoveNext method");
+    }
+}