Fix mod assembly loading on Windows.

OpenRA.Game/FileSystem/FileSystem.cs

@@ -21,8 +21,6 @@ namespace OpenRA.FileSystem
 	{
 		public IEnumerable<IReadOnlyPackage> MountedPackages { get { return mountedPackages.Keys; } }
 		readonly Dictionary<IReadOnlyPackage, int> mountedPackages = new Dictionary<IReadOnlyPackage, int>();
-
-		static readonly Dictionary<string, Assembly> AssemblyCache = new Dictionary<string, Assembly>();
 		Cache<string, List<IReadOnlyPackage>> fileIndex = new Cache<string, List<IReadOnlyPackage>>(_ => new List<IReadOnlyPackage>());
 
 		public IReadWritePackage CreatePackage(string filename, Dictionary<string, byte[]> content)
@@ -217,30 +215,5 @@ namespace OpenRA.FileSystem
 			else
 				return mountedPackages.Keys.Any(f => f.Contains(name));
 		}
-
-		public static Assembly ResolveAssembly(object sender, ResolveEventArgs e)
-		{
-			foreach (var assembly in AppDomain.CurrentDomain.GetAssemblies())
-				if (assembly.FullName == e.Name)
-					return assembly;
-
-			var frags = e.Name.Split(',');
-			var filename = frags[0] + ".dll";
-
-			Assembly a;
-			if (AssemblyCache.TryGetValue(filename, out a))
-				return a;
-
-			if (Game.ModData.ModFiles.Exists(filename))
-				using (var s = Game.ModData.ModFiles.Open(filename))
-				{
-					var buf = s.ReadBytes((int)s.Length);
-					a = Assembly.Load(buf);
-					AssemblyCache.Add(filename, a);
-					return a;
-				}
-
-			return null;
-		}
 	}
 }

OpenRA.Game/Game.cs

@@ -235,8 +235,6 @@ namespace OpenRA
 		{
 			Console.WriteLine("Platform is {0}", Platform.CurrentPlatform);
 
-			AppDomain.CurrentDomain.AssemblyResolve += FileSystem.FileSystem.ResolveAssembly;
-
 			InitializeSettings(args);
 
 			Log.AddChannel("perf", "perf.log");

OpenRA.Game/ModData.cs

@@ -43,11 +43,7 @@ namespace OpenRA
 			Manifest = new Manifest(mod);
 			ModFiles.LoadFromManifest(Manifest);
 
-			// Allow mods to load types from the core Game assembly, and any additional assemblies they specify.
-			var assemblies = new[] { typeof(Game).Assembly }
-					.Concat(Manifest.Assemblies.Select(path => Assembly.Load(ModFiles.Open(path).ReadAllBytes())))
-					.ToList();
-			ObjectCreator = new ObjectCreator(assemblies);
+			ObjectCreator = new ObjectCreator(Manifest, ModFiles);
 			Manifest.LoadCustomData(ObjectCreator);
 
 			if (useLoadScreen)

OpenRA.Game/ObjectCreator.cs

@@ -10,23 +10,74 @@
 
 using System;
 using System.Collections.Generic;
+using System.IO;
 using System.Linq;
 using System.Reflection;
+using System.Security.Cryptography;
+using OpenRA.FileSystem;
 using OpenRA.Primitives;
 
 namespace OpenRA
 {
 	public class ObjectCreator
 	{
+		// .NET does not support unloading assemblies, so mod libraries will leak across mod changes.
+		// This tracks the assemblies that have been loaded since game start so that we don't load multiple copies
+		static readonly Dictionary<string, Assembly> ResolvedAssemblies = new Dictionary<string, Assembly>();
+
 		readonly Cache<string, Type> typeCache;
 		readonly Cache<Type, ConstructorInfo> ctorCache;
 		readonly Pair<Assembly, string>[] assemblies;
 
-		public ObjectCreator(IEnumerable<Assembly> sourceAssemblies)
+		public ObjectCreator(Assembly a)
 		{
 			typeCache = new Cache<string, Type>(FindType);
 			ctorCache = new Cache<Type, ConstructorInfo>(GetCtor);
-			assemblies = sourceAssemblies.SelectMany(asm => asm.GetNamespaces().Select(ns => Pair.New(asm, ns))).ToArray();
+			assemblies = a.GetNamespaces().Select(ns => Pair.New(a, ns)).ToArray();
+		}
+
+		public ObjectCreator(Manifest manifest, FileSystem.FileSystem modFiles)
+		{
+			typeCache = new Cache<string, Type>(FindType);
+			ctorCache = new Cache<Type, ConstructorInfo>(GetCtor);
+
+			// Allow mods to load types from the core Game assembly, and any additional assemblies they specify.
+			var assemblyList = new List<Assembly>() { typeof(Game).Assembly };
+			foreach (var path in manifest.Assemblies)
+			{
+				var data = modFiles.Open(path).ReadAllBytes();
+
+				// .NET doesn't provide any way of querying the metadata of an assembly without either:
+				//   (a) loading duplicate data into the application domain, breaking the world.
+				//   (b) crashing if the assembly has already been loaded.
+				// We can't check the internal name of the assembly, so we'll work off the data instead
+				string hash;
+				using (var ms = new MemoryStream(data))
+					using (var csp = SHA1.Create())
+						hash = new string(csp.ComputeHash(data).SelectMany(a => a.ToString("x2")).ToArray());
+
+				Assembly assembly;
+				if (!ResolvedAssemblies.TryGetValue(hash, out assembly))
+				{
+					assembly = Assembly.Load(data);
+					ResolvedAssemblies.Add(hash, assembly);
+				}
+
+				assemblyList.Add(assembly);
+			}
+
+			AppDomain.CurrentDomain.AssemblyResolve += ResolveAssembly;
+			assemblies = assemblyList.SelectMany(asm => asm.GetNamespaces().Select(ns => Pair.New(asm, ns))).ToArray();
+			AppDomain.CurrentDomain.AssemblyResolve -= ResolveAssembly;
+		}
+
+		Assembly ResolveAssembly(object sender, ResolveEventArgs e)
+		{
+			foreach (var a in AppDomain.CurrentDomain.GetAssemblies())
+				if (a.FullName == e.Name)
+					return a;
+
+			return assemblies.Select(a => a.First).FirstOrDefault(a => a.FullName == e.Name);
 		}
 
 		public static Action<string> MissingTypeAction =

OpenRA.Test/OpenRA.Game/ActorInfoTest.cs

@@ -108,7 +108,7 @@ namespace OpenRA.Test
 			var yaml = MiniYaml.Merge(sources.Select(s => MiniYaml.FromString(s)));
 			var allUnits = yaml.ToDictionary(node => node.Key, node => node.Value);
 			var unit = allUnits[name];
-			var creator = new ObjectCreator(new[] { typeof(ActorInfoTest).Assembly });
+			var creator = new ObjectCreator(typeof(ActorInfoTest).Assembly);
 			return new ActorInfo(creator, name, unit);
 		}
 	}

OpenRA.Utility/Program.cs

@@ -42,8 +42,6 @@ namespace OpenRA.Utility
 				return;
 			}
 
-			AppDomain.CurrentDomain.AssemblyResolve += FileSystem.FileSystem.ResolveAssembly;
-
 			Log.AddChannel("perf", null);
 			Log.AddChannel("debug", null);