initial commit, 4.5 stable

modules/mono/glue/GodotSharp/GodotPlugins/GodotPlugins.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net8.0</TargetFramework>
+    <LangVersion>12</LangVersion>
+    <Nullable>enable</Nullable>
+    <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
+
+    <!-- To generate the .runtimeconfig.json file-->
+    <EnableDynamicLoading>true</EnableDynamicLoading>
+    <RollForward>LatestMajor</RollForward>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\GodotSharp\GodotSharp.csproj" />
+  </ItemGroup>
+
+</Project>

modules/mono/glue/GodotSharp/GodotPlugins/Main.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+using System.Runtime.InteropServices;
+using System.Runtime.Loader;
+using Godot.Bridge;
+using Godot.NativeInterop;
+
+namespace GodotPlugins
+{
+    public static class Main
+    {
+        // IMPORTANT:
+        // Keeping strong references to the AssemblyLoadContext (our PluginLoadContext) prevents
+        // it from being unloaded. To avoid issues, we wrap the reference in this class, and mark
+        // all the methods that access it as non-inlineable. This way we prevent local references
+        // (either real or introduced by the JIT) to escape the scope of these methods due to
+        // inlining, which could keep the AssemblyLoadContext alive while trying to unload.
+        private sealed class PluginLoadContextWrapper
+        {
+            private PluginLoadContext? _pluginLoadContext;
+            private readonly WeakReference _weakReference;
+
+            private PluginLoadContextWrapper(PluginLoadContext pluginLoadContext, WeakReference weakReference)
+            {
+                _pluginLoadContext = pluginLoadContext;
+                _weakReference = weakReference;
+            }
+
+            public string? AssemblyLoadedPath
+            {
+                [MethodImpl(MethodImplOptions.NoInlining)]
+                get => _pluginLoadContext?.AssemblyLoadedPath;
+            }
+
+            public bool IsCollectible
+            {
+                [MethodImpl(MethodImplOptions.NoInlining)]
+                // if _pluginLoadContext is null we already started unloading, so it was collectible
+                get => _pluginLoadContext?.IsCollectible ?? true;
+            }
+
+            public bool IsAlive
+            {
+                [MethodImpl(MethodImplOptions.NoInlining)]
+                get => _weakReference.IsAlive;
+            }
+
+            [MethodImpl(MethodImplOptions.NoInlining)]
+            public static (Assembly, PluginLoadContextWrapper) CreateAndLoadFromAssemblyName(
+                AssemblyName assemblyName,
+                string pluginPath,
+                ICollection<string> sharedAssemblies,
+                AssemblyLoadContext mainLoadContext,
+                bool isCollectible
+            )
+            {
+                var context = new PluginLoadContext(pluginPath, sharedAssemblies, mainLoadContext, isCollectible);
+                var reference = new WeakReference(context, trackResurrection: true);
+                var wrapper = new PluginLoadContextWrapper(context, reference);
+                var assembly = context.LoadFromAssemblyName(assemblyName);
+                return (assembly, wrapper);
+            }
+
+            [MethodImpl(MethodImplOptions.NoInlining)]
+            internal void Unload()
+            {
+                _pluginLoadContext?.Unload();
+                _pluginLoadContext = null;
+            }
+        }
+
+        private static readonly List<AssemblyName> SharedAssemblies = new();
+        private static readonly Assembly CoreApiAssembly = typeof(global::Godot.GodotObject).Assembly;
+        private static Assembly? _editorApiAssembly;
+        private static PluginLoadContextWrapper? _projectLoadContext;
+        private static bool _editorHint = false;
+
+        private static readonly AssemblyLoadContext MainLoadContext =
+            AssemblyLoadContext.GetLoadContext(Assembly.GetExecutingAssembly()) ??
+            AssemblyLoadContext.Default;
+
+        private static DllImportResolver? _dllImportResolver;
+
+        // Right now we do it this way for simplicity as hot-reload is disabled. It will need to be changed later.
+        [UnmanagedCallersOnly]
+        // ReSharper disable once UnusedMember.Local
+        private static unsafe godot_bool InitializeFromEngine(IntPtr godotDllHandle, godot_bool editorHint,
+            PluginsCallbacks* pluginsCallbacks, ManagedCallbacks* managedCallbacks,
+            IntPtr unmanagedCallbacks, int unmanagedCallbacksSize)
+        {
+            try
+            {
+                _editorHint = editorHint.ToBool();
+
+                _dllImportResolver = new GodotDllImportResolver(godotDllHandle).OnResolveDllImport;
+
+                SharedAssemblies.Add(CoreApiAssembly.GetName());
+                NativeLibrary.SetDllImportResolver(CoreApiAssembly, _dllImportResolver);
+
+                AlcReloadCfg.Configure(alcReloadEnabled: _editorHint);
+                NativeFuncs.Initialize(unmanagedCallbacks, unmanagedCallbacksSize);
+
+                if (_editorHint)
+                {
+                    _editorApiAssembly = Assembly.Load("GodotSharpEditor");
+                    SharedAssemblies.Add(_editorApiAssembly.GetName());
+                    NativeLibrary.SetDllImportResolver(_editorApiAssembly, _dllImportResolver);
+                }
+
+                *pluginsCallbacks = new()
+                {
+                    LoadProjectAssemblyCallback = &LoadProjectAssembly,
+                    LoadToolsAssemblyCallback = &LoadToolsAssembly,
+                    UnloadProjectPluginCallback = &UnloadProjectPlugin,
+                };
+
+                *managedCallbacks = ManagedCallbacks.Create();
+
+                return godot_bool.True;
+            }
+            catch (Exception e)
+            {
+                Console.Error.WriteLine(e);
+                return godot_bool.False;
+            }
+        }
+
+        [StructLayout(LayoutKind.Sequential)]
+        private struct PluginsCallbacks
+        {
+            public unsafe delegate* unmanaged<char*, godot_string*, godot_bool> LoadProjectAssemblyCallback;
+            public unsafe delegate* unmanaged<char*, IntPtr, int, IntPtr> LoadToolsAssemblyCallback;
+            public unsafe delegate* unmanaged<godot_bool> UnloadProjectPluginCallback;
+        }
+
+        [UnmanagedCallersOnly]
+        private static unsafe godot_bool LoadProjectAssembly(char* nAssemblyPath, godot_string* outLoadedAssemblyPath)
+        {
+            try
+            {
+                if (_projectLoadContext != null)
+                    return godot_bool.True; // Already loaded
+
+                string assemblyPath = new(nAssemblyPath);
+
+                (var projectAssembly, _projectLoadContext) = LoadPlugin(assemblyPath, isCollectible: _editorHint);
+
+                string loadedAssemblyPath = _projectLoadContext.AssemblyLoadedPath ?? assemblyPath;
+                *outLoadedAssemblyPath = Marshaling.ConvertStringToNative(loadedAssemblyPath);
+
+                ScriptManagerBridge.LookupScriptsInAssembly(projectAssembly);
+
+                return godot_bool.True;
+            }
+            catch (Exception e)
+            {
+                Console.Error.WriteLine(e);
+                return godot_bool.False;
+            }
+        }
+
+        [UnmanagedCallersOnly]
+        private static unsafe IntPtr LoadToolsAssembly(char* nAssemblyPath,
+            IntPtr unmanagedCallbacks, int unmanagedCallbacksSize)
+        {
+            try
+            {
+                string assemblyPath = new(nAssemblyPath);
+
+                if (_editorApiAssembly == null)
+                    throw new InvalidOperationException("The Godot editor API assembly is not loaded.");
+
+                var (assembly, _) = LoadPlugin(assemblyPath, isCollectible: false);
+
+                NativeLibrary.SetDllImportResolver(assembly, _dllImportResolver!);
+
+                var method = assembly.GetType("GodotTools.GodotSharpEditor")?
+                    .GetMethod("InternalCreateInstance",
+                        BindingFlags.Static | BindingFlags.NonPublic | BindingFlags.Public);
+
+                if (method == null)
+                {
+                    throw new MissingMethodException("GodotTools.GodotSharpEditor",
+                        "InternalCreateInstance");
+                }
+
+                return (IntPtr?)method
+                           .Invoke(null, new object[] { unmanagedCallbacks, unmanagedCallbacksSize })
+                       ?? IntPtr.Zero;
+            }
+            catch (Exception e)
+            {
+                Console.Error.WriteLine(e);
+                return IntPtr.Zero;
+            }
+        }
+
+        private static (Assembly, PluginLoadContextWrapper) LoadPlugin(string assemblyPath, bool isCollectible)
+        {
+            string assemblyName = Path.GetFileNameWithoutExtension(assemblyPath);
+
+            var sharedAssemblies = new List<string>();
+
+            foreach (var sharedAssembly in SharedAssemblies)
+            {
+                string? sharedAssemblyName = sharedAssembly.Name;
+                if (sharedAssemblyName != null)
+                    sharedAssemblies.Add(sharedAssemblyName);
+            }
+
+            return PluginLoadContextWrapper.CreateAndLoadFromAssemblyName(
+                new AssemblyName(assemblyName), assemblyPath, sharedAssemblies, MainLoadContext, isCollectible);
+        }
+
+        [UnmanagedCallersOnly]
+        private static godot_bool UnloadProjectPlugin()
+        {
+            try
+            {
+                return UnloadPlugin(ref _projectLoadContext).ToGodotBool();
+            }
+            catch (Exception e)
+            {
+                Console.Error.WriteLine(e);
+                return godot_bool.False;
+            }
+        }
+
+        private static bool UnloadPlugin(ref PluginLoadContextWrapper? pluginLoadContext)
+        {
+            try
+            {
+                if (pluginLoadContext == null)
+                    return true;
+
+                if (!pluginLoadContext.IsCollectible)
+                {
+                    Console.Error.WriteLine("Cannot unload a non-collectible assembly load context.");
+                    return false;
+                }
+
+                Console.WriteLine("Unloading assembly load context...");
+
+                pluginLoadContext.Unload();
+
+                int startTimeMs = Environment.TickCount;
+                bool takingTooLong = false;
+
+                while (pluginLoadContext.IsAlive)
+                {
+                    GC.Collect(GC.MaxGeneration, GCCollectionMode.Forced);
+                    GC.WaitForPendingFinalizers();
+
+                    if (!pluginLoadContext.IsAlive)
+                        break;
+
+                    int elapsedTimeMs = Environment.TickCount - startTimeMs;
+
+                    if (!takingTooLong && elapsedTimeMs >= 200)
+                    {
+                        takingTooLong = true;
+
+                        // TODO: How to log from GodotPlugins? (delegate pointer?)
+                        Console.Error.WriteLine("Assembly unloading is taking longer than expected...");
+                    }
+                    else if (elapsedTimeMs >= 1000)
+                    {
+                        // TODO: How to log from GodotPlugins? (delegate pointer?)
+                        Console.Error.WriteLine(
+                            "Failed to unload assemblies. Possible causes: Strong GC handles, running threads, etc.");
+
+                        return false;
+                    }
+                }
+
+                Console.WriteLine("Assembly load context unloaded successfully.");
+
+                pluginLoadContext = null;
+                return true;
+            }
+            catch (Exception e)
+            {
+                // TODO: How to log exceptions from GodotPlugins? (delegate pointer?)
+                Console.Error.WriteLine(e);
+                return false;
+            }
+        }
+    }
+}

modules/mono/glue/GodotSharp/GodotPlugins/PluginLoadContext.cs

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+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Reflection;
+using System.Runtime.Loader;
+
+namespace GodotPlugins
+{
+    public class PluginLoadContext : AssemblyLoadContext
+    {
+        private readonly AssemblyDependencyResolver _resolver;
+        private readonly ICollection<string> _sharedAssemblies;
+        private readonly AssemblyLoadContext _mainLoadContext;
+
+        public string? AssemblyLoadedPath { get; private set; }
+
+        public PluginLoadContext(string pluginPath, ICollection<string> sharedAssemblies,
+            AssemblyLoadContext mainLoadContext, bool isCollectible)
+            : base(isCollectible)
+        {
+            _resolver = new AssemblyDependencyResolver(pluginPath);
+            _sharedAssemblies = sharedAssemblies;
+            _mainLoadContext = mainLoadContext;
+
+            if (string.IsNullOrEmpty(AppContext.BaseDirectory))
+            {
+                // See https://github.com/dotnet/runtime/blob/v6.0.0/src/libraries/System.Private.CoreLib/src/System/AppContext.AnyOS.cs#L17-L35
+                // but Assembly.Location is unavailable, because we load assemblies from memory.
+                string? baseDirectory = Path.GetDirectoryName(pluginPath);
+                if (baseDirectory != null)
+                {
+                    if (!Path.EndsInDirectorySeparator(baseDirectory))
+                        baseDirectory += Path.DirectorySeparatorChar;
+                    // This SetData call effectively sets AppContext.BaseDirectory
+                    // See https://github.com/dotnet/runtime/blob/v6.0.0/src/libraries/System.Private.CoreLib/src/System/AppContext.cs#L21-L25
+                    AppDomain.CurrentDomain.SetData("APP_CONTEXT_BASE_DIRECTORY", baseDirectory);
+                }
+                else
+                {
+                    // TODO: How to log from GodotPlugins? (delegate pointer?)
+                    Console.Error.WriteLine("Failed to set AppContext.BaseDirectory. Dynamic loading of libraries may fail.");
+                }
+            }
+        }
+
+        protected override Assembly? Load(AssemblyName assemblyName)
+        {
+            if (assemblyName.Name == null)
+                return null;
+
+            if (_sharedAssemblies.Contains(assemblyName.Name))
+                return _mainLoadContext.LoadFromAssemblyName(assemblyName);
+
+            string? assemblyPath = _resolver.ResolveAssemblyToPath(assemblyName);
+            if (assemblyPath != null)
+            {
+                AssemblyLoadedPath = assemblyPath;
+
+                // Load in memory to prevent locking the file
+                using var assemblyFile = File.Open(assemblyPath, FileMode.Open, FileAccess.Read, FileShare.Read);
+                string pdbPath = Path.ChangeExtension(assemblyPath, ".pdb");
+
+                if (File.Exists(pdbPath))
+                {
+                    using var pdbFile = File.Open(pdbPath, FileMode.Open, FileAccess.Read, FileShare.Read);
+                    return LoadFromStream(assemblyFile, pdbFile);
+                }
+
+                return LoadFromStream(assemblyFile);
+            }
+
+            return null;
+        }
+
+        protected override IntPtr LoadUnmanagedDll(string unmanagedDllName)
+        {
+            string? libraryPath = _resolver.ResolveUnmanagedDllToPath(unmanagedDllName);
+            if (libraryPath != null)
+                return LoadUnmanagedDllFromPath(libraryPath);
+
+            return IntPtr.Zero;
+        }
+    }
+}