Optional recursive dependency pulls and fallback dependency load (#1595)

* Optional recursive dependency pulls and fallback dependency load

* add api10 todo

---------

Co-authored-by: goat <16760685+goaaats@users.noreply.github.com>

Dalamud/Plugin/Internal/Loader/AssemblyLoadContextBuilder.cs

@@ -131,9 +131,16 @@ internal class AssemblyLoadContextBuilder
     /// or the default app context.
     /// </summary>
     /// <param name="assemblyName">The name of the assembly.</param>
+    /// <param name="recursive">Pull assmeblies recursively.</param>
     /// <returns>The builder.</returns>
-    public AssemblyLoadContextBuilder PreferDefaultLoadContextAssembly(AssemblyName assemblyName)
+    public AssemblyLoadContextBuilder PreferDefaultLoadContextAssembly(AssemblyName assemblyName, bool recursive)
     {
+        if (!recursive)
+        {
+            this.defaultAssemblies.Add(assemblyName.Name);
+            return this;
+        }
+
         var names = new Queue<AssemblyName>(new[] { assemblyName });
 
         while (names.TryDequeue(out var name))

Dalamud/Plugin/Internal/Loader/LoaderConfig.cs

@@ -46,7 +46,7 @@ internal class LoaderConfig
     /// Gets a list of assemblies which should be unified between the host and the plugin.
     /// </summary>
     /// <seealso href="https://github.com/natemcmaster/DotNetCorePlugins/blob/main/docs/what-are-shared-types.md">what-are-shared-types</seealso>
-    public ICollection<AssemblyName> SharedAssemblies { get; } = new List<AssemblyName>();
+    public ICollection<(AssemblyName Name, bool Recursive)> SharedAssemblies { get; } = new List<(AssemblyName Name, bool Recursive)>();
 
     /// <summary>
     /// Gets or sets a value indicating whether attempt to unify all types from a plugin with the host.

Dalamud/Plugin/Internal/Loader/ManagedLoadContext.cs

@@ -194,7 +194,18 @@ internal class ManagedLoadContext : AssemblyLoadContext
             }
         }
 
-        return null;
+        // https://learn.microsoft.com/en-us/dotnet/core/dependency-loading/loading-managed#algorithm
+        // > These assemblies are loaded (load-by-name) as needed by the runtime.
+        // For load-by-name assembiles, the following will happen in order:
+        // (1) this.Load will be called.
+        // (2) AssemblyLoadContext.Default's cache will be referred for lookup.
+        // (3) Default probing will be done from PLATFORM_RESOURCE_ROOTS and APP_PATHS.
+        // https://learn.microsoft.com/en-us/dotnet/core/dependency-loading/default-probing#managed-assembly-default-probing
+        // > TRUSTED_PLATFORM_ASSEMBLIES: List of platform and application assembly file paths.
+        // > APP_PATHS: is not populated by default and is omitted for most applications.
+        // If we return null here, if the assembly has not been already loaded, the resolution will fail.
+        // Therefore as the final attempt, we try loading from the default load context.
+        return this.defaultLoadContext.LoadFromAssemblyName(assemblyName);
     }
 
     /// <summary>

Dalamud/Plugin/Internal/Loader/PluginLoader.cs

@@ -146,18 +146,14 @@ internal class PluginLoader : IDisposable
             builder.ShadowCopyNativeLibraries();
         }
 
-        foreach (var assemblyName in config.SharedAssemblies)
+        foreach (var (assemblyName, recursive) in config.SharedAssemblies)
         {
-            builder.PreferDefaultLoadContextAssembly(assemblyName);
+            builder.PreferDefaultLoadContextAssembly(assemblyName, recursive);
         }
 
-        // This allows plugins to search for dependencies in the Dalamud directory when their assembly
-        // load would otherwise fail, allowing them to resolve assemblies not already loaded by Dalamud
-        // itself yet.
-        builder.AddProbingPath(Path.GetDirectoryName(Assembly.GetExecutingAssembly().Location));
-
-        // Also make sure that plugins do not load their own Dalamud assembly.
-        builder.PreferDefaultLoadContextAssembly(Assembly.GetExecutingAssembly().GetName());
+        // Note: not adding Dalamud path here as a probing path.
+        // It will be dealt as the last resort from ManagedLoadContext.Load.
+        // See there for more details.
 
         return builder;
     }

Dalamud/Plugin/Internal/Types/LocalPlugin.cs

@@ -627,8 +627,18 @@ internal class LocalPlugin : IDisposable
         config.IsUnloadable = true;
         config.LoadInMemory = true;
         config.PreferSharedTypes = false;
-        config.SharedAssemblies.Add(typeof(Lumina.GameData).Assembly.GetName());
-        config.SharedAssemblies.Add(typeof(Lumina.Excel.ExcelSheetImpl).Assembly.GetName());
+
+        // Pin Lumina and its dependencies recursively (compatibility behavior).
+        // It currently only pulls in System.* anyway.
+        // TODO(api10): Remove this. We don't want to pin Lumina anymore, plugins should be able to provide their own.
+        config.SharedAssemblies.Add((typeof(Lumina.GameData).Assembly.GetName(), true));
+        config.SharedAssemblies.Add((typeof(Lumina.Excel.ExcelSheetImpl).Assembly.GetName(), true));
+
+        // Make sure that plugins do not load their own Dalamud assembly.
+        // We do not pin this recursively; if a plugin loads its own assembly of Dalamud, it is always wrong,
+        // but plugins may load other versions of assemblies that Dalamud depends on.
+        config.SharedAssemblies.Add((typeof(EntryPoint).Assembly.GetName(), false));
+        config.SharedAssemblies.Add((typeof(Common.DalamudStartInfo).Assembly.GetName(), false));
     }
 
     private void EnsureLoader()