fix: introduce a custom AssemblyResolver to resolve AssemblyResolutionException in Mono.Cecil

Assets/Scripts/Editor/AssemblyPostProcess/AddInternalsVisibleToForAllUserAssembliesPostProcess.cs

@@ -1,4 +1,7 @@
-using System.IO;
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
 using System.Reflection;
 using Mono.Cecil;
 using UnityEditor;
@@ -7,21 +10,22 @@
 namespace FastScriptReload.Editor.AssemblyPostProcess
 {
     [InitializeOnLoad]
-    public static class AddInternalsVisibleToForAllUserAssembliesPostProcess 
+    public static class AddInternalsVisibleToForAllUserAssembliesPostProcess
     {
         public static readonly DirectoryInfo AdjustedAssemblyRoot;
 
         static AddInternalsVisibleToForAllUserAssembliesPostProcess()
         {
             AdjustedAssemblyRoot = new DirectoryInfo(Path.Combine(Application.dataPath, "..", "Temp", "Fast Script Reload", "AdjustedDlls"));
         }
-        
+
         public static string CreateAssemblyWithInternalsContentsVisibleTo(Assembly changedAssembly, string visibleToAssemblyName)
         {
-            if(!AdjustedAssemblyRoot.Exists)
-                    AdjustedAssemblyRoot.Create();
+            if (!AdjustedAssemblyRoot.Exists)
+                AdjustedAssemblyRoot.Create();
 
-            using (var assembly = AssemblyDefinition.ReadAssembly(changedAssembly.Location, new ReaderParameters { ReadWrite = false }))
+            var assemblyResolver = new UnityMonoEditorAssemblyResolver(changedAssembly.Location);
+            using (var assembly = AssemblyDefinition.ReadAssembly(changedAssembly.Location, new ReaderParameters { ReadWrite = false, AssemblyResolver = assemblyResolver }))
             {
                 var mainModule = assembly.MainModule;
 
@@ -35,12 +39,106 @@ public static string CreateAssemblyWithInternalsContentsVisibleTo(Assembly chang
                 );
 
                 assembly.CustomAttributes.Add(attribute);
-                
+
                 var newAssemblyPath = new FileInfo(Path.Combine(AdjustedAssemblyRoot.FullName, assembly.Name.Name) + ".dll").FullName;
                 assembly.Write(newAssemblyPath);
 
                 return newAssemblyPath;
             }
         }
     }
+
+    class UnityMonoEditorAssemblyResolver : IAssemblyResolver
+    {
+        static readonly HashSet<string> s_unityEditorSearchDirs;
+        static UnityMonoEditorAssemblyResolver()
+        {
+            // s_unityEditorSearchDirs will be populated on each domain reload
+            s_unityEditorSearchDirs = new();
+            foreach (var loadedAssembly in AppDomain.CurrentDomain.GetAssemblies())
+            {
+                if (loadedAssembly.IsDynamic) continue;
+                if (!File.Exists(loadedAssembly.Location)) continue;
+                var assemblyDir = Path.GetDirectoryName(loadedAssembly.Location);
+                s_unityEditorSearchDirs.Add(assemblyDir);
+            }
+        }
+
+        private Dictionary<string, AssemblyDefinition> cache;
+        private string majorSearchDir;
+
+        public UnityMonoEditorAssemblyResolver(string targetAssemblyPath)
+        {
+            cache = new();
+            majorSearchDir = Path.GetDirectoryName(targetAssemblyPath);
+        }
+
+        private AssemblyDefinition GetAssembly(string file, ReaderParameters parameters)
+        {
+            parameters.AssemblyResolver ??= this;
+            return ModuleDefinition.ReadModule(file, parameters).Assembly;
+        }
+
+        private bool TryResolveAssemblyInDirectory(string directory, ReaderParameters parameters, AssemblyNameReference name, out AssemblyDefinition assembly)
+        {
+            const string AssemblyExtension = ".dll";
+            var filepath = Path.Combine(directory, name.Name + AssemblyExtension);
+            assembly = null;
+            if (File.Exists(filepath))
+            {
+                try
+                {
+                    assembly = GetAssembly(filepath, parameters);
+                    return true;
+                }
+                catch { }
+            }
+
+            return false;
+        }
+
+        private AssemblyDefinition ResolveInternalCacheLess(AssemblyNameReference name, ReaderParameters parameters)
+        {
+            if (TryResolveAssemblyInDirectory(majorSearchDir, parameters, name, out var assembly))
+            {
+                return assembly;
+            }
+
+            foreach (var dir in s_unityEditorSearchDirs)
+            {
+                if (TryResolveAssemblyInDirectory(dir, parameters, name, out assembly))
+                {
+                    return assembly;
+                }
+            }
+
+            throw new AssemblyResolutionException(name);
+        }
+
+        public AssemblyDefinition Resolve(AssemblyNameReference name)
+        {
+            return Resolve(name, new ReaderParameters());
+        }
+
+        public AssemblyDefinition Resolve(AssemblyNameReference name, ReaderParameters parameters)
+        {
+            if (!cache.TryGetValue(name.FullName, out var value))
+            {
+                cache[name.FullName] = value = ResolveInternalCacheLess(name, parameters);
+            }
+
+            return value;
+        }
+
+        public void Dispose()
+        {
+            foreach (var (path, assembly) in cache)
+            {
+                assembly.Dispose();
+            }
+
+            cache.Clear();
+        }
+
+    }
 }