refactor: optimize, performance and the following

- remove old logic
- public interface updates
- text encoding option
- follow attribute guideline
- OverwriteIfFileExists is now enabled by default

Editor/Attributes.cs

@@ -1,18 +1,23 @@
 using System;
+using System.Text;
 
 namespace SatorImaging.UnitySourceGenerator
 {
     ///<summary>NOTE: Implement "IUnitySourceGenerator" (C# 11.0)</summary>
     [AttributeUsage(AttributeTargets.Class, Inherited = false, AllowMultiple = false)]
     public sealed class UnitySourceGeneratorAttribute : Attribute
     {
+        Type generatorClass;
+
         public UnitySourceGeneratorAttribute(Type generatorClass = null)
         {
-            GeneratorClass = generatorClass;
+            this.generatorClass = generatorClass;
         }
 
-        public bool OverwriteIfFileExists { get; set; } = false;
-        public Type GeneratorClass { get; set; }
+        public Type GeneratorClass => generatorClass;
+
+        public bool OverwriteIfFileExists { get; set; } = true;
+        public Encoding OutputFileEncoding { get; set; } = Encoding.UTF8;
 
     }
 }

Editor/USGEngine.cs

@@ -15,19 +15,22 @@ namespace SatorImaging.UnitySourceGenerator
 {
     public class USGEngine : AssetPostprocessor
     {
-        ///<summary>This will be disabled after Unity Editor import event automatically.</summary>
+        ///<summary>This will be disabled automatically after Unity Editor import event.</summary>
         public static bool IgnoreOverwriteSettingByAttribute = false;
 
 
+        const int BUFFER_LENGTH = 61_440;
+        const int BUFFER_MAX_CHAR_LENGTH = BUFFER_LENGTH / 3;  // worst case of UTF-8
         const string GENERATOR_PREFIX = ".";
         const string GENERATOR_EXT = ".g";
-        const string GENERATOR_DIR = @"/USG.g";   // don't append last slash. this is used by .EndsWith()
+        const string GENERATOR_DIR = @"/USG.g";   // don't append last slash. used to determine file is generated one or not.
         const string ASSETS_DIR_NAME = "Assets";
-        const string ASSETS_DIR_SLASH = "Assets/";
+        const string ASSETS_DIR_SLASH = ASSETS_DIR_NAME + "/";
         const string TARGET_FILE_EXT = @".cs";
         const string PATH_PREFIX_TO_IGNORE = @"Packages/";
         readonly static char[] DIR_SEPARATORS = new char[] { '\\', '/' };
 
+        // OPTIMIZE: Avoiding explicit static ctor is best practice for performance???
         readonly static string s_projectDirPath;
         static USGEngine()
         {
@@ -36,76 +39,67 @@ static USGEngine()
                 s_projectDirPath = s_projectDirPath.Substring(0, s_projectDirPath.Length - ASSETS_DIR_NAME.Length);
         }
 
-        readonly static HashSet<string> s_targetFilePaths = new();
-        static void AddAppropriateTarget(string filePath)
+        static bool IsAppropriateTarget(string filePath)
         {
             if (!filePath.EndsWith(TARGET_FILE_EXT) ||
                 !filePath.StartsWith(ASSETS_DIR_SLASH))
             {
-                return;
+                return false;
             }
-            s_targetFilePaths.Add(filePath);
-        }
-
-
-        void OnPreprocessAsset()
-        {
-            AddAppropriateTarget(assetPath);
+            return true;
         }
 
 
-        // NOTE: To avoid event invoked twice on file deletion.
-        static bool s_processingJobQueued = false;
-
         static void OnPostprocessAllAssets(
             string[] importedAssets, string[] deletedAssets, string[] movedAssets, string[] movedFromAssetPaths)
         {
             // NOTE: Do NOT handle deleted assets because Unity tracking changes perfectly.
             //       Even if delete file while Unity shutted down, asset deletion event happens on next Unity launch.
             //       As a result, delete/import event loops infinitely and file cannot be deleted.
-            for (int i = 0; i < importedAssets.Length; i++)
-            {
-                AddAppropriateTarget(importedAssets[i]);
-            }
-
-            if (s_processingJobQueued) return;
-            s_processingJobQueued = true;
 
             // TODO: Unity sometimes reloads updated scripts by Visual Studio in background automatically.
             //       In this situation, code generation will be done with script data right before saving.
             //       It cannot be solved on C#, simply restart Unity.
             //       Using [DidReloadScripts] or EditorApplication.delayCall, It works fine with Reimport
             //       menu command but OnPostprocessAllAssets event doesn't work as expected.
-            //       (script runs with static field cleared even though .Clear() is only in ProcessingFiles())
+            //       (script runs with static field cleared even though .Clear() is only in ProcessingFiles().
+            //        it's weird that event happens and asset paths retrieved but hashset items gone.)
             ////EditorApplication.delayCall += () =>
             {
-                ProcessingFiles();
+                ProcessingFiles(importedAssets);
             };
         }
 
 
         readonly static HashSet<string> s_updatedGeneratorNames = new();
-        static void ProcessingFiles()
+        static void ProcessingFiles(string[] targetPaths)
         {
             bool somethingUpdated = false;
-            foreach (string path in s_targetFilePaths)
+            for (int i = 0; i < targetPaths.Length; i++)
             {
-                if (ProcessFile(path))
+                // NOTE: Do NOT early return in this method.
+                //       check path here to allow generator class can be lie outside of Assets/ folder.
+                if (!IsAppropriateTarget(targetPaths[i])) continue;
+
+                if (ProcessFile(targetPaths[i]))
                     somethingUpdated = true;
             }
 
             // TODO: more efficient way to process related targets
+            var overwriteEnabledByCaller = IgnoreOverwriteSettingByAttribute;
             foreach (var generatorName in s_updatedGeneratorNames)
             {
                 foreach (var info in s_typeNameToInfo.Values)
                 {
-                    if (info.TargetClass == null) continue;
-                    if (info.Attribute.GeneratorClass?.Name != generatorName) continue;
+                    if (info.TargetClass == null ||
+                        info.Attribute.GeneratorClass?.Name != generatorName)
+                        continue;
 
-                    var path = USGUtility.GetScriptFileByName(info.TargetClass.Name);
-                    if (path != null)
+                    var path = USGUtility.GetAssetPathByName(info.TargetClass.Name);
+                    if (path != null && IsAppropriateTarget(path))
                     {
-                        IgnoreOverwriteSettingByAttribute = true;
+                        IgnoreOverwriteSettingByAttribute = overwriteEnabledByCaller
+                            || info.Attribute.OverwriteIfFileExists;
                         if (ProcessFile(path))
                             somethingUpdated = true;
                     }
@@ -114,11 +108,10 @@ static void ProcessingFiles()
 
             if (somethingUpdated)
                 AssetDatabase.Refresh();
-            s_targetFilePaths.Clear();
+
             s_updatedGeneratorNames.Clear();
 
             IgnoreOverwriteSettingByAttribute = false;  // always turn it off.
-            s_processingJobQueued = false;
         }
 
 
@@ -176,15 +169,14 @@ public static bool ProcessFile(string assetsRelPath)
             outputPath = Path.Combine(outputPath, info.OutputFileName);
 
 
+            // do it.
             var context = new USGContext
             {
                 TargetClass = info.TargetClass,
                 AssetPath = assetsRelPath.Replace('\\', '/'),
                 OutputPath = outputPath.Replace('\\', '/'),
             };
 
-
-            // do it.
             var sb = new StringBuilder();
             sb.AppendLine($"// <auto-generated>{generatorCls.Name}</auto-generated>");
 
@@ -199,25 +191,44 @@ public static bool ProcessFile(string assetsRelPath)
                 throw;
             }
 
+            //save??
             if (!isSaveFile || sb == null || string.IsNullOrWhiteSpace(context.OutputPath))
                 return false;
 
+            if (File.Exists(context.OutputPath) &&
+                (!info.Attribute.OverwriteIfFileExists && !IgnoreOverwriteSettingByAttribute)
+                )
+            {
+                return false;
+            }
 
 
             var outputDir = Path.GetDirectoryName(context.OutputPath);
             if (!Directory.Exists(outputDir)) Directory.CreateDirectory(outputDir);
 
-            if (File.Exists(context.OutputPath) &&
-                (!info.Attribute.OverwriteIfFileExists && !IgnoreOverwriteSettingByAttribute)
-                )
+#if UNITY_2021_3_OR_NEWER
+
+            // OPTIMIZE: use sb.GetChunks() in future release of Unity. 2021 LTS doesn't support it.
+            using (var fs = new FileStream(context.OutputPath, FileMode.Create, FileAccess.Write))
             {
-                return false;
+                Span<byte> buffer = stackalloc byte[BUFFER_LENGTH];
+                var span = sb.ToString().AsSpan();
+                for (int i = 0; i < span.Length; i += BUFFER_MAX_CHAR_LENGTH)
+                {
+                    var len = BUFFER_MAX_CHAR_LENGTH;
+                    if (len + i > span.Length) len = span.Length - i;
+
+                    int written = info.Attribute.OutputFileEncoding.GetBytes(span.Slice(i, len), buffer);
+                    fs.Write(buffer.Slice(0, written));
+                }
+                fs.Flush();
             }
 
+#else
+            File.WriteAllText(context.OutputPath, sb.ToString(), info.Attribute.OutputFileEncoding);
+#endif
 
-            File.WriteAllText(context.OutputPath, sb.ToString());
             Debug.Log($"[{nameof(UnitySourceGenerator)}] Generated: {context.OutputPath}");
-
             return true;
         }
 

Editor/USGUtility.cs

@@ -26,9 +26,10 @@ static void ForceGenerateSelectedScripts()
         }
 
 
-        public static void ForceGenerate(string clsName, bool showInProjectPanel = true)
+        ///<summary>UNSAFE on use in build event due to this method calls fancy UI methods and fire import event. Use `GetAssetPathByName()` instead.</summary>
+        public static void ForceGenerateInEditor(string clsName, bool showInProjectPanel = true)
         {
-            var path = GetScriptFileByName(clsName);
+            var path = GetAssetPathByName(clsName);
             if (path == null) return;
 
             if (showInProjectPanel)
@@ -38,7 +39,8 @@ public static void ForceGenerate(string clsName, bool showInProjectPanel = true)
         }
 
 
-        internal static string GetScriptFileByName(string clsName)
+        ///<summary>Returns "Assets/" rooted path of the script file.</summary>
+        public static string GetAssetPathByName(string clsName)
         {
             var GUIDs = AssetDatabase.FindAssets(clsName);
             foreach (var GUID in GUIDs)

README.md

@@ -36,6 +36,8 @@ As you already know, Roslyn's source generator is too sophisticated. This framew
 - [Copyright](#copyright)
 - [License](#license)
 - [Devnote](#devnote)
+    - [TODO](#todo)
+    - [Memo](#memo)
 
 <!------- End of Details EN Tag -------></details></p>
 
@@ -132,7 +134,7 @@ namespace Sample
 
 Here is target-less generator example.
 
-It is useful to generate static database that cannot be generated on Unity runtime. For example, asset GUIDs database, resource integrity tables, etc.
+It is useful to generate static database that cannot be generated on Unity runtime. For example, build asset GUIDs database using `UnityEditor.AssetDatabase`, resource integrity tables, etc.
 
 
 
@@ -206,12 +208,12 @@ There are utility functions to perform source code generation on build event.
 
 
 ```csharp
-// perform by known asset path.
-USGEngine.IgnoreOverwriteSettingByAttribute = true;  // force overwrite
-USGEngine.ProcessFile(pathToGeneratorScriptFile);
+// search by class name if you don't know where it is.
+var assetPath = USGUtility.GetAssetPathByName(nameof(MinimalGenerator));
 
-// search by class name.
-USGUtility.ForceGenerate(nameof(MinimalGenerator));
+// perform code generation.
+USGEngine.IgnoreOverwriteSettingByAttribute = true;  // force overwrite
+USGEngine.ProcessFile(assetPath);
 ```
 
 
@@ -355,4 +357,16 @@ SOFTWARE.
 
 # Devnote
 
+
+## TODO
+
+- Add new attribute option `UseCustomWriter` to use it's own file writer instead of builtin writer. For the "non-allocation" addicted developers.
+    - `USGEngine.ProcessingFile()` doesn't care what happens in custom writer. just returns true in this situation.
+    - Option is for generator class. Referenced generator class doesn't have `UnitySourceGenerator` attribute so that need to retrieve it from target classes. (how handle conflicts?)
+    - `USGContext.UseCustomWriter` can be used to prevent writing file but `StringBuilder` is built prior to `Emit()` method.
+
+
+
+## Memo
+
 Unity doesn't invoke import event if Visual Studio is not launch by current session of Unity...?

package.json

@@ -1,7 +1,7 @@
 {
   "name": "com.sator-imaging.alt-source-generator",
   "displayName": "Alternative Source Generator for Unity",
-  "version": "1.1.0",
+  "version": "1.2.0",
   "unity": "2021.3",
   "description": "Ease-of-Use Source Generator Alternative for Unity.",
   "author": {