feat: in Unity 2020.2 or later, initialize CSharpCompilerSettings for first compilation

Author: mob-sakai

Plugins/ExternalCSharpCompiler.meta

@@ -0,0 +1,16 @@
+{
+    "name": "ExternalCSharpCompiler_",
+    "references": [],
+    "optionalUnityReferences": [],
+    "includePlatforms": [
+        "Editor"
+    ],
+    "excludePlatforms": [],
+    "allowUnsafeCode": false,
+    "overrideReferences": false,
+    "precompiledReferences": [],
+    "autoReferenced": false,
+    "defineConstraints": [
+        "CSC_SETTINGS_DEVELOP"
+    ]
+}

Plugins/ExternalCSharpCompiler/ExternalCSharpCompiler.asmdef

@@ -0,0 +1,65 @@
+using System;
+using System.IO;
+using UnityEditor;
+using System.Linq;
+using System.Reflection;
+using System.Runtime.CompilerServices;
+
+namespace Coffee.CSharpCompilerSettings
+{
+    internal class ExternalCSharpCompiler
+    {
+        [InitializeOnLoadMethod]
+        static void InitializeOnLoad()
+        {
+            var coreAssemblyName = typeof(ExternalCSharpCompiler).Assembly.GetName().Name;
+            if (coreAssemblyName == "ExternalCSharpCompiler_") return;
+
+            Console.WriteLine("[CSharpCompilerSettings] Initialize CSharpCompilerSettings for first compilation: " + typeof(ExternalCSharpCompiler));
+
+            var filepath = "Temp/" + typeof(ExternalCSharpCompiler).Assembly.GetName().Name + ".loaded";
+            if (File.Exists(filepath)) return;
+            File.WriteAllText(filepath, "");
+
+            var cscTypes = AssetDatabase.FindAssets("t:DefaultAsset CSharpCompilerSettings")
+                .Select(AssetDatabase.GUIDToAssetPath)
+                .Where(x => x.EndsWith(".dll"))
+                .Select(Assembly.LoadFrom)
+                .SelectMany(x => x.GetTypes())
+                .ToArray();
+
+            var initializeOnLoadTypes = cscTypes
+                .Where(x => 0 < x.GetCustomAttributes(typeof(InitializeOnLoadAttribute), false).Length);
+
+            var initializeOnLoadMethods = cscTypes
+                .SelectMany(x => x.GetMethods(BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic))
+                .Where(x => 0 < x.GetCustomAttributes(typeof(InitializeOnLoadMethodAttribute), false).Length);
+
+            foreach (var type in initializeOnLoadTypes)
+            {
+                try
+                {
+                    Console.WriteLine("  > InitializeOnLoadAttribute: " + type);
+                    RuntimeHelpers.RunClassConstructor(type.TypeHandle);
+                }
+                catch (Exception e)
+                {
+                    Console.Error.WriteLine(e.ToString());
+                }
+            }
+
+            foreach (var method in initializeOnLoadMethods)
+            {
+                try
+                {
+                    Console.WriteLine("  > InitializeOnLoadMethodAttribute: " + method);
+                    method.Invoke(null, new object[0]);
+                }
+                catch (Exception e)
+                {
+                    Console.Error.WriteLine(e.ToString());
+                }
+            }
+        }
+    }
+}