Add Lua debug logging API

example/assets/games/flight/scripts/runtime_defs.lua

@@ -552,6 +552,7 @@
 
 ---@class RuntimeImportApi
 ---@field import fun(moduleName: string): table
+---@field log fun(...: any)
 
 ---@type RuntimeImportApi
 runtime = runtime

example/assets/games/ludo/scripts/runtime_defs.lua

@@ -552,6 +552,7 @@
 
 ---@class RuntimeImportApi
 ---@field import fun(moduleName: string): table
+---@field log fun(...: any)
 
 ---@type RuntimeImportApi
 runtime = runtime

example/assets/games/showcase/scripts/runtime_defs.lua

@@ -552,6 +552,7 @@
 
 ---@class RuntimeImportApi
 ---@field import fun(moduleName: string): table
+---@field log fun(...: any)
 
 ---@type RuntimeImportApi
 runtime = runtime

example/assets/games/template/scripts/runtime_defs.lua

@@ -552,6 +552,7 @@
 
 ---@class RuntimeImportApi
 ---@field import fun(moduleName: string): table
+---@field log fun(...: any)
 
 ---@type RuntimeImportApi
 runtime = runtime

lib/runtime/diagnostics/runtime_diagnostics.dart

@@ -130,6 +130,7 @@ String _formatDebugValue(Object? value) {
 }
 
 enum RuntimeDiagnosticType {
+  luaLog,
   luaEventError,
   diffApplyError,
   packageActivationError,

lib/runtime/game/lua_game_widget.dart

@@ -1,6 +1,7 @@
 import 'package:flame/game.dart';
 import 'package:flutter/widgets.dart';
 
+import '../diagnostics/runtime_diagnostics.dart';
 import '../packages/game_package_repository.dart';
 import '../scripting/lua_dardo_script_engine.dart';
 import 'flame_lua_game.dart';
@@ -24,10 +25,13 @@ class LuaGameWidget extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
+    final diagnostics = RuntimeDiagnostics();
     return GameWidget(
       game: FlameLuaGame(
-        scriptEngine: LuaDardoScriptEngine(),
+        scriptEngine: LuaDardoScriptEngine(diagnostics: diagnostics),
-        scriptEngineFactory: LuaDardoScriptEngine.new,
+        scriptEngineFactory: () =>
+            LuaDardoScriptEngine(diagnostics: diagnostics),
+        diagnostics: diagnostics,
         packageRepository:
             packageRepository ??
             (serverUrl == null

lib/runtime/scripting/lua_dardo_script_engine.dart

@@ -1,11 +1,16 @@
 import 'package:lua_dardo_plus/lua.dart';
 
+import '../diagnostics/runtime_diagnostics.dart';
 import '../models/game_diff.dart';
 import '../models/runtime_event.dart';
 import '../packages/game_package.dart';
 import 'script_engine.dart';
 
 class LuaDardoScriptEngine implements ScriptEngine {
+  LuaDardoScriptEngine({RuntimeDiagnostics? diagnostics})
+    : _diagnostics = diagnostics;
+
+  final RuntimeDiagnostics? _diagnostics;
   late final LuaState _lua;
   late final Map<String, String> _moduleScripts;
   final Set<String> _loadingModules = {};
@@ -104,9 +109,28 @@ class LuaDardoScriptEngine implements ScriptEngine {
     _lua.pushDartFunction(_importModule);
     _lua.setField(-2, 'import');
 
+    _lua.pushDartFunction(_log);
+    _lua.setField(-2, 'log');
+
     _lua.setGlobal('runtime');
   }
 
+  int _log(LuaState lua) {
+    final argumentCount = lua.getTop();
+    final messageParts = <String>[];
+    for (var index = 1; index <= argumentCount; index++) {
+      messageParts.add(_formatLuaLogValue(lua, index));
+    }
+    final message = messageParts.join(' ');
+
+    _diagnostics?.record(
+      type: RuntimeDiagnosticType.luaLog,
+      message: message,
+      context: {'argumentCount': argumentCount},
+    );
+    return 0;
+  }
+
   int _importModule(LuaState lua) {
     final moduleName = lua.toStr(1);
     if (moduleName == null || moduleName.isEmpty) {
@@ -179,6 +203,25 @@ class LuaDardoScriptEngine implements ScriptEngine {
     }
   }
 
+  String _formatLuaLogValue(LuaState lua, int index) {
+    if (lua.isNil(index) || lua.isNone(index)) {
+      return 'nil';
+    }
+    if (lua.isBoolean(index)) {
+      return lua.toBoolean(index).toString();
+    }
+    if (lua.isInteger(index)) {
+      return lua.toInteger(index).toString();
+    }
+    if (lua.isNumber(index)) {
+      return lua.toNumber(index).toString();
+    }
+    if (lua.isString(index)) {
+      return lua.toStr(index) ?? '';
+    }
+    return lua.typeName2(index);
+  }
+
   bool _isSafeModuleName(String value) {
     return RegExp(r'^[A-Za-z0-9_.-]+$').hasMatch(value) &&
         !value.contains('..') &&

test/runtime/scripting/lua_dardo_script_engine_test.dart

@@ -1,5 +1,6 @@
 import 'dart:io';
 
+import 'package:flame_lua_runtime/runtime/diagnostics/runtime_diagnostics.dart';
 import 'package:flame_lua_runtime/runtime/packages/game_package.dart';
 import 'package:flame_lua_runtime/runtime/packages/game_package_manifest.dart';
 import 'package:flame_lua_runtime/runtime/models/runtime_event.dart';
@@ -895,6 +896,51 @@ end
       expect(c.y, 53);
     });
 
+    test('runtime.log records Lua debug messages in diagnostics', () async {
+      final package = await _createPackage(
+        mainScript: '''
+function smoke_test(ctx)
+  runtime.log("smoke", ctx.runtimeApiVersion)
+  return true
+end
+
+function init(ctx)
+  runtime.log("init", true, nil)
+  return {}
+end
+
+function on_event(event)
+  runtime.log("event", event.type, event.target)
+  return {}
+end
+''',
+      );
+      final diagnostics = RuntimeDiagnostics();
+      final engine = LuaDardoScriptEngine(diagnostics: diagnostics);
+
+      await engine.loadPackage(package);
+      expect(engine.smokeTest({'runtimeApiVersion': 1}), isTrue);
+      engine.init({'runtimeApiVersion': 1});
+      engine.dispatchEvent(
+        const RuntimeEvent(
+          type: RuntimeEventType.tap,
+          target: 'debug_button',
+          handler: 'debug',
+        ),
+      );
+
+      expect(
+        diagnostics.entries.map((entry) => entry.type),
+        everyElement(RuntimeDiagnosticType.luaLog),
+      );
+      expect(diagnostics.entries.map((entry) => entry.message), [
+        'smoke 1',
+        'init true nil',
+        'event tap debug_button',
+      ]);
+      expect(diagnostics.entries.first.context, {'argumentCount': 2});
+    });
+
     test('rejects undeclared module imports', () async {
       final package = await _createPackage(
         mainScript: '''

tool/lua_runtime_defs_common.lua

@@ -552,6 +552,7 @@
 
 ---@class RuntimeImportApi
 ---@field import fun(moduleName: string): table
+---@field log fun(...: any)
 
 ---@type RuntimeImportApi
 runtime = runtime