[native_doc_dartifier] Retry loop to fix compile errors of generated snippets (#2416)

* Add a simple retry loop that attempts to fix compilation errors in the generated Dart snippets.
* Switched to using a chat-based interface instead of independent prompts.

Author: marshelino-maged

pkgs/native_doc_dartifier/lib/src/code_processor.dart

@@ -0,0 +1,82 @@
+// Copyright (c) 2025, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io';
+
+class CodeProcessor {
+  final Directory _tempDir;
+  final String _dartifiedCodeFileName = 'dartified_code.dart';
+  final String _helperCodeFileName = 'helper_code.dart';
+
+  CodeProcessor() : _tempDir = Directory('${Directory.current.path}/temp') {
+    if (!_tempDir.existsSync()) {
+      _tempDir.createSync(recursive: true);
+    }
+  }
+
+  Future<String> analyzeCode(String mainCode, String helperCode) async {
+    await _saveCodeToFile(mainCode, helperCode);
+    final dartifiedFile = File('${_tempDir.path}/$_dartifiedCodeFileName');
+    final analysisResult = await Process.run('dart', [
+      'analyze',
+      dartifiedFile.absolute.path,
+    ], runInShell: true);
+
+    var errorMessage = '';
+    if (analysisResult.exitCode != 0) {
+      final allLines = analysisResult.stdout.toString().trim().split('\n');
+      final errorLines =
+          allLines.where((line) => line.trim().startsWith('error -')).toList();
+
+      errorMessage = errorLines.join('\n');
+      print(errorMessage);
+    } else {
+      print('Dart analysis completed successfully with no errors.');
+    }
+    await _cleanUp();
+    return errorMessage;
+  }
+
+  Future<void> _saveCodeToFile(String mainCode, String helperCode) async {
+    try {
+      final dartifiedFile = File('${_tempDir.path}/$_dartifiedCodeFileName');
+      await dartifiedFile.writeAsString(mainCode);
+
+      final helperFile = File('${_tempDir.path}/$_helperCodeFileName');
+      await helperFile.writeAsString(helperCode);
+    } catch (e) {
+      print('Error saving code to file: $e');
+    }
+  }
+
+  String addImports(String code, List<String> imports) {
+    final buffer = StringBuffer();
+    for (final import in imports) {
+      buffer.writeln("import '$import';");
+    }
+    buffer.writeln("import '$_helperCodeFileName';");
+    buffer.writeln();
+    buffer.write(code);
+    return buffer.toString();
+  }
+
+  String removeImports(String code) {
+    final lines = code.split('\n');
+    final filteredLines = lines.where((line) => !line.startsWith('import'));
+    return filteredLines.join('\n');
+  }
+
+  Future<void> _cleanUp() async {
+    try {
+      if (await _tempDir.exists()) {
+        final files = _tempDir.listSync().whereType<File>();
+        for (final file in files) {
+          await file.delete();
+        }
+      }
+    } catch (e) {
+      print('Error cleaning up temporary directory: $e');
+    }
+  }
+}

pkgs/native_doc_dartifier/lib/src/dartify_code.dart

@@ -4,13 +4,14 @@
 
 import 'dart:io';
 import 'package:google_generative_ai/google_generative_ai.dart';
+import 'code_processor.dart';
 import 'prompts.dart';
 import 'public_abstractor.dart';
 
 Future<String> dartifyNativeCode(String sourceCode, String bindingsPath) async {
-  final file = File(bindingsPath);
+  final bindingsFile = File(bindingsPath);
 
-  if (!await file.exists()) {
+  if (!await bindingsFile.exists()) {
     stderr.writeln('File not found: $bindingsPath');
     exit(1);
   }
@@ -22,7 +23,7 @@ Future<String> dartifyNativeCode(String sourceCode, String bindingsPath) async {
     exit(1);
   }
 
-  final bindings = await file.readAsString();
+  final bindings = await bindingsFile.readAsString();
 
   final model = GenerativeModel(
     model: 'gemini-2.0-flash',
@@ -41,12 +42,35 @@ Future<String> dartifyNativeCode(String sourceCode, String bindingsPath) async {
     generateBindingsSummary(bindings),
   );
 
-  print('Prompt:\n${translatePrompt.prompt}\n');
+  final chatSession = model.startChat();
 
-  final content = [Content.text(translatePrompt.prompt)];
+  final response = await chatSession.sendMessage(
+    Content.text(translatePrompt.prompt),
+  );
+  var mainCode = translatePrompt.getParsedResponse(response.text ?? '');
+  var helperCode = '';
+
+  final codeProcessor = CodeProcessor();
+  mainCode = codeProcessor.addImports(mainCode, [
+    'package:jni/jni.dart',
+    bindingsFile.path,
+  ]);
 
-  final response = await model.generateContent(content);
-  final dartCode = translatePrompt.getParsedResponse(response.text ?? '');
+  for (var i = 0; i < 3; i++) {
+    final errorMessage = await codeProcessor.analyzeCode(mainCode, helperCode);
+    if (errorMessage.isEmpty) {
+      break;
+    }
+    stderr.writeln('Dart analysis found issues: $errorMessage');
+    final fixPrompt = FixPrompt(mainCode, helperCode, errorMessage);
+    final fixResponse = await chatSession.sendMessage(
+      Content.text(fixPrompt.prompt),
+    );
+    final fixedCode = fixPrompt.getParsedResponse(fixResponse.text ?? '');
 
-  return dartCode;
+    mainCode = fixedCode.mainCode;
+    helperCode = fixedCode.helperCode;
+  }
+  mainCode = codeProcessor.removeImports(mainCode);
+  return mainCode;
 }

pkgs/native_doc_dartifier/lib/src/prompts.dart

@@ -118,3 +118,61 @@ $_schema
     return dartCode;
   }
 }
+
+class FixPrompt implements Prompt {
+  final String mainDartCode;
+  final String helperDartCode;
+  final String analysisResult;
+
+  FixPrompt(this.mainDartCode, this.helperDartCode, this.analysisResult);
+
+  // Change this will require changing the getParsedResponse() method.
+  final String _schema = '''
+Output the response in JSON format:
+{
+  "mainDartCode": "Dart code here",
+  "helperDartCode": "Dart code here"
+}
+  ''';
+
+  @override
+  String get prompt => '''
+  You are an expert Dart code fixer. Your task is to fix the provided main Dart code based on the analysis results.
+  Here is the main Dart file code that needs fixing:
+  $mainDartCode
+  Here is the helper Dart file that you can use to add initialization code or other necessary imports to fix the issues in the main Dart code file:
+  $helperDartCode
+  Here are the issues found in the main Dart code:
+  $analysisResult
+
+  $_schema
+
+  try to add initialization or imports or whatever in the helper Dart file to fix the errors as the main Dart file import this helper Dart file.
+  change the main Dart file only if you can't fix the issues by adding code to the helper Dart file.
+  do not make a full initializaiton or completed code in the helper Dart file, just add the necessary code to fix the issues in the main Dart file even if not complete.
+
+  Make sure to not use a backslash (`\\`) before Dollar sign ('\$') in the Dart code, as it is not a valid Dart.
+  ''';
+
+  @override
+  FixResponse getParsedResponse(String response) {
+    print('Response: $response');
+    final json = jsonDecode(response) as Map<String, dynamic>;
+    var mainDartCode = '';
+    var tempDartCode = '';
+    if (json.containsKey('mainDartCode')) {
+      mainDartCode = json['mainDartCode'].toString();
+    }
+    if (json.containsKey('helperDartCode')) {
+      tempDartCode = json['helperDartCode'].toString();
+    }
+    return FixResponse(mainCode: mainDartCode, helperCode: tempDartCode);
+  }
+}
+
+class FixResponse {
+  final String mainCode;
+  final String helperCode;
+
+  FixResponse({required this.mainCode, required this.helperCode});
+}

pkgs/native_doc_dartifier/tool/prepare_dartify_test.dart

@@ -59,7 +59,10 @@ void compileJavaPackage() {
 void generateDartSnippets() async {
   for (final snippet in snippets) {
     final sourceCode = snippet['code'] as String;
-    final dartCode = await dartifyNativeCode(sourceCode, bindingsPath);
+    final dartCode = await dartifyNativeCode(
+      sourceCode,
+      File(bindingsPath).absolute.path,
+    );
     final fileName = snippet['fileName'];
     final outputFile = File('$workingDir/$dartifiedSnippetsDir/$fileName');
     if (!outputFile.parent.existsSync()) {