Program: 13868
Project: 13868
Buggy source:
private void generate(TypeElement element,Configuration configuration,ResourceLoader resourceLoader) throws Exception {
  LOGGER.fine(() -> "String_Node_Str" + processingEnvClassName);
  Messager messager=processingEnv.getMessager();
  Filer filer=processingEnv.getFiler();
  Types types=processingEnv.getTypeUtils();
  Elements elements=processingEnv.getElementUtils();
  if (!resourceLoader.hasSourcePaths())   messager.printMessage(Kind.WARNING,"String_Node_Str" + ConfigurationOptionKeys.SOURCEPATH + "String_Node_Str");
 else {
    LOGGER.fine(() -> "String_Node_Str" + resourceLoader);
  }
  STTemplates templates=new STTemplates(resourceLoader,configuration);
  ModelBuilder clazzFactory=new ModelBuilder(types,elements,(msgElement,kind,err) -> {
    if (msgElement != null)     messager.printMessage(kind,err,msgElement);
 else     messager.printMessage(kind,err);
  }
,element,configuration,resourceLoader,templates);
  Clazz clazz=clazzFactory.buildNewCLazz();
  if (clazz == null)   return;
  LOGGER.info(() -> "String_Node_Str" + System.lineSeparator() + clazz.toString());
  String fileName=stripGenericQualifier(clazz.getName());
  JavaFileObject target=filer.createSourceFile(fileName,element);
  STCodeWriter writer=new STCodeWriter(clazz,configuration,templates);
  try (PrintWriter targetWriter=new PrintWriter(target.openWriter())){
    String output=writer.outputClass();
    if (output != null) {
      targetWriter.write(output);
      LOGGER.info(() -> "String_Node_Str" + fileName + "String_Node_Str"+ System.lineSeparator()+ output);
    }
  }
 }

Fixed version (ground truth):
private void generate(TypeElement element,Configuration configuration,ResourceLoader resourceLoader) throws Exception {
  LOGGER.fine(() -> "String_Node_Str" + processingEnvClassName);
  Messager messager=processingEnv.getMessager();
  Filer filer=processingEnv.getFiler();
  Types types=processingEnv.getTypeUtils();
  Elements elements=processingEnv.getElementUtils();
  if (!resourceLoader.hasSourcePaths())   messager.printMessage(Kind.WARNING,"String_Node_Str" + ConfigurationOptionKeys.SOURCEPATH + "String_Node_Str");
 else {
    LOGGER.fine(() -> "String_Node_Str" + resourceLoader);
  }
  STTemplates templates=new STTemplates(resourceLoader,configuration);
  ModelBuilder clazzFactory=new ModelBuilder(types,elements,(msgElement,kind,err) -> {
    if (msgElement != null)     messager.printMessage(kind,err,msgElement);
 else     messager.printMessage(kind,err);
  }
,element,configuration,resourceLoader,templates);
  Clazz clazz=clazzFactory.buildNewCLazz();
  if (clazz == null)   return;
  LOGGER.info(() -> "String_Node_Str" + System.lineSeparator() + clazz.toString());
  String fileName=stripGenericQualifier(clazz.getQualifiedName());
  JavaFileObject target=filer.createSourceFile(fileName,element);
  STCodeWriter writer=new STCodeWriter(clazz,configuration,templates);
  try (PrintWriter targetWriter=new PrintWriter(target.openWriter())){
    String output=writer.outputClass();
    if (output != null) {
      targetWriter.write(output);
      messager.printMessage(Kind.NOTE,"String_Node_Str" + target.getName());
      LOGGER.info(() -> "String_Node_Str" + fileName + "String_Node_Str"+ System.lineSeparator()+ output);
    }
  }
 }