Program: 172351
Project: 172351
Buggy source:
/** 
 * Execute action implementation
 */
@Override protected void executeImpl(Action ruleAction,NodeRef actionedUponNodeRef){
  if (this.nodeService.exists(actionedUponNodeRef) == true) {
    QName categoryAspect=(QName)ruleAction.getParameterValue(PARAM_CATEGORY_ASPECT);
    NodeRef categoryValue=(NodeRef)ruleAction.getParameterValue(PARAM_CATEGORY_VALUE);
    if (this.dictionaryService.isSubClass(categoryAspect,ContentModel.ASPECT_CLASSIFIABLE) == true) {
      QName categoryProperty=null;
      Map<QName,PropertyDefinition> propertyDefs=this.dictionaryService.getAspect(categoryAspect).getProperties();
      for (      Map.Entry<QName,PropertyDefinition> entry : propertyDefs.entrySet()) {
        if (DataTypeDefinition.CATEGORY.equals(entry.getValue().getDataType().getName()) == true) {
          categoryProperty=entry.getKey();
          break;
        }
      }
      if (categoryAspect != null) {
        if (this.nodeService.hasAspect(actionedUponNodeRef,categoryAspect) == false) {
          Map<QName,Serializable> properties=new HashMap<QName,Serializable>();
          properties.put(categoryProperty,categoryValue);
          this.nodeService.addAspect(actionedUponNodeRef,categoryAspect,properties);
        }
 else {
          Serializable value=this.nodeService.getProperty(actionedUponNodeRef,categoryProperty);
          Collection<NodeRef> categories=DefaultTypeConverter.INSTANCE.getCollection(NodeRef.class,value);
          categories.add(categoryValue);
          this.nodeService.setProperty(actionedUponNodeRef,categoryProperty,(Serializable)categories);
        }
      }
    }
  }
}

Fixed version (ground truth):
/** 
 * Execute action implementation
 */
@Override protected void executeImpl(Action ruleAction,NodeRef actionedUponNodeRef){
  if (this.nodeService.exists(actionedUponNodeRef) == true) {
    QName categoryAspect=(QName)ruleAction.getParameterValue(PARAM_CATEGORY_ASPECT);
    NodeRef categoryValue=(NodeRef)ruleAction.getParameterValue(PARAM_CATEGORY_VALUE);
    if (this.dictionaryService.isSubClass(categoryAspect,ContentModel.ASPECT_CLASSIFIABLE) == true) {
      QName categoryProperty=null;
      Map<QName,PropertyDefinition> propertyDefs=this.dictionaryService.getAspect(categoryAspect).getProperties();
      for (      Map.Entry<QName,PropertyDefinition> entry : propertyDefs.entrySet()) {
        if (DataTypeDefinition.CATEGORY.equals(entry.getValue().getDataType().getName()) == true) {
          categoryProperty=entry.getKey();
          break;
        }
      }
      if (categoryAspect != null) {
        if (this.nodeService.hasAspect(actionedUponNodeRef,categoryAspect) == false) {
          Map<QName,Serializable> properties=new HashMap<QName,Serializable>();
          properties.put(categoryProperty,categoryValue);
          this.nodeService.addAspect(actionedUponNodeRef,categoryAspect,properties);
        }
 else {
          Serializable value=this.nodeService.getProperty(actionedUponNodeRef,categoryProperty);
          Collection<NodeRef> categories=DefaultTypeConverter.INSTANCE.getCollection(NodeRef.class,value);
          if (categories.contains(categoryValue) == false) {
            categories.add(categoryValue);
            this.nodeService.setProperty(actionedUponNodeRef,categoryProperty,(Serializable)categories);
          }
        }
      }
    }
  }
}