Grails, GORM - No dirty properties when binding OneToMany data - grails

Question

I have a problem with data binding and dirty properties.
There are two simple domains
class Parent {
String name
static hasMany = [children: Child]
}
class Child {
String name
static belongsTo = [parent: Parent]
}
I created a simple rest controller to check all options
class TestController {
static responseFormats = ['json']
#Transactional
def add() {
def parent = new Parent(name: params.name).save()
respond(parent)
}
#Transactional
def parents() {
def parents = Parent.findAll()
respond(parents)
}
#Transactional
def testWithCommand(ParentCmd cmd) {
Parent parent = Parent.findById(cmd.id)
bindData(parent, cmd)
parent.save()
respond(parent)
}
#Transactional
def testWithParams() {
Parent parent = Parent.findById(params.id)
bindData(parent, params)
parent.save()
respond(parent)
}
#Transactional
def testWithRelation(ParentCmd cmd) {
Parent tempParent = new Parent()
bindData(tempParent, cmd)
Parent parent = Parent.findById(cmd.id)
for (Child child : tempParent.children) {
parent.addToChildren(child)
}
parent.save()
respond(parent)
}
}
so we have 3 update options: cmd with binding, params with binding and cmd with addTo*
I created simple event to catch dirty properties
class TestEventListener extends AbstractPersistenceEventListener {
protected TestEventListener(Datastore datastore) {
super(datastore)
}
#Override
protected void onPersistenceEvent(AbstractPersistenceEvent event) {
if (event.entityObject instanceof Parent) {
List<String> dirtyProperties = new ArrayList<String>(((DirtyCheckable) event.entityObject).listDirtyPropertyNames())
println("DIRTY PROPERTIES: " + dirtyProperties.size())
println(dirtyProperties.join(", "))
}
}
#Override
boolean supportsEventType(Class<? extends ApplicationEvent> eventType) {
eventType == PreUpdateEvent.class
}
}
Then I used Postman, I created one record and updated it in each of three ways.
In two cases there was no dirty properties.
Only when I used addToChildren() I saw children in dirty properties.
Does anyone have any knowledge about this?
Did you have problems with binding? Is it normal or did I miss something?
I will be grateful for every answer.
Thx,
A.