Cannot get nil value from BackingStore with delta query when a property value was changed to nil (empty)

I am trying to implement the delta query to track user changes.

For example, I changed First name and Last name to empty on https://entra.microsoft.com/ .

I got the below response. You can see givenName and surname are detected as null values.

{
  "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#users",
  "@odata.deltaLink": "https://graph.microsoft.com/v1.0/users/delta()?$deltatoken=dqOf4D0FeifmTE8LZ08sKG_0pMPP7gZ...",
  "value": [
    {
      "givenName": null,
      "surname": null,
      "id": "a8d67d70-f83b-453d-9666-1f280a609bf6"
    }
  ]
}

But, I cannot know whether the givenName and surname were changed to null since the Enumerate() or EnumerateKeysForValuesChangedToNil() methods don't return the values (nil).

var user models.Userable
...
b := user.GetBackingStore()
fmt.Println(b.GetInitializationCompleted())
fmt.Println(b.GetReturnOnlyChangedValues())
for i, v := range b.EnumerateKeysForValuesChangedToNil() {
	fmt.Printf(" - %v, %+v\n", i, v)
}
for k, v := range b.Enumerate() {
	fmt.Printf(" - %s, %+v\n", k, v)
}

- additionalData, map[]
- odataType, 0x140005803b0
- id, 0x14000580320

Another sample code to confirm the user data.

json, _ := serialization.SerializeToJson(user)
fmt.Println(string(json))

Also, the user data doesn't have both givenName and surname properties.

{"id":"a8d67d70-f83b-453d-9666-1f280a609bf6","@odata.type":"#microsoft.graph.user"}

In my debugging, InMemoryBackingStore doesn't handle a nil value in User.GetFieldDeserializers() method.

res["surname"] = func(n i878a80d2330e89d26896388a3f487eef27b0a0e6c010c493bf80be1452208f91.ParseNode) error {
	val, err := n.GetStringValue()
	if err != nil {
		return err
	}
	if val != nil {
		m.SetSurname(val)
	}
	return nil
}

func (m *User) SetSurname(value *string) {
	err := m.GetBackingStore().Set("surname", value)
	if err != nil {
		panic(err)
	}
}

Could you tell me how do I check both givenName and surname properties were changed to nil via msgraph-sdk-go API?

Reference

• https://learn.microsoft.com/en-us/graph/delta-query-overview
• https://github.com/microsoftgraph/msgraph-sdk-go/issues/643

Start with User.GetFieldDeserializers and InMemoryBackingStore, then reproduce the delta response where givenName and surname are null. Trace how the deserializer and backing store handle those values; done means the API lets callers distinguish properties changed to nil, with the behavior checked against the sample delta response.