Hide Duplicate Reference Box Attribute

Indicates that Odin should hide the reference box, if this property would otherwise be drawn as a reference to another property, due to duplicate reference values being encountered. Note that if the value is referencing itself recursively, then the reference box will be drawn regardless of this attribute in all recursive draw calls. 

[PropertyOrder(1)]
public ReferenceTypeClass firstObject;

[PropertyOrder(3)]
public ReferenceTypeClass withReferenceBox;

[PropertyOrder(5)]
[HideDuplicateReferenceBox]
public ReferenceTypeClass withoutReferenceBox;

[OnInspectorInit]
public void CreateData()
{
    this.firstObject = new ReferenceTypeClass();
    this.withReferenceBox = this.firstObject;
    this.withoutReferenceBox = this.firstObject;
    this.firstObject.recursiveReference = this.firstObject;
}

public class ReferenceTypeClass
{
    [HideDuplicateReferenceBox]
    public ReferenceTypeClass recursiveReference;

    [OnInspectorGUI, PropertyOrder(-1)]
    private void MessageBox()
    {
        SirenixEditorGUI.WarningMessageBox("Recursively drawn references will always show the reference box regardless, to prevent infinite depth draw loops.");
    }
}

[OnInspectorGUI, PropertyOrder(0)]
private void MessageBox1()
{
    SirenixEditorGUI.Title("The first reference will always be drawn normally", null, TextAlignment.Left, true);
}

[OnInspectorGUI, PropertyOrder(2)]
private void MessageBox2()
{
    GUILayout.Space(20);
    SirenixEditorGUI.Title("All subsequent references will be wrapped in a reference box", null, TextAlignment.Left, true);
}

[OnInspectorGUI, PropertyOrder(4)]
private void MessageBox3()
{
    GUILayout.Space(20);
    SirenixEditorGUI.Title("With the [HideDuplicateReferenceBox] attribute, this box is hidden", null, TextAlignment.Left, true);
}