AssetModificationProcessor.OnWillCreateAsset(string)

Description

Unity calls this method when it is about to create an Asset you haven't imported (for example, .meta files).

public class CustomAssetModificationProcessor : UnityEditor.AssetModificationProcessor
{
    static void OnWillCreateAsset(string assetName)
    {
        Debug.Log("OnWillCreateAsset is being called with the following asset: " + assetName + ".");
    }
}