AssetModificationProcessor.OnWillCreateAsset(string)

Description

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

using UnityEngine;

public class CustomAssetModificationProcessor : UnityEditor.AssetModificationProcessor
{
    static void OnWillCreateAsset(string path)
    {
        Debug.Log("Asset is being created at: " + path);
    }
}