ImportAtPathImmediate is not supported for assets with import dependencies.

I have just updated to 2018.3 from 2018.2 for one of my projects and now I am getting this error when I make prefab out of an object that contains procedural meshes. Everything worked fine in 2018.2 the mesh assets would created in the porject and the prefab that was then created would use them just fine. Now when i call AssetDatabase.CreateAsset for each mesh in the object I get the error:

ImportAtPathImmediate is not supported for assets with import dependencies.

The whole object is procedural, the meshes are generated at prefab creation time so where is this 'import dependency' coming from and how do I get around it. I have tried changing to AssetDatabase.AddObjectToAsset and that works in as far as the meshes are added to the prefab but the prefab objects no longer reference those meshes and all the meshfilters for the prefabs have empty meshes.

 

I'm probably necroing this thread but I was scratching my head for a few hours with this.

In my case I was calling

Code (CSharp):

1. ScriptableTest obj = ScriptableObject.CreateInstance<ScriptableTest>();
2. AssetDatabase.CreateAsset(obj, assetPath + ".prefab");

But obj was not a prefab or a GameObject. It was just an instance of a ScriptableObject so I changed the line to:

Code (CSharp):

1. AssetDatabase.CreateAsset(obj, assetPath + ".asset");

And I can sleep tonight

TL;DR: Watch the ".prefab" or ".asset" extension when calling AssetDatabase.CreateAsset

There might be other reasons why you get this error, but just in case check that your path extensions make sense for CreateAsset