gistfile1.txt

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
using UnityEditor.Experimental.AssetImporters;
using System.IO;
using UnityEditor;
using UnityEngine.Assertions;
using System.Linq;

[ScriptedImporter(1, "cube")]
public class CubeImporter : ScriptedImporter
{
	public override void OnImportAsset(AssetImportContext ctx)
	{
		var cube = AssetDatabase.LoadMainAssetAtPath(ctx.assetPath) as GameObject;

		cube = GameObject.CreatePrimitive(PrimitiveType.Cube);
		cube.transform.localScale = new Vector3(1, 1, 1);

		var assets = AssetDatabase.LoadAllAssetsAtPath (ctx.assetPath);
		var material = assets.FirstOrDefault (c => c.name == "Cube Material") as Material;
		if (material == null) {
			material = new Material(Shader.Find("Standard"));
			material.name = "Cube Material";
		}

		cube.GetComponent<MeshRenderer> ().material = material;

		try
		{
			var scale = JsonUtility.FromJson<Vector3>(File.ReadAllText(ctx.assetPath));
			cube.transform.localScale = scale;
		}catch (System.Exception e) {
			Debug.LogError (e.Message, cube);
		}

		ctx.AddObjectToAsset(material.name, material);
		ctx.AddObjectToAsset("CUBE", cube);
		ctx.SetMainObject(cube);
	}
}