Unityでupm内にあるreadonlyなprefabのvariantを作るエディタ拡張

PrefabVariantGenerator.cs

// Copyright 2022 KOGA Mitsuhiro Authors. All rights reserved.
// Use of this source code is governed by a MIT-style
// license that can be found in the LICENSE file.

using System.IO;
using UnityEditor;
using UnityEngine;

public class PrefabVariantGenerator : EditorWindow
{
    private GameObject _source;

    [MenuItem("Tools/PrefabVariantGenerater")]
    public static void Window()
    {
        GetWindow<PrefabVariantGenerator>($"{nameof(PrefabVariantGenerator)}");
    }

    public void OnGUI()
    {
        _source = EditorGUILayout.ObjectField("Source Prefab", _source, typeof(GameObject), false) as GameObject;
        if (!_source)
        {
            EditorGUILayout.LabelField("Missing:", "Select an prefab first");
            return;
        }

        if (!PrefabUtility.IsPartOfPrefabAsset(_source))
        {
            EditorGUILayout.LabelField("Failure:", $"{_source.name} is not prefab");
            return;
        }

        var path = AssetDatabase.GetAssetPath(_source);
        if (string.IsNullOrWhiteSpace(path))
        {
            return;
        }

        var baseName = Path.GetFileNameWithoutExtension(path);
        if (GUILayout.Button($"Create Variant {baseName}"))
        {
            var requestPath = EditorUtility.SaveFilePanel(
                $"Create Variant of {baseName}",
                Application.dataPath,
                $"{baseName}Variant.prefab",
                "prefab");

            if (!string.IsNullOrWhiteSpace(requestPath) && requestPath.StartsWith(Application.dataPath))
            {
                var leaf = new DirectoryInfo(Application.dataPath).Name;
                var savePath = requestPath.Replace(Application.dataPath, leaf);
                var successSave = false;
                try
                {
                    AssetDatabase.StartAssetEditing();
                    if (PrefabUtility.InstantiatePrefab(_source) is GameObject objSource)
                    {
                        PrefabUtility.SaveAsPrefabAssetAndConnect(objSource, savePath,
                            InteractionMode.UserAction, out successSave);
                        DestroyImmediate(objSource);
                    }
                }
                finally
                {
                    AssetDatabase.StopAssetEditing();
                }

                if (successSave && File.Exists(savePath))
                {
                    var savedAsset = AssetDatabase.LoadMainAssetAtPath(savePath);
                    if (savedAsset)
                    {
                        Selection.objects = new[] { savedAsset };
                        EditorGUIUtility.PingObject(savedAsset);
                    }
                }
            }
        }
    }
}