PrefabPreprocessor.cs

using System;
using System.Linq;
using System.Reflection;
using UnityEditor;
using UnityEditor.Build;
using UnityEditor.Build.Reporting;
using UnityEngine;
using Object = UnityEngine.Object;

namespace Improbable.Gdk.Subscriptions.Editor
{
    /// <summary>
    ///     A prefab processor which disables any Monobehaviours on top-level GameObjects in the Resources folder
    ///     which have fields with the <see cref="RequireAttribute"/> on them.
    /// </summary>
    /// <remarks>
    ///     This processes the prefabs when you build or when you press play in the Unity Editor.
    /// </remarks>
    [InitializeOnLoad]
    public class PrefabPreprocessor : IPreprocessBuildWithReport
    {
        // Needed for IPreprocessBuildWithReport
        public int callbackOrder => 0;

        static PrefabPreprocessor()
        {
            EditorApplication.playModeStateChanged += OnPlaymodeStateChanged;
        }

        void IPreprocessBuildWithReport.OnPreprocessBuild(BuildReport report)
        {
            PreprocessPrefabs();
        }

        private static void OnPlaymodeStateChanged(PlayModeStateChange playModeStateChange)
        {
            if (playModeStateChange == PlayModeStateChange.ExitingEditMode)
            {
                PreprocessPrefabs();
            }
        }

        private static void PreprocessPrefabs()
        {
            var allPrefabObjectsInResources = AssetDatabase.FindAssets("t:Prefab")
                .Select(AssetDatabase.GUIDToAssetPath)
                .Where(assetPath => assetPath.Contains("Resources")).ToArray();

            AssetDatabase.StartAssetEditing();
            foreach (var prefabPath in allPrefabObjectsInResources)
            {
                try
                {
                    var prefabObject = PrefabUtility.LoadPrefabContents(prefabPath);
                    if (prefabObject == null)
                    {
                        continue;
                    }

                    var changed = false;

                    foreach (var monoBehaviour in prefabObject
                        .GetComponents<MonoBehaviour>()
                        .Where(DoesBehaviourNeedFixing))
                    {
                        monoBehaviour.enabled = false;
                        changed = true;
                    }

                    if (changed)
                    {
                        PrefabUtility.SaveAsPrefabAsset(prefabObject, prefabPath);
                    }

                    PrefabUtility.UnloadPrefabContents(prefabObject);
                }
                catch
                {
                    Debug.LogError($"Failed to process prefab {prefabPath}");
                    throw;
                }
            }

            AssetDatabase.StopAssetEditing();
        }

        private static bool IsBehaviourEnabledInEditor(Object obj)
        {
            return !ReferenceEquals(obj, null) && EditorUtility.GetObjectEnabled(obj) == 1;
        }

        private static bool DoesBehaviourNeedConditionalEnabling(Type targetType)
        {
            return
                targetType.GetCustomAttribute<WorkerTypeAttribute>() != null ||
                targetType
                    .GetFields(BindingFlags.Instance | BindingFlags.NonPublic | BindingFlags.Public)
                    .Any(field => Attribute.IsDefined(field, typeof(RequireAttribute), false));
        }

        private static bool DoesBehaviourNeedFixing(MonoBehaviour monoBehaviour)
        {
            return IsBehaviourEnabledInEditor(monoBehaviour) &&
                DoesBehaviourNeedConditionalEnabling(monoBehaviour.GetType());
        }
    }
}