1.8.0: Added AssetsOnly, SceneObjectsOnly, AssignAssetIfNull, AssignComponentIfNull

- Attributes: Added AssetsOnly, SceneObjectsOnly, AssignAssetIfNull, AssignComponentIfNull
- Attributes: Replaced AssignIfNull with AssignComponentIfNull

Editor/ValueModifiers/AssignAssetIfNullAttributeDrawer.cs

@@ -0,0 +1,43 @@
+using System;
+using UnityEditor;
+using Object = UnityEngine.Object;
+
+namespace Module.Inspector.Editor
+{
+    [CustomPropertyDrawer(typeof(AssignAssetIfNullAttribute))]
+    internal sealed class AssignAssetIfNullAttributeDrawer : ValueModifierPropertyDrawer
+    {
+        public override void Modify(ValueModifierPropertyAttribute attribute, SerializedProperty property)
+        {
+            if (property.propertyType != SerializedPropertyType.ObjectReference)
+                return;
+            if (property.objectReferenceValue != null)
+                return;
+
+            var att = (AssignAssetIfNullAttribute)attribute;
+            Type type = att.useType ? att.type : property.GetValueType();
+            property.objectReferenceValue = AssignAsset(type, att.filter, att.searchFolders);
+        }
+
+        private static Object AssignAsset(Type type, string filter, string[] folders)
+        {
+            string[] guids;
+            
+            if (folders != null && folders.Length != 0)
+                guids = AssetDatabase.FindAssets($"{type.Name} {filter}", folders);
+            else
+                guids = AssetDatabase.FindAssets($"{type.Name} {filter}");
+
+            for (var i = 0; i < guids.Length; i++)
+            {
+                string path = AssetDatabase.GUIDToAssetPath(guids[i]);
+                Object obj = AssetDatabase.LoadAssetAtPath(path, type);
+
+                if (obj != null)
+                    return obj;
+            }
+
+            return null;
+        }
+    }
+}