Hide empty dropdown items and collapse items with single child

Editor/Builders/AssetsItemBuilder.cs

@@ -1,5 +1,6 @@
-using System;
+using System;
 using System.Collections.Generic;
+using System.Linq;
 using TNRD.Items;
 using TNRD.Utilities;
 using UnityEditor;
@@ -46,7 +47,60 @@ public AdvancedDropdownItem Build()
                 }
             }
 
-            return root;
+            return Collapse(root);
+        }
+
+        private AdvancedDropdownItem Collapse(AdvancedDropdownItem root)
+        {
+            AdvancedDropdownItem[] rootChildren = root.children.ToArray();
+
+            if (root is IDropdownItem)
+            {
+                return root;
+            }
+
+            if (rootChildren.Length == 0)
+            {
+                return null;
+            }
+            AdvancedDropdownItem newRoot = new(root.name)
+            {
+                icon = root.icon,
+                enabled = root.enabled,
+                id = root.id,
+            };
+
+            while (rootChildren.Length == 1 && rootChildren[0] is {} singleChild and not IDropdownItem)
+            {
+                newRoot = new AdvancedDropdownItem(CollapseName($"{newRoot.name}/{singleChild.name}"))
+                {
+                    icon = singleChild.icon,
+                    id = singleChild.id,
+                };
+                rootChildren = singleChild.children.ToArray();
+            }
+            bool addedChildren = false;
+            foreach (var child in rootChildren)
+            {
+                AdvancedDropdownItem newChild = Collapse(child);
+                if (newChild != null)
+                {
+                    newRoot.AddChild(newChild);
+                    addedChildren = true;
+                }
+            }
+            return addedChildren ? newRoot : null;
+        }
+
+        private const int MAX_NAME_LENGTH = 90;
+        private const int HALF_LENGTH = (MAX_NAME_LENGTH - 4) / 2;
+        private string CollapseName(string name)
+        {
+            if (name.Length > MAX_NAME_LENGTH)
+            {
+                return $"{name[..HALF_LENGTH]}...{name[^HALF_LENGTH..]}";
+            }
+            return name;
         }
 
         private void CreateItemForPath(AdvancedDropdownItem root, string path)

Editor/Builders/ClassesItemBuilder.cs

@@ -1,5 +1,6 @@
-using System;
+using System;
 using System.Collections.Generic;
+using System.Linq;
 using TNRD.Items;
 using TNRD.Utilities;
 using UnityEditor;
@@ -35,6 +36,10 @@ public AdvancedDropdownItem Build()
                 AdvancedDropdownItem parent = GetOrCreateParentItem(type, root);
                 parent.AddChild(new ClassDropdownItem(type));
             }
+            if (!root.children.Any())
+            {
+                return null;
+            }
 
             return root;
         }

Editor/Builders/SceneItemBuilder.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Linq;
 using TNRD.Items;
 using TNRD.Utilities;
@@ -26,10 +26,7 @@ public AdvancedDropdownItem Build()
         {
             if (scene == null || !scene.Value.IsValid())
             {
-                return new AdvancedDropdownItem("Scene")
-                {
-                    enabled = false
-                };
+                return null;
             }
 
             AdvancedDropdownItem root = new AdvancedDropdownItemWrapper("Scene");
@@ -40,6 +37,10 @@ public AdvancedDropdownItem Build()
             {
                 CreateItemsRecursive(rootGameObject.transform, root);
             }
+            if (!root.children.Any())
+            {
+                return null;
+            }
 
             return root;
         }

Editor/Items/ClassDropdownItem.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Linq;
 using TNRD.Utilities;
 using UnityEditor.IMGUI.Controls;
@@ -14,7 +14,9 @@ public ClassDropdownItem(Type type)
             : base(type.Name)
         {
             this.type = type;
-            enabled = type.GetConstructors().Any(x => x.GetParameters().Length == 0);
+            // Needs a parameterless constructor or be a value type
+            enabled = type.GetConstructors().Any(x => x.GetParameters().Length == 0)
+                || type.IsValueType;
             icon = IconUtility.ScriptIcon;
         }
 

Editor/Utilities/AdvancedDropdownItemWrapper.cs

@@ -1,4 +1,4 @@
-using UnityEditor.IMGUI.Controls;
+using UnityEditor.IMGUI.Controls;
 
 namespace TNRD.Utilities
 {
@@ -12,7 +12,10 @@ public AdvancedDropdownItemWrapper(string name)
 
         public new AdvancedDropdownItemWrapper AddChild(AdvancedDropdownItem child)
         {
-            base.AddChild(child);
+            if (child != null)
+            {
+                base.AddChild(child);
+            }
             return this;
         }
 

Editor/Utilities/SerializableInterfaceAdvancedDropdown.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Linq;
 using System.Reflection;
 using TNRD.Builders;
@@ -60,10 +60,7 @@ protected override AdvancedDropdownItem BuildRoot()
                 item.AddChild(new SceneItemBuilder(interfaceType, relevantScene).Build());
             }
 
-            foreach (AdvancedDropdownItem dropdownItem in item.children)
-            {
-                dropdownItem.AddChild(new NoneDropdownItem());
-            }
+            item.AddChild(new NoneDropdownItem());
 
             if (canSort)
             {