TagAttribute - attribute to display string, List<string> and string[] as dropdown with tags

TagAttribute.cs

using System;

[AttributeUsage(AttributeTargets.Field | AttributeTargets.Property)]
public class TagAttribute : Attribute { }

TagAttributeDrawer.cs

using System.Collections.Generic;
using System.Linq;
using System.Reflection;
using Sirenix.OdinInspector;
using Sirenix.OdinInspector.Editor;
using UnityEditor;
using UnityEngine;

public class TagStringDrawer : OdinAttributeDrawer<TagAttribute, string>
{
	private GUIContent m_buttonContent = new GUIContent();
	
	protected override void Initialize() => UpdateButtonContent();

	private void UpdateButtonContent()
	{
		m_buttonContent.text = ValueEntry.SmartValue;
	}

	protected override void DrawPropertyLayout(GUIContent label)
	{
		var rect = EditorGUILayout.GetControlRect(label != null);

		if (label == null)
			rect = EditorGUI.IndentedRect(rect);
		else
			rect = EditorGUI.PrefixLabel(rect, label);
		
		if (!EditorGUI.DropdownButton(rect, m_buttonContent, FocusType.Passive)) return;

		var selector = new GenericSelector<string>(UnityEditorInternal.InternalEditorUtility.tags);
		selector.SetSelection(ValueEntry.SmartValue);
		selector.ShowInPopup(rect.position);
			
		selector.SelectionChanged += x =>
		{
			ValueEntry.Property.Tree.DelayAction(() =>
			{
				ValueEntry.SmartValue = x.FirstOrDefault();
				
				UpdateButtonContent();
			});
		};
	}
}

public abstract class TagStringListBaseDrawer<T> : OdinAttributeDrawer<TagAttribute, T> where T : IList<string>
{
	private GUIContent m_buttonContent = new GUIContent();

	protected override void Initialize() => UpdateButtonContent();

	private void UpdateButtonContent()
	{
		m_buttonContent.text = m_buttonContent.tooltip = string.Join(", ", ValueEntry.SmartValue);
	}

	protected override void DrawPropertyLayout(GUIContent label)
	{
		var rect = EditorGUILayout.GetControlRect(label != null);

		if (label == null)
			rect = EditorGUI.IndentedRect(rect);
		else
			rect = EditorGUI.PrefixLabel(rect, label);
		
		if (!EditorGUI.DropdownButton(rect, m_buttonContent, FocusType.Passive)) return;

		var selector = new TagSelector(UnityEditorInternal.InternalEditorUtility.tags);

		rect.y += rect.height;
		
		selector.SetSelection(ValueEntry.SmartValue);
		selector.ShowInPopup(rect.position);

		selector.SelectionChanged += x =>
		{
			ValueEntry.Property.Tree.DelayAction(() =>
			{
				UpdateValue(x);

				UpdateButtonContent();
			});
		};
	}

	protected abstract void UpdateValue(IEnumerable<string> x);
}

[DrawerPriority(1)]
[DontApplyToListElements]
public class TagStringArrayDrawer : TagStringListBaseDrawer<string[]>
{
	protected override void UpdateValue(IEnumerable<string> x) => ValueEntry.SmartValue = x.ToArray();
}

[DrawerPriority(1)]
[DontApplyToListElements]
public class TagStringListDrawer : TagStringListBaseDrawer<List<string>>
{
	protected override void UpdateValue(IEnumerable<string> x) => ValueEntry.SmartValue = x.ToList();
}

public class TagSelector : GenericSelector<string>
{
	private FieldInfo m_requestCheckboxUpdate;

	public TagSelector(string[] tags) : base(tags)
	{
		CheckboxToggle = true;

		m_requestCheckboxUpdate = typeof(GenericSelector<string>).GetField("requestCheckboxUpdate",
			BindingFlags.NonPublic | BindingFlags.Instance);
	}

	protected override void DrawSelectionTree()
	{
		base.DrawSelectionTree();

		EditorGUILayout.BeginHorizontal();

		if (GUILayout.Button("None"))
		{
			SetSelection(new List<string>());
			
			m_requestCheckboxUpdate.SetValue(this, true);
			TriggerSelectionChanged();
		}
		
		if (GUILayout.Button("All"))
		{
			SetSelection(UnityEditorInternal.InternalEditorUtility.tags);
			
			m_requestCheckboxUpdate.SetValue(this, true);
			TriggerSelectionChanged();
		}
		
		EditorGUILayout.EndHorizontal();
	}
}