BehaviourDesigner – Manual Error Checking for Custom Tasks

CustomTaskExample.cs

public class CustomTaskExample : Action, ITaskWithErrorCheck
{
  public bool ShowError = true;

#if UNITY_EDITOR
  public CustomTaskExample() => this.RegisterErrorCheck();
  public bool AnyErrorInTask() => ShowError;
#endif
}

ITaskWithErrorCheck.cs

using BehaviorDesigner.Runtime;
using BehaviorDesigner.Runtime.Tasks;

public interface ITaskWithErrorCheck
{
#if UNITY_EDITOR
  bool AnyErrorInTask();
  NodeData NodeData { get; }
#endif
}

TaskErrorCheck.cs

#if UNITY_EDITOR
using System;
using System.Collections.Generic;
using UnityEditor;

namespace Gameplay.Actions
{
	[InitializeOnLoad]
	public static class TaskErrorCheck
	{
		private static readonly List<WeakReference<ITaskWithErrorCheck>> Tasks = new();
		
		static TaskErrorCheck()
		{
			EditorApplication.update += CheckTasks;
				
			void CheckTasks()
			{
				for (int i = 0; i < Tasks.Count; i++)
				{
					var taskReference = Tasks[i];
					if (!taskReference.TryGetTarget(out var task))
					{
						Tasks.RemoveAt(i);
						continue;
					}
					
					if (task.NodeData?.NodeDesigner == null) continue;

					((BehaviorDesigner.Editor.NodeDesigner)task.NodeData.NodeDesigner).HasError = task.AnyErrorInTask();
				}
			}
		}
		
		public static void RegisterErrorCheck(this ITaskWithErrorCheck task)
		{
			Tasks.Add(new WeakReference<ITaskWithErrorCheck>(task, false));
		}
	}
}
#endif

Error checking in BehaviourDesigner is not very flexible. For instance, if you want to display a custom serialized class and want the error to appear if one of its fields is null, or make a custom type with a validation more complex than mere null ref check - [RequiredField] and [SharedRequired] wouldn't help you. With this, you can create custom error checks easily, to quickly identify troublesome places in the tree: