module-project-validator/Editor/Validators/GameObject/GameObjectValidatorDuplicateComponents.cs

using System;
using System.Collections.Generic;
using System.Reflection;
using UnityEngine;
using UnityEngine.Pool;

namespace Module.ProjectValidator.Editor
{
    internal sealed class GameObjectValidatorDuplicateComponents : IGameObjectValidator
    {
        public void Validate(GameObject gameObject, List<ValidatorResult> results)
        {
            using var _ = ListPool<Component>.Get(out var list);
            gameObject.GetComponents(list);
            list.Sort((c0, c1) => c0.GetType().GetHashCode().CompareTo(c1.GetType().GetHashCode()));

            if (list.Count == 0)
                return;
            
            var type = list[0].GetType();
            var count = 1;
            
            for (var i = 1; i < list.Count; i++)
            {
                var t = list[i].GetType();

                if (type == t)
                {
                    count++;
                }
                else
                {
                    if (count > 1 && IsMultipleComponentsAllowed(type))
                        results.Add(ValidatorResult.Create(EValidatorSeverity.Warning, $"GameObject has duplicate '{type.Name}' ({count}) components"));
                    
                    type = t;
                    count = 1;
                }
            }
            
            if (count > 1 && IsMultipleComponentsAllowed(type))
                results.Add(ValidatorResult.Create(EValidatorSeverity.Warning, $"GameObject has duplicate '{type.Name}' ({count}) components"));
        }

        private static bool IsMultipleComponentsAllowed(Type type)
        {
            return type.GetCustomAttribute<DisallowMultipleComponent>(true) == null;
        }
    }
}