ConstructorSelector.cs

using System.Reflection;
using Moq.AutoMock.Extensions;

namespace Moq.AutoMock;

internal static class ConstructorSelector
{
    public static ConstructorInfo SelectCtor(this Type type, Type[] existingTypes, BindingFlags bindingFlags)
    {
        ConstructorInfo? best = type
            .GetConstructors(bindingFlags)
            .Where(constructor =>
            {
                var parameters = constructor.GetParameters();

                return parameters.Length is 0 || parameters
                    .Select(parameter => parameter.ParameterType)
                    .All(type => existingTypes.Contains(type)
                        || type.IsMockable()
                        || type.IsArray);
            })
            .Aggregate<ConstructorInfo, ConstructorInfo?>(null, (value, constructor) =>
            {
                if (value is null) return constructor;
                return value.GetParameters().Length >= constructor.GetParameters().Length ? value : constructor;
            });

        return best
            ?? Empty(type)
            ?? throw new ArgumentException(
                $"Did not find a best constructor for `{type}`. If your type has a non-public constructor, set the 'enablePrivate' parameter to true for this AutoMocker method.",
                nameof(type));

        static ConstructorInfo Empty(Type type) => type
            .GetConstructors(BindingFlags.Instance | BindingFlags.NonPublic)
            .FirstOrDefault(x => x.GetParameters().Length is 0);
    }
}