Setup cannot invoke callback with different number of parameters in Moq 4.8.1

[Caraul]

Hi,

looks like adding ValidateReturnDelegate makes extension methods unusable in zero argument methods such as property getters. Here is small repro that fails at Setup phase with ArgumentException:

using Moq;

namespace TestMoq
{
	internal class Program
	{
		internal static void Main()
		{
			var a = new A();
			var mock = new Mock<A>();
			mock.SetupGet(aa => aa.P).Returns(a.Pext);
		}
	}

	public class A
	{
		public virtual string P { get; set; }
	}

	internal static class Aext
	{
		public static string Pext(this A a)
		{
			return "42";
		}
	}
}

Not sure if this is expected effect - please could anyone tell is such behavior correct?

[stakx]

@Caraul, thanks for reporting. Without looking into this in detail, this looks like a regression introduced in 4.8.0. This used to work in Moq 4.7.145, but I'm not sure whether that was by design or incidental. Will try to look into this in the next few days.

[stakx]

It's indeed a regression caused by #520 / commit 104c646 (which aimed to make delegate validation more strict, as you've already found out). We didn't have a test for the extension method case you've provided. I'll add a regression test for this to the test suite, and fix the problem sometime in the next few days... or would you prefer to submit a PR yourself?

[Caraul]

Well, fix won't take weeks but one week maybe cause I need to go deeper inside Moq - if next week ASAP is acceptable then I'm in with PR.

[stakx]

@Caraul, that is fine. 👍

I expect that a local fix in just that validation method should be possible; check whether the callback is an extension method (IsStatic & IsDefined(typeof(ExtensionAttribute))), and if so, subtract 1 from the parameter count when matching. Something like that.

Please don't forget to also add one or more unit tests to the test suite. :)

Thank you!

[Caraul]

Thanks for moving Moq forward - Good job! 👍

[stakx]

Moq 4.8.2 (which includes your patch, see changelog) has just been published on NuGet.

[Caraul]

Great news, thank you very much!