Support runtimes where ReflectedType exists such as NetStandard2.0 compatible runtimes

[csMACnz]

This relates to issue #1983

The calling code that fails is this particular call in DataDiscoverer:

xunit/src/xunit.core/Sdk/DataDiscoverer.cs

Line 32 in 4db2e39

var reflectionTestMethodType = reflectionTestMethod.Type as IReflectionTypeInfo;

This change should restore the functionality that worked on NetStandard 2.0 compatible runtimes with v2.4.0 that breaks when upgrading to 2.4.1 (where NetStandard2.0 target was removed breaking this particular call.

I think the missing unit tests are possible but still working out where they go into this file. Potentially alongside this test case?

xunit/test/test.xunit.execution/Acceptance/Xunit2TheoryAcceptanceTests.cs

Lines 869 to 888 in 4db2e39

	[Fact]
	public void CanUseFieldDataFromBaseType()
	{
	var testMessages = Run<ITestResultMessage>(typeof(ClassWithBaseClassData));
	var passed = Assert.Single(testMessages.Cast<ITestPassed>());
	Assert.Equal("Xunit2TheoryAcceptanceTests+FieldDataTests+ClassWithBaseClassData.TestViaFieldData(x: 42)", passed.Test.DisplayName);
	}
	class BaseClass
	{
	public static IEnumerable<object[]> DataSource = new[] { new object[] { 42 } };
	}
	class ClassWithBaseClassData : BaseClass
	{
	[Theory]
	[MemberData("DataSource")]
	public void TestViaFieldData(int x) { }
	}

EDIT: After some playing around I've realised none of these theory tests light up for non .Net Full Framework anyway.

I've tried to do this as low impact as possible.

I investigated just using DeclaringType but there is a subtle difference, which is exactly what the DataDiscoverer is using it for.
(DeclaringType would resolve to the base class while ReflectedType will correctly use the derived test class type, according to Stack Overflow)

Thanks in Advance. All feedback appreciated

[bradwilson]

Obviously we would want some tests here. I'm fine with the approach of dynamically looking for ReflectedType, though it should be done in a cached lookup since these wrappers get used a lot.

[csMACnz]

Time to actually tackle the tests on this has stalled.

I've found a quick workaround using an alternate DataAttribute custom class though:

    internal class BugFixMemberDataAttribute : MemberDataAttributeBase
    {
        public BugFixMemberDataAttribute(string memberName, params object[] parameters)
            : base(memberName, parameters)
        {
        }

        public override IEnumerable<object[]?>? GetData(MethodInfo testMethod)
        {
            MemberType = testMethod.ReflectedType;
            return base.GetData(testMethod);
        }

        protected override object[]? ConvertDataItem(MethodInfo testMethod, object item)
        {
            if (item == null)
            {
                return null;
            }

            return (item as object[]) ?? throw new ArgumentException($"Property {MemberName} on {MemberType ?? testMethod.DeclaringType} yielded an item that is not an object[]");
        }
    }

YMMV

[bradwilson]

I wrote the acceptance test for this. I would've pushed the changes into your branch and merged, but you wrote them directly into your v2 branch, which I didn't want to clutter up with my stuff (since it would've required a force push). So your changes are merged here: e813b31

Thanks!