VerifySet breaks with System.NullReferenceException for WriteOnly-Indexed-Properties

[Epicycle23]

Version: 4.14.4
Language: Visual Basic
Environment: Visual Studio 2019 16.6.2

Steps to reproduce

<TestClass()>
Public Class UnitTest1


    Public Interface ITest
        WriteOnly Property Value(key As String)
    End Interface

    <TestMethod()>
    Public Sub TestMethod1()

        Dim mock As New Mock(Of ITest)
        mock.Object.Value("key") = "value"
        mock.VerifySet(Sub(x) x.Value("key") = It.IsAny(Of String), Times.Once)

    End Sub

End Class

Was working fine with version 4.8.3.
I ran into this issue when trying to update to 4.14.4

[stakx]

Hi @Epicycle23 , thanks for reporting. I'll take a look a little later.

[stakx]

OK, this broke between versions 4.10.1 and 4.11.0, and the problem lies in this line of code:

https://github.com/moq/moq4/blob/be325ce3971d7d4efa432f8ebcbe10763f027e91/src/Moq/ExpressionExtensions.cs#L262

This is supposed to extract the method from the expression tree, and obviously always choosing the getter won't do any good for write-only indexers.

For regular properties, we have a different code path that accounts for the write-only special case:

https://github.com/moq/moq4/blob/be325ce3971d7d4efa432f8ebcbe10763f027e91/src/Moq/ExpressionExtensions.cs#L290-L297

However, splitting assignment expressions and both code paths mentioned above need some improving, they're rather hard to understand. I'll see what I can come up with.

[stakx]

OK, this should be fixed. The expression tree logic I had to change is somewhat difficult to understand, so I might do some refactoring before releasing a bugfix version on NuGet. It should happen sometime during the next few days.

Thanks again for reporting this regression!

[Epicycle23]

Thanks for the fast response/fix, can't wait to update.

[stakx]

can't wait to update

Update: Version 4.14.5 should become available on NuGet shortly.

---

If you're in a hurry and you cannot wait, you can use the CI NuGet feed at https://ci.appveyor.com/nuget/moq4, or download the NuGet packages generated on the CI server from https://ci.appveyor.com/project/MobileEssentials/moq4/build/artifacts.

(Mind that the package version of the CI packages isn't right, so if you do use those packages, you'll need to flush them from your NuGet package cache before switching to the official package.)

I'll likely do a release today or tomorrow.