Completion crashes with InvalidCastException on CompletionList type

Extension version: 1.23.2 VS Code version: Code 1.49.2 (e5e9e69aed6e1984f7499b7af85b3d05f9a6883a, 2020-09-24T16:29:41.983Z) OS version: Windows_NT x64 10.0.19041

Steps to reproduce problem:

1. create console project with ‘dotnet new console’
2. start to write some c# code
3. no code completion for c# extension 1.23.2 version
4. after downgrading c# extension to 1.23.1 code completion works OK

System.InvalidCastException: Nie można zrzutować 
[A]System.Threading.Tasks.Task`1[System.ValueTuple`2[Microsoft.CodeAnalysis.Completion.CompletionList,System.Boolean]] na 
[B]System.Threading.Tasks.Task`1[System.ValueTuple`2[Microsoft.CodeAnalysis.Completion.CompletionList,System.Boolean]]. 
 
 Typ A pochodzi od mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 w kontekście LoadNeither w lokalizacji C:\\\\WINDOWS\\\\Microsoft.Net\\\\assembly\\\\GAC_64\\\\mscorlib\\\\v4.0_4.0.0.0__b77a5c561934e089\\\\mscorlib.dll. 
 
 Typ B pochodzi od mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089 w kontekście LoadNeither w lokalizacji C:\\\\WINDOWS\\\\Microsoft.Net\\\\assembly\\\\GAC_64\\\\mscorlib\\\\v4.0_4.0.0.0__b77a5c561934e089\\\\mscorlib.dll.\\r\\n   
 
 w OmniSharp.Roslyn.CSharp.Services.Intellisense.CompletionItemExtensions.GetCompletionsInternalAsync(CompletionService completionService, Document document, Int32 caretPosition, CompletionTrigger trigger, ImmutableHashSet`1 roles, OptionSet options, CancellationToken cancellationToken) w D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Roslyn.CSharp\\\\Services\\\\Intellisense\\\\CompletionItemExtensions.cs:wiersz 64\\r\\n   w OmniSharp.Roslyn.CSharp.Services.Completion.CompletionService.<Handle>d__7.MoveNext() w D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Roslyn.CSharp\\\\Services\\\\Completion\\\\CompletionService.cs:wiersz 120\\r\\n--- Koniec śladu stosu z poprzedniej lokalizacji, w której wystąpił wyjątek ---\\r\\n   w System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   w System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   w OmniSharp.Endpoint.EndpointHandler`2.<GetFirstNotEmptyResponseFromHandlers>d__19.MoveNext()\\r\\n--- Koniec śladu stosu z poprzedniej lokalizacji, w której wystąpił wyjątek ---\\r\\n   w System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   w System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   w OmniSharp.Endpoint.EndpointHandler`2.<HandleRequestForLanguage>d__20.MoveNext() w D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Host\\\\Endpoint\\\\EndpointHandler.cs:wiersz 230\\r\\n--- Koniec śladu stosu z poprzedniej lokalizacji, w której wystąpił wyjątek ---\\r\\n   w System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   w System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   w OmniSharp.Endpoint.EndpointHandler`2.<Process>d__16.MoveNext() w D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Host\\\\Endpoint\\\\EndpointHandler.cs:wiersz 131\\r\\n--- Koniec śladu stosu z poprzedniej lokalizacji, w której wystąpił wyjątek ---\\r\\n   w System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()\\r\\n   w System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)\\r\\n   w OmniSharp.Stdio.Host.<HandleRequest>d__13.MoveNext() w D:\\\\a\\\\1\\\\s\\\\src\\\\OmniSharp.Stdio\\\\Host.cs:wiersz 215

[mbp]

Ok, I found something.

If I modify file OmniSharp.exe.config located in .vscode\extensions\ms-dotnettools.csharp-1.23.13\.omnisharp\1.37.12 and remove this section:

<assemblyBinding xmlns="urn:schemas-microsoft-com:asm.v1">
  <dependentAssembly>
    <assemblyIdentity name="System.ValueTuple" publicKeyToken="cc7b13ffcd2ddd51" culture="neutral" />
    <bindingRedirect oldVersion="0.0.0.0-4.0.3.0" newVersion="4.0.3.0" />
  </dependentAssembly>
</assemblyBinding>

Then the exception goes away, and code completion starts working!

I don’t know why this binding redirect is added on compilation, however I discovered McMaster.Extensions.CommandLineUtils/2.2.4 was depending on 4.4.0 of System.ValueTuple while omnisharp-roslyn depends on 4.5.0. Newer versions of McMaster.Extensions.CommandLineUtils depend on 4.5.0. When I upgraded the dependency, the binding redirect was no longer added to OmniSharp.exe.config

I have made a pull request in omnisharp-roslyn to upgrade the dependency.

[JoeRobich]

Multiple loading of the OmniSharp.MSBuild assembly should be resolved with the following two changes being merged https://github.com/OmniSharp/omnisharp-vscode/pull/4642 & https://github.com/OmniSharp/omnisharp-vscode/pull/4643. We expect to have a pre-release build shortly that we will validate for publishing.