Biztalk 2020 Build fails with AddBizTalkHiddenReferences after adding certain nuget packages - biztalk

Question

Reproduction steps:
Stack: Windows 10, Visual Studio 2019 professional, BizTalk Server 2020 developer edition CU1.
In Visual Studio create a new Biztalk Server Project
Manage Nuget Package, Add a nuget package. pick one:
Known to break the build
autofac 6.0, 6.1, 6.2
nodatime 3.0.5
Azure.Storage.Blobs 12.9.1
Known to not break the build
autofac 5.2
many others I tested.
F6 (Build) or run msbuild
As far as my testing was going, whenever the nuget packages directly list a variant with a .net framework as a dependency, it works. Listing only .net standard and .net 5 as a dependency, as in the list above, fails the buil.
actual error:
PS C:\code\autofacRepro> msbuild
Microsoft (R) Build Engine version 16.11.0+0538acc04 for .NET Framework
Copyright (C) Microsoft Corporation. All rights reserved.
Building the projects in this solution one at a time. To enable parallel build, please add the "-m" switch.
Build started 8/24/2021 3:01:10 PM.
Project "C:\code\autofacRepro\autofacRepro.sln" on node 1 (default targets).
ValidateSolutionConfiguration:
Building solution configuration "Debug|Any CPU".
Project "C:\code\autofacRepro\autofacRepro.sln" (1) is building "C:\code\autofacRepro\autofacRepro.btproj" (2) on node 1 (default targets).
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: The "AddBizTalkHiddenReferences" task failed unexpectedly. [C:\code\autofacRepro\autofacRepro.btproj]
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: System.ArgumentException: String cannot have zero length. [C:\code\autofacRepro\autofacRepro.btproj]
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: at System.Reflection.AssemblyName..ctor(String assemblyName) [C:\code\autofacRepro\autofacRepro.btproj]
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: at Microsoft.VisualStudio.BizTalkProject.BuildTasks.AddBizTalkHiddenReferences.GetAssemblyNamesFromItems(ITaskItem[] items) [C:\co
de\autofacRepro\autofacRepro.btproj]
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: at Microsoft.VisualStudio.BizTalkProject.BuildTasks.AddBizTalkHiddenReferences.Execute() [C:\code\autofacRepro\autofacRepro.btproj
]
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: at Microsoft.Build.BackEnd.TaskExecutionHost.Microsoft.Build.BackEnd.ITaskExecutionHost.Execute() [C:\code\autofacRepro\autofacRep
ro.btproj]
C:\Program Files (x86)\MSBuild\Microsoft\BizTalk\BizTalkCommon.targets(190,9): error MSB4018: at Microsoft.Build.BackEnd.TaskBuilder.<ExecuteInstantiatedTask>d__26.MoveNext() [C:\code\autofacRepro\autofacRepro.btproj]
Done Building Project "C:\code\autofacRepro\autofacRepro.btproj" (default targets) -- FAILED.
Done Building Project "C:\code\autofacRepro\autofacRepro.sln" (default targets) -- FAILED.
Build FAILED.
A repro zip package is available in this github issue. (at first I thougt, it was a special issue with autofac, but it is not)
My old stack (windows server 2016, visual studio 2015, biztalk 2016) is not affected. We are using autofac 6.1 in biztalk projects there without any issue.
I feel like this is a BizTalk bug but I am not smart enough to find the way Microsoft allows reporting it.
So finally the question is, is there a workaround or a bugfix?

Answer 1

I've had this with one of my own packages. This package was targeting .NET Standard 2.0. I had to add .NET Framework 4.8 (in my case) specifically as a target framework in the class library and recreate the package for it.
For public packages, you may want to create a PR or make a fork to include targeting of .NET Framework. Your BizTalk project then needs to reference the .NET Framework assembly rather than the .NET Standard one.