Could not upgrade projects to new 2.2.100 sdk getting conflict warnings

Could not upgrade all projects to new 2.2.100 sdk, as we got conflict warnings for among others

1:7>/usr/local/share/dotnet/sdk/2.2.100/Microsoft.Common.CurrentVersion.targets(2110,5): warning MSB3277: Found conflicts between different versions of "Microsoft.AspNetCore.Authentication.Abstractions" that couldnot be resolved.  These reference conflicts are listed in the build log when log verbosity is set to detailed. [/projpath]

• Microsoft.Extensions.Options
• Microsoft.Extensions.DependencyInjection.Abstractions
• Microsoft.AspNetCore.Http.Abstractions
• Microsoft.Extensions.Configuration.Abstractions
• Microsoft.AspNetCore.Hosting
• Microsoft.AspNetCore.Hosting.Abstractions
• Microsoft.EntityFrameworkCore
• Microsoft.AspNetCore.WebUtilities
• Microsoft.AspNetCore.Authentication.Abstractions

What all of these packages have in common is that they list a 2.2.0 release on nuget.org https://www.nuget.org/packages/Microsoft.Extensions.Options/2.2.0 and if you look carefully they are all at Downloads: 0.

Which is why msbuild detailed logs gives errors like these

         Dependency "Microsoft.Extensions.Options, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60".
             Could not resolve this reference. Could not locate the assembly "Microsoft.Extensions.Options, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60". Check to make sure the assembly exists on disk. If this reference is required by your code, you may get compilation errors.
[...]
There was a conflict between "Microsoft.Extensions.Options, Version=2.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" and "Microsoft.Extensions.Options, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60".
             "Microsoft.Extensions.Options, Version=2.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" was chosen because it was primary and "Microsoft.Extensions.Options, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" was not.
             References which depend on "Microsoft.Extensions.Options, Version=2.1.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" [/Users/nfloris/.nuget/packages/microsoft.extensions.options/2.1.0/lib/netstandard2.0/Microsoft.Extensions.Options.dll].
                 /Users/nfloris/.nuget/packages/microsoft.extensions.options/2.1.0/lib/netstandard2.0/Microsoft.Extensions.Options.dll
                   Project file item includes which caused reference "/Users/nfloris/.nuget/packages/microsoft.extensions.options/2.1.0/lib/netstandard2.0/Microsoft.Extensions.Options.dll".
                     /Users/nfloris/.nuget/packages/microsoft.extensions.options/2.1.0/lib/netstandard2.0/Microsoft.Extensions.Options.dll
             References which depend on "Microsoft.Extensions.Options, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60" [].
                 myproj/bin/Debug/netcoreapp2.2/myproj.dll
                   Project file item includes which caused reference "myproj/bin/Debug/netcoreapp2.2/myproj.dll".
                     myproj/bin/Debug/netcoreapp2.2/myproj.dll

Could not resolve this reference. Could not locate the assembly “Microsoft.Extensions.Options, Version=2.2.0.0, Culture=neutral, PublicKeyToken=adb9793829ddae60”.

Now that seems like a problem

[natemcmaster]

I think the problem more-or-less boils down to this: https://github.com/dotnet/sdk/issues/2420. Microsoft.AspNetCore.App does not yet flow transitively across ProjectReference. You have to have a reference to this in every project which uses it (directly or transitively). It’s something we hope to address in 3.0.

[natemcmaster]

But why weren’t those warnings present while we had the same proj content during 2.1?

That’s a great question. I don’t know why.

You’re saying that even in those common cases such a workaround is the only option?

Yes.