Incompatible change to NuGet package resolution

[Zastai]

NuGet Product Used

dotnet.exe, MSBuild.exe

Product Version

6.0.300 / 17.2

Worked before?

6.0.20x / 17.1

Impact

It's more difficult to complete my work

Repro Steps & Context

We have a company nuget server (using Nexus), which hosts not only our own packages, but also any versions of third-party packages that have been allowlisted (so no nuget.org access).

We only target version 4.7.2 (or very occasionally 4.8) of the .NET framework, and our builds are set up to reference microsoft.netframework.referenceassemblies 1.0.0 to ensure that works everywhere.

Previous NuGet resolution only pulled in microsoft.netframework.referenceassemblies itself, plus microsoft.netframework.referenceassemblies.net472 and/or microsoft.netframework.referenceassemblies.net48, matching what we target.

However, the same projects now fail to restore with the 6.0.300 SDK that comes with VS2022 17.2:

error NU1101: Unable to find package Microsoft.NETFramework.ReferenceAssemblies.net461. No packages exist with this id in source(s): <company feed>

(And the project in question does NOT target net461.)
This feels like a pretty significant regression.

To Reproduce

• set up a feed containing only microsoft.netframework.referenceassemblies and its net472 and net48 sub-packages
• create a project targeting net472 or net48 (plus optionally something else, like netstandard2.1)
• add a package reference to microsoft.netframework.referenceassemblies
• run dotnet restore

Verbose Logs

No response

[nkolev92]

Hey @Zastai,

What you are seeing is a change in 6.2, https://docs.microsoft.com/en-us/nuget/release-notes/nuget-6.2#summary-whats-new-in-62, best described in https://github.com/NuGet/Samples/tree/main/AssetTargetFallbackTransitiveDependencies.

The tldr is when AssetTargetFallback was being used before, the dependencies weren't being downloaded.

Because you have microsoft.netframework.referenceassemblies as a dependency in a .NET Standard project you were effectively installed microsoft.netframework.referenceassemblies and because the fallback was incorrectly not considered you were never getting the dependencies that were going to be seen as incompatible.

The solution here for you is to conditionally include the PackageReference microsoft.netframework.referenceassemblies and not include it for .NET Standard.

Let me know if that works for you.

[Zastai]

I wish there was more care taken with introducing breaking changes in point releases...

Now I'll need to add a conditional, one something that has no "nice" variable to test, because AFAIK there is no property set to the "class" of target specified by $(TargetFramework) (something with a value like "netfx", "netstandard", "netcore").

I'll have to hope that something like $(TargetFramework.StartsWith('net4')) is going to be sufficient and futureproof (well, until we hit NET 40.0 in 2055 anyway). That does resolve the issue for now though (but then, so would refreshing our nuget server using a nuget client that has this behaviour).

[nkolev92]

Consider using the MSBuild property functions instead:

https://docs.microsoft.com/en-us/visualstudio/msbuild/property-functions?view=vs-2022#msbuild-targetframework-and-targetplatform-functions

You might be able to condition on the TargetFrameworkIdentifier as well.

<Project Sdk="Microsoft.NET.Sdk">

  <PropertyGroup>
    <TargetFrameworks>netstandard2.0;net472</TargetFrameworks>
  </PropertyGroup>

  <ItemGroup Condition=" '$(TargetFrameworkIdentifier)' == '.NETFramework' ">
    <PackageReference Include="Newtonsoft.Json" Version="9.0.1" />
  </ItemGroup>

  <ItemGroup Condition=" $([MSBuild]::IsTargetFrameworkCompatible('netstandard2.0', '$(TargetFramework)'))">
    <PackageReference Include="NuGet.Common" Version="5.8.0" />
  </ItemGroup>

</Project>

here's the dotnet list package of the above project:

C:\Code\Temp\Conditional [master +0 ~1 -0 !]> dotnet list package
Project 'Conditional' has the following package references
   [net472]:
   Top-level Package      Requested   Resolved
   > Newtonsoft.Json      9.0.1       9.0.1

   [netstandard2.0]:
   Top-level Package             Requested   Resolved
   > NETStandard.Library   (A)   [2.0.3, )   2.0.3
   > NuGet.Common                5.8.0       5.8.0

(A) : Auto-referenced package.