Work that needs to happen for .NET 5 TFMs

[terrajobst]

The spec for .NET 5 TFMs can be found here.

Runtime/SDK

• Ensure SDK explodes .NET 5 TargetFramework into TargetFramework* and TargetPlatform* properties
• Make the build fail when a TFM with an unsupported OS or OS version is being used
• Update RIDs for Xamarin platforms
• Add preprocessor symbols for OS
• Handle new TFMs in runtimeconfig and host
• Produce a warning when a net5.0 project references netcoreapp3.1 (or earlier) with WPF/WinForms
• Cut
  • Add shared framework for Xamarin platforms
  • Add SDK-style build support for Xamarin

NuGet

• net5 tfm: framework precedence rules
• net5 tfm: produce error when missing TPV
• net5 tfm: "hydrating" empty TargetPlatformVersions
• net5.0 VS APIs
• With multi targeted projects, NuGet should read the target framework related information from the inner build.
• NuGet pack should catch incorrect omitting of the dot in version numbers
• Cut
  • Make NuGet understand that the existing Xamarin TFMs can be installed into the new net5.0-xxx TFMs (Xamarin is pushed to .NET 6)
  • Fail pack when packing equivalent TFMs like net5.0-ios and net5.0-ios13.0 (this state is impossible now)
  • Produce a warning when a project consumes a library with a higher TargetPlatformMinVersion (handled by analyzer)
  • net5 tfm: TargetPlatformMinVersion in packed nuspec (handled by analyzer)
• Future
  • Add a TFM for Unity's DOTS profile

MSBuild

• Allow TFM/TPM checks in a concise, understandable way

Project System

• Pass the correct information to NuGet restore, specifically TFI, TFV, TPI, TPV

@rainersigwald @dsplaisted @rrelyea @ericstj @ViktorHofer Please help me complete the list of items. Also, we would make sure that each item is linked to a corresponding GitHub issue.

[marek-safar]

Add shared framework for Xamarin platforms

What do you mean by that?

Add SDK-style build support for Xamarin

Don’t think this should be here, it’s not required for runtime but build on top of that as other workloads

[vitek-karas]

Should add whatever work comes out of this issue: #34033

[hypeartist]

Is that related: https://github.com/dotnet/runtime/issues/34060 ?

[terrajobst]

Add shared framework for Xamarin platforms

What do you mean by that?

We need to figure out how a project targeting say net5.0-ios13.0 references the platform, which includes both the BCL as well as the Xamarin specific bits on top. Implicit PackageReference? FrameworkReference?

Add SDK-style build support for Xamarin

Don’t think this should be here, it’s not required for runtime but build on top of that as other workloads

The point of this issue to group all the work that is happening for bringer this work to life; the point isn't to design the items themselves. @mhutch, do you want to file a similar uber item for Xamarin work? It should track things like the SDK style project, how the framework is being referenced etc. I would just link this one instead.

[danmoseley]

cc @ViktorHofer

[steveisok]

+1 to the uber item for Xamarin.

[dsplaisted]

@terrajobst Additional item for NuGet (underway now):

• Update NuGet TargetFramework parsing to parse TargetPlatformIdentifier and TargetPlatformVersion

[danmoseley]

@dsplaisted do you see any work here for the Mono or Libraries teams? My impression is no -- this is what I understand from @terrajobst last week as well (the "Runtime/SDK" section seems all SDK except the last one which is @vitek-karas ). Do I read that right?

[steveisok]

• Add shared framework for Xamarin platforms

@terrajobst We're adding runtime packs for Microsoft.NETCore.App.Runtime.<Mobile RID> and Xamarin iOS/Android. What do you mean by 'shared framework'? Did you mean the same thing? I could be misunderstanding the broader view.