Discuss opt-out feature for workloads

[steveisok]

As found in dotnet/runtime#52991 and discussed internally, building dotnet/runtime with a system-wide dotnet fails with something like:

C:\Program Files\dotnet\sdk\6.0.100-preview.5.21262.3\Sdks\Microsoft.NET.Sdk\targets\Microsoft.NET.Sdk.ImportWorkloads.targets(24,5): error NETSDK1147: The following workload packs were not installed: Microsoft.iOS.Sdk Microsoft.iOS.Windows.Sdk

The reason for the error is that some projects include net6.0-Android or net6.0-iOS in their <TargetFrameworks>. In this context, we don't mean Xamarin Android or Xamarin iOS, but instead we mean that the runtime is being built for android / iOS.

I want to open a discussion about the best way to work around the problem.

Current Workarounds

• Set MSBuildEnableWorkloadResolver=false
• build.cmd/sh in runtime to use the in repo dotnet

Possible Solution

Each workload would be responsible for defining a <DisableXYZWorkload> property and each AutoImport.props and WorkloadManifest.targets would need to check it.

/cc @dsplaisted @lewing @jonathanpeppers

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[ericstj]

What if we just had a target that ran before _CheckForMissingWorkload that removed the MissingWorkloadPack items which we don't require? If we wanted the SDK to support this directly they could define a public item (AllowMissingWorkloadPack) that acts as an exclusion.

sdk/src/Tasks/Microsoft.NET.Build.Tasks/targets/Microsoft.NET.Sdk.ImportWorkloads.targets

Lines 20 to 25 in c53c8ac

	<Target Name="_CheckForMissingWorkload"
	BeforeTargets="_CheckForInvalidConfigurationAndPlatform;_CheckForUnsupportedTargetPlatformIdentifier"
	Condition="'@(MissingWorkloadPack)' != ''">
	<ShowMissingWorkloads MissingWorkloadPacks="@(MissingWorkloadPack)"/>
	</Target>

cc @ViktorHofer

[marcpopMSFT]

@steveisok is this still something you want us to look into?

[steveisok]

@steveisok is this still something you want us to look into?

Yes, I think this is going to be a need in .net 8.