User Story: Package authors can multi-target between runtime identifiers (RID)

[terrajobst]

Spec TBD

[danmoseley]

Currently multitargeting is supported via TargetFrameworks but not really for multiple RID's. In our own build, we have to do custom build gymnastics to achieve this.

[danmoseley]

The libraries team part here is representing our needs as we'd like to move over to this supported mechanism once it exists.

[cdmihai]

I think that adding a new first class concept to MSBuild, that of arbitrary build dimensions, would solve these 'we want to bolt on yet another hardcoded dimension' types of issues once and for all. A build dimension could be defined as a key value map: {foo:"bar", zoo:"roo"} {TargetFramework:"net472", RuntimeId:"win", Configuration="Debug", Architecture="x64"}. In MSBuild they could be expressed via regular items, or we could introduce new MSBuild expressions with well defined semantics. The engine could know about them to make it easier to specify multitargeting and whatnot. We could also borrow BuildXL's design of build dimensions

[danmoseley]

We should get an engineering owner assigned to this, like every P0 story, to avoid disconnects. It can always change later. It would most likely be the M1 where most of the work will happen. Is that you @marcpopMSFT or someone on your team?

[marcpopMSFT]

My understanding is that the largest set of the work for this would be from NuGet so @aortiz-msft would probably be the M1 owner.

[danmoseley]

@aortiz-msft thoughts?

[ViktorHofer]

I think for this a decent amount of work needs to be done by MSBuild, NuGet and the SDK.

[aortiz-msft]

Yes, we discussed this in our Monday meeting last week, and this is not something we think we can deliver in NET 6.0. However, let's understand the customer feedback around this and start validating the problem and solution hypotheses.