Remove references to PlatformAbstractions.

[eerhardt]

This will allow us to remove the PlatformAbstractions library from dotnet/runtime.

I needed to update the SDK used so I can use the new RuntimeInformation.RuntimeIdentifier API that is only in .NET 5.

Contributes to dotnet/runtime#3470

This emulates a similar change in dotnet/runtime: dotnet/runtime@a1af15d

cc @NikolaMilosavljevic @dagood @AdamYoblick

[AdamYoblick]

@vatsan-madhavan I'm not sure who to tag on this from WPF. Just wanted to make sure that moving windowsdesktop repo to .net 5 won't break anything from wpf?

[vatsan-madhavan]

@AdamYoblick, please tag @dotnet/wpf-developers 😄

I worry that it has the potential to break something in our tests... but maybe it's benign after all. I can't answer this without research unfortunately.

@fabiant3, can someone please vet this change and signoff ?

[eerhardt]

Any thoughts/feedback on this? PlatformAbstractions is about to be removed.

[fabiant3]

@ryalanms for awareness.

[mmitche]

I think we need this to go into master and then be cherry-picked to p5.

/cc @lukas-lansky

[mmitche]

@AdamYoblick Can this be merged?

[AdamYoblick]

I think so? I'm really not familiar enough with this repo to say for sure. Also, someone from wpf should also sign off since this is a shared packaging repo.

[mmitche]

Yeah. I think this is blocking p5 at the moment. @vatsan-madhavan @eerhardt thoughts on merging this?

[eerhardt]

I have no objections to merging this, but there aren't any approvals yet.

[AdamYoblick]

I've approved for winforms, but @ryalanms (or someone else) should probably approve for wpf. 😄

[vatsan-madhavan]

I take back my previous comment about potential for breaking (wpf) tests etc. I really can't tell without research; I also don't have a strong reason to think that this would cause problems. Please proceed as if I didn't say anything in the first place 😀.

I usually like to give these sorts of changes a thorough once-over and understand (a) impact to the product and (b) impact to immediate (build-time or run-time) dependencies and (c) impact to customers. There is just not enough information in the PR to make any of those judgments easily; (a) is sort of cryptic ("go read something in dotnet/runtime" is what I'm seeing... "remove PlatformAbstractions".. but why?), (b) requires at least a basic bit of analysis of closely related repos (like wpf*, winforms etc.) - probably no impact there but good to make sure nothing from there relies on content from "PlatformAbstractions", and I'm not sure what's needed for (c). I don't have the time to go digging any further -deferring to @fabiant3 .

[eerhardt]

(a) impact to the product

There shouldn't be any impact to the product, this solely a build infrastructure change.

(b) impact to immediate (build-time or run-time) dependencies

This removes a build-time dependency on the Microsoft.DotNet.PlatformAbstractions library. The reason it is being removed is because the library is being obsoleted.

This change has no impact on run-time dependencies.

(c) impact to customers

There shouldn't be any impact to customers, this solely a build infrastructure change.

[vatsan-madhavan]

Was it used in this repo purely to power the build-task functionality in GetTargetMachineInfo.cs ? If yes, and if it wasn't present to support any other purpose related to winforms or wpf, then this change seems reasonable to me.

[eerhardt]

Was it used in this repo purely to power the build-task functionality in GetTargetMachineInfo.cs ?

Correct. Previously, PlatformAbstractions was the only way to get the current RuntimeIdentifier of the machine. The only thing used from GetTargetMachineInfo.cs was to get the "host RuntimeIdentifier", which I replaced with the new API: $([System.Runtime.InteropServices.RuntimeInformation]::RuntimeIdentifier).