Don't require targetversion to be latest for Class Libraries

[dotMorten]

Describe the bug
When building a class library, the target version should not matter, as long as it's at least minversion. That check should only apply to app projects.

This check is done here and should have a condition for class libraries to ignore it (or check that target is at least minversion):

microsoft-ui-xaml/build/NuSpecs/MUXControls-Nuget-Common.targets

Lines 16 to 18 in 8f8cd0f

	<Error
	Text="Microsoft.UI.Xaml nuget package requires TargetPlatformVersion &gt;= 10.0.18362.0 (current project is $(MicrosoftUIXamlTargetPlatformCheckValue))"
	Condition="$(MicrosoftUIXamlTargetPlatformCheckValue) &lt; 18362" />

Steps to reproduce the bug

1. Create a .NET Class Library and set target version to 17134.
2. Add WinUI nuget package.
3. Build

Expected behavior
Build succeeds

Actual behavior
Build error:

C:\Users\username\.nuget\packages\microsoft.ui.xaml\2.3.191211002\buildTransitive\Common.targets(16,5): error : Microsoft.UI.
Xaml nuget package requires TargetPlatformVersion >= 10.0.18362.0 (current project is 17134) [E:\src\myclasslibrary.csproj]

Version Info
2.3.191211002

[ranjeshj]

@jevansaks @llongley any ideas why 19H1 is required ?

[jevansaks]

Agree that the check for class libraries could be different. This check is serving two purposes:

1. For apps, it makes sure that you are running against a version high enough that we won't get "quirked" behavior from OS XAML.
2. For apps and class libraries, it's trying to avoid a confusing error message down the line because the WinUI WinMDs reference types in the Windows SDK that weren't introduced until later versions of Windows.

Now for class libraries the #2 check still needs to be there, but perhaps the Windows SDK we require can be lowered?

I think if someone can suggest a fix here that covers all the various project types we would be happy to accept it.

@dotMorten is there a challenge in having your class library target the 18362 SDK?

[dotMorten]

is there a challenge in having your class library target the 18362 SDK?

I prefer keeping min and max version the same. This to avoid having to ensure we don't call APIs that aren't supported on that platform. If I don't need the latest features, why enable them?

I don't really get your second point. Why is it confusing to not see APIs that you can't call on the version you're targeting? It's way more confusing to see your app crash on an older PC because we called an API not available on that device.

[jevansaks]

The problem is that the WinUI metadata has types it references that weren't introduced until a later version of the Windows SDK. You will get a bizarre compiler error about not being able to resolve types if you disable the check and target too old of a Windows SDK.

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be closed in 5 days.

[dotMorten]

I’m ok with closing this