Include SupportedOSPlatformAttribute in C#/WinRT projections for non-polyfill APIs?

[Scottj1s]

Windows App SDK claims 100% compatibility as far downlevel as it is supported, to Windows 10 October 2018 Update (build 17763 / version 1809). Features that are not supported in the OS are then polyfilled. In the May 2022 WinUI Community Call, it was discussed that not all features are (or can be) polyfilled. I don't have details on which ones. But if that's true, then such APIs should at least inform the developer of the minimum OS requirement. For C# apps, the way to do that is via the SupportedOSPlatformAttribute.

Starting as a discussion, as there are some assumptions above.