Xamarin developers get warnings when they call APIs that aren't available on the OS version they target

[terrajobst]

We already have the analyzer, but this work captures ensuring the Xamarin bindings for Apple & Android platform are using the platform compatibility annotations (as opposed to ones specific to the bindings).

https://github.com/dotnet/designs/blob/main/accepted/2020/platform-checks/platform-checks.md#attributes

Work Items

• Apply [SupportedOSPlatform] and [UnsupportedOSPlatform] annotations for new platforms in dotnet/runtime Apply [SupportedOSPlatform] and [UnsupportedOSPlatform] annotations for new platforms in dotnet/runtime #44912
• Xamarin.iOS annotations Decorate all APIs with correct SupportedOSPlatform attributes macios#10170
• Xamarin.Android annotations Decorate all APIs with correct SupportedOSPlatform attributes android#5338

[dotMorten]

Is this the reason I'm seeing all these (invalid) warnings when targeting net6.0-ios13 ?

warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.StopUpdatingHeading()' is only supported on: 'macOS/OSX' 11.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.RequestWhenInUseAuthorization()' is only supported on: 'macOS/OSX' 11.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.StartUpdatingHeading()' is only supported on: 'macOS/OSX' 11.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'UIApplication.StatusBarOrientation.get' is unsupported on: 'ios' 9.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'UIApplication.StatusBarOrientation' is unsupported on: 'ios' 9.0 and later, 'macOS/OSX' 10.14 and later, 'maccatalyst' 13.1 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.AuthorizationStatus.get' is only supported on: 'macOS/OSX' 11.0 and later, 'tvos' 14.0 and later, 'ios' 14.0 and later, 'maccatalyst' 14.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.AuthorizationStatus' is only supported on: 'macOS/OSX' 11.0 and later, 'tvos' 14.0 and later, 'ios' 14.0 and later, 'maccatalyst' 14.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.Status.get' is unsupported on: 'ios' 14.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.Status' is unsupported on: 'ios' 14.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLFloor.Level' is only supported on: 'macOS/OSX' 10.15 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Floor.get' is only supported on: 'macOS/OSX' 10.15 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Floor' is only supported on: 'macOS/OSX' 10.15 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Course' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Course.get' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLFloor.Level' is only supported on: 'macOS/OSX' 10.15 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Floor.get' is only supported on: 'macOS/OSX' 10.15 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Floor' is only supported on: 'macOS/OSX' 10.15 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Speed.get' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Speed' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Course' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Course.get' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Speed' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocation.Speed.get' is only supported on: 'tvos' 13.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.HeadingAvailable.get' is only supported on: 'macOS/OSX' 11.0 and later.
warning CA1416: This call site is reachable on: 'iOS' 13.0 and later. 'CLLocationManager.HeadingAvailable' is only supported on: 'macOS/OSX' 11.0 and later.

[jeffhandley]

Is this the reason I'm seeing all these (invalid) warnings when targeting net6.0-ios13 ?

This does look related. @dotMorten, if this is still happening with Preview 7, could you please file a fresh issue for those invalid diagnostics? Please tag @steveisok, @buyaa-n, and me in the issue. Thanks for the help!

[dotMorten]

@jeffhandley Thanks! I literally just got to upgrade and noticed warnings were still there, so wanted to go find this issue so I could comment that it hasn't be solved. Thanks for the notification so I didn't have to go search for it :)