Decorate all APIs with correct SupportedOSPlatform attributes

[marek-safar]

As part of netcore migration, we need to correctly annotate all APIs with .NET 6 to work correctly with existing tooling (primary existing analyzers). The attributes already exist in .NET5 and could be extended if necessary.

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

[AmrAlSayed0]

After reading the Platform compatibility analyzer doc page I saw attributes like [SupportedOSPlatform("Android6.0")]. I'm curious if the effort for this issue is going to include the android only API? For example:

//This is the C# class that is a binding of android.view.View
//(https://developer.android.com/reference/android/view/View.html)
public class View
{
    [SupportedOSPlatform("Android8.0")] // This means that this property can only be used on Android 8.0 or above
    //which corresponds to API 26 or above since this is the version it was added in
    //(https://developer.android.com/reference/android/view/View.html#getTooltipText())
    public string TooltipText { get; set; }
}

Or is only the net5.0 API going to be annotated?

[marek-safar]

This issue is for Android APIs only

[jonathanpeppers]

I think the attributes will actually be the API level such as:

[SupportedOSPlatform("android30")]

See: dotnet/runtime#43531

We'll have to see if we have to see if we have to put android30.0, I but I think we should try leaving off the .0.

[jonathanpeppers]

Correction: https://docs.microsoft.com/dotnet/standard/analyzers/platform-compat-analyzer#how-the-analyzer-determines-platform-dependency

major.minor is required

So I think we will have to use android30.0, etc.

[jonpryor]

Additionally, SupportedOSPlatform is only available in .NET 5+; thus, generator output will need to wrap it into a #if NET5 block:

	// Metadata.xml XPath class reference: path="/api/package[@name='android.app']/class[@name='Activity']"
	[global::Android.Runtime.Register ("android/app/Activity", DoNotGenerateAcw=true)]
#if NET5_0_OR_GREATER
	[global: System.Runtime.Versioning.SupportedOSPlatform ("android")]
#endif  // NET5_0_OR_GREATER
	public partial class Activity {
		public virtual unsafe bool IsActivityTransitionRunning {
			// Metadata.xml XPath method reference: path="/api/package[@name='android.app']/class[@name='Activity']/method[@name='isActivityTransitionRunning' and count(parameter)=0]"
			[Register ("isActivityTransitionRunning", "()Z", "GetIsActivityTransitionRunningHandler", ApiSince = 26)]
#if NET5_0_OR_GREATER
			[global::System.Runtime.Versioning.SupportedOSPlatform ("android26.0")]
#endif  // NET5_0_OR_GREATER
			get {…}
		}
	}

Related: https://github.com/dotnet/designs/blob/main/accepted/2020/or-greater-defines/or-greater-defines.md#doc-changes

[jpobst]

I think it's probably easier to define our own [SupportedOSPlatform] attribute and include it if not targeting net5.0+.

[marek-safar]

I think it's probably easier to define our own [SupportedOSPlatform] attribute and include it if not targeting net5.0+.

You could public [Conditional("NEVER")] on the local version of SupportedOSPlatformAttribute to be always removed by compiler for non-netcore builds

[jpobst]

Implementation details aside, the good news is we do already have this data and already put it in our bindings, just in a different place (ApiSince), so it won't be hard to add the new annotations.

[global::Android.Runtime.Register ("android/accessibilityservice/FingerprintGestureController$FingerprintGestureCallback", DoNotGenerateAcw=true, ApiSince = 26)]
public abstract partial class FingerprintGestureCallback : Java.Lang.Object
{
  [Register (".ctor", "()V", "", ApiSince = 26)]
  public unsafe FingerprintGestureCallback () : base (IntPtr.Zero, JniHandleOwnership.DoNotTransfer)
  {
    ...
  }
}

We will probably need to manually audit our hand-bound code also.