Remove custom types marking for types which XA does not own for netcore

This is or will be handled by BCL libraries and XA tooling should try
not to interfere with more fine tuned handling done by BCL.

src/Microsoft.Android.Sdk.ILLink/ApplyPreserveAttributeBase.cs

@@ -11,10 +11,7 @@
 namespace Microsoft.Android.Sdk.ILLink
 {
 
-	public abstract class ApplyPreserveAttributeBase : BaseSubStep {
-
-		// set 'removeAttribute' to true if you want the preserved attribute to be removed from the final assembly
-		protected abstract bool IsPreservedAttribute (ICustomAttributeProvider provider, CustomAttribute attribute, out bool removeAttribute);
+	public class ApplyPreserveAttribute : BaseSubStep {
 
 		public override SubStepTargets Targets {
 			get {
@@ -66,7 +63,7 @@ public override void ProcessEvent (EventDefinition @event)
 
 		void MarkMethodIfPreserved (MethodDefinition method)
 		{
-			foreach (var attribute in GetPreserveAttributes (method)) 
+			foreach (var attribute in GetPreserveAttributes (method))
 				MarkMethod (method, attribute);
 		}
 
@@ -126,6 +123,9 @@ void PreserveUnconditional (IMetadataTokenProvider provider)
 
 		void TryApplyPreserveAttribute (TypeDefinition type)
 		{
+			if (!type.HasCustomAttributes)
+				return;
+
 			foreach (var attribute in GetPreserveAttributes (type)) {
 				Annotations.Mark (type);
 
@@ -138,28 +138,12 @@ void TryApplyPreserveAttribute (TypeDefinition type)
 			}
 		}
 
-		List<CustomAttribute> GetPreserveAttributes (ICustomAttributeProvider provider)
+		IEnumerable<CustomAttribute> GetPreserveAttributes (ICustomAttributeProvider provider)
 		{
-			List<CustomAttribute> attrs = new List<CustomAttribute> ();
-
-			if (!provider.HasCustomAttributes)
-				return attrs;
-
-			var attributes = provider.CustomAttributes;
-
-			for (int i = attributes.Count - 1; i >= 0; i--) {
-				var attribute = attributes [i];
-
-				bool remote_attribute;
-				if (!IsPreservedAttribute (provider, attribute, out remote_attribute))
-					continue;
-
-				attrs.Add (attribute);
-				if (remote_attribute)
-					attributes.RemoveAt (i);
-			}
-
-			return attrs;
+			yield return provider.CustomAttributes.Where (a => {
+				var type = a.Constructor.DeclaringType;
+				return type.Namespace == "Android.Runtime" && type.Name == "PreserveAttribute";
+			});
 		}
 	}
 }

src/Microsoft.Android.Sdk.ILLink/Microsoft.Android.Sdk.ILLink.csproj

@@ -28,6 +28,7 @@
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\LinkerOptions.cs" />
 
     <!--Steps that are upstreamed, these are OK to remove-->
+    <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\ApplyPreserveAttribute.cs" />
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\OutputStepWithTimestamps.cs" />
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\PreserveCode.cs" />
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\PreserveDynamicTypes.cs" />
@@ -36,6 +37,7 @@
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\PreserveRuntimeSerialization.cs" />
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\PreserveTlsProvider.cs" />
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\PreserveTypeConverters.cs" />
+    <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\RemoveAttributes.cs" />
 
     <!--TODO: Subclasses MarkStep-->
     <Compile Remove="..\Xamarin.Android.Build.Tasks\Linker\MonoDroid.Tuner\MonoDroidMarkStep.cs" />

src/Microsoft.Android.Sdk.ILLink/SetupStep.cs

@@ -43,7 +43,6 @@ protected override void Process ()
 			subSteps2.Add (new PreserveApplications ());
 			subSteps2.Add (new PreserveRegistrations (cache));
 			subSteps2.Add (new PreserveJavaInterfaces ());
-			subSteps2.Add (new RemoveAttributes ());
 
 			InsertAfter (new FixAbstractMethodsStep (cache), "RemoveUnreachableBlocksStep");
 			InsertAfter (subSteps2, "RemoveUnreachableBlocksStep");

src/Mono.Android/ILLink/ILLink.LinkAttributes.xml

@@ -0,0 +1,10 @@
+<linker>
+  <assembly fullname="*">
+    <type fullname="Android.Runtime.PreserveAttribute">
+      <attribute internal="RemoveAttributeInstances" />
+    </type>
+    <type fullname="Android.Runtime.IntDefinitionAttribute">
+      <attribute internal="RemoveAttributeInstances" />
+    </type>
+  </assembly>
+</linker>

src/Mono.Android/Mono.Android.csproj

@@ -85,6 +85,8 @@
 
   <ItemGroup Condition=" '$(TargetFramework)' == 'netcoreapp3.1' ">
     <ProjectReference Include="..\..\external\Java.Interop\src\Java.Interop\Java.Interop.csproj" />
+
+    <EmbeddedResource Include="ILLink/ILLink.LinkAttributes.xml" />
   </ItemGroup>
 
   <ItemGroup>