[Microsoft.Android.Sdk.ILLink] preserve types with `IJniNameProviderA…

…ttribute` (#9099)

Fixes: #8940
Context: TobiasBuchholz/Plugin.Firebase#144

Using the NuGet package:

    <PackageReference Include="Plugin.Firebase.CloudMessaging" Version="3.0.0" />

Includes a service:

    namespace Plugin.Firebase.CloudMessaging.Platforms.Android;

    [Service(Exported = true)]
    [IntentFilter(new[] { "com.google.firebase.MESSAGING_EVENT" })]
    public class MyFirebaseMessagingService : FirebaseMessagingService

Unfortunately, using `TrimMode=full` completely trims away the above
service, which is required for push notifications to work.

I could reproduce this problem in a test using the above NuGet package.

To fix this, we can modify `MarkJavaObjects` to preserve types with
attributes that implement `Java.Interop.IJniNameProviderAttribute`,
and the new test now passes.

With one exception, `Android.Runtime.RegisterAttribute`, should not be
preserved as that would be any Java type bound for C#.

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

@@ -4,9 +4,9 @@
 using Mono.Cecil;
 using Mono.Linker;
 using Mono.Linker.Steps;
-using Mono.Tuner;
 using Java.Interop.Tools.Cecil;
 using Xamarin.Android.Tasks;
+using Profile = Microsoft.Android.Sdk.ILLink.Profile;
 
 namespace MonoDroid.Tuner {
 
@@ -27,7 +27,14 @@ public override void Initialize (LinkContext context, MarkContext markContext)
 
 		bool IsActiveFor (AssemblyDefinition assembly)
 		{
-			return assembly.MainModule.HasTypeReference ("System.Net.Http.HttpMessageHandler") || assembly.MainModule.HasTypeReference ("Android.Util.IAttributeSet");
+			if (Profile.IsSdkAssembly (assembly))
+				return false;
+			if (Profile.IsProductAssembly (assembly))
+				return false;
+
+			return assembly.MainModule.HasTypeReference ("System.Net.Http.HttpMessageHandler") ||
+				assembly.MainModule.HasTypeReference ("Java.Lang.Object") ||
+				assembly.MainModule.HasTypeReference ("Android.Util.IAttributeSet");
 		}
 
 		public void ProcessAssembly (AssemblyDefinition assembly, string androidHttpClientHandlerType, Dictionary<string, HashSet<string>> customViewMap)
@@ -47,14 +54,42 @@ public void ProcessAssembly (AssemblyDefinition assembly, string androidHttpClie
 					}
 				}
 
-				// Custom views in Android .xml files
+				// Continue if not an IJavaObject
 				if (!type.ImplementsIJavaObject (cache))
 					continue;
+
+				// Custom views in Android .xml files
 				if (customViewMap.ContainsKey (type.FullName)) {
 					Annotations.Mark (type);
 					PreserveJavaObjectImplementation (type);
+					continue;
+				}
+
+				// Types with Java.Interop.IJniNameProviderAttribute attributes
+				if (ShouldPreserveBasedOnAttributes (type)) {
+					Annotations.Mark (type);
+					PreserveJavaObjectImplementation (type);
+					continue;
+				}
+			}
+		}
+
+		bool ShouldPreserveBasedOnAttributes (TypeDefinition type)
+		{
+			if (!type.HasCustomAttributes)
+				return false;
+
+			foreach (var attr in type.CustomAttributes) {
+				// Ignore Android.Runtime.RegisterAttribute
+				if (attr.AttributeType.FullName == "Android.Runtime.RegisterAttribute") {
+					continue;
+				}
+				if (attr.AttributeType.Implements ("Java.Interop.IJniNameProviderAttribute", cache)) {
+					return true;
 				}
 			}
+
+			return false;
 		}
 
 		public void ProcessType (TypeDefinition type)

src/Xamarin.Android.Build.Tasks/Tests/Xamarin.Android.Build.Tests/Tasks/LinkerTests.cs

@@ -598,6 +598,40 @@ public void PreserveIX509TrustManagerSubclasses ([Values(true, false)] bool hasS
 			}
 		}
 
+		[Test]
+		public void PreserveServices ()
+		{
+			var proj = new XamarinAndroidApplicationProject {
+				IsRelease = true,
+				TrimModeRelease = TrimMode.Full,
+				PackageReferences = {
+					new Package { Id = "Plugin.Firebase.CloudMessaging", Version = "3.0.0" },
+				}
+			};
+			proj.MainActivity = proj.DefaultMainActivity
+				.Replace ("//${FIELDS}",
+					"""
+					protected override void OnNewIntent (Android.Content.Intent? intent)
+					{
+						base.OnNewIntent (intent);
+						Plugin.Firebase.CloudMessaging.FirebaseCloudMessagingImplementation.OnNewIntent (intent);
+					}
+					""")
+				.Replace ("//${AFTER_ONCREATE}", "Plugin.Firebase.Core.Platforms.Android.CrossFirebase.Initialize (this);");
+
+			using var b = CreateApkBuilder ();
+			Assert.IsTrue (b.Build (proj), "Build should have succeeded.");
+
+			var assemblyPath = BuildTest.GetLinkedPath (b, isRelease: true, "Plugin.Firebase.CloudMessaging.dll");
+			FileAssert.Exists (assemblyPath);
+			using var assembly = AssemblyDefinition.ReadAssembly (assemblyPath);
+			var types = new [] { "Plugin.Firebase.CloudMessaging.Platforms.Android.MyFirebaseMessagingService" };
+			foreach (var typeName in types) {
+				var td = assembly.MainModule.GetType (typeName);
+				Assert.IsNotNull (td, $"{typeName} should not have been linked out!");
+			}
+		}
+
 		[Test]
 		public void DoNotErrorOnPerArchJavaTypeDuplicates ([Values(true, false)] bool enableMarshalMethods)
 		{