[One .NET] Add AddKeepAlivesStep (#5447)

Fixes: #5427

Context: e88cfbc

Update the .NET 6 linker to include `AddKeepAlivesStep.cs`, update
`AddKeepAlivesStep` so that it builds on .NET 6, add the custom
step to the .NET 6 `illink` custom step, and let the
`LinkerTests.AndroidAddKeepAlives()` test run on .NET 6.

Author: radekdoulik

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

@@ -28,7 +28,6 @@
     <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\AddKeepAlivesStep.cs" />
     <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" />

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

@@ -52,6 +52,10 @@ protected override void Process ()
 			if (Context.TryGetCustomData ("ProguardConfiguration", out proguardPath))
 				InsertAfter (new GenerateProguardConfiguration (proguardPath),  "CleanStep");
 
+			string addKeepAlivesStep;
+			if (Context.TryGetCustomData ("AddKeepAlivesStep", out addKeepAlivesStep) && bool.TryParse (addKeepAlivesStep, out var bv) && bv)
+				InsertAfter (new AddKeepAlivesStep (cache), "CleanStep");
+
 			InsertAfter (new StripEmbeddedLibraries (),  "CleanStep");
 		}
 

src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/AddKeepAlivesStep.cs

@@ -106,7 +106,13 @@ bool AddKeepAlives (TypeDefinition type)
 					changed = true;
 
 					if (methodKeepAlive == null)
-						methodKeepAlive = Context.GetMethod ("mscorlib", "System.GC", "KeepAlive", new string [] { "System.Object" });
+						methodKeepAlive = Context.GetMethod (
+#if NETCOREAPP
+							"System.Private.CoreLib",
+#else
+							"mscorlib",
+#endif
+							"System.GC", "KeepAlive", new string [] { "System.Object" });
 
 					processor.InsertBefore (end, GetLoadArgumentInstruction (method.IsStatic ? i : i + 1, method.Parameters [i]));
 					processor.InsertBefore (end, Instruction.Create (OpCodes.Call, module.ImportReference (methodKeepAlive)));

src/Xamarin.Android.Build.Tasks/Linker/MonoDroid.Tuner/Extensions.cs

@@ -46,11 +46,14 @@ public static object GetSettableValue (this CustomAttributeArgument arg)
 			return td != null ? td.FullName + "," + td.Module.Assembly.FullName : arg.Value;
 		}
 
-#if !NETCOREAPP
 		public static AssemblyDefinition GetAssembly (this LinkContext context, string assemblyName)
 		{
 			AssemblyDefinition ad;
+#if !NETCOREAPP
 			context.TryGetLinkedAssembly (assemblyName, out ad);
+#else
+			ad = context.GetLoadedAssembly (assemblyName);
+#endif
 			return ad;
 		}
 
@@ -60,15 +63,14 @@ public static TypeDefinition GetType (this LinkContext context, string assemblyN
 			return ad == null ? null : GetType (ad, typeName);
 		}
 
-		public static MethodDefinition GetMethod (this LinkContext context, string ns, string typeName, string name, string [] parameters)
+		public static MethodDefinition GetMethod (this LinkContext context, string assemblyName, string typeName, string name, string [] parameters)
 		{
-			var type = context.GetType (ns, typeName);
+			var type = context.GetType (assemblyName, typeName);
 			if (type == null)
 				return null;
 
 			return GetMethod (type, name, parameters);
 		}
-#endif
 
 		public static MethodDefinition GetMethod (TypeDefinition td, string name)
 		{

src/Xamarin.Android.Build.Tasks/Microsoft.Android.Sdk/targets/Microsoft.Android.Sdk.ILLink.targets

@@ -26,7 +26,7 @@ This file contains the .NET 5-specific targets to customize ILLink
   <Target Name="_PrepareLinking"
       Condition=" '$(PublishTrimmed)' == 'true' "
       AfterTargets="ComputeResolvedFilesToPublishList"
-      DependsOnTargets="GetReferenceAssemblyPaths">
+      DependsOnTargets="GetReferenceAssemblyPaths;_CreatePropertiesCache">
     <ItemGroup>
       <!-- Mark all assemblies to be linked for AndroidLinkMode=Full -->
       <ResolvedFileToPublish
@@ -51,6 +51,10 @@ This file contains the .NET 5-specific targets to customize ILLink
       <_AdditionalTaskAssemblyDirectory>$(XamarinSdkRootDirectory)tools/dotnet-linker/</_AdditionalTaskAssemblyDirectory>
       <_AdditionalTaskAssembly>$(_AdditionalTaskAssemblyDirectory)dotnet-linker.dll</_AdditionalTaskAssembly>
     </PropertyGroup>
+    <PropertyGroup
+        Condition=" '$(AndroidAddKeepAlives)' != '' ">
+      <_ExtraTrimmerArgs>$(_ExtraTrimmerArgs) --custom-data AddKeepAlivesStep="$(AndroidAddKeepAlives)"</_ExtraTrimmerArgs>
+    </PropertyGroup>
     <PropertyGroup
         Condition=" '$(_ProguardProjectConfiguration)' != '' ">
       <_ExtraTrimmerArgs>$(_ExtraTrimmerArgs) --custom-data ProguardConfiguration="$(_ProguardProjectConfiguration)"</_ExtraTrimmerArgs>

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

@@ -56,7 +56,7 @@ public void BuildBasicApplication ([ValueSource (nameof (SupportedTargetFramewor
 			}
 		}
 
-		string GetLinkedPath (ProjectBuilder builder, bool isRelease, string filename)
+		public static string GetLinkedPath (ProjectBuilder builder, bool isRelease, string filename)
 		{
 			return Builder.UseDotNet && isRelease ?
 				builder.Output.GetIntermediaryPath (Path.Combine ("android.21-arm64", "linked", filename)) :

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

@@ -290,7 +290,6 @@ public AttributedButtonStub (Context context) : base (context)
 		}
 
 		[Test]
-		[Category ("DotNetIgnore")]
 		public void AndroidAddKeepAlives ()
 		{
 			var proj = new XamarinAndroidApplicationProject {
@@ -327,7 +326,7 @@ public unsafe bool MyMethod (Android.OS.IBinder windowToken, [global::Android.Ru
 			using (var b = CreateApkBuilder ()) {
 				Assert.IsTrue (b.Build (proj), "Building a project should have succeded.");
 
-				var assemblyPath = b.Output.GetIntermediaryPath (Path.Combine ("android", "assets", "UnnamedProject.dll"));
+				var assemblyPath = BuildTest.GetLinkedPath (b,  true, "UnnamedProject.dll");
 				using (var assembly = AssemblyDefinition.ReadAssembly (assemblyPath)) {
 					Assert.IsTrue (assembly != null);