Fix nullable Func delegate, whitespace, and csproj comment in PostTrimmingPipeline

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

@@ -9,7 +9,7 @@ namespace MonoDroid.Tuner
 {
 	static class AddKeepAlivesHelper
 	{
-		internal static bool AddKeepAlives (AssemblyDefinition assembly, IMetadataResolver resolver, Func<AssemblyDefinition> getCorlibAssembly, Action<string> logMessage)
+		internal static bool AddKeepAlives (AssemblyDefinition assembly, IMetadataResolver resolver, Func<AssemblyDefinition?> getCorlibAssembly, Action<string> logMessage)
 		{
 			if (!assembly.MainModule.HasTypeReference ("Java.Lang.Object"))
 				return false;
@@ -27,9 +27,9 @@ internal static bool AddKeepAlives (AssemblyDefinition assembly, IMetadataResolv
 			return changed;
 		}
 
-		static bool ProcessType (TypeDefinition type, IMetadataResolver resolver, ref MethodDefinition? methodKeepAlive, Func<AssemblyDefinition> getCorlibAssembly, Action<string> logMessage)
+		static bool ProcessType (TypeDefinition type, IMetadataResolver resolver, ref MethodDefinition? methodKeepAlive, Func<AssemblyDefinition?> getCorlibAssembly, Action<string> logMessage)
 		{
-  			bool changed = false;
+			bool changed = false;
 			if (MightNeedFix (type, resolver))
 				changed |= AddKeepAlives (type, ref methodKeepAlive, getCorlibAssembly, logMessage);
 
@@ -47,7 +47,7 @@ static bool MightNeedFix (TypeDefinition type, IMetadataResolver resolver)
 			return !type.IsAbstract && type.IsSubclassOf ("Java.Lang.Object", resolver);
 		}
 
-		static bool AddKeepAlives (TypeDefinition type, ref MethodDefinition? methodKeepAlive, Func<AssemblyDefinition> getCorlibAssembly, Action<string> logMessage)
+		static bool AddKeepAlives (TypeDefinition type, ref MethodDefinition? methodKeepAlive, Func<AssemblyDefinition?> getCorlibAssembly, Action<string> logMessage)
 		{
 			bool changed = false;
 			foreach (MethodDefinition method in type.Methods) {
@@ -97,7 +97,7 @@ static bool AddKeepAlives (TypeDefinition type, ref MethodDefinition? methodKeep
 			return changed;
 		}
 
-		static MethodDefinition? GetKeepAliveMethod (Func<AssemblyDefinition> getCorlibAssembly, Action<string> logMessage)
+		static MethodDefinition? GetKeepAliveMethod (Func<AssemblyDefinition?> getCorlibAssembly, Action<string> logMessage)
 		{
 			var corlibAssembly = getCorlibAssembly ();
 			if (corlibAssembly == null)

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

@@ -13,10 +13,10 @@ namespace MonoDroid.Tuner;
 class PostTrimmingAddKeepAlivesStep : IAssemblyModifierPipelineStep
 {
 	readonly IMetadataResolver cache;
-	readonly Func<AssemblyDefinition> getCorlibAssembly;
+	readonly Func<AssemblyDefinition?> getCorlibAssembly;
 	readonly Action<string> logMessage;
 
-	public PostTrimmingAddKeepAlivesStep (IMetadataResolver cache, Func<AssemblyDefinition> getCorlibAssembly, Action<string> logMessage)
+	public PostTrimmingAddKeepAlivesStep (IMetadataResolver cache, Func<AssemblyDefinition?> getCorlibAssembly, Action<string> logMessage)
 	{
 		this.cache = cache;
 		this.getCorlibAssembly = getCorlibAssembly;

src/Xamarin.Android.Build.Tasks/Tasks/PostTrimmingPipeline.cs

@@ -48,8 +48,22 @@ public override bool RunTask ()
 		var steps = new List<IAssemblyModifierPipelineStep> ();
 		steps.Add (new StripEmbeddedLibrariesStep (Log));
 		if (AddKeepAlives) {
+			// Memoize the corlib resolution so the attempt (and any error logging) happens at most once,
+			// regardless of how many assemblies/methods need KeepAlive injection.
+			AssemblyDefinition? corlibAssembly = null;
+			bool corlibResolutionAttempted = false;
 			steps.Add (new PostTrimmingAddKeepAlivesStep (cache,
-				() => resolver.Resolve (AssemblyNameReference.Parse ("System.Private.CoreLib")),
+				() => {
+					if (!corlibResolutionAttempted) {
+						corlibResolutionAttempted = true;
+						try {
+							corlibAssembly = resolver.Resolve (AssemblyNameReference.Parse ("System.Private.CoreLib"));
+						} catch (AssemblyResolutionException ex) {
+							Log.LogErrorFromException (ex, showStackTrace: false);
+						}
+					}
+					return corlibAssembly;
+				},
 				(msg) => Log.LogDebugMessage (msg)));
 		}
 

src/Xamarin.Android.Build.Tasks/Xamarin.Android.Build.Tasks.csproj

@@ -44,7 +44,8 @@
     <None Remove="Tests\**" />
     <Compile Include="..\..\bin\Build$(Configuration)\XABuildConfig.cs" />
 
-    <!-- Include only the linker sources required for LinkAssembliesNoShrink - AddKeepAlivesStep, FixAbstractMethodsStep, FixLegacyResourceDesignerStep -->
+    <!-- Include only the linker sources required for the build tasks (LinkAssembliesNoShrink and PostTrimmingPipeline) -->
+    <!-- These include: AddKeepAlivesStep, AddKeepAlivesHelper, StripEmbeddedLibrariesStep, PostTrimmingAddKeepAlivesStep, FixAbstractMethodsStep, FixLegacyResourceDesignerStep -->
     <Compile Remove="Linker\**" />
     <Compile Include="Linker\MonoDroid.Tuner\FindTypeMapObjectsStep.cs" />
     <Compile Include="Linker\MonoDroid.Tuner\FindJavaObjectsStep.cs" />